JP4202855B2 - Magnetic resonance imaging system - Google Patents

Description

The present invention relates to a magnetic resonance imaging (hereinafter referred to as “MRI”) apparatus that obtains a tomographic image of a subject using a nuclear magnetic resonance phenomenon, and more particularly to a technique for shortening the total imaging time in parallel imaging.

  As a high-speed imaging method in an MRI apparatus, a parallel imaging method is known ([Non-Patent Document 3]). This is a technique that uses multiple receiving coils consisting of multiple receiving coils to measure by thinning out phase encoding steps at equal intervals, and develops an image using the sensitivity distribution of each receiving coil to obtain an unfolded image. It is. In MRI imaging, the number of phase encoding steps and the imaging time are in a proportional relationship. Therefore, in parallel imaging, the imaging time can be shortened by reducing the number of phase encodings to be measured.

  Two methods shown in FIG. 2 are known as a k-space filling method in parallel imaging. One is a pre-scan calibration method that collects sensitivity data 201 by pre-scanning, and collects only data (hereinafter referred to as “wrapping data”) 202 in which the phase encoding step is thinned out according to the set factor. [Patent Document 1]) The other is a self-calibration method in which sensitivity data and aliasing data are collected (203) at a time in this measurement and then divided into sensitivity data 204 and aliasing data 205 ([Patent Literature 2] ). In the pre-scan calibration method, the phase encoding step is thinned out according to the set factor in this measurement, so the shooting time is exactly 1 / (set factor). Although both methods have different timings for collecting sensitivity data, the point that the phase encoding step is thinned out according to the setting factor is common.

The above is the imaging method of parallel imaging. In either method, when parallel imaging is performed, sensitivity data and aliasing data are collected every time imaging is performed.
Special Table 2002-505613 Japanese Patent Laid-Open No. 2001-161657 Magnetic Resonance in Medicine 30: 142-145,1993, JBRa, CYRim, Fast Imaging Using Subencoding Data Sets from Multiple Detectors

  However, in the pre-scan calibration method, sensitivity data is collected by pre-scan, so that the pre-scan time is extended, and if the movement is large, the image may be blurred. On the other hand, the self-calibration method is characterized by being resistant to the movement of the subject without extending the pre-scan time. However, since the data of the low-frequency component region is collected densely, the self-calibration method is more effective than the pre-scan calibration method. The imaging time for measurement becomes longer.

  When performing parallel imaging with either method, the sensitivity data and aliasing data are collected each time each image is taken, so the shooting time is not simply reduced to 1 / (setting factor), and sensitivity data is collected. It takes an extra minute.

  Therefore, in any method, since it is necessary to collect sensitivity data in order to obtain an unfolded image in parallel imaging, the total imaging time is extended, which is a characteristic feature of parallel imaging. Reduce the effect of time shooting. This problem is not considered in [Non-Patent Document 1].

  Accordingly, an object of the present invention is to further reduce the total imaging time and obtain a good image without aliasing in parallel imaging.

In order to solve the above problems, the MRI apparatus of the present invention is configured as follows. That is,
A static magnetic field generating means for applying a static magnetic field to a subject; a gradient magnetic field generating means for applying a gradient magnetic field in a slice direction, a phase encoding direction, and a frequency encoding direction; and a high frequency magnetic field for inducing nuclear magnetic resonance in a nuclear spin in the subject A high-frequency magnetic field transmitting means for irradiating a pulse;
Provided with multiple RF receiving coils comprising a plurality of RF receiving coils for detecting echo signals emitted from the subject by nuclear magnetic resonance, the sensitivity data for each RF receiving coil and the phase encoding step of the measurement space are thinned out. Echo signal receiving means for measuring the image data,
Using the image data and the sensitivity data for each RF receiving coil, signal processing means for acquiring an image by calculation based on parallel imaging ;
Pulse sequence control means for controlling a pulse sequence for receiving the echo signal;
With
Re-measurement data selection means for selecting whether or not to re-measure one or both of the sensitivity data and the image data is provided, and the data selected by the re-measurement data selection means is re-measured.

  Thereby, in parallel imaging, it is not necessary to measure data that does not need to be remeasured, so that the total photographing time can be further shortened and a good image without aliasing can be acquired.

According to a preferred embodiment, in the MRI apparatus of the present invention, when the remeasurement data selection unit selects remeasurement of only the sensitivity data, and only the sensitivity data is remeasured, the signal The processing means acquires an image from the measured image data and the remeasured sensitivity data by a calculation based on the parallel imaging .

Accordingly, in parallel imaging, only the sensitivity data is remeasured and time-consuming image data is not remeasured, so that the image data measurement time can be reduced, and the total imaging time can be further reduced.
In particular, in abdominal breath-hold imaging, if the breath-hold level differs between sensitivity data measurement and image data measurement, the total imaging time reduction by re-measurement of sensitivity data with a short measurement time is Great effect.

According to a preferred embodiment, in the MRI apparatus of the present invention, when the remeasurement data selection unit selects remeasurement of only the image data, and only the image data is remeasured, The signal processing unit obtains an image from the measured sensitivity data and the remeasured image data by an operation based on the parallel imaging .

Thereby, in parallel imaging, only the image data is remeasured and the sensitivity data is not remeasured, so the sensitivity data measurement time can be shortened and the total imaging time can be further shortened. In particular, if the subject moves during time-consuming image data measurement, the effect of shortening the total imaging time is increased by re-measurement of the image data after the movement.

Moreover, according to a preferred embodiment, the MRI apparatus of the present invention, the re-measurement data selection means, in the case of instrumented of the sensitivity data Ji same slice position and the same as when the measured FOV, the image choose to re-measurement only use data.

  Thus, in parallel imaging, when the same slice position and the same FOV are used, it is not necessary to remeasure sensitivity data, so that the total photographing time can be further reduced and a good image without aliasing can be acquired.

  According to a preferred embodiment, in the MRI apparatus of the present invention, when the imaging of the same cross section of the subject is continuously repeated a plurality of times, the sensitivity data measured in the first imaging in the second and subsequent imaging. Is used.

  This makes it possible to perform the second and subsequent shooting at high speed, particularly in dynamic scanning and fluoroscopy measurement. Alternatively, if the same slice position is taken as a T1-weighted image, a T2-weighted image, and a FLAIR image, if sensitivity data is collected at the time of acquiring the T1-weighted image, the sensitivity data is measured when the subsequent T2-weighted image and FLAIR image are acquired. Can be omitted, and the time for the entire photographing can be further shortened.

  According to the present invention, in parallel imaging, which is a technique for shortening imaging time in an MRI apparatus, either sensitivity data or aliasing data measurement necessary for acquisition of a composite image is performed at the time of acquisition of a composite image from the next time onward. When it is not necessary to re-measure the image, the measured data can be used without re-measurement, which can further reduce the total shooting time and obtain a good image without aliasing. it can.

  In particular, when there is body movement of the subject, only re-measurement of the data that requires re-measurement, or when the same cross-section of the subject, such as dynamic scan or fluoroscopy measurement, is repeated multiple times in succession In addition, since the re-measurement of sensitivity data can be omitted in the second and subsequent imaging, the total imaging time can be further shortened and the burden on the subject can be reduced.

Hereinafter, embodiments of an MRI apparatus to which the present invention is applied will be described in detail with reference to the drawings.
FIG. 7 is a block diagram showing a schematic overall configuration of the MRI apparatus according to the present invention. This MRI apparatus is for obtaining a tomographic image of a subject using a nuclear magnetic resonance phenomenon, a static magnetic field generation system 701, a gradient magnetic field generation system 702, a transmission system 703, a reception system 704, a signal processing system 705, It comprises a sequencer 706, a central processing unit 707, and an operation unit (not shown).

  The static magnetic field generation system 701 is composed of either a permanent magnet, a normal conducting magnet, or a superconducting magnet arranged in a measurement space having a certain extent around the subject 708, and the body axis around the subject 708. A uniform static magnetic field is generated in a direction or a direction perpendicular to the body axis of the subject.

  The gradient magnetic field generation system 702 includes a gradient magnetic field coil 709 wound in three axial directions of X, Y, and Z, and a gradient magnetic field power supply 710 that supplies current to each of these coils. By applying a current to each coil of the power supply 710, gradient magnetic fields Gs, Gp, and Gf in three axial directions of X, Y, and Z are applied to the subject 708. By applying this gradient magnetic field, a cross section for imaging and displaying the subject 708 is set.

  The transmission system 703 includes a high-frequency oscillator 711, a modulator 712, a high-frequency amplifier 713, and a high-frequency irradiation coil 714, and the atomic nuclei constituting the biological tissue of the imaging cross section of the subject 708 set by the gradient magnetic field generation system 702. In order to excite and cause nuclear magnetic resonance, the high-frequency pulse output from the high-frequency oscillator 711 is amplitude-modulated by the modulator 712, amplified by the high-frequency amplifier 713, and then placed in the vicinity of the subject 708. A coil 714 is supplied to irradiate the subject.

  The receiving system 704 includes a high-frequency receiving coil 715, a receiving circuit 716, and an analog / digital (hereinafter referred to as “A / D”) converter 717, and a subject 708 due to electromagnetic waves irradiated from the high-frequency irradiation coil 714 of the transmitting system 703. NMR signal, which is an echo signal generated by nuclear magnetic resonance of the nuclei of the living body tissue, is detected by the high-frequency receiving coil 715 disposed in the vicinity of the subject 708 and input to the A / D converter 717 via the receiving circuit 716. Then, it is converted into a digital signal, and the signal data is sent to the signal processing system 5 as collected data sampled at a timing according to a command from the sequencer 706.

  The signal processing system 705 includes a CPU 707 that performs Fourier transform and control of the sequencer 706 on the collected data, and a signal processing device that includes correction means of the present invention and performs processing necessary for reconstructing correction calculations and collected data into tomographic images. 718, memorizes the image analysis processing over time and the specified measurement sequence program, parameters used in the execution, etc., and the measurement parameters obtained in advance measurement performed on the subject and the receiving system 704 A memory 719 for temporarily storing the collected data from the NMR signal detected in step 1 and an image used for setting the region of interest and storing parameters for setting the region of interest, a data storage unit for storing the reconstructed image data, and A magnetic disk 720, an optical disk 721, and a display 722 that visualizes image data read from these disks and displays them as a tomographic image. Rannahli, an image is displayed performs image reconstruction operation using the NMR signal detected by the receiving system 704.

The sequencer 706 operates under the control of the CPU 707 to repeatedly generate slice encoding, phase encoding, and frequency encoding gradient magnetic fields and high-frequency magnetic field pulses in a predetermined pulse sequence, and obtains tomographic image data of the subject 708. Various commands necessary for the above are sent to the gradient magnetic field generation system 702, the transmission system 703, and the reception system 704.
An operation unit (not shown) includes a trackball, a mouse, a keyboard, or the like, and inputs control information for processing performed by the signal processing system 705.

Next, an imaging method using the MRI apparatus having the above configuration will be described.
FIG. 3 shows a general gradient echo sequence. A radio frequency (RF) pulse 301 is applied together with the slice selective gradient magnetic field pulse 302 to excite a nuclear spin in a specific region of the subject to generate transverse magnetization, and then a phase encode gradient magnetic field pulse 303 is applied, followed by readout A gradient magnetic field pulse 304 is applied and an echo signal 305 is measured. The time (echo time) TE from the radio frequency (RF) pulse 301 to the echo signal 305 is one of the parameters for determining the image contrast, and is set in advance in consideration of the target tissue and the like.

Such a sequence is repeated, for example, a plurality of times while changing the area of the phase encoding gradient magnetic field 303 (the value obtained by integrating the magnetic field intensity with respect to the application time), and data in the k space is measured. In parallel imaging, measurement is performed by thinning out the phase encoding step according to a set factor using a multiple receiving coil including a plurality of receiving coils. This measurement data is sent to the signal processing system (705) for each receiving coil (715). Here, as shown in FIG. 4, the sensitivity distribution calculation 402 of each receiving coil and the signal combining processing from each receiving coil are performed. 404 is done. That is, the signal e _n (kx, ky) from each coil 401 the sensitivity distribution image W _n (x, y) of each coil with Request 403. In FIG. 4, n is a coil number, and in this embodiment, n = 1, 2, 3 or 4. Further, (kx, ky) represents the coordinates in the k space, and (x, y) represents the position in the real space. The entire image S (x, y) 405 is synthesized using the sensitivity distribution and the received signal. The sensitivity distribution calculation 402 and the synthesis process 404 will be described in further detail.

First, a procedure for calculating the sensitivity distribution of RF coil from signal e _n (kx, ky) 401 in each receiving coil. First, a low-frequency pass filter (LPF) is applied in the phase encoding direction for sensitivity data (data in k space). As a result, all the data in the high frequency region becomes zero, and the boundary where the signal is collected and the boundary between the zero data are smoothly connected to zero. Next, the entire k-space is subjected to two-dimensional Fourier transform (2DFT), and only the low frequency component is imaged. It is known that this image can be regarded as a sensitivity distribution (data in real space) of the RF coil, and this is also referred to as a sensitivity distribution W _n (x, y) in this embodiment.

Next, a synthesis operation 404 that removes aliasing using the sensitivity distribution W _n (x, y) will be described. There are a method of performing a composition operation in an image space (real space) and a method of performing it in a measurement space (k space).

  FIG. 5 illustrates a method performed in the image space. Here, in order to simplify the explanation, an example in which two coils are arranged on the left and right sides of the FOV is shown. The signal at point A overlaps with point B due to the aliasing caused by thinning out the phase encoding step. By decomposing the B point signal into the original A point signal S (x + Δx, y) and the B point signal S (x, y), an unfolded image is obtained. Here, Δx means a folding distance.

The sensitivity coefficients FOV disposed on the left side coil1 (501) is obtained from the image 504 to generate _{W 1 (x + Δx, y} ), W 1 (x, y), image coil2 arranged in FOV right (502) to produce The sensitivity coefficient obtained from 505 is defined as W ₂ (x + Δx, y), W ₂ (x, y). From these, the following equation is established.
Measured signal strength S ₁ (x, y) at point B of coil 1
= W ₁ (x + Δx, y) ・ S (x + Δx, y) + W ₁ (x, y) ・ S (x, y)
Measured signal strength S ₂ (x, y) at point B of coil 2
= W ₂ (x + Δx, y) ・ S (x + Δx, y) + W ₂ (x, y) ・ S (x, y)
The measured signal intensity at point B of each coil is measured, and S (x + Δx, y) and S (x, y) are calculated by simultaneous equations. Thus, from the signal strength S ₁ (x, y), S ₂ (x, y) of the folded image generated by each coil, the original signal strength S (( x + Δx, y), S (x, y) can be calculated. If this calculation is performed for all voxels, an image 506 from which aliasing is removed is obtained. Details of the method performed in this image space are described in [Non-Patent Document 2].

SENSE: Sensitivity Encoding for Fast MRI (Klass P. Pruessmann et.al), Magnetic Resonance in Medicine 42: 952-962 (1999)

  Next, a method for synthesizing signals in the measurement space will be described. This method creates insufficient data in the measurement space by determining weights so that a combined sensitivity distribution obtained by combining the sensitivity distributions of small RF coils with a suitable weight has a desired frequency.

For example, the sensitivity distribution W _n (x, y) of the receiving coil is synthesized with an appropriate weight C _n , and the synthesized sensitivity distribution Wcomp (x, y) in the form of exp (i · mΔk _y · y) [m is an integer] ) Is obtained.
Wcomp (x, y) = ΣC _j W _j (x, y) = exp (imΔk _y y) (1)
The signal S (k _x , k _y ) synthesized at this time is expressed by the following equation.
S (k _x , k _y ) = ∬dxdy Wcomp (x, y) ρ (x, y) exp [-ik _x x-ik _y y]
= ∬dxdyρ (x, y) exp [-ik _x x-i (k _y -mΔk _y ) y]
= ρ ^ (k _x , k _y -mΔk _y ) (2)
In the equation (2), ρ represents a magnetization density, and ρ ^ represents a two-dimensional Fourier transform of ρ. As can be seen from equation (2), ρ ^ (k _x , k _y- mΔk _y ) can be obtained from ρ ^ (k _x , k _y ) by using the composite sensitivity distribution Wcomp (x, y). . This means that the data between the data of the phase encoding step thinned out in the k space is made up. Details of the method performed in the measurement space are described in [Non-Patent Document 3].

Simultaneous acquisition of spatial harmonics (SMASH): fast imaging with radiofrequency coil arrays (Daniel KSodickson, Warren J Manning), Magnetic Resonance in Medicine 38: 591-603, (1997)

  FIG. 6 is a diagram conceptually showing this method. As shown in the figure, first, sensitivity distribution is obtained from sensitivity data 601 by LPF, zero padding, and two-dimensional Fourier transform (2DFT). Next, with respect to the return data 602, deficient data (corresponding to the dotted line in the enlarged view 603) is created from the data already obtained by the above calculation (corresponding to the solid line in the enlarged view 603). The number of new data that can be created in this way (number of dotted lines) depends on the number of small RF coils, and when there are four small RF coils, up to four new data can be created. In the example shown in the figure, the factor is 4 and three data are created.

The data after supplementing the new data in this manner is the same as the data measured without thinning out the entire area of the k space, and an image without aliasing is obtained by performing a two-dimensional Fourier transform.
Parallel imaging is performed according to the above procedure, and using this makes it possible to shorten the imaging time compared to normal imaging.

  Next, a first embodiment of the present invention that enables further time reduction in the collection of sensitivity data or aliasing data will be described with reference to FIG. In the first embodiment of the present invention, the photographing time is shortened by diverting the measured sensitivity data without re-measuring the sensitivity data.

  FIG. 1 (a) is a processing flowchart showing a first embodiment of the pre-scan calibration method. In the case of the prescan calibration method, in the first parallel imaging, the sensitivity data 101 is collected in the prescan, and the return data 102 is collected in the main measurement. Thereafter, the sensitivity distribution is calculated 103 by reconstruction, the signals are combined 104, and an image 105 is displayed. When performing the second parallel imaging, it is determined whether or not the previously collected sensitivity data can be used in order to perform aliasing removal only by collecting aliasing data without collecting sensitivity data again (106). ) (Remeasurement data selection means). The conditions when diversion is possible include the following conditions, for example. In addition, this invention is not limited by this example.

Sensitivity data diversion conditions: When the previous sensitivity data was collected,
Same slice position and same FOV
If the above conditions are met and sensitivity data is used, sensitivity data is not collected by pre-scan, but only return data is collected in this measurement. Are combined 104 and an image is displayed 105. If the condition is not met, the same processing as the first shooting is repeated.

  FIG. 1B is a process flow diagram showing a first embodiment of the self-calibration method. In the case of the self-calibration method, in the first parallel imaging, sensitivity data and aliasing data are collected 107 simultaneously in the main measurement, sensitivity distribution is calculated by reconstruction 108, a signal is synthesized 109, and an image 110 is displayed. . In the second and subsequent shootings, it is determined whether the diversion conditions are satisfied (110). If they are satisfied, only the return data is collected 112 in this measurement, and then the signal is used using the sensitivity distribution obtained in the first shooting. To display an image. If diversion is not possible, the same processing as the first shooting is repeated.

  As described above, if the already collected sensitivity data can be diverted, select either the diversion method or the method of recollecting the sensitivity data again in the next shooting as in the conventional method. Is possible.

  Next, a second embodiment of the present invention that enables further time reduction by not re-measuring either sensitivity data or aliasing data will be described with reference to FIG. In the second embodiment of the present invention, the one that does not need to be re-measured is automatically or manually selected.

  Figure 8 shows that if the image after reconstruction by the pre-scan calibration method is not good, a good image can be obtained by re-measuring only one of the sensitivity data or the aliasing data instead of re-measuring from the beginning. It is a processing flow figure made possible.

  Dotted line sensitivity data 801 and loopback data 802 are obtained by diverting previously collected data, or collected again. The sensitivity distribution is calculated from this sensitivity data 801 (803), the signals are combined (804), and the image is displayed (805). Alternatively, only one of the return data or both of the data is automatically or manually measured (806). First, the image is displayed and recommended to the operator as to whether the system should re-measure either or both by automatic detection, and the operator considers the image and the recommendation from the system together, or either Instruct whether to re-measure both. According to the instruction, the selected one is re-measured. Note that the person selected by automatic detection may be automatically re-measured without making an operator's decision.

As described above, an instruction is issued automatically or manually, and only one or both of the data is re-measured, so that re-imaging is performed in a shorter time than re-measurement of all the data. A method for automatically detecting which data should be re-measured will be described with reference to examples shown in FIGS.
In addition, since it is the same as that of the past when measuring both data, it abbreviate | omits below.

  First, as an example of re-measuring only sensitivity data, a breath holding measurement for abdominal radiography is given. If you hold your breath when you measure sensitivity data, and you take a free breath after the measurement, and then hold your breath again when you measure the return data, the abdomen position will be different due to the difference in the breath-hold level at each data measurement, and it will be completely parallel May not be able to fold and the return may remain strong. In this case, it is possible to accurately remove the aliasing by holding the breath at the same level as when the aliasing data is measured and measuring the sensitivity data again and using the aliasing data measured earlier in parallel.

  As this re-recovery condition, for example, there is a method of automatically detecting the positional deviation of sensitivity data and aliasing data by the center of gravity method. The centroid method will be described with reference to FIG. In the sensitivity image 901 and the folded image 902, the coordinates having signals are extracted, and the center of each image is calculated by averaging the coordinates (903, 904). It is determined whether the difference between the centers of the images is within the threshold value (905). If the difference is smaller than the determination value, it is determined that there is no displacement (906). If it is equal to or greater than the determination value, it is determined that the position of the image between the sensitivity data and the aliasing data is shifted (907), and recommendation or instruction is given to re-acquire only the sensitivity data (908). The determination value is calculated based on user input or set internally.

  Next, an example in which only the return data is remeasured is an example in which the subject moves during the return data measurement. Since the measurement of the return data is longer than the sensitivity data measurement time, the subject may move greatly during the measurement. In this case, it is necessary to re-measure the return data, but the total imaging time can be shortened by re-measurement of the return data after the subject moves. As a method for recognizing movement during measurement, for example, navigation echo can be used.

  An example of processing for determining body movement using navigation echo will be described using the EPI sequence of FIG. 10 (a) as an example. Applying 90 ° and 180 ° radio frequency (RF) pulses 1001 along with slice-select gradient magnetic field pulses 1002 to excite nuclear spins in specific regions of the subject and before applying phase encoding gradient magnetic field pulses 1003 A readout gradient magnetic field pulse 1004 is applied for echo measurement, and a navigation echo signal 1005 is measured.

In this way, navigation echo data (hereinafter referred to as “Navi echo data”) is measured in the pre-scan and main measurement, and the primary phase gradient 1006 is calculated by performing a one-dimensional Fourier transform on each Navi echo data. The average is used as a reference value (FIG. 10 (b)). From the reference value, the number of Navi echo data whose primary slope exceeds the threshold (α _{6 in} Fig. 10 (b)) is measured (1007), and the number of α deviating from the threshold is compared with the set value. If it is less than the set value (1008), it is determined that there is no displacement (1009). If the value is equal to or greater than the set value, it is determined that there is a position shift (1010), and recommendation or instruction is made to retake the loopback data (1011). The threshold value and setting value are calculated based on user input or set internally.

  Although automatic detection is performed as in the above example, if the operator instructs re-taking after viewing the image with reference to this result, whether or not to re-measure depending on the degree of folding artifacts, motion artifacts, etc. Which data is used for determination is determined.

  Reducing the imaging time by reusing existing sensitivity data without re-measuring the above sensitivity data is also applicable to dynamic scan and fluoroscopy measurement, which repeats the same measurement multiple times, especially the second time. Subsequent shooting can be performed at high speed.

FIG. 3 is a process flow diagram for the first embodiment of the present invention. Schematic diagram of parallel imaging k-space filling method using MRI apparatus. The figure which shows one Example of the pulse sequence which the MRI apparatus of this invention employ | adopts. The schematic diagram which shows one Example of the process of the signal processing system of the MRI apparatus of this invention. The figure explaining the method of carrying out the aliasing removal in the image space in the parallel imaging by the MRI apparatus of this invention. The figure explaining the method of carrying out the aliasing removal in the measurement space in the parallel imaging by the MRI apparatus of this invention. 1 is a schematic configuration diagram of a magnetic resonance imaging apparatus according to the present invention. The processing flowchart about the 2nd example of the present invention. The processing flow figure which judges automatically that sensitivity data is taken again. The processing flow figure of the center of gravity method.

Explanation of symbols

  708 ... subject, 701 ... static magnetic field generation system, 702 ... gradient magnetic field generation system, 706 ... sequencer, 703 ... transmission system, 704 ... reception system, 705 ... signal processing system, 707 ... central processing unit (CPU), 709 ... Gradient magnetic field coil, 710 ... Gradient magnetic field power supply, 711 ... High frequency oscillator, 712 ... Modulator, 713 ... High frequency amplifier, 714 ... Irradiation coil (transmission side), 715 ... Reception coil (reception side), 716 ... Reception circuit, 717 ... A / D converter, 718 ... signal processing device, 720 ... magnetic disk, 721 ... optical disk, 722 ... display

Claims (6)

A static magnetic field generating means for applying a static magnetic field to a subject; a gradient magnetic field generating means for applying a gradient magnetic field in a slice direction, a phase encoding direction, and a frequency encoding direction; and a high frequency magnetic field for inducing nuclear magnetic resonance in a nuclear spin in the subject A high-frequency magnetic field transmitting means for irradiating a pulse;
A multiple RF receiving coil comprising a plurality of RF receiving coils for detecting echo signals emitted from the subject by nuclear magnetic resonance is provided, and the sensitivity data for each RF receiving coil and the phase encoding step of the measurement space are thinned out. Echo signal receiving means for measuring the image data,
Signal processing means for acquiring an image by calculation based on parallel imaging using the image data and the sensitivity data for each RF receiving coil;
In a magnetic resonance imaging apparatus comprising: a pulse sequence control unit that controls a pulse sequence for receiving the echo signal;
Re-measurement data selection means for selecting whether to re-measure one or both of the sensitivity data and the image data, and re-measure the data selected by the re-measurement data selection means A magnetic resonance imaging apparatus. 2. The magnetic resonance imaging apparatus according to claim 1, wherein when the remeasurement data selection unit selects remeasurement of only the sensitivity data and only the sensitivity data is remeasured, the signal processing unit performs measurement. A magnetic resonance imaging apparatus characterized in that an image is acquired from the completed image data and the re-measured sensitivity data by a calculation based on the parallel imaging . 2. The magnetic resonance imaging apparatus according to claim 1, wherein when the remeasurement data selection unit selects remeasurement of only the image data and only the image data is remeasured, the signal processing unit is A magnetic resonance imaging apparatus characterized in that an image is acquired by a calculation based on the parallel imaging from the measured sensitivity data and the remeasured image data. The magnetic resonance imaging apparatus according to claim 1, wherein the re-measurement data selection means, for the same slice position and the same FOV as the case of measuring the instrumented of the sensitivity data, re-measurement of the image data only A magnetic resonance imaging apparatus.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the signal processing unit performs an operation based on the parallel imaging in an image space.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the signal processing unit performs an operation based on the parallel imaging in the measurement space.

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