JP2009160014A - Mri apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI apparatus capable of fetching data again. <P>SOLUTION: The level L3 of respiratory signals Sr at the end time t3 of a data gathering period P3 and a threshold TH are compared and whether or not L3 is larger than TH is judged. Since it is L3>TH, the data gathering period P3 includes a period during which body movement by respiration is large. Thus, when data gathered in the data gathering period P3 are used for the data of image reconfiguration, there is the risk of generating body movement artifacts in MR images. Then, in a data gathering period P5, the data gathered in the data gathering period P3 are fetched again. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an MRI apparatus using a respiratory synchronization method.

Conventionally, the imaging region of a subject is divided into a plurality of slices (or a plurality of slabs), the start of data collection is synchronized with respiration, and data from the slices (or slabs) is obtained while the body movement due to the respiration of the subject is small. It is done to collect.
JP 2006-158762 A

  However, body movement due to respiration may increase while data is collected from a slice (or slab) due to disturbance of the subject's respiration. In this case, since data of slices (or slabs) collected during a period in which body motion is large are also used for image reconstruction, body motion artifacts occur in the MR image. Therefore, it is desirable that data can be re-acquired when body movement increases while data is being collected.

  In view of the above circumstances, an object of the present invention is to provide an MRI apparatus capable of re-taking data.

The first MRI apparatus of the present invention that achieves the above-described problem is:
An MRI apparatus that divides an imaging region of a subject into a plurality of slices or slabs and collects data from the imaging region during an imaging period,
Respiration information acquisition means for acquiring respiration information of the subject;
A threshold value determining means for determining a threshold value as a reference for determining whether the body movement due to breathing of the subject is large or small;
Data collection means for collecting data from the imaging region in a data collection period in the imaging period in synchronization with the breathing of the subject;
Using the respiration information and the threshold value, a determination unit that determines whether or not the data collection period includes a period during which body movement due to respiration of the subject is large, and the determination unit includes: When it is determined that the data collection period includes a period of large body movement due to breathing of the subject, data re-retrieving means for re-acquiring data collected during the data collection period;
have.

The second MRI apparatus of the present invention that achieves the above-described problem is
An MRI apparatus that divides an imaging region of a subject into a plurality of slices or slabs and collects data from the imaging region during an imaging period,
Respiration information acquisition means for acquiring respiration information of the subject;
A threshold value determining means for determining a threshold value as a reference for determining whether the body movement due to breathing of the subject is large or small;
Data collection means for collecting data from the imaging region in a data collection period in the imaging period in synchronization with the breathing of the subject;
A determination means for determining whether or not the data collection period includes a period of large body movement due to respiration of the subject, using the respiratory information and the threshold value;
If the determination means determines that the period during which the subject's breathing is large is included in the data collection period, whether the operator of the MRI apparatus recaptures the data collected during the data collection period Display means for displaying re-judgment judgment information used for judging whether or not and re-decision to decide whether or not to re-collect data collected during the data collection period according to the operation of the operator means,
Have
When the re-decision determining unit determines to re-acquire data collected during the data collection period, the data collection unit re-acquires data collected during the data collection period during the re-imaging period.

The data re-fetching method of the present invention that achieves the above object
A data recovery determination method for determining whether to recover data collected from an imaging region of a subject using an MRI apparatus,
A respiratory information acquisition step of acquiring respiratory information of the subject;
A threshold value determining step for determining a threshold value serving as a reference for determining whether the body movement due to breathing of the subject is large or small;
A data collection step for collecting data from the imaging region in a data collection period in the imaging period in synchronization with the breathing of the subject;
A determination step of determining whether or not the data collection period includes a period of large body movement due to respiration of the subject using the respiratory information and the threshold value;
If the determination step determines that the data collection period includes a period of large body movement due to breathing of the subject, whether the operator of the MRI apparatus recaptures the data collected during the data collection period A display step for displaying re-judgment judgment information used to judge whether or not, and a re-judgment decision to decide whether or not to re-collect the data collected during the data collection period according to the operation of the operator Step,
have.

  In the first MRI apparatus of the present invention, when it is determined that the data collection period includes a period in which body movement due to breathing of the subject is large, data collection for re-acquiring data collected during the data collection period is performed. A repairing means is provided. Therefore, the data considered to be affected by the body movement is re-taken, and the re-taken data is used as image reconstruction data. For this reason, MR images with reduced body motion artifacts can be acquired.

  When the second MRI apparatus of the present invention decides to retake the data collected during the data collection period, the data is retaken during the re-imaging period. Therefore, the data considered to be affected by the body movement is re-taken, and the re-taken data is used as image reconstruction data. For this reason, MR images with reduced body motion artifacts can be acquired.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention.

1. First Embodiment FIG. 1 is a block diagram of an MRI (Magnetic Resonance Imaging) apparatus 100 according to a first embodiment of the present invention.

  The MRI apparatus 100 has a magnet assembly 101. The magnet assembly 101 has a bore 114 for inserting the subject 10. The magnet assembly 101 has a static magnetic field coil 101C, a gradient coil 101G, and a transmission coil 101T.

  The static magnetic field coil 101 </ b> C applies a constant static magnetic field in the bore 114. The gradient coil 101G is connected to the gradient coil drive circuit 103, and generates gradient magnetic fields of the X axis, the Y axis, and the Z axis. The transmit coil 101T is connected to the RF power amplifier 104 and supplies RF pulses in the bore 114.

  The MRI apparatus 100 has a bellows 102. The bellows 102 detects the respiration of the subject 10 and transmits a respiration signal Sr to the computer 107. The computer 107 calculates the respiratory state of the subject 10 based on the received respiratory signal Sr and outputs the calculation result to the sequencer 108.

  The sequencer 108 controls the gradient coil drive circuit 103 and the gate modulation circuit 109 according to the command received from the computer 107. The gradient coil drive circuit 103 drives the gradient coil 101G according to a command from the sequencer 108. As a result, the gradient coil 101G applies a gradient pulse to the subject 10. The gate modulation circuit 109 modulates the carrier wave from the RF oscillation circuit 110 according to a command from the sequencer 108 and outputs the modulated signal to the RF power amplifier 104. The RF power amplifier 104 power-amplifies the modulated signal and then applies it to the transmission coil 101T. As a result, the transmission coil 101T applies a transmission pulse to the subject 10.

  Further, the MRI apparatus 100 has a receiving coil 101R. The receiving coil 101R is connected to the preamplifier 105, and receives the MR signal from the subject 10. This MR signal is amplified by the preamplifier 105 and supplied to the receiver 112. The receiver 112 converts the amplified MR signal into a digital signal and outputs it to the computer 107.

  The computer 107 reconstructs an image based on the digital signal from the receiver 112. The reconstructed image is displayed on the display device 106.

  Next, the imaging operation of the MRI apparatus 100 configured as described above will be described.

  FIG. 2 is an example of a functional block diagram of the computer 107.

  The computer 107 includes a threshold determination unit 11, a data collection period start unit 12, a slice selection unit 13, a count unit 14, a data collection period end unit 15, a body movement determination unit 16, and a data replay determination. Part 17.

  The threshold value determination unit 11 determines a threshold value TH that serves as a reference for whether the body movement due to respiration of the subject 10 is large or small from the respiration signal Sr of the subject 10. The data collection period start unit 12 controls the timing of starting data collection based on the respiratory signal Sr. The slice selection unit 13 controls the slice position where data is collected. The counting unit 14 counts the number of slices for which data collection has been completed. The data collection period end unit 15 ends the data collection period when the count value of the count unit 14 reaches a predetermined value. The body movement determination unit 16 determines whether or not the data collection period includes a period with a large body movement. The data re-receipt determination unit 17 determines whether to re-acquire data.

  Next, a processing flow of the MRI apparatus 100 in the first embodiment will be described.

  FIG. 3 is an example of a flowchart of the MRI apparatus 100 in the first embodiment.

  Before imaging the subject 10, in step S11, the respiratory signal Sr of the subject 10 is acquired, and a threshold that is a criterion for whether the body movement due to the respiration of the subject 10 is large or small is obtained from the acquired respiratory signal Sr. The value TH is determined.

  FIG. 4 is an explanatory diagram of an example of a method for determining the threshold value TH.

  In step S <b> 11, the computer 107 receives the respiration signal Sr from the bellows 102. The calculator 107 calculates the minimum values MIN1, MIN2, MIN3,... And the maximum values MAX1, MAX2, MAX3,... Of the respiratory signal Sr for each respiratory cycle from the respiratory signal Sr. Thereafter, the calculator 107 calculates an average value MINave of the minimum values MIN1, MIN2, MIN3,... And an average value MAXave of the maximum values MAX1, MAX2, MAX3,. The computer 107 calculates an intermediate value between the calculated MINave and MAXave, and sets the intermediate value as a threshold value TH that serves as a reference for whether the body movement due to respiration is large or small. Here, an intermediate value between MINave and MAXave is used as the threshold value TH. However, for example, a value smaller or larger than the intermediate value may be used as the threshold value.

  After step S11 is completed, data is collected in step S12, and an image is displayed in step S13. Hereinafter, the process of step S12 will be described in detail.

  In step S12, data is collected from the imaging region 10a of the subject 10.

  FIG. 5 is a diagram illustrating the imaging region 10 a of the subject 10.

  The imaging region 10a is divided into N slices. In the first embodiment, the imaging region 10a is divided into 20 slices (N = 20). However, the number of slices is not limited to 20 and can be more or less than 20.

  The imaging region 10a is imaged with the R period of the respiratory signal Sr as the repetition time TR. Also, data is collected from n slices during each cycle of the respiratory signal Sr. In the first embodiment, imaging is performed using two cycles (R = 2) of the respiratory signal Sr as the repetition time TR. Furthermore, during the first period of the two periods (R = 2) of the respiratory signal Sr, data is collected from 10 slices (slice numbers b = 1 to 10), and during the next period. Data is collected from the remaining 10 slices (slice number b = 11 to 20). In the first embodiment, data is collected from 10 slices during each cycle. However, the number of slices from which data is collected may be different in each cycle of the respiratory signal Sr.

  FIG. 6 is an example of a flowchart of data collection executed in step S12, and FIG. 7 explains at what timing data is collected from each slice by executing the flowchart of FIG. FIG.

  Below, the flowchart of FIG. 6 is demonstrated, referring FIG.

  In step S121, the parameter v is initialized. v is a parameter that defines a line number (see FIG. 8 described later) in the k space. In step S121, the line number v is set to v = 1. Next, the process proceeds to step S122.

  In step S122, parameters r, NS, and b are initialized. r is a parameter that defines the respiratory cycle of the respiratory signal. NS is a parameter that defines the number of slices for which data has been collected in each respiratory cycle (hereinafter referred to as “data collected slice number”). b is a parameter that defines the slice number. In step S122, the respiratory cycle r, the number of data-collected slices NS, and the slice number b are initialized to r = 1, NS = 0, and b = 1, respectively. Thereafter, the process proceeds to step S123.

  In step S123, a data collection period is started. First, the data collection period P1 (see FIG. 7) is started. The data collection period P1 starts when a certain delay time Td has elapsed from the peak A1 of the respiratory signal Sr.

  Note that the delay time Td is determined based on the respiratory characteristics of the subject 10 while the body movement due to respiration of the subject 10 is small (that is, while the respiratory signal Sr is smaller than the threshold value TH). It is set to start.

  When the data collection period P1 starts, in step S124, data of the vth line in the k space is collected from the bth slice.

  FIG. 8 is a conceptual diagram of the k space.

  The k space of each slice is composed of V0 lines. In the first embodiment, V0 = 128, but another value may be used. When the respiratory cycle r is r = 1, data is collected from the first to the tenth slices. Since the slice number b and the line number v are set to b = 1 and v = 1, respectively, first, in the data collection period P1, data of the first line in the k space is collected from the first slice. The Thereafter, the process proceeds to step S125.

  In step S125, the data-collected slice number NS is incremented. Since NS = 0 at the start of the data collection period P1 (see step S122), NS is incremented to be updated to NS = 1. After updating NS, the process proceeds to step S126.

  In step S126, it is determined whether the data-collected slice number NS has reached n. In the first embodiment, since n = 10, it is determined whether NS = n = 10 has been reached. If it is determined that NS = 10, the process proceeds to step S128, and the data collection period (here, the data collection period P1) ends. On the other hand, if it is determined in step S126 that NS = 10 has not yet been reached, the process proceeds to step S127.

  At the time when the data of the first line in the k space is collected from the first slice, the number NS of slices from which the data has been collected is NS = 1. Therefore, since NS = 10 has not been reached, the process proceeds from step S126 to step S127.

  In step S127, the line number v is not updated, but the slice number b is updated. Therefore, the line number v remains v = 1, but the slice number b is updated to b = 2. Thereafter, the process returns to step S124.

  In step S124, since b = 2 and v = 1, data of the first line (v = 1) in the k space is collected from the second slice (b = 2). Thereafter, similarly, the steps S124 to S127 are repeatedly executed, and the data of the first line in the k space is collected from the third slice,..., The tenth slice. Each time data is collected from each slice, the number NS of data collected slices is updated. When data of the first line in the k space is collected from the 10th slice in step S124, NS is updated to NS = 10 in step S125, and the process proceeds to step S126.

  Since data has been collected from the first to tenth slices, it is determined in step S126 that the number of slices with data collected NS = n (= 10), the process proceeds to step S128, and the data collection period P1 ends (FIG. 7). Time t1).

  When the data collection period P1 ends, the process proceeds to step S129.

  In step S129, the level Lr (r = 1, 2, 3,... Z) of the respiratory signal Sr at the end time te (e = 1, 2, 3,... Z) of each data collection period is set. The threshold value TH is compared. From this comparison result, it is determined whether the data collected during the data collection period is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. Here, since the data collection period P1 has ended, the level L1 of the respiratory signal Sr at the end time t1 of the data collection period P1 is compared with the threshold value TH.

  When L1 is compared with TH, as shown in FIG. 7, L1 is smaller than TH, and therefore, L1 <TH is determined. L1 <TH means that the data collection period P1 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P1 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P1 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S130, and the data collected in the data collection period P1 is recorded as “valid data”. After this recording, the process proceeds to step S131.

  In step S131, it is determined whether the respiratory cycle r = R. If r = R, the process proceeds to step S133. If r = R is not satisfied, the process proceeds to step S132. In the first embodiment, since R = 2, it is determined whether or not the respiratory cycle r = 2. Since r = 1 at the end of the data collection period P1 (see FIG. 7), the process proceeds to step S132.

  In step S132, the line number v is not updated, but the respiratory cycle r and the slice number b are updated. At the end of the data collection period P1, the respiratory cycle r, slice number b, and line number v are r = 1, b = 10, and v = 1, respectively (see FIG. 7). Therefore, by executing step S132, the respiratory cycle r, slice number b, and line number v are set to r = 2, b = 11, and v = 1, respectively. In addition, the number NS of data-collected slices is reset to zero. After step S132, the process returns to step S123.

  When the process returns to step S123, the next data collection period P2 is started, and the process proceeds to step S124.

  In step S124, data of the vth line in the k space is collected from the bth slice. In the data collection period P2, the respiratory cycle r = 2. When the respiratory cycle r is r = 2, data is collected from the 11th to 20th slices. Since the slice number b and the line number v are b = 11 and v = 1, respectively, first, in the data collection period P2, data of the first line in the k space is collected from the 11th slice. Thereafter, the process proceeds to step S126.

  In step S126, it is determined whether the data-collected slice number NS has reached n. In the first embodiment, since n = 10, it is determined whether NS = 10 has been reached. At the time when the data of the first line in the k space is collected from the 11th slice, the number NS of slices from which the data has been collected is NS = 1. Therefore, since NS = 10 has not been reached, the process proceeds from step S126 to step S127.

  In step S127, the slice number b is updated to b = 12, and the process returns to step S124. In step S124, data of the first line in the k space is collected from the twelfth slice. Similarly, the loop of step S124 to step S127 is repeatedly executed, and data of the first line in the k space is collected from the 13th slice,..., The 20th slice. Each time data is collected from each slice, the number NS of data collected slices is updated. When data of the first line in the k space is collected from the 20th slice in step S124, NS is updated to NS = 10 in step S125, and the process proceeds to step S126. In step S126, it is determined that the number of slices of data collected NS = n (= 10), the process proceeds to step S128, and the data collection period P2 (see time t2 in FIG. 7) ends.

  When the data collection period P2 ends, the process proceeds to step S129.

  In step S129, the level L2 of the respiratory signal Sr at the end time t2 of the data collection period P2 is compared with the threshold value TH. From this comparison result, it is determined whether the data collected in the data collection period P2 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. .

  When comparing L2 and TH, as shown in FIG. 7, L2 is smaller than TH, and therefore it is determined that L2 <TH. L2 <TH means that the data collection period P2 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P2 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P2 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S130, and the data collected in the data collection period P2 is recorded as “valid data”. After recording as “valid data”, the process proceeds to step S131.

  In step S131, it is determined whether or not the respiratory cycle r = R (= 2). Since r = R (= 2) when the data collection period P2 ends (see FIG. 7), the process proceeds to step S133.

  In step S133, it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected in the data collection periods P1 and P2 of the repetition time TR are all determined to be valid data as shown in FIG. Therefore, in step S133, it is determined that NG data does not exist, and the process proceeds to step S135.

  In step S135, it is determined whether or not the line number v = V0. In the first embodiment, since V0 = 128 (see FIG. 8), it is determined whether or not the line number v = 128. When the line number v = 128, it is determined that the data of all the lines 1 to 128 in the k space have been collected from all the slices, and the data collection is terminated. On the other hand, if v = 128 is not satisfied, there is still data that has not been collected, so the process proceeds to step S136 to continue collecting data. Since v = 1 at the end of the data collection period P2 (see time t2 in FIG. 7), the process proceeds to step S136.

  In step S136, the line number v is updated. When the data collection period P2 ends, the line number v is v = 1 (see time t2 in FIG. 7). Therefore, the line number v is set to v = 2 by executing step S136. In addition, the breathing cycle r and the slice number b are reset to 1, and the data-collected slice number NS is reset to zero. After step S136, the process returns to step S123.

  When the process returns to step S123, the next data collection period P3 is started, and the process proceeds to step S124. Since the respiratory cycle r = 1, the slice number b = 1, and the line number v = 2 at the start of the data collection period P3, the first to tenth slices are performed by repeatedly executing steps S124 to S127. To the data of the second line in the k space are collected in order. Each time data is collected from each slice, the number NS of data collected slices is updated. When the data of the second line in the k space is collected from the tenth slice in step S124, NS = 10 is updated in step S125, and the process proceeds to step S126. In step S126, it is determined that the number of slices of data collected NS = n (= 10), the process proceeds to step S128, and the data collection period P3 (see time t3 in FIG. 7) ends.

  When the data collection period P3 ends, the process proceeds to step S129.

  In step S129, the level L3 of the respiratory signal Sr at the end time t3 of the data collection period P3 is compared with the threshold value TH. From this comparison result, it is determined whether the data collected in the data collection period P3 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. .

  When comparing L3 and TH, as shown in FIG. 7, L3 is larger than TH, and therefore it is determined that L3> TH. L3> TH means that the respiration signal Sr has exceeded the threshold value TH before the end of the data collection period P3. Therefore, it is determined that the data collection period P3 includes a period M in which body movement due to respiration is large. In this case, if the data collected during the data collection period P3 is used as the data for image reconstruction, body motion artifacts on the MR image may increase. Therefore, it is determined that the data collected during the data collection period P3 is NG data that is greatly affected by body movement due to respiration and cannot be used for image reconstruction. Thereafter, the process proceeds to step S130, and the data collected in the data collection period P3 is recorded as “NG data”. After recording “NG data”, the process proceeds to step S131.

  In step S131, it is determined whether or not the respiratory cycle r = R (= 2). Since r = 1 at the end of the data collection period P3 (see FIG. 7), r = R (= 2) has not yet been reached. Accordingly, the process proceeds to step S132.

  In step S132, the line number v is not updated, but the respiratory cycle r and the slice number b are updated. At the end of the data collection period P3, the respiratory cycle r, slice number b, and line number v are r = 1, b = 10, and v = 2, respectively (see FIG. 7). Therefore, by executing step S132, the respiratory cycle r, slice number b, and line number v are set to r = 2, b = 11, and v = 2, respectively. In addition, the number NS of data-collected slices is reset to zero. After step S132, the process returns to step S123.

  When the process returns to step S123, the next data collection period P4 is started, and the process proceeds to step S124. Since the respiratory cycle r = 2, the slice number b = 11, and the line number v = 2 at the start of the data collection period P4, the 11th to 20th slices are performed by repeatedly executing steps S124 to S127. To the data of the second line in the k space are collected in order. Each time data is collected from each slice, the number NS of data collected slices is updated. When the data of the second line in the k-space is collected from the 20th slice in step S124, NS is updated to NS = 10 in step S125, and the process proceeds to step S126. In step S126, it is determined that the number of slices with data collected NS = n (= 10), the process proceeds to step S128, and the data collection period P4 (see time t4 in FIG. 7) ends.

  When the data collection period P4 ends, the process proceeds to step S129.

  In step S129, the level L4 of the respiratory signal Sr at the end time t4 of the data collection period P4 is compared with the threshold value TH.

  When comparing L4 and TH, as shown in FIG. 7, L4 is smaller than TH, and therefore, L4 <TH is determined. L4 <TH means that the data collection period P4 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P4 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P4 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S130, and the data collected in the data collection period P4 is recorded as “valid data”. After recording as “valid data”, the process proceeds to step S131.

  In step S131, it is determined whether or not the respiratory cycle r = R (= 2). Since r = R (= 2) at the end of the data collection period P4 (see FIG. 7), the process proceeds to step S133.

  In step S133, it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected in the data collection period P4 in the second half of the repetition time TR is determined as valid data as shown in FIG. 7, but the data collected in the data collection period P3 in the first half of the repetition time TR. Is determined to be NG data. Therefore, in step S133, it is determined that NG data exists. If the data collected during the data collection period P3 is used as data for image reconstruction, body motion artifacts on the MR image may increase. Therefore, data re-reading is executed. Comparing the data collection periods P3 and P4, only the data collected in the data collection period P3 is NG data, and the data collected in the data collection period P4 is valid data. However, in the first embodiment, not only the data collected in the data collection period P3 but also the data collected in the data collection period P4 is reacquired for the purpose of keeping the repetition time TR constant. If it is determined that NG data exists in order to re-acquire data, the process proceeds from step S133 to step S134.

  In step S134, the line number v is not updated. Therefore, the line number v remains v = 2. In addition, the breathing cycle r and the slice number b are reset to 1, and the data-collected slice number NS is reset to zero. After step S134, the process returns to step S123.

  When returning to step S123, the next data collection period P5 is started, and the process proceeds to step S124. Since the respiratory cycle r = 1, the slice number b = 1, and the line number v = 2 at the start of the data collection period P5, the first to tenth slices are performed by repeatedly executing steps S124 to S127. Thus, the data of the second line in the k space is retaken. Each time data is acquired from each slice, the number NS of data-collected slices is updated. When the data of the second line in the k space is collected from the tenth slice in step S124, NS = 10 is updated in step S125, and the process proceeds to step S126. In step S126, it is determined that the number of slices of data collected NS = n (= 10), the process proceeds to step S128, and the data collection period P5 (see time t5 in FIG. 7) ends.

  When the data collection period P5 ends, the process proceeds to step S129.

  In step S129, the level L5 of the respiratory signal Sr at the end time t5 of the data collection period P5 is compared with the threshold value TH.

  When comparing L5 and TH, as shown in FIG. 7, L5 is smaller than TH, and therefore, it is determined that L5 <TH. L5 <TH means that the data collection period P5 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P5 does not include a period during which body movement due to respiration is large. In this case, even if the data collected in the data collection period P5 is used for image reconstruction, the body motion artifact on the MR image is small. Therefore, the data (slice number b = 1 to 10, line number v = 2) recaptured during the data collection period P5 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. It is judged. Thereafter, the process proceeds to step S130.

  In step S130, the data (slice number b = 1 to 10, line number v = 2) recaptured during the data collection period P5 is recorded as “valid data”. Further, the NG data collected during the data collection period P3 is deleted. Thereafter, the process proceeds to step S131.

  In step S131, it is determined whether or not the respiratory cycle r = R (= 2). Since r = 1 at the end of the data collection period P5 (see FIG. 7), the process proceeds to step S132.

  In step S132, the line number v is not updated, but the respiratory cycle r and the slice number b are updated. At the end of the data collection period P5, the respiratory cycle r, slice number b, and line number v are r = 1, b = 10, and v = 2, respectively (see FIG. 7). Therefore, by executing step S132, the respiratory cycle r, slice number b, and line number v are set to r = 2, b = 11, and v = 2, respectively. In addition, the number NS of data-collected slices is reset to zero. After step S132, the process returns to step S123.

  When returning to step S123, the next data collection period P6 is started, and the process proceeds to step S124. In the data collection period P6, as in the data collection period P4, data of the second line in the k space is collected from the 11th to 20th slices. In step S128, the data collection period P6 (time t6 in FIG. 7) is collected. Reference) ends.

  When the data collection period P6 ends, the process proceeds to step S129.

  In step S129, the level L6 of the respiratory signal Sr at the end time t6 of the data collection period P6 is compared with the threshold value TH.

  When comparing L6 and TH, as shown in FIG. 7, L6 is smaller than TH, and therefore, L6 <TH is determined. L6 <TH means that the data collection period P6 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P6 does not include a period during which body movement due to respiration is large. In this case, the data (slice number b = 11-20, line number v = 2) recaptured during the data collection period P6 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. It is judged that there is. Thereafter, the process proceeds to step S130.

  In step S130, the data (slice number b = 11 to 20, line number v = 2) recaptured during the data collection period P6 is recorded as “valid data”. Note that the data (slice number b = 11 to 20, line number v = 2) recaptured in the data collection period P6 has already been collected in the data collection period P4. Similarly to the data collected in the data collection period P6, the data collected in the data collection period P4 is determined to be “valid data”. Therefore, when image reconstruction is performed, data collected during the data collection period P4 may be used, or data retrieved during the data collection period P6 may be used. After step S130, the process proceeds to step S131.

  In step S131, it is determined whether or not the respiratory cycle r = R (= 2). Since r = R (= 2) at the end of the data collection period P6 (see FIG. 7), the process proceeds to step S133.

  In step S133, it is determined whether or not NG data exists in the data collected at the repetition time TR. As shown in FIG. 7, the data recovered in the data collection periods P5 and P6 of the repetition time TR are all determined to be valid data. Therefore, in step S133, it is determined that NG data does not exist, and the process proceeds to step S135.

  In step S135, it is determined whether v = V0 (= 128). Since v = 2 at the end of the data collection period P6 (see time t6 in FIG. 7), the process proceeds to step S136, the line number v is updated, and the process returns to step S123.

  When returning to step S123, the loop of steps S123 to S136 is repeatedly executed according to the procedure described above. As a result, data of each line in the k space is sequentially collected from the first to twentieth slices, and two data collection periods Pz-1 and Pz (see FIG. 7) are provided at the last repetition time TR. .

  In the data collection period Pz-1, data of the 128th line in the k space is collected from the first to the tenth slices. After the end of the data collection period Pz-1, the process proceeds to step S129, and it is determined whether or not the level Lz-1 of the respiratory signal Sr at time tz-1 is greater than the threshold value TH. Since Lz-1 <TH, “valid data” is recorded in step S130, and the process proceeds to step S131. Since r = 1 in the data collection period Pz-1 (see FIG. 7), the process proceeds to step S132, the respiratory cycle r is updated to r = 2, and the process returns to step S123.

  When returning to step S123, the data collection period Pz is started. In the data collection period Pz, data of the 128th line in the k space is collected from the 11th to 20th slices. After the end of the data collection period Pz, the process proceeds to step S129, and it is determined whether or not the level Lz of the respiratory signal Sr at time tz is greater than the threshold value TH. Since Lz <TH, “valid data” is recorded in step S130, and the process proceeds to step S131. Since r = 2 in the data collection period Pz (see FIG. 7), the process proceeds to step S133, and it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected in the data collection periods Pz-1 and Pz of the repetition time TR are all determined to be valid data as shown in FIG. Therefore, in step S133, it is determined that NG data does not exist, and the process proceeds to step S135.

  In step S135, it is determined whether v = V0 (= 128). Since v = 128 at the time when the data collection period Pz ends (see time tz in FIG. 7), it is determined that v = 128, and the imaging ends.

  By repeatedly executing the loop of steps S121 to S136, data acquisition periods P1 to Pz are provided during the imaging period ACQ, and as a result, all data necessary to fill the k-space is collected from all slices. Is done.

  After collecting all the data, the image is reconstructed.

  In the first embodiment, the level Lr of the respiratory signal Sr at the end time of each data collection period is compared with the threshold value TH. When Lr> TH, it is determined that the body movement due to breathing has increased before the end of the data collection period, and the data is automatically reacquired. In the case of image reconstruction, the re-acquired data is used as image reconstruction data. Therefore, MR images with reduced body motion artifacts can be acquired.

  Depending on the respiratory state of the subject 10, the level of the respiratory signal Sr exceeds the threshold value TH during the data collection period, but the level of the respiratory signal Sr is less than the threshold value TH before the end of the data collection period. May return. In this case, it is not possible to accurately determine whether or not the data collection period includes a period during which body movement is large due to respiration only by obtaining the level Lr of the respiratory signal Sr at the time when each data collection period ends. . In order to solve such a problem, the level of the respiratory signal Sr may be obtained every time data is collected from each slice. If the level of the respiration signal Sr is obtained every time data is collected from each slice, the data collection period will be the body due to respiration even if the level of the respiration signal Sr returns below the threshold value TH before the end of the data collection period. It is possible to accurately determine whether or not a period of high movement is included.

  In the first embodiment, whether or not the data collection period includes a period in which body movement due to respiration is large is determined by comparing the level Lr of the respiration signal Sr with the threshold value TH. It has been broken. However, the determination of whether or not the data collection period includes a period in which body movement due to respiration is large can be performed in another manner. In the following, another method will be described in the second embodiment.

2. Second Embodiment In the description of the second embodiment, differences from the first embodiment will be mainly described.

  In the second embodiment, the hardware configuration of the MRI apparatus is almost the same as that of the first embodiment, but the functional blocks of the computer 107 are different.

  FIG. 9 is an example of a functional block diagram of the computer 107 in the second embodiment.

  The difference between the first embodiment and the second embodiment is that an end time recording unit 21 is provided between the slice selection unit 13 and the count unit 14. The end time recording unit 21 records the end time for each slice in the data collection period.

  Next, a processing flow of the MRI apparatus 100 in the second embodiment will be described.

  The processing flow of the MRI apparatus 100 in the second embodiment can be described using the flowchart shown in FIG. That is, also in the second embodiment, in step S <b> 11, a threshold value serving as a reference for whether the body movement due to breathing of the subject 10 is large or small is determined. The threshold value determination method is the same as the method described with reference to FIG.

  After step S11 is completed, data is collected in step S12, and an image is displayed in step S13. However, in the second embodiment, the processing flow in step S12 is different from that in the first embodiment. Below, the process of step S12 in 2nd Embodiment is demonstrated in detail.

  FIG. 10 is a flowchart showing the specific processing of step S12, and FIG. 11 is a diagram for explaining at what timing data is collected from each slice by executing the flowchart of FIG. is there.

  The flowchart of FIG. 10 will be described below with reference to FIG.

  The operations in steps S221 to S229 are almost the same as the operations in steps S121 to S128 in the flowchart (see FIG. 6) of the first embodiment. However, the second embodiment is different from the first embodiment in that step S225 for recording the end time te is provided between step S224 and step S226.

  Step S225 is a step of recording the time te when the collection of the data of the vth line in the k space is completed from the bth slice. In the second embodiment, since step S225 is provided, the data collection end time te is recorded each time the collection of data of the vth line in the k space from each slice is completed. Since data is collected from the first to tenth slices in the data collection period P1, every time data is collected from each of the first to tenth slices, the end time te = t11, t12 in step S225. ,..., T19, t20 are recorded (see FIG. 11). After the end time te = t20 is recorded, the process proceeds to step S226, the data-collected slice number NS is updated to NS = 10, and the process proceeds to step S227. In step S227, it is determined that the number of data-collected slices NS = n (= 10), the process proceeds to step S229, and the data collection period P1 ends.

  When the data collection period P1 ends, the process proceeds to step S230.

  Further, in the second embodiment, as shown in FIG. 11, the time when the respiratory signal Sr reaches the threshold value TH from a value smaller than the threshold value TH (hereinafter referred to as “threshold reached”). Tth (= T1, T2, T3,... Tz) is calculated. In step S230, the end time te for each slice in each data collection period is compared with the threshold arrival time Tth. From this comparison result, it is determined whether the data collected during the data collection period is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. Here, since the data collection period P1 has ended, in step S230, the end time te (= t11, t12,... T19, t20) for each slice of the data collection period P1 and the threshold arrival time T1. Are compared.

  When the end time te (= t11, t12,... T19, t20) is compared with the threshold arrival time T1, the end time t20 and the threshold arrival time T1 are first compared. When t20 and T1 are compared, t20 <T1. This means that the data collection period P1 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P1 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P1 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S231, and the data collected in the data collection period P1 is recorded as “valid data”. After this recording, the process proceeds to step S232.

  The operations from step S232 to step 237 are the same as the operations from step S131 to step S136 in the flowchart (see FIG. 6) of the first embodiment. At the end of the data collection period P1, the respiratory cycle r = 1, the slice number b = 1, and the line number v = 1 (see FIG. 11). Therefore, the process proceeds from step S232 to step S233, where the respiration cycle r = 2, the slice number b = 11, the line number v = 1, and the number of data-collected slices NS = 0 are set, and the process returns to step S223.

  When the process returns to step S223, the next data collection period P2 is started, and the process proceeds to step S224. Since the respiratory cycle r = 2, the slice number b = 11, and the line number v = 1 at the start of the data collection period P2, the 11th to 20th slices are executed by repeatedly executing steps S224 to S228. To the data of the second line in the k space are collected in order. Each time data is collected from each slice, the number NS of data collected slices is updated. When the data of the first line in the k space is collected from the 20th slice in step S224, the end time te = t30 is recorded in step S225, updated to NS = 10 in step S226, and the process proceeds to step S227. In step S227, it is determined that the number of data-collected slices NS = n (= 10), the process proceeds to step S229, and the data collection period P2 ends.

  When the data collection period P2 ends, the process proceeds to step S230.

  In step S230, the end time te (= t21, t22,... T29, t30) for each slice in the data collection period P2 is compared with the threshold arrival time T2. From this comparison result, it is determined whether the data collected in the data collection period P2 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. .

  When comparing the end time te (= t21, t22,... T29, t30) and the threshold arrival time T2, the end time t30 and the threshold arrival time T2 are first compared. When t30 and T2 are compared, t30 <T2. This means that the data collection period P2 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P2 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P2 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S231, and the data collected in the data collection period P1 is recorded as “valid data”. After this recording, the process proceeds to step S232.

  Since the respiratory cycle r = R (= 2) at the end of the data collection period P2, the process proceeds to step S234.

  In step S234, it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected in the data collection periods P1 and P2 of the repetition time TR are all determined to be valid data as shown in FIG. Therefore, in step S234, it is determined that NG data does not exist, and the process proceeds to step S236.

  In step S236, it is determined whether v = V0 (= 128). Since v = 1 at the end of the data collection period P2 (see time t30 in FIG. 11), the process proceeds to step S237, and the respiratory cycle r = 1, slice number b = 1, line number v = 2, data collected The number of slices NS is set to 0, and the process returns to step S223.

  When the process returns to step S223, the next data collection period P3 is started, and the process proceeds to step S224. Since the respiratory cycle r = 1, the slice number b = 1, and the line number v = 2 at the start of the data collection period P3, the first to tenth slices are executed by repeatedly executing steps S224 to S228. To the data of the second line in the k space are collected in order. If it is determined in step S227 that NS = n (= 10), the process proceeds to step S229, and the data collection period P3 ends.

  When the data collection period P3 ends, the process proceeds to step S230.

  In step S230, the end time te (= t31, t32,... T39, t40) for each slice in the data collection period P3 is compared with the threshold arrival time T3. From this comparison result, it is determined whether the data collected in the data collection period P3 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. .

  When comparing the end time te (= t31, t32,... T39, t40) with the threshold arrival time T3, first, the end time t40 is compared with the threshold arrival time T3. When t40 and T3 are compared, t40> T3. This means that the respiration signal Sr has exceeded the threshold value TH before the end of the data collection period P3. Therefore, it is determined that the data collection period P3 includes a period M in which body movement due to respiration is large. In this case, if the data collected during the data collection period P3 is used as the data for image reconstruction, body motion artifacts on the MR image may increase. Therefore, it is determined that the data collected during the data collection period P3 is NG data that is greatly affected by body movement due to respiration and cannot be used for image reconstruction. Thereafter, the process proceeds to step S231, and the data collected in the data collection period P3 is recorded as “NG data”. After recording “NG data”, the process proceeds to step S232.

  At the end of the data collection period P3, the respiratory cycle r = 1 (see time t40 in FIG. 11). Therefore, the process proceeds from step S232 to step S233, where the respiration cycle r = 2, the slice number b = 11, the line number v = 2, and the number of data-collected slices NS = 0 are set, and the process returns to step S223.

  When the process returns to step S223, the next data collection period P4 is started, and the process proceeds to step S224. Since the respiratory cycle r = 2, the slice number b = 11, and the line number v = 2 at the start of the data collection period P4, the 11th to 20th slices are executed by repeatedly executing steps S224 to S228. To the data of the second line in the k space are collected in order. If it is determined in step S227 that NS = n (= 10), the process proceeds to step S229, and the data collection period P4 ends.

  When the data collection period P4 ends, the process proceeds to step S230.

  In step S230, the end time te (= t41, t42,... T49, t50) for each slice in the data collection period P4 is compared with the threshold arrival time T4.

  When comparing the end time te (= t41, t42,... T49, t50) and the threshold arrival time T4, first, the end time t50 and the threshold arrival time T4 are compared. When t50 is compared with T4, t50 <T4. This means that the data collection period P4 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P4 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P4 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S231, and the data collected in the data collection period P4 is recorded as “valid data”. After this recording, the process proceeds to step S232.

  In step S232, it is determined whether respiration cycle r = R (= 2). Since r = R (= 2) at the end of the data collection period P4 (see FIG. 11), the process proceeds to step S234.

  In step S234, it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected in the data collection period P4 in the second half of the repetition time TR is determined to be valid data as shown in FIG. 11, but the data collected in the data collection period P3 in the first half of the repetition time TR. Is determined to be NG data. Therefore, in step S234, it is determined that NG data exists. If the data collected during the data collection period P3 is used as data for image reconstruction, body motion artifacts on the MR image may increase. Therefore, data re-reading is executed. Comparing the data collection periods P3 and P4, only the data collected in the data collection period P3 is NG data, and the data collected in the data collection period P4 is valid data. However, in order to keep the repetition time TR constant, not only the data collected in the data collection period P3 but also the data collected in the data collection period P4 are retrieved again. If it is determined that NG data exists in order to re-acquire the data, the process proceeds from step S234 to step S235, and returns to step S223.

  When the process returns to step S223, the next data collection period P5 is started, and the process proceeds to step S224. Since the respiratory cycle r = 1, the slice number b = 1, and the line number v = 2 at the start of the data collection period P5, the first to tenth slices are performed by repeatedly executing steps S224 to S228. Thus, the data of the second line in the k space is retaken. If it is determined in step S227 that the number of slices NS has been collected NS = n (= 10), the process proceeds to step S229, and the data collection period P5 (see time t60 in FIG. 11) ends.

  When the data collection period P5 ends, the process proceeds to step S230.

  In step S230, the end time te (= t51, t52,... T59, t60) for each slice in the data collection period P5 is compared with the threshold arrival time T5.

  When comparing the end time te (= t51, t52,... T59, t60) and the threshold arrival time T5, first, the end time t60 and the threshold arrival time T5 are compared. When t60 and T5 are compared, t60 <T5. This means that the data collection period P5 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P5 does not include a period during which body movement due to respiration is large. In this case, even if the data collected in the data collection period P5 is used for image reconstruction, the body motion artifact on the MR image is small. Therefore, the data (slice number b = 1 to 10, line number v = 2) recaptured during the data collection period P5 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. It is judged. Then, it progresses to step S231.

  In step S231, the data (slice number b = 1 to 10, line number v = 2) recaptured during the data collection period P5 is recorded as “valid data”. Further, the NG data collected during the data collection period P3 is deleted. Thereafter, the process proceeds to step S232.

  In step S232, it is determined whether respiration cycle r = R (= 2). Since r = 1 when the data collection period P5 ends (see FIG. 7), r = R (= 2) has not yet been reached. Accordingly, the process proceeds from step S232 to step S233, and returns to step S223.

  When the process returns to step S223, the next data collection period P6 is started, and the process proceeds to step S224. Since the respiratory cycle r = 2, the slice number b = 11, and the line number v = 2 at the start of the data collection period P6, the 11th to 20th slices are performed by repeatedly executing steps S224 to S228. The data of the second line in the k space is retaken sequentially. If it is determined in step S227 that NS = n (= 10), the process proceeds to step S229, and the data collection period P6 ends.

  When the data collection period P6 ends, the process proceeds to step S230.

  In step S230, the end time te (= t61, t62,... T69, t70) for each slice in the data collection period P6 is compared with the threshold arrival time T6.

  When comparing the end time te (= t61, t62,... T69, t70) and the threshold arrival time T6, first, the end time t70 and the threshold arrival time T6 are compared. When t70 and T6 are compared, t70 <T6. This means that the data collection period P6 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P6 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data recaptured during the data collection period P6 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Then, it progresses to step S231.

  In step S231, the data (slice number b = 11 to 20, line number v = 2) recaptured in the data collection period P6 is recorded as “valid data”. Note that the data (slice number b = 11 to 20, line number v = 2) recaptured in the data collection period P6 has already been collected in the data collection period P4. Similarly to the data collected in the data collection period P6, the data collected in the data collection period P4 is determined to be “valid data”. Therefore, when performing image reconstruction, data collected during the data collection period P4 may be used, or data collected during the data collection period P6 may be used. After step S231, the process proceeds to step S232.

  In step S232, it is determined whether respiration cycle r = R (= 2). Since r = R (= 2) at the end of the data collection period P6 (see FIG. 11), the process proceeds to step S234.

  In step S234, it is determined whether or not NG data exists in the data collected at the repetition time TR. As shown in FIG. 11, the data recovered in the data collection periods P5 and P6 of the repetition time TR are all determined to be valid data. Therefore, in step S234, it is determined that NG data does not exist, and the process proceeds to step S236.

  In step S236, it is determined whether v = V0 (= 128). Since v = 2 at the end of the data collection period P6 (see time t70 in FIG. 11), the process proceeds to step S237, the line number v is updated, and the process returns to step S223.

  When returning to step S223, the loop of step S223 to step S237 is repeatedly executed according to the procedure described above. As a result, data of each line in the k space is sequentially collected from the first to twentieth slices, and two data collection periods Pz-1 and Pz (see FIG. 11) are provided at the last repetition time TR. .

  The data collected during the data collection periods Pz-1 and Pz are both determined to be valid data (see FIG. 11), and are recorded as “valid data” in step S231. Thereafter, in step S234, it is determined that no NG data exists, and in step S236, it is determined that v = V0 (= 128), and the imaging ends.

  By repeatedly executing the loop of step S221 to step S237, data collection periods P1 to Pz are provided during the imaging period ACQ. As a result, all the data necessary to fill the k-space is obtained from all slices. Collected.

  After collecting all the data, the image is reconstructed. The reconstructed MR image is displayed on the display device 106 (see FIG. 1).

  In the second embodiment, each end time te for each slice in the data collection period is compared with the threshold arrival time Tth, and when te> Tth, the period M in which the body movement is large in the data collection period. Is included, and the data is automatically retrieved. In image reconstruction, the re-acquired data is used as image reconstruction data. Therefore, MR images with reduced body motion artifacts can be acquired.

  In the first and second embodiments, when NG data is generated during the repetition time TR, the data is re-read at the next repetition time TR. However, the data re-take does not necessarily have to be executed at the next repetition time TR, and may be executed until the image is reconstructed.

  In the first embodiment and the second embodiment, when it is determined that the data collection period includes the period M with a large body movement, the data is automatically retrieved. However, the operator of the MRI apparatus 100 may determine whether or not to retake data. Hereinafter, a method for causing the operator of the MRI apparatus 100 to determine whether or not to retake data will be described in the third to fifth embodiments.

3. Third Embodiment In the third embodiment, the hardware configuration of the MRI apparatus is almost the same as in the first and second embodiments, but the functional blocks of the computer 107 are different.

  FIG. 12 is an example of a functional block diagram of the computer 107 in the third embodiment.

  The computer 107 includes a threshold value determination unit 31, a data collection period start unit 32, a slice selection unit 33, a count unit 34, a data collection period end unit 35, a body movement determination unit 36, and re-take determination information It has a calculation unit 37 and a data recovery determination unit 38.

  The threshold value determination unit 31 determines a threshold value TH that serves as a reference for whether the body movement due to respiration of the subject 10 is large or small from the respiration signal Sr of the subject 10. The data collection period start unit 32 controls the timing for starting data collection based on the respiratory signal Sr. The slice selector 33 controls the slice position where data is collected. The counting unit 34 counts the number of slices for which data collection has been completed. The data collection period end unit 35 ends the data collection period when the count value of the count unit 34 reaches a predetermined value. The body movement determination unit 36 determines whether or not the data collection period includes a period with a large body movement. The re-judgment determination information calculation unit 37 calculates re-judgement determination information necessary for the operator of the MRI apparatus 100 to determine whether or not to re-retrieve data. The data re-reading determination unit 38 determines whether or not to re-read data according to the operation of the operator of the MRI apparatus 100.

  Next, a processing flow of the MRI apparatus 100 in the third embodiment will be described.

  The processing flow of the MRI apparatus 100 in the third embodiment can be described using the flowchart shown in FIG. That is, also in the third embodiment, in step S11, a threshold value serving as a reference for determining whether the body movement due to breathing of the subject 10 is large or small is determined. The threshold value determination method is the same as the method described with reference to FIG.

  After step S11 is completed, data is collected in step S12, and an image is displayed in step S13. However, in the third embodiment, the processing flow in step S12 is different from those in the first and second embodiments. Hereinafter, the process of step S12 in the third embodiment will be described in detail.

  FIGS. 13 and 14 are flowcharts showing the specific processing of step S12. FIGS. 15 and 16 execute the flowcharts of FIGS. 13 and 14 so that data is sent from each slice at any timing. It is a figure explaining whether it is collected.

  The flowcharts of FIGS. 13 and 14 will be described below with reference to FIGS. 15 and 16.

  The operations in steps S321 to S328 are the same as the operations in steps S121 to S128 in the flowchart shown in FIG. Therefore, the data collection period P1 ends by executing Steps S321 to S328 (see time t1 in FIG. 15).

  When the data collection period P1 ends, the process proceeds to step S329.

  In step S329, the level L1 of the respiratory signal Sr at the end time t1 of the data collection period P1 is compared with the threshold value TH. From this comparison result, it is determined whether the data collected in the data collection period P1 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. When L1 and TH are compared, L1 <TH. This means that the data collection period P1 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P1 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P1 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. After making this determination, the process proceeds to step S330.

  In step S330, it is recorded whether the data collected in the data collection period P1 is valid data or NG data. Since the data collected in the data collection period P1 is determined to be valid data, “valid data” is recorded. Thereafter, the process proceeds to step S331.

  In step S331, it is determined whether the respiratory cycle r = R. If r = R, the process proceeds to step S333. If r = R is not satisfied, the process proceeds to step S332. In the third embodiment, since R = 2, it is determined whether or not the respiratory cycle r = 2. Since r = 1 at the end of the data collection period P1 (see FIG. 15), the process proceeds to step S332.

  The operation in step S332 is the same as the operation in step S132 in the flowchart shown in FIG. At the end of the data collection period P1, the respiratory cycle r, slice number b, and line number v are r = 1, b = 10, and v = 1, respectively (see FIG. 15). Therefore, by executing step S332, the respiratory cycle r, the slice number b, and the line number v are set to r = 2, b = 11, and v = 1, respectively. In addition, the number NS of data-collected slices is reset to zero. After step S332, the process returns to step S323.

  When returning to step S323, the next data collection period P2 is started. By repeatedly executing the loop of steps S324 to S327, data of the first line in the k space is collected from the 11th to 20th slices, and the data collection period P2 ends (see time t2 in FIG. 15). ).

  When the data collection period P2 ends, the process proceeds to step S329.

  In step S329, the level L2 of the respiratory signal Sr at the end time t2 of the data collection period P2 is compared with the threshold value TH. From this comparison result, it is determined whether the data collected during the data collection period P2 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. When L2 and TH are compared, L2 <TH. Therefore, it is determined that the data collection period P2 does not include a period during which body movement due to respiration is large, and the data collected during the data collection period P2 is less affected by body movement due to breathing and can be used for image reconstruction. It is determined that the data is valid. Thereafter, the process proceeds to step S330, and the data collected in the data collection period P2 is recorded as “valid data”. After recording “valid data”, the process proceeds to step S331.

  Since the respiratory cycle r = R (= 2) and the line number v = 1 at the time when the data collection period P2 ends (see time t2 in FIG. 15), the process proceeds from step S331 to step S333 and step S334. In step S334, the respiratory cycle r = 1, the slice number b = 1, the line number v = 2, and the number of data-collected slices NS = 0 are set, and the process returns to step S323.

  When returning to step S323, the next data collection period P3 is started. By repeatedly executing the loop of steps S324 to S327, data of the second line in the k space is collected from the first to tenth slices, and the data collection period P3 ends (see time t3 in FIG. 15). ).

  When the data collection period P3 ends, the process proceeds to step S329.

  In step S329, the level L3 of the respiratory signal Sr at the end time t3 of the data collection period P3 is compared with the threshold value TH. From this comparison result, it is determined whether the data collected in the data collection period P3 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. When L3 and TH are compared, L3> TH. This means that the respiration signal Sr has exceeded the threshold value TH before the end of the data collection period P3. Therefore, it is determined that the data collection period P3 includes a period M in which body movement due to respiration is large. In this case, if the data collected in the data collection period P3 is used as image reconstruction data, there is a possibility that body motion artifacts may occur in the MR image. Therefore, it is determined that the data collected during the data collection period P3 is NG data that is greatly affected by body movement due to respiration and cannot be used for image reconstruction. After being determined as “NG data”, the process proceeds to step S330.

  In step S330, whether the data collected in the data collection period P3 is valid data or NG data is recorded. Since it is determined that the data collected in the data collection period P3 is NG data, “NG data” is recorded. Further, when “NG data” is recorded, other information related to the data collected in the data collection period P3 is also recorded. As other information, the following two pieces of information E1 and E2 are recorded.

(E1) Slice number b = 1 to 10 in the data collection period P3
(E2) k-space line number v = 2 in the data collection period P3

  After recording these pieces of information, the process proceeds to step S331.

  Since the respiratory cycle r = 1 and the line number v = 2 at the end of the data collection period P3 (see time t3 in FIG. 15), the process proceeds from step S331 to step S332. In step S332, the respiratory cycle r = 2, the slice number b = 11, the line number v = 2, and the number of data-collected slices NS = 0 are set, and the process returns to step S323.

  When returning to step S323, the next data collection period P4 is started. By repeatedly executing the loop of steps S324 to S327, the data of the second line in the k space is collected from the 11th to 20th slices, and the data collection period P4 ends (see time t4 in FIG. 15). ).

  When the data collection period P4 ends, the process proceeds to step S329.

  In step S329, the level L4 of the respiratory signal Sr at the end time t4 of the data collection period P4 is compared with the threshold value TH. When L4 and TH are compared, L4 <TH. Therefore, it is determined that the data collection period P4 does not include a period during which body movement due to respiration is large, and the data collected during the data collection period P4 is less affected by body movement due to breathing and can be used for image reconstruction. It is determined that the data is valid. Thereafter, the process proceeds to step S330, where the data collected in the data collection period P4 is recorded as “valid data”, and the process proceeds to step S331.

  Since r = R (= 2) and v = 2 at the end of the data collection period P4 (see time t4 in FIG. 15), the process proceeds from step S331 to step S333 and step S334. In step S334, the respiratory cycle r = 1, the slice number b = 1, the line number v = 3, and the number of data-collected slices NS = 0 are set, and the process returns to step S323.

  When returning to step S323, the next data collection period P5 is started. By repeatedly executing the loop of steps S324 to S327, data of the third line in the k space is collected from the first to tenth slices, and the data collection period P5 ends (see time t5 in FIG. 15). ).

  When the data collection period P5 ends, the process proceeds to step S329.

  In step S329, the level L5 of the respiratory signal Sr at the end time t5 of the data collection period P5 is compared with the threshold value TH. When L5 and TH are compared, L5 <TH. Therefore, it is determined that the data collection period P5 does not include a period during which body movement due to respiration is large, and the data collected during the data collection period P5 is less affected by body movement due to breathing and can be used for image reconstruction. It is determined that the data is valid. Thereafter, the process proceeds to step S330, where the data collected in the data collection period P5 is recorded as “valid data”, and the process proceeds to step S331.

  Since r = 1 at the end of the data collection period P5 (see time t5 in FIG. 15), the process proceeds from step S331 to step S332. In step S332, the respiratory cycle r = 2, the slice number b = 11, the line number v = 3, and the number of data-collected slices NS = 0 are set, and the process returns to step S323.

  When returning to step S323, the next data collection period P6 is started. By repeatedly executing the loop of steps S324 to S327, the data of the third line in the k space is collected from the 11th to 20th slices, and the data collection period P6 ends (see time t6 in FIG. 15). ).

  When the data collection period P6 ends, the process proceeds to step S329.

  In step S329, the level L6 of the respiratory signal Sr at the end time t6 of the data collection period P6 is compared with the threshold value TH. When L6 and TH are compared, L6 <TH. Therefore, it is determined that the data collection period P6 does not include a period during which body movement due to respiration is large, and the data collected during the data collection period P6 is less affected by body movement due to breathing and can be used for image reconstruction. It is determined that the data is valid. Thereafter, the process proceeds to step S330, where the data collected in the data collection period P6 is recorded as “valid data”, and the process proceeds to step S331.

  Since r = 2 and v = 3 when the data collection period P6 ends (see time t6 in FIG. 15), the process proceeds from step S331 to step S333 and step S334. In step S334, the respiratory cycle r = 1, the slice number b = 1, the line number v = 4, and the number of data-collected slices NS = 0 are set, and the process returns to step S323.

  When returning to step S323, the loop of step S323 to step S334 is repeatedly executed in the above-described procedure. As a result, data of each line in the k space is sequentially collected from the first to twentieth slices, and two data collection periods P255 and P256 (see FIG. 15) are provided in the last repetition time TR.

  The data collected in the data collection periods P255 and P256 are both determined to be valid data (see FIG. 15), and are recorded as “valid data” in step S330. When the data collection period P256 ends, since the respiratory cycle r = R (= 2) and the line number v = V0 (= 128), the process proceeds from step S331 to step S333, where it is determined that v = V0, and imaging ends. To do. In the third embodiment, data collected during the data collection periods P3 and P195 is determined to be NG data.

  By repeatedly executing the loop of step S323 to step S334, data collection periods P1 to P256 are provided during the imaging period ACQ, and as a result, data corresponding to each line in the k space is collected from all slices. Is done.

  However, the data collected during the imaging period ACQ includes NG data that is greatly affected by body movement and is not suitable for image reconstruction (in the data collection periods P3 and P195 of the imaging period ACQ). Data collected). When NG data is generated, in the first embodiment, data is re-acquired in the imaging period ACQ (see FIG. 7). In the third embodiment, data is re-acquired in the imaging period ACQ. Instead, it is left to the operator of the MRI apparatus 100 to determine whether or not to perform re-taking. In the third embodiment, the MRI apparatus 100 determines that v = V0 (= 128) in step S333 so that the operator of the MRI apparatus 100 can determine whether or not to execute re-taking. It operates as follows.

  The MRI apparatus 100 exits the loop of steps S321 to S334, and then proceeds to step S335 (see FIG. 14).

  In step S335, it is determined whether or not NG data exists in the data collected during the imaging period ACQ. If it is determined that NG data does not exist, the loop ends. If it is determined that NG data exists, the process proceeds to step S336. In the third embodiment, as shown in FIG. 15, two NG data (data collection periods P3 and P195) are generated. Therefore, in step S335, it is determined that there is NG data, and the process proceeds to step S336.

  In step S336, information necessary for the operator of the MRI apparatus 100 to determine whether or not to regain NG data (hereinafter referred to as “recovery determination information”) is calculated. Here, the NG occurrence rate Rng and the recapture imaging time Tr are calculated as the recapture determination information.

  The NG occurrence rate Rng is the ratio of the number of NG data n to the total number N of valid data and NG data. That is, Rng = n / N. In the third embodiment, N = 256, and n = 2 (data in the data collection period P3 and data in the data collection period P195). Therefore, Rng = 2/256.

  Further, the re-capturing imaging time Tr is a time necessary for re-acquisition of data. Here, it is the time required to re-acquire data collected in the data collection periods P3 and P195. However, in the third embodiment, in order to make the repetition time TR constant, when data collected in the data collection period P3 is retrieved, the data collected in the data collection period P4 is also retrieved. Similarly, when the data collected in the data collection period P195 is retrieved again, the data collected in the data collection period P196 is also retrieved. Therefore, the recapturing imaging time Tr is a repetition time TR necessary for recapturing data collected in the data collection periods P3 and P4 and a recursion necessary for recapturing data collected in the data collection periods P195 and P196. This is the total with the return time TR.

  After calculating the NG occurrence rate Rng and the recaptured imaging time Tr, the process proceeds to step S337, where the NG occurrence rate Rng and the recaptured imaging time Tr are displayed on the display device 106 (see FIG. 1).

  FIG. 17 is an example of a display screen of the display device 106.

  On the display screen, an NG occurrence rate Rng and a recapture imaging time Tr are displayed, and a recapture button B1 and an end button B2 are displayed on the lower right of the display screen. After such display, the process proceeds to step S338.

  On the other hand, the operator determines whether or not to reacquire data from the NG occurrence rate Rng displayed on the display device 106 and the recaptured imaging time Tr. When the operator determines that re-doing is unnecessary, the operator clicks the end button B2, and when it is determined that re-handling is necessary, the operator clicks the re-cut button B1.

  In step S338, the MRI apparatus 100 waits for the operator to click the retake button B1 or the end button B2. When the operator clicks the end button B2, the MRI apparatus 100 determines that “data is not retaken” and the imaging of the subject 10 ends without providing a re-imaging period. On the other hand, when the operator clicks the re-take button B1, the MRI apparatus 100 determines “re-retrieve data” and provides a re-imaging period ACQ ′ (see FIG. 16). When the re-imaging period ACQ 'is provided, the process proceeds to step S339.

  In step S339, the MRI apparatus 100 acquires data again during the re-imaging period ACQ '. The re-imaging period ACQ 'includes four data collection periods P1', P2 ', P3', and P4 '. The data collection periods P1 'and P2' are periods for re-acquiring data collected in the data collection periods P3 and P4, respectively. Data collection periods P3 'and P4' are periods for re-acquiring data collected in data collection periods P195 and P196, respectively.

  In step S339, first, in the data collection period P1 ', the data collected in the data collection period P3 (slice number b = 1 to 10, k-space line number v = 2) is retaken. After re-acquiring data during the data collection period P1 ', the process proceeds to step S340.

  In step S340, the level L1 'of the respiratory signal Sr at the end time t1' of the data collection period P1 'is compared with the threshold value TH. From this comparison result, it is determined whether the data collected in the data collection period P1 ′ is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. . When L1 'and TH are compared, L1' <TH. Therefore, it is determined that the data collection period P1 ′ does not include a period during which body movement due to respiration is large, and the data collected during the data collection period P1 ′ is less affected by body movement due to breathing and used for image reconstruction. It is determined that the data is valid. After making this determination, the process proceeds to step S341, and the data collected in the data collection period P1 'is recorded as "valid data". Thereafter, the process proceeds to step S342.

  In step S342, it is determined whether respiration cycle r = R (= 2). Since r = 1 when the data collection period P1 'ends (see FIG. 16), the process returns to step S339.

  Returning to step S339, in the data collection period P2 ', the data collected in the data collection period P4 (slice number b = 11 to 20, k-space line number v = 2) is retaken. After the data is re-acquired during the data collection period P2 ', the process proceeds to step S340.

  In step S340, the level L2 'of the respiratory signal Sr at the end time t2' of the data collection period P2 'is compared with the threshold value TH. When L2 'is compared with TH, L2' <TH. Therefore, it is determined that the data collection period P2 ′ does not include a period during which body movement due to respiration is large, and the data collected during the data collection period P2 ′ is less affected by body movement due to breathing and used for image reconstruction. It is determined that the data is valid. After making this determination, the process proceeds to step S341, and the data collected in the data collection period P2 'is recorded as "valid data". Thereafter, the process proceeds to step S342.

  Since r = R (= 2) at the end of the data collection period P2 '(see FIG. 16), the process proceeds to step S343.

  In step S343, it is determined whether re-taking is completed. Here, the re-acquisition of data collected in the data collection periods P3 and P4 is completed, but the re-acquisition of data collected in the data collection periods P195 and P196 is not completed. Therefore, the process returns to step S339.

  Hereinafter, similarly, Step S339 to Step S343 are executed. In the data collection period P3 ', L3'> TH. Therefore, the data collection period P3 'includes a period M in which body movement due to respiration is large, and the data collected in the data collection period P3' is recorded as "NG data". In the data collection period P4 ', L4' <TH. Therefore, the data collection period P4 'does not include a period in which body movement due to respiration is large, and the data collected in the data collection period P4' is recorded as "valid data".

  When the data recovery is completed in the data collection periods P3 'and P4', it is determined that all NG data has been recovered, and the process returns from step S343 to step S335.

  Since the data retrieved in the data collection period P1 'in the re-imaging period ACQ' is valid data, the data collected in the data collection period P3 in the imaging period ACQ has been successfully retrieved. However, since the data recovered in the data collection period P3 'of the re-imaging period ACQ' is NG data, the re-acquisition of data collected in the data collection period P195 of the imaging period ACQ has failed. Therefore, in step S335, it is determined that NG data remains, and the process proceeds to step S336.

  In step S336, the NG occurrence rate Rng shown in FIG. 17 is updated in consideration of the recording result in step S341. The data recaptured in the data acquisition period P3 ′ of the reimaging period ACQ ′ is NG data, while the data recaptured in the data acquisition periods P1 ′, P2 ′ and P4 ′ of the reimaging period ACQ ′ is valid data. is there. Therefore, two NG data existed when the imaging period ACQ ends (see FIG. 15), but the NG data becomes one by executing the re-imaging period ACQ '. As a result, the NG occurrence rate Rng is 1/256.

  In addition, since the data acquired in the data collection periods P1 'and P2' of the re-imaging period ACQ 'is valid data, it is not necessary to acquire the data again. Accordingly, the retaking imaging time Tr is also updated.

  After updating the NG occurrence rate Rng and the recaptured imaging time Tr, the process proceeds to step S337, and the updated NG occurrence rate Rng and the recaptured imaging time Tr are displayed on the display device 106 (see FIG. 1). Thereafter, the process proceeds to step S338.

  On the other hand, the operator determines whether or not to reacquire data from the updated NG occurrence rate Rng and the recapture imaging time Tr. When the operator determines that re-doing is unnecessary, the operator clicks the end button B2, and when it is determined that re-handling is necessary, the operator clicks the re-cut button B1.

  In step S338, the MRI apparatus 100 waits for the operator to click the retake button B1 or the end button B2. When the operator clicks the end button B2, the MRI apparatus 100 determines that “data is not retaken”, exits the loop of step S335 to step S343, and the imaging of the subject 10 ends. On the other hand, when the operator clicks the re-take button B1, the MRI apparatus 100 determines “re-retrieve data”, proceeds to step S339, and re-retrieves data collected in the data collection periods P3 ′ and P4 ′.

  In step S339, after re-acquiring the data, as described above, the process proceeds to step S340, step S341, step S342, and step S343. Step S343 is repeatedly performed.

  If the operator clicks the end button B2 while steps S335 to S343 are repeatedly executed, or if it is determined in step S335 that there is no NG data, the imaging ends.

  In the third embodiment, as in the first embodiment, in the imaging period ACQ, the level Lr of the respiratory signal Sr at the end time of each data collection period is compared with the threshold value TH. However, in the third embodiment, even if it is determined that Lr> TH, the data is not immediately recovered, and data corresponding to each line in the k space is collected from all slices. After all the data is collected, the re-judgment determination information (NG occurrence rate Rng and re-shooting imaging time Tr) is displayed on the display device 106. The operator can determine from the information displayed on the display device 106 whether or not to retake. Therefore, when the operator determines that re-taking is unnecessary, re-imaging is not performed, so that image reconstruction can be performed immediately without spending extra re-imaging time. On the other hand, when the operator determines that re-taking is necessary, the data is re-taken, so that a high-quality MR image can be acquired.

  In the third embodiment, even if NG data is generated, re-reading determination information (NG occurrence rate Rng and re-shooting imaging time Tr) is not displayed immediately, but from all slices to k-space. After collecting data corresponding to each line, the re-judgment judgment information is displayed (see FIG. 17). However, the re-judgment determination information may be displayed (or updated) when NG data is generated.

4). Fourth Embodiment In the description of the fourth embodiment, differences from the third embodiment will be mainly described.

  In the fourth embodiment, the hardware configuration of the MRI apparatus is almost the same as that of the third embodiment, but the functional blocks of the computer 107 are different.

  FIG. 18 is an example of a functional block diagram of the computer 107 in the fourth embodiment.

  The difference between the third embodiment and the fourth embodiment is that an end time recording unit 41 is provided between the slice selection unit 33 and the count unit 34. The end time recording unit 41 records the end time for each slice in the data collection period.

  Next, a processing flow of the MRI apparatus 100 in the fourth embodiment will be described.

  The processing flow of the MRI apparatus 100 in the fourth embodiment can be described using the flowchart shown in FIG. That is, also in the fourth embodiment, in step S <b> 11, a threshold value serving as a reference for whether the body movement due to breathing of the subject 10 is large or small is determined. The threshold value determination method is the same as the method described with reference to FIG.

  After step S11 is completed, data is collected in step S12, and an image is displayed in step S13. However, in the fourth embodiment, the processing flow in step S12 is different from those in the first to third embodiments. Hereinafter, the process of step S12 in the fourth embodiment will be described in detail.

  FIGS. 19 and 20 are flowcharts showing the specific processing of step S12, and FIGS. 21 and 22 execute the flowcharts of FIGS. 19 and 20 to obtain data from each slice at any timing. It is a figure explaining whether it is collected.

  The flowcharts of FIGS. 19 and 20 will be described below with reference to FIGS.

  The operations in steps S421 to S429 are almost the same as the operations in steps S321 to S328 in the flowchart shown in FIG. 13 of the third embodiment. However, the fourth embodiment differs from the third embodiment in that step S425 for recording the end time te is provided between step S424 and step S426.

  Step S425 is a step of recording a time te at which the collection of data of the vth line in the k space has been completed from the bth slice. In the fourth embodiment, since step S425 is provided, the data collection end time te is recorded each time the collection of data of the vth line in the k space from each slice is completed. Since data is collected from the first to tenth slices in the data collection period P1, every time data is collected from each of the first to tenth slices, the end time te = t11, t12 in step S425. ,..., T19, t20 are recorded (see FIG. 21). After the end time te = t20 is recorded, the process proceeds to step S427. If it is determined that the number of slices of data-collected slices NS = n (= 10), the process proceeds to step S429 and the data collection period P1 ends (FIG. 21). (See time t20).

  When the data collection period P1 ends, the process proceeds to step S430.

  In the fourth embodiment, the time when the respiratory signal Sr reaches the threshold value TH from a value smaller than the threshold value TH (hereinafter referred to as “threshold value arrival time”) Tth (= T1, T2, T3,... T256) are calculated. In step S430, the end time te for each slice in the data collection period is compared with the threshold arrival time Tth. From this comparison result, it is determined whether the data collected during the data collection period is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. Here, since the data collection period P1 has ended, in step S430, the end time te (= t11, t12,... T19, t20) for each slice of the data collection period P1 and the threshold arrival time T1. Are compared.

  When the end time te (= t11, t12,... T19, t20) is compared with the threshold arrival time T1, the end time t20 and the threshold arrival time T1 are first compared. When t20 and T1 are compared, t20 <T1. This means that the data collection period P1 has ended before the respiratory signal Sr exceeds the threshold value TH. Therefore, it is determined that the data collection period P1 does not include a period during which body movement due to respiration is large. In this case, the comparison result is “OK”, and it is determined that the data collected in the data collection period P1 is valid data that is less affected by body movement due to respiration and can be used for image reconstruction. Thereafter, the process proceeds to step S431, and the data collected in the data collection period P1 is recorded as “valid data”. After this recording, the process proceeds to step S432.

  The operations in steps S432 to S435 are the same as the operations in steps S331 to S334 in the flowchart shown in FIG. 13 of the third embodiment. Since r = 1 at the end of the data collection period P1 (see FIG. 21), r = R (= 2) has not yet been reached. Accordingly, the process proceeds from step S432 to step S433, where the line number v = 1, the respiratory cycle r = 2, the slice number b = 11, and the number of data-collected slices NS = 0 is set, and the process returns to step S423.

  When returning to step S423, the next data collection period P2 is started. By repeatedly executing the loop of step S424 to step S428, data of the first line in the k space is collected from the 11th to 20th slices (see FIG. 21), and the data collection period P2 ends.

  When the data collection period P2 ends, the process proceeds to step S430.

  In step S430, the end time te (= t21, t22,... T29, t30) for each slice in the data collection period P2 is compared with the threshold arrival time T2. From this comparison result, it is determined whether the data collected in the data collection period P2 is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. .

  In the data collection period P2, the end time t30 is earlier than the threshold arrival time T2. Therefore, it is determined that the data collection period P2 does not include a period during which body movement due to respiration is large. In this case, the comparison result is “OK”, and it is determined that the data collected in the data collection period P2 is valid data that is less affected by body movement due to respiration and can be used for image reconstruction. Thereafter, the process proceeds to step S431, and the data collected in the data collection period P2 is recorded as “valid data”, and the process proceeds to step S432.

  Since the respiratory cycle r = R (= 2) and the line number v = 1 at the end of the data collection period P2 (see time t30 in FIG. 21), the process proceeds from step S432 to steps S434 and S435. In step S435, the line number v = 2, the respiratory cycle r = 1, the slice number b = 1, and the number of data-collected slices NS = 0 are set, and the process returns to step S423.

  When returning to step S423, the next data collection period P3 is started. By repeatedly executing Steps S424 to S428, data of the second line in the k space is collected from the first to tenth slices (see FIG. 21), and the data collection period P3 ends.

  When the data collection period P3 ends, the process proceeds to step S430.

  In step S430, the end time te (= t31, t32,... T39, t40) for each slice of the data collection period P3 and the threshold arrival time T3 are compared and collected in the data collection period P3. It is determined whether the data is valid data or NG data.

  In the data collection period P3, the end time t40 is later than the threshold arrival time T3. This means that the respiration signal Sr has exceeded the threshold value TH before the end of the data collection period P3. Therefore, it is determined that the data collection period P3 includes a period M in which body movement due to respiration is large. In this case, the comparison result is “NG”, and it is determined that the data collected in the data collection period P3 is NG data that is greatly affected by body movement due to respiration and is not suitable for image reconstruction.

  If it is determined that the data is NG data, the other end times t31 to t39 are also compared with the threshold arrival time T3. When the other end times t31 to t39 are compared with the threshold arrival time T3, the end time t39 and the threshold arrival time T3 are first compared. When t39 and T3 are compared, t39 <T3. This means that the data of the second line in the k space has been collected from the ninth slice before the respiratory signal Sr exceeds the threshold value TH. Therefore, the comparison result is “OK”. The remaining end times t31 to t38 are also t31 to t38 <T3. Thus, after comparing the end time with the threshold arrival time T4, the process proceeds to step S431.

  In step S431, whether the data collected in the data collection period P3 is valid data or NG data is recorded. Since it is determined that the data collected in the data collection period P3 is NG data, “NG data” is recorded. Further, when “NG data” is recorded, other information related to data collected in the data collection period P3 is also recorded. As other information, the following three pieces of information E1, E2, and E3 are recorded.

(E1) Slice number b = 1 to 10 in the data collection period P3
(E2) k-space line number v = 2 in the data collection period P3
(E3) In the data collection period P3, the slice number b = 10 where the comparison result is “NG”.

  After recording these pieces of information, the process proceeds to step S432.

  When the data collection period P3 ends, since the respiratory cycle r = 1 (see time t40 in FIG. 21), the process proceeds from step S432 to step S433. The line number v = 2, the respiratory cycle r = 2, the slice number b = 11, and the number of data-collected slices NS = 0 are set, and the process returns to step S423.

  When returning to step S423, the next data collection period P4 is started. By repeatedly executing Steps S424 to S428, data of the second line in the k space is collected from the 11th to 20th slices (see FIG. 21), and the data collection period P4 ends.

  When the data collection period P4 ends, the process proceeds to step S430.

  In step S430, the end time te (= t41, t42,... T49, t50) for each slice of the data collection period P4 and the threshold arrival time T4 are compared and collected in the data collection period P4. It is determined whether the data is valid data or NG data.

  In the data collection period P4, the end time t50 is earlier than the threshold arrival time T4. Therefore, it is determined that the data collection period P4 does not include a period during which body movement due to respiration is large. In this case, the comparison result is “OK”, and it is determined that the data collected in the data collection period P4 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S431, where the data collected in the data collection period P4 is recorded as “valid data”, and the process proceeds to step S432.

  Since the respiratory cycle r = R (= 2) and the line number v = 2 at the end of the data collection period P4 (see time t50 in FIG. 21), the process proceeds from step S432 to steps S434 and S435. In step S435, the line number v = 3, the respiratory cycle r = 1, the slice number b = 1, and the number of data-collected slices NS = 0 are set, and the process returns to step S423.

  When returning to step S423, the loop of step S423 to step S435 is repeatedly executed in the above-described procedure. As a result, data of each line in the k space is sequentially collected from the first to twentieth slices, and two data collection periods P255 and P256 (see FIG. 21) are provided at the last repetition time TR.

  The data collected in the data collection periods P255 and P256 are both determined to be valid data (see FIG. 21), and are recorded as “valid data” in step S431. When the data collection period P256 ends, since the breathing cycle r = R (= 2) and the line number v = V0 (= 128), the process proceeds from step S432 to step S434, where v = V0 is determined, and imaging is completed. To do. In the fourth embodiment, data collected during the data collection periods P3 and P195 is determined to be NG data.

  By repeatedly executing the loop of step S421 to step S435, data collection periods P1 to P256 are provided during the imaging period ACQ. As a result, data corresponding to each line in the k space is collected from all slices. Is done.

  However, the data collected during the imaging period ACQ includes NG data that is greatly affected by body movement and is not suitable for image reconstruction (data collected during the data collection periods P3 and P195). ). When NG data is generated, in the fourth embodiment, similarly to the third embodiment, the determination whether or not to perform the re-reading without executing the re-reading of the data during the imaging period ACQ is performed by MRI. It is left to the operator of the apparatus 100. In the fourth embodiment, the MRI apparatus 100 determines that v = V0 (= 128) in step S434 so that the operator of the MRI apparatus 100 can determine whether or not to perform re-taking. It operates as follows.

  If the MRI apparatus 100 determines in step S434 that v = V0 (= 128), the MRI apparatus 100 proceeds to step S436 (see FIG. 20). The operations in steps S436 to 444 shown in FIG. 20 are substantially the same as the operations described in steps S335 to S343 (see FIG. 14) of the third embodiment, but there are some differences. The differences are mainly explained.

  In step S436, it is determined whether there is NG data.

  In the fourth embodiment, since the data collected in the data collection periods P3 and P195 is determined to be NG data (see FIG. 21), it is determined in step S436 that there is NG data, and the process proceeds to step S437.

  In step S437, re-take determination information is calculated, and in step S438, re-take determination information is displayed. However, in the fourth embodiment, unlike the third embodiment, three re-judgment determination information is displayed on the display device 106 (see FIG. 1). Next, the three re-judgment determination information will be described.

  FIG. 23 is an example of a display screen that displays three re-judgment determination information.

  Of the three re-judgment determination information, two are the NG occurrence rate Rng and the re-shooting imaging time Tr, as in the third embodiment (see FIG. 17). However, in the fourth embodiment, the number of NG slices Nng is displayed on the display device 106 in addition to the NG occurrence rate Rng and the recapturing imaging time Tr.

  The number of NG slices Nng is the number of slices in which the comparison result is “NG” among the first to twentieth slices. In the fourth embodiment, in the data collection periods P3 and P195, the comparison result is “NG” when the slice number b = 10. Therefore, of the 20 slices, only one slice (b = 10) has the comparison result “NG”. For this reason, the number of NG slices Nng is displayed as Nng = 1.

  The operator of the MRI apparatus 100 can determine whether or not to perform re-imaging from the three re-reading determination information. When the operator clicks the end button B2, the loop from step S436 to step S444 is exited, and the imaging is completed. On the other hand, when the operator clicks the re-take button B1, the process proceeds from step S439 to step S440.

  In step S440, the MRI apparatus 100 reacquires data during the re-imaging period ACQ ′ (see FIG. 22). The re-imaging period ACQ 'includes four data collection periods P1', P2 ', P3', and P4 '. The data collection periods P1 'and P2' are periods for re-acquiring data collected in the data collection periods P3 and P4, respectively. Data collection periods P3 'and P4' are periods for re-acquiring data collected in data collection periods P195 and P196, respectively.

  In step S440, first, in the data collection period P1 ', the data collected in the data collection period P3 (slice number b = 1 to 10, k-space line number v = 2) is retaken. After re-acquiring data during the data collection period P1 ', the process proceeds to step S441.

  In step S441, the end time te ′ (= t11 ′, t12 ′,... T19 ′, t20 ′) for each slice in the data collection period P1 ′ is compared with the threshold arrival time T1 ′. From this comparison result, it is determined whether the data collected during the data collection period P1 ′ is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. The In the data collection period P1 ', the end time t20' is earlier than the threshold arrival time T1 '. Therefore, it is determined that the data collection period P1 'does not include a period during which body movement due to respiration is large. In this case, the comparison result is “OK”, and it is determined that the data collected in the data collection period P1 ′ is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S442, where the data collected in the data collection period P1 'is recorded as “valid data”, and the process proceeds to step S443.

  In step S443, it is determined whether respiration cycle r = R (= 2). Since r = 1 when the data collection period P1 'ends (see FIG. 22), the process returns to step S440.

  Returning to step S440, in the data collection period P2 ', the data collected in the data collection period P4 (slice number b = 11 to 20, k-space line number v = 2) is retaken. After re-acquiring data during the data collection period P2 ', the process proceeds to step S441.

  In step S441, the end time te '(= t21', t22 ', ... t29', t30 ') for each slice in the data collection period P2' is compared with the threshold arrival time T2 '.

  In the data collection period P2 ', the end time t30' is earlier than the threshold arrival time T2 '. Therefore, it is determined that the data collection period P2 'does not include a period during which body movement due to respiration is large. In this case, the comparison result is “OK”, and it is determined that the data collected in the data collection period P2 ′ is effective data that can be used for image reconstruction with little influence of body movement due to respiration. Thereafter, the process proceeds to step S442, and the data collected in the data collection period P2 'is recorded as “valid data”, and the process proceeds to step S443.

  Since r = R (= 2) at the end of the data collection period P2 '(see FIG. 22), the process proceeds to step S444.

  In step S444, it is determined whether re-taking is completed. Here, the re-acquisition of data collected in the data collection periods P3 and P4 is completed, but the re-acquisition of data collected in the data collection periods P195 and P196 is not completed. Therefore, the process returns to step S440.

  Returning to step S440, in the data collection period P3 ', the data collected in the data collection period P195 (slice number b = 1 to 10, k-space line number v = 98) is retaken. After re-acquiring data in the data collection period P3 ', the process proceeds to step S441.

  In step S441, the end time te '(= t31', t32 ', ... t39', t40 ') for each slice in the data collection period P3' is compared with the threshold arrival time T3 '.

  When t40 'is compared with T3', t40 '> T3'. Therefore, the data collection period P3 'includes a period M in which body movement due to respiration is large. In this case, the comparison result is “NG”, and the data collected in the data collection period P3 ′ is determined as “NG data”. Next, when the end time t39 'is compared with the threshold arrival time T3', t39 '<T3'. Therefore, the comparison result is “OK”, and the process proceeds to step S442.

  In step S442, it is recorded whether the data collected in the data collection period P3 'is valid data or NG data. Since it is determined that the data collected during the data collection period P3 'is NG data, "NG data" is recorded. When “NG data” is recorded, other information related to data collected in the data collection period P3 ′ is also recorded. As other information, the following three pieces of information E1, E2, and E3 are recorded.

(E1) Slice number b = 1 to 10 in the data collection period P3 ′
(E2) k-space line number v = 98 in the data collection period P3 ′
(E3) In the data collection period P3 ′, the slice number b = 10 whose comparison result is “NG”.

  After recording these pieces of information, the process proceeds to step S443.

  Since r = 1 when the data collection period P3 'ends (see FIG. 22), the process returns to step S440.

  Returning to step S440, in the data collection period P4 ', the data collected in the data collection period P196 (slice number b = 11 to 20, k-space line number v = 98) is retaken. After the data is re-acquired during the data collection period P4 ', the process proceeds to step S441.

  In the data collection period P4 ', the end time t40' is earlier than the threshold arrival time T4 '. Therefore, it is determined that the data collection period P4 'does not include a period during which body movement due to respiration is large. In this case, the comparison result is “OK”, and it is determined that the data collected in the data collection period P4 ′ is valid data that is less affected by body movement due to respiration and can be used for image reconstruction. Thereafter, the process proceeds to step S442, where the data collected in the data collection period P4 'is recorded as “valid data”, and the process proceeds to step S443.

  Since r = R (= 2) at the end of the data collection period P2 '(see FIG. 22), the process proceeds to step S444.

  Since the data collection periods P1 ′ to P4 ′ are executed during the re-imaging period ACQ ′, all the data collected in the data collection periods P3, P4, P195, and P196 of the imaging period ACQ (see FIG. 21) Retry has been completed. Therefore, in step S444, it is determined that the re-take has been completed, and the process returns to step S436.

  Since the data retrieved in the data collection period P1 'in the re-imaging period ACQ' is valid data, the data collected in the data collection period P3 in the imaging period ACQ has been successfully retrieved. However, since the data recovered in the data collection period P3 'of the re-imaging period ACQ' is NG data, the re-acquisition of data collected in the data collection period P195 of the imaging period ACQ has failed. Therefore, in step S436, it is determined that NG data remains, and the process proceeds to step S437.

  In step S437, the NG occurrence rate Rng shown in FIG. 23 is updated in consideration of the recording result in step S442. The data recaptured in the data acquisition period P3 ′ of the reimaging period ACQ ′ is NG data, while the data recaptured in the data acquisition periods P1 ′, P2 ′ and P3 ′ of the reimaging period ACQ ′ is valid data. is there. Therefore, two NG data existed when the imaging period ACQ ends (see FIG. 21), but the NG data becomes one by executing the re-imaging period ACQ '. As a result, the NG occurrence rate Rng is updated to 1/256.

  In addition, since the data acquired in the data collection periods P1 'and P2' of the re-imaging period ACQ 'is valid data, it is not necessary to acquire the data again. Accordingly, the retaking imaging time Tr is also updated.

  However, since the data recaptured in the data acquisition period P3 'of the re-imaging period ACQ' is NG data, one slice (b = 10) of the 20 slices is the comparison result "NG". Therefore, the number of NG slices Nng is not updated, and Nng = 1 remains.

  After updating the NG occurrence rate Rng and the recaptured imaging time Tr, the process proceeds to step S438, and the updated NG occurrence rate Rng and the recaptured imaging time Tr are displayed on the display device 106 (see FIG. 1). Thereafter, the process proceeds to step S439.

  In step S439, the MRI apparatus 100 waits for the operator to click the retake button B1 or the end button B2. When the operator clicks the end button B2, the MRI apparatus 100 determines that “data is not retaken”, exits the loop of step S436 to step S444, and the imaging of the subject 10 ends. On the other hand, when the operator clicks the replay button B1, the MRI apparatus 100 determines that “data is reacquired”, proceeds to step S440, and reacquires data collected in the data collection periods P3 ′ and P4 ′.

  In step S440, after re-acquiring data, it progresses to step S441, step S442, step S443, and step S444. If it is determined in step S444 that the re-take has been completed, the process returns to step S436, and steps S436 to S444 are repeated.

  If the operator clicks the end button B2 while step S436 to step S444 are repeatedly executed, or if it is determined in step S436 that there is no NG data, the imaging ends.

  In the fourth embodiment, since the slice number whose comparison result is “NG” is recorded (step S431), the number of NG slices Nng can also be displayed as the re-judgment determination information. Therefore, the operator of the MRI apparatus 100 can determine whether or not to perform re-imaging using more information than in the case of the third embodiment.

  Further, in the fourth embodiment, even when NG data is generated, the re-judgment determination information (NG occurrence rate Rng, re-shooting imaging time Tr, NG slice number Nng) is not displayed immediately, but all slices are displayed. After collecting data corresponding to each line in the k-space, the re-judgment judgment information is displayed. However, the re-judgment determination information may be displayed (or updated) when NG data is generated.

  Note that an MR image can be used as the re-judgement determination information. Hereinafter, a method of using an MR image as the re-judgement determination information will be described in the fifth embodiment.

5. Fifth Embodiment Since the fifth embodiment is almost the same as the fourth embodiment, differences from the fourth embodiment will be mainly described.

  The flowchart of the fifth embodiment is the same as the flowchart of the fourth embodiment (see FIGS. 19 and 20). However, in the fifth embodiment, unlike the fourth embodiment, four re-judgment determination information is displayed on the display device 106 (see FIG. 1) in step S438. Of the four re-judgment determination information, the three re-judgment determination information includes the NG occurrence rate Rng, the re-shooting imaging time Tr, and the number of NG slices Nng, as in the fourth embodiment (see FIG. 23). However, in the fifth embodiment, an MR image of the imaging region 10a (see FIG. 1) is also displayed in addition to these three re-judgment determination information.

  FIG. 24 is an example of a display screen of the display device 106.

  In addition to the NG occurrence rate Rng, the recaptured imaging time Tr, and the number of NG slices Nng, the MR image 50 of the imaging region is displayed on the display screen. Further, a replay button B1 and an end button B2 are displayed at the lower left of the display screen. After such display, the process proceeds to step S439.

  On the other hand, the operator determines whether or not to reacquire data from the displayed NG occurrence rate Rng, recaptured imaging time Tr, NG slice number Nng, and MR image 50 of the imaging region. When the operator determines that re-doing is unnecessary, the operator clicks the end button B2, and when it is determined that re-handling is necessary, the operator clicks the re-cut button B1.

  In step S439, the MRI apparatus 100 waits for the operator to click the retake button B1 or the end button B2. When the operator clicks the end button B2, the MRI apparatus 100 determines that “data is not retaken”, and the imaging of the subject 10 ends without providing a re-imaging period. On the other hand, when the operator clicks the re-take button B1, the MRI apparatus 100 determines “re-retrieve data” and proceeds to step S440. The operations in steps S440 to S444 are the same as in the case of the fourth embodiment.

  In the fifth embodiment, since the MR image 50 of the imaging region 10a is also displayed on the display device 106, the operator of the MRI apparatus 100 more accurately determines whether or not the data needs to be read again. Can do.

  In the fifth embodiment, by comparing the end time te of the data collection period and the threshold arrival time Tth, it is determined whether or not a period during which body movement due to respiration is large is included. Yes. However, instead of comparing the end time te of the collection period and the threshold arrival time Tth, the level Lr of the respiratory signal Sr and the threshold TH are compared as in the third embodiment. May be.

  In the first to fifth embodiments, breathing information is acquired using a bellows. However, you may acquire respiratory information using a navigator method, without using a bellows. The case where respiratory information is acquired using the navigator method will be described below in the sixth embodiment.

6). Sixth Embodiment In the description of the sixth embodiment, differences from the first embodiment will be mainly described.

  The processing flow of the MRI apparatus 100 in the sixth embodiment can be described using the flowchart shown in FIG.

  First, in step S11, a navigator sequence (for example, a line scan type sequence that intersects a 90-degree pulse and a 180-degree pulse or a 2D selective excitation type sequence) is continuously executed, and a navigator echo is emitted from the subject 10. collect. After the navigator echoes are collected, a threshold value is determined as a reference for whether the body movement due to respiration of the subject 10 is large or small.

  After step S11 is completed, data is collected in step S12, and an image is displayed in step S13. However, in the sixth embodiment, the processing flow in step S12 is different from those in the first to fifth embodiments. Hereinafter, the process of step S12 in the sixth embodiment will be described in detail.

  FIG. 25 and FIG. 26 are flowcharts showing the specific processing of step S12. FIG. 27 shows the timing at which data is collected from each slice by executing the flowcharts of FIG. 25 and FIG. It is a figure explaining whether.

  The flowcharts of FIGS. 25 and 26 will be described below with reference to FIG.

  The operations in steps S621 and S622 are the same as the operations in steps S121 and S122 (see FIG. 6) in the flowchart of the first embodiment. After step S622, the process proceeds to step S623.

  In step S623, navigator echoes are collected in each navigator period, and respiratory data Nr (= N1, N2,...) Is calculated. In step S623, first, the respiration data Nr for the first navigator period NAV # 1 is calculated. In the first navigator period NAV # 1, Nr = N1. After calculating the respiration data N1, the process proceeds to step S624.

  In step S624, it is determined whether or not the calculated respiration data Nr is smaller than a threshold value TH. If Nr = TH or Nr <TH, the process returns to step S623. If Nr> TH, the process proceeds to step S625. Since the respiration data N1 in the first navigator period NAV # 1 is smaller than the threshold value TH, N1 <TH. Accordingly, the process proceeds to step S625.

  In step S625, it is determined whether or not there is respiratory data Nr-1 for the previous navigator period. When the breath data Nr-1 for the previous navigator period exists, the process proceeds to step S626. When the breath data Nr-1 for the previous navigator period does not exist, the process returns to step S623. At the time when the first navigator period NAV # 1 ends, the previous navigator period respiratory data Nr-1 does not yet exist, and the process returns to step S623.

  Returning to step S623, navigator echoes are collected in the second navigator period NAV # 2, and respiration data Nr = N2 is calculated. Since N2 <TH, the process proceeds to step S625.

  In step S625, it is determined whether or not there is respiratory data Nr-1 for the previous navigator period. At the end of the second navigator period NAV # 2, there is respiratory data N1 for the previous navigator period NAV # 1. Accordingly, the process proceeds to step S626.

  In step S626, it is determined whether or not the respiration data Nr-1 of the previous navigator period satisfies Nr-1> TH. When the respiration data Nr-1 is Nr-1> TH, the process proceeds to step S627, and the data collection period is started. On the other hand, if the respiration data Nr-1 is Nr-1 = TH or Nr-1 <TH, the process returns to step S623. The respiration data Nr-1 (= N1) of the previous navigator period NAV # 1 is N1 <TH. Therefore, the process returns to step S623.

  Returning to step S623, navigator echoes are collected in the third navigator period NAV # 3, and respiratory data Nr = N3 is calculated. Since N3> TH, the process returns to step S623.

  Thereafter, similarly, the loop of step S623 to step S626 is repeatedly executed, navigator echoes are collected in each navigator period NAV # 4, NAV # 5, NAV # 6, and respiratory data N4, N5, N6 are calculated. . The respiration data N6 of the sixth navigator period NAV # 6 is N6 <TH, and the respiration data N5 of the previous fifth navigator period NAV # 5 is N5> TH. Therefore, the process proceeds from step S624 to step S625 and step S626. In step S626, it is determined that N5> TH, and the process proceeds to step S627.

  The operations in steps S627 to S632 are the same as the operations in steps S123 to S128 (see FIG. 6) in the flowchart of the first embodiment. Therefore, the data collection period P1 starts immediately after the navigator period NAV # 6. In the data collection period P1, data of the first line in the k space is collected from the first to the tenth slices.

  When the data collection period P1 ends, the process proceeds to step S633.

  In step S633, a navigator period NAV is provided immediately after the end of the data collection period. Navigator echoes are collected during the navigator period NAV, and respiratory data Nr is calculated. Here, since the data collection period P1 has ended, navigator echoes are collected in the navigator period NAV # 7, and respiratory data Nr (= N7) is calculated. After the respiration data Nr (= N7) is calculated, the process proceeds to step S634.

  In step S634, the respiration data Nr immediately after each data collection period is compared with the threshold value TH. From this comparison result, it is determined whether the data collected during the data collection period is valid data that can be used for image reconstruction or NG data that cannot be used for image reconstruction. Here, since the data collection period P1 has ended, the respiration data Nr (= N7) immediately after the data collection period P1 is compared with the threshold value TH.

  When comparing N7 and TH, as shown in FIG. 27, N7 is smaller than TH, and therefore N7 <TH is determined. N7 <TH means that the data collection period P1 has ended before the respiratory level exceeds the threshold value TH. Therefore, it is determined that the data collection period P1 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P1 is effective data that can be used for image reconstruction with little influence of body movement due to respiration. After making this determination, the process proceeds to step S635, and the data collected in the data collection period P1 is recorded as “valid data”. Thereafter, the process proceeds to step S636 (see FIG. 26).

  The operations in steps S636 to S641 are the same as those in steps S131 to S136 (see FIG. 6) in the flowchart according to the first embodiment. Since r = 1 at the end of the data collection period P1 (see FIG. 27), r = R (= 2) has not yet been reached. Therefore, the process proceeds from step S636 to step S637, where the respiratory cycle r = 2, the slice number b = 11, the line number v = 1, and the number of data-collected slices NS = 0 are set, and the process returns to step S623 (see FIG. 25).

  When returning to step S623, the loop of step S623 to step S626 is repeatedly executed, navigator echoes are collected in the eighth navigator period NAV # 8 to the eleventh navigator period NAV # 11, and respiratory data is calculated. The respiration data N11 of the eleventh navigator period NAV # 11 is N11 <TH, and the respiration data N10 of the previous tenth navigator period NAV # 10 is N10> TH. Therefore, the process proceeds from step S624 to steps S625 and S626. In step S626, it is determined that N10> TH, and the process proceeds to step S627.

  In step S627, the data collection period P2 is started immediately after the navigator period NAV # 11.

  When the data collection period P2 starts, Steps S628 to S631 are repeatedly executed, and the data of the first line in the k space is collected from the 11th to 20th slices (see FIG. 27), and the data collection period P2 is set. finish. After the data collection period P2 ends, the process proceeds to step S633, and a navigator period NAV # 12 is provided immediately after the data collection period P2. Navigator echoes are collected during the navigator period NAV # 12 and respiration data Nr (= N12) is calculated. After the respiration data Nr (= N12) is calculated, the process proceeds to step S634.

  In step S634, the respiration data Nr (= N12) immediately after the data collection period P2 is compared with the threshold value TH.

  When N12 and TH are compared, as shown in FIG. 27, N12 is smaller than TH, and therefore N12 <TH is determined. N12 <TH means that the data collection period P2 has ended before the respiratory level exceeds the threshold value TH. Therefore, it is determined that the data collection period P2 does not include a period during which body movement due to respiration is large. In this case, it is determined that the data collected in the data collection period P2 is valid data that is not affected by body movement due to respiration and can be used for image reconstruction. After making this determination, the process proceeds to step S635, and the data collected in the data collection period P2 is recorded as “valid data”. Thereafter, the process proceeds to step S636 (see FIG. 26).

  Since the respiratory cycle r = R (= 2) at the end of the data collection period P2, the process proceeds to step S638.

  In step S638, it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected during the data collection periods P1 and P2 of the repetition time TR are all determined to be valid data as shown in FIG. Therefore, in step S638, it is determined that NG data does not exist, and the process proceeds to step S640.

  In step S640, it is determined whether v = V0 (= 128). Since v = 1 at the end of the data collection period P2 (see FIG. 27), the process proceeds to step S641, and the respiratory cycle r = 1, slice number b = 11, line number v = 2, number of data collected slices NS = 0 is set, and the process returns to step S623.

  Returning to step S623, steps S623 to S626 are repeatedly executed, navigator echoes are collected in the thirteenth navigator period NAV # 13 to the sixteenth navigator period NAV # 16, and respiratory data is calculated. The respiration data N16 of the 16th navigator period NAV # 16 is N16 <TH, and the respiration data N15 of the previous 15th navigator period NAV # 15 is N15> TH. Therefore, the process proceeds from step S624 to step S625 and step S626. In step S626, it is determined that N15> TH, and the process proceeds to step S627.

  In step S627, the data collection period P3 is started immediately after the 16th navigator period NAV # 16.

  When the data collection period P3 starts, Steps S628 to S631 are repeatedly executed, and the data of the second line in the k space is collected from the first to the tenth slices (see FIG. 27). finish.

  After the data collection period P3 ends, the process proceeds to step S633, and a navigator period NAV # 17 is provided immediately after the data collection period P3. Navigator echoes are collected during the navigator period NAV # 17, and respiratory data Nr (= N17) is calculated. After the respiration data Nr (= N17) is calculated, the process proceeds to step S634.

  In step S634, the respiration data Nr (= N17) immediately after the data collection period P3 is compared with the threshold value TH.

  When N17 and TH are compared, as shown in FIG. 27, N17 is larger than TH, and therefore N17> TH is determined. N17> TH means that the respiratory level has exceeded the threshold value TH before the end of the data collection period P3. Therefore, it is determined that the data collection period P3 includes a period M in which body movement due to respiration is large. In this case, if the data collected during the data collection period P3 is used as the data for image reconstruction, body motion artifacts on the MR image may increase. Therefore, it is determined that the data collected during the data collection period P3 is NG data that is greatly affected by body movement due to respiration and cannot be used for image reconstruction. After making this determination, the process proceeds to step S635, and the data collected in the data collection period P3 is recorded as “NG data”. After recording “NG data”, the process proceeds to step S636.

  At the time when the data collection period P3 ends, since the respiratory cycle r = 1 (see FIG. 27), the process proceeds from step S636 to step S637, the respiratory cycle r = 2, slice number b = 11, line number v = 2, The number NS of data-collected slices is set to 0, and the process returns to step S623.

  When returning to step S623, steps S623 to S626 are repeatedly executed, navigator echoes are collected in the 18th navigator period NAV # 18 and the 19th navigator period NAV # 19, and respiratory data is calculated. The respiration data N19 of the 19th navigator period NAV # 19 is N19 <TH, and the respiration data N18 of the previous 18th navigator period NAV # 18 is N18> TH. Therefore, the process proceeds from step S624 to step S625 and step S626. In step S626, it is determined that N18> TH, and the process proceeds to step S627.

  In step S627, a data collection period P4 is started immediately after the 19th navigator period NAV # 19.

  When the data collection period P4 starts, steps S628 to S631 are repeatedly executed, and the data of the second line in the k space is collected from the 11th to 0th slices (see FIG. 27). finish.

  Since r = R (= 2) at the end of the data collection period P4 (see FIG. 27), the process proceeds from step S636 to step S638.

  In step S638, it is determined whether or not NG data exists in the data collected at the repetition time TR. The data collected in the data collection period P4 in the second half of the repetition time TR is determined as valid data as shown in FIG. 27, but the data collected in the data collection period P3 in the first half of the repetition time TR. Is determined to be NG data. Therefore, in step S638, it is determined that NG data exists. If the data collected during the data collection period P3 is used as data for image reconstruction, body motion artifacts on the MR image may increase. Therefore, data re-reading is executed. Comparing the data collection periods P3 and P4, only the data collected in the data collection period P3 is NG data, and the data collected in the data collection period P4 is valid data. However, in order to keep the repetition time TR constant, not only the data collected in the data collection period P3 but also the data collected in the data collection period P4 are retrieved again. If it is determined that NG data exists in order to re-acquire the data, the process proceeds from step S638 to step S639.

  In step S639, the line number v is not updated. Therefore, the line number v remains v = 2. In addition, the breathing cycle r and the slice number b are reset to 1, and the data-collected slice number NS is reset to zero. After step S639, the process returns to step S623.

  When returning to step S623, as described above, steps S623 to S641 are repeatedly executed, and data is re-acquired in the data collection periods P5 and P6.

  As shown in FIG. 27, the data retrieved during the data collection periods P5 and P6 is “valid data”. Therefore, in step S638, it is determined that NG data does not exist, and the process proceeds to step S640. Since v = 2 at the end of the data collection period P6, the process proceeds from step S640 to step S641. In step S641, the respiratory cycle r = 1, the slice number b = 1, the line number v = 3, the line number v = 3, and the number of data-collected slices NS = 0 are set, and the process returns to step S623.

  Hereinafter, similarly, all the data necessary to fill the k space is collected from all slices by repeatedly executing the loop of step S623 to step S641.

  After collecting all the data, the image is reconstructed.

  In the sixth embodiment, if Nr> TH, it is determined that the data collection period includes a period in which body movement due to respiration is large, and data is reacquired. Therefore, an MR image with reduced artifacts can be acquired.

  In the sixth embodiment, the threshold value TH used in steps S624 to S626 and the threshold value TH used in step S634 are the same. However, these thresholds may be different.

  In addition, about 1st and 3rd embodiment, instead of acquiring respiratory information using a bellows, respiratory information can be acquired using a navigator method.

  In the first to sixth embodiments, the case where the imaging region of the subject is divided into a plurality of slices is described. However, the present invention can be applied even when the imaging region of the subject is divided into a plurality of slabs.

  Furthermore, in the first to sixth embodiments, data for one line in k-space is collected from each slice during each data collection period. However, data for two or more lines may be collected. Good.

1 is a block diagram of an MRI apparatus 100 according to a first embodiment of the present invention. 3 is an example of a functional block diagram of a computer 107. FIG. It is an example of the flowchart of the MRI apparatus 100 in 1st Embodiment. It is explanatory drawing of an example of the determination method of threshold value TH. 2 is a diagram illustrating an imaging region 10a of a subject 10. FIG. It is an example of the flowchart of the data collection performed in step S12. FIG. 7 is a diagram illustrating at what timing data is collected from each slice by executing the flowchart of FIG. 6. It is a conceptual diagram of k space. It is an example of the functional block diagram of the computer 107 in 2nd Embodiment. It is a flowchart showing the specific process of step S12. FIG. 11 is a diagram for explaining at what timing data is collected from each slice by executing the flowchart of FIG. 10. It is an example of the functional block diagram of the computer 107 in 3rd Embodiment. It is a flowchart showing the specific process of step S12. It is a flowchart showing the specific process of step S12. FIG. 15 is a diagram illustrating at what timing data is collected from each slice by executing the flowcharts of FIGS. 13 and 14. FIG. 15 is a diagram illustrating at what timing data is collected from each slice by executing the flowcharts of FIGS. 13 and 14. 3 is an example of a display screen of the display device 106. It is an example of the functional block diagram of the computer 107 in 4th Embodiment. It is a flowchart showing the specific process of step S12. It is a flowchart showing the specific process of step S12. FIG. 21 is a diagram for explaining at what timing data is collected from each slice by executing the flowcharts of FIGS. 19 and 20. FIG. 21 is a diagram for explaining at what timing data is collected from each slice by executing the flowcharts of FIGS. 19 and 20. It is an example of the display screen which displays three re-taking judgment information. 3 is an example of a display screen of the display device 106. It is a flowchart showing the specific process of step S12. It is a flowchart showing the specific process of step S12. FIG. 27 is a diagram for explaining at what timing data is collected from each slice by executing the flowcharts of FIGS. 25 and 26.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Subject 100 MRI apparatus 101 Magnet assembly 102 Bellows 103 Gradient coil drive circuit 104 RF power amplifier 105 Preamplifier 106 Display apparatus 107 Computer 108 Sequencer 109 Gate modulation circuit 110 RF transmission circuit 112 Receiver 113 Console 114 Bore

Claims (32)

An MRI apparatus that divides an imaging region of a subject into a plurality of slices or slabs and collects data from the imaging region during an imaging period,
Respiration information acquisition means for acquiring respiration information of the subject;
A threshold value determining means for determining a threshold value as a reference for determining whether the body movement due to breathing of the subject is large or small;
Data collection means for collecting data from the imaging region in a data collection period in the imaging period in synchronization with the breathing of the subject;
Using the respiration information and the threshold value, a determination unit that determines whether or not the data collection period includes a period during which body movement due to respiration of the subject is large, and the determination unit includes: When it is determined that the data collection period includes a period of large body movement due to breathing of the subject, data re-retrieving means for re-acquiring data collected during the data collection period;
An MRI apparatus.   The MRI apparatus according to claim 1, wherein the data collection unit collects data from at least two slices or slabs of the plurality of slices or slabs during the data collection period. An MRI apparatus that divides an imaging region of a subject into a plurality of slices or slabs and collects data from the imaging region during an imaging period,
Respiration information acquisition means for acquiring respiration information of the subject;
A threshold value determining means for determining a threshold value as a reference for determining whether the body movement due to breathing of the subject is large or small;
Data collection means for collecting data from the imaging region in a data collection period in the imaging period in synchronization with the breathing of the subject;
A determination means for determining whether or not the data collection period includes a period of large body movement due to respiration of the subject, using the respiratory information and the threshold value;
If the determination means determines that the period during which the subject's breathing is large is included in the data collection period, whether the operator of the MRI apparatus recaptures the data collected during the data collection period Display means for displaying re-judgment judgment information used for judging whether or not and re-decision to decide whether or not to re-collect data collected during the data collection period according to the operation of the operator means,
Have
The MRI apparatus, wherein the data collection unit re-collects data collected during the data collection period during the re-imaging period when the re-determination determination unit decides to re-collect data collected during the data collection period. When the determination means determines that the data collection period includes a period in which body movement due to breathing of the subject is large, the data collected during the data collection period is used as the body by breathing of the subject. Recording means for recording NG data affected by motion,
The MRI apparatus according to claim 3.   When the determination unit determines that the data collection period includes a period during which body movement due to breathing of the subject is large, the recording unit includes a slice number of data collected during the data collection period and The MRI apparatus according to claim 4, wherein the MRI apparatus records a k-space line number.   The MRI apparatus according to claim 4 or 5, wherein the re-take determination information is a ratio of the NG data to all data collected during the imaging period.   The MRI apparatus according to claim 4 or 5, wherein the re-judgment determination information is an imaging time required for re-taking the NG data.   The MRI apparatus according to claim 3, wherein the data collection unit collects data from at least two slices or slabs of the plurality of slices or slabs during the data collection period.   9. The MRI according to claim 8, wherein the re-judgment determination information is the number of slices or slabs whose data has been collected during a period when body movement due to respiration of the subject is large among the plurality of slices or slabs. apparatus. The MRI apparatus has image reconstruction means for reconstructing an image using data collected by the data collection means,
The MRI apparatus according to claim 3, wherein the re-taking determination information is an image reconstructed by the image reconstructing unit. The imaging period has a plurality of data collection periods,
4. The MRI apparatus according to claim 1, wherein the determination unit determines whether each of the plurality of data collection periods includes a period during which body movement due to respiration of the subject is large. 5.   The MRI apparatus according to claim 1, wherein the breathing information acquisition unit includes a bellows that detects breathing of the subject and outputs a breathing signal. The determination means includes
The level of the respiration signal at the end time of the data collection period is determined whether it exceeds a threshold value that is a criterion for whether the body movement due to respiration of the subject is large or small. MRI equipment. The determination means includes
The method according to claim 12, wherein before the end of the data collection period, it is determined whether the level of the respiration signal exceeds a threshold value that is a criterion for whether the body movement due to respiration of the subject is large or small. MRI equipment.   The MRI apparatus according to claim 14, wherein the determination unit compares a threshold arrival time at which the level of the respiratory signal reaches the threshold with an end time at which the data collection period ends.   The MRI apparatus according to claim 1, wherein the respiratory information acquisition unit acquires respiratory data from the subject by a navigator echo method.   The respiratory information acquisition unit according to claim 16, wherein the respiratory information acquisition unit acquires respiratory data from the subject by collecting navigator echoes from the subject before the start of the data collection period and after the end of the data collection period. MRI equipment. A data recovery determination method for determining whether to recover data collected from an imaging region of a subject using an MRI apparatus,
A respiratory information acquisition step of acquiring respiratory information of the subject;
A threshold value determining step for determining a threshold value serving as a reference for determining whether the body movement due to breathing of the subject is large or small;
A data collection step for collecting data from the imaging region in a data collection period in the imaging period in synchronization with the breathing of the subject;
A determination step of determining whether or not the data collection period includes a period of large body movement due to respiration of the subject using the respiratory information and the threshold value;
If the determination step determines that the data collection period includes a period of large body movement due to breathing of the subject, whether the operator of the MRI apparatus recaptures the data collected during the data collection period A display step for displaying re-judgment judgment information used to judge whether or not, and a re-judgment decision to decide whether or not to re-collect the data collected during the data collection period according to the operation of the operator Step,
A method for determining data recovery. When it is determined by the determination step that the data collection period includes a period in which body movement due to breathing of the subject is large, the data collected during the data collection period is determined by the breathing of the subject. Recording step for recording with NG data affected by body movement,
The method of determining re-taking data according to claim 18.   When it is determined by the determination step that the data collection period includes a period in which body movement due to breathing of the subject is large, the recording step includes a slice number of data collected in the data collection period 20. The method of determining data redrawing according to claim 19, wherein the line number in k-space is recorded.   21. The data replay determination method according to claim 19 or 20, wherein the replay determination information is a ratio of the NG data to all data collected during the imaging period.   21. The data redrawing determination method according to claim 19 or 20, wherein the redrawing determination information is an imaging time required to retake the NG data.   The method of claim 18, wherein the data collection step collects data from at least two slices or slabs of the plurality of slices or slabs during the data collection period.   24. The data according to claim 23, wherein the re-judgment determination information is the number of slices or slabs whose data has been collected during a period when body movement due to respiration of the subject is large among the plurality of slices or slabs. Re-decision method. The data recovery determination method includes an image reconstruction step of reconstructing an image using the data collected in the data collection step,
The data redrawing determination method according to claim 18, wherein the redrawing determination information is an image reconstructed by the image reconstructing means. The imaging period has a plurality of data collection periods,
The data reversion determination method according to claim 18, wherein the determination unit determines whether each of the plurality of data collection periods includes a period during which body movement due to respiration of the subject is large.   27. The data reversion determination method according to any one of claims 18 to 26, wherein the respiration information acquisition step includes a bellows that detects respiration of the subject and outputs a respiration signal. The determination step includes
The level of the respiratory signal at the end time of the data collection period is determined whether it exceeds a threshold value that is a criterion for whether the body movement due to breathing of the subject is large or small. Data recovery decision method. The determination step includes
28. Before the end of the data collection period, it is determined whether the level of the respiration signal has exceeded a threshold value that is a criterion for whether body movement due to respiration of the subject is large or small. Data re-determination decision method.   30. The data reversion determination method according to claim 29, wherein the determination step compares a threshold arrival time at which the level of the respiratory signal reaches the threshold and an end time at which the data collection period ends. .   27. The data recovery determination method according to any one of claims 18 to 26, wherein the respiratory information acquisition step acquires respiratory data from the subject by a navigator echo method.   The respiratory information acquisition step according to claim 31, wherein the respiratory information acquisition step acquires respiratory data from the subject by collecting navigator echoes from the subject before the start of the data collection period and after the end of the data collection period. Data recovery decision method.

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