JP5087172B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a medical magnetic resonance imaging apparatus.

  Magnetic resonance imaging is an imaging method in which a nuclear spin of a subject placed in a static magnetic field is magnetically excited with a high-frequency signal of its Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation. .

  One imaging method that has recently attracted attention in the field of magnetic resonance imaging is non-contrast angiography. In other words, this is an imaging method for obtaining blood vessel images and blood flow information in a subject without administering a contrast agent to the subject. When performing this non-contrast angiography, a three-dimensional imaging scan is preferred from the viewpoint of the amount of information obtained.

  When performing the above-described non-contrast angiography, the imaging scan is often executed in a state where the parameters of the pulse sequence that affect the quality of the MR image of the subject are not necessarily optimal.

  An example of this parameter is a dephasing pulse that suppresses a flow void phenomenon. If a flow void phenomenon occurs due to blood flow, problems such as a decrease in the intensity of the echo signal to be collected occur. Therefore, the degree of this flow void must be grasped in advance and the flow void taken into account. It is preferable to set the imaging conditions for each subject.

  For example, when imaging blood vessels of the lower limbs by non-contrast MR angiography, the flow velocity of blood vessels varies considerably depending on individual differences, and there is a considerable difference only between healthy subjects and patients. Even in the lower limbs of the same subject, the blood flow velocity differs if the part to be scanned is different.

  However, in practice, there has been little research on the optimization of various parameters of a pulse sequence used in an imaging scan before imaging. For this reason, it has been difficult for the operator to see the inside of the subject before the three-dimensional imaging scan and accurately know the degree of the flow void in the desired readout direction. Therefore, the operator has only been able to estimate the degree of the flow void based on experience or on the ground with thought and error and reflect this in the imaging conditions. Although it is possible to estimate the degree of flow void by performing a trial scan, in that case, the total imaging time required for one patient becomes longer and patient throughput decreases. In addition, the patient's SAR often increases.

  In performing non-contrast angiography, the parameters of the pulse sequence used in the imaging scan are not limited to the above-mentioned flow void values, but are effective echo time TEeff, flow compensation, inversion recovery (IR) time, echo There are an interval ETS (echo train spacing), a flip angle of the fat suppression pulse, an inversion time TI after applying the fat suppression pulse, a flip angle of the MT pulse, a flip angle of the refocus pulse, and the like.

  Conventionally, Japanese Patent Laid-Open No. 11-239571 has proposed a method of performing a scan for measuring an optimal electrocardiographic synchronization timing in advance when performing an imaging scan based on the electrocardiographic synchronization method. However, the method described in this publication considers ECG synchronization timing, and lacks the viewpoint of considering a wide range of other scan parameters.

  The present invention has been made to overcome such a current situation. Echo information reflecting a desired parameter of a pulse sequence used in an imaging scan is collected before imaging of the imaging scan, and the parameter is obtained from the collected information. An object of the present invention is to provide a magnetic resonance imaging apparatus that can surely know the optimum value in the imaging scan.

In order to achieve the above object, a magnetic resonance imaging apparatus according to an aspect of the present invention is a magnetic resonance imaging apparatus that performs an imaging scan for obtaining an MR image of a subject . Input means for inputting desired parameter designation information from a plurality of parameters, and specified by the input means among a plurality of parameters of a pulse sequence used in the imaging scan based on data collected by the preparation scan. A preparation image generating means for generating a plurality of preparation images corresponding to a plurality of different parameter amounts for the desired parameter, and reflecting a parameter amount of a specific preparation image among the plurality of preparation images in the imaging scan, This parameter amount is reflected Imaging scan execution means for executing a scanning scan, wherein the preparation scan is a two-dimensional scan, the imaging scan is a three-dimensional scan by an electrocardiogram synchronization method, and a plurality of parameters corresponding to the plurality of different parameter amounts The preparation image is based on data obtained by performing a preparation scan with the same delay time.

The functional block diagram which shows an example of a structure of the magnetic resonance imaging apparatus which concerns on embodiment of this invention. Prep. In the embodiment. FIG. 5 is a diagram for explaining the front-rear relationship between scan and time of a scanning scan. Prep. 4 is a schematic flowchart illustrating a selection process of parameters whose values are changed by scanning and a subsequent process. prep. Schematic pulse sequence showing an example of scanning. prep. 6 is a schematic pulse sequence showing another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning. prep. 6 is a schematic pulse sequence showing still another example of scanning.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings.

  A schematic configuration of a magnetic resonance imaging apparatus according to this embodiment is shown in FIG.

  This magnetic resonance imaging apparatus includes a bed part on which a patient P as a subject is placed, a static magnetic field generation part for generating a static magnetic field, a gradient magnetic field generation part for adding position information to the static magnetic field, and RF (high frequency) A transmission / reception unit for transmitting / receiving signals, a control / calculation unit responsible for overall system control and image reconstruction, an electrocardiogram measurement unit for measuring an ECG (electrocardiogram) signal as a signal representing the cardiac phase of the patient P, and a patient A breath-hold command unit that commands P to hold the breath is functionally provided.

  The static magnetic field generation unit includes, for example, a superconducting magnet 1 and a static magnetic field power supply 2 that supplies current to the magnet 1, and a longitudinal axis of a cylindrical opening (diagnostic space) into which the subject P is loosely inserted. A static magnetic field H0 is generated in the direction (Z-axis direction). In addition, the shim coil 14 is provided in this magnet part. The shim coil 14 is supplied with a current for homogenizing a static magnetic field from a shim coil power supply 15 under the control of a host computer to be described later. The couch portion can removably insert the top plate on which the subject P is placed into the opening of the magnet 1.

  The gradient magnetic field generator includes a gradient magnetic field coil unit 3 incorporated in the magnet 1. The gradient coil unit 3 includes three sets (types) of x, y, and z coils 3x to 3z for generating gradient magnetic fields in the X, Y, and Z axis directions orthogonal to each other. The gradient magnetic field unit further includes a gradient magnetic field power supply 4 that supplies current to the x, y, z coils 3x to 3z. This gradient magnetic field power supply 4 supplies a pulse current for generating a gradient magnetic field to the x, y, z coils 3x to 3z under the control of a sequencer described later.

  By controlling the pulse current supplied from the gradient magnetic field power source 4 to the x, y, z coils 3x to 3z, the gradient magnetic fields in the three-axis X, Y, and Z directions are synthesized, and the slice direction gradient magnetic field GS and phase encoding are synthesized. Each direction of the direction gradient magnetic field GE and the reading direction (frequency encoding direction) gradient magnetic field GR can be arbitrarily set and changed. Each gradient magnetic field in the slice direction, the phase encoding direction, and the readout direction is superimposed on the static magnetic field H0.

  The transmission / reception unit includes an RF (high frequency) coil 7 disposed in the vicinity of the patient P in the imaging space in the magnet 1, and a transmitter 8T and a receiver 8R connected to the RF coil 7. Under the control of a sequencer described later, the transmitter 8T supplies an RF current pulse having a Larmor frequency for exciting magnetic resonance (NMR) to the RF coil 7, while the receiver 8R receives the RF coil 7. The received MR signal (high frequency signal) is received, and various received signal processing is performed on the received signal to form corresponding digital data.

  The control / arithmetic unit further includes a sequencer (also referred to as a sequence controller) 5, a host computer 6, an arithmetic unit 10, a storage unit 11, a display device 12, and an input device 13. Among these, the host computer 6 has a function of commanding the pulse sequence information to the sequencer 5 according to the stored software procedure and overseeing the operation of the entire apparatus including the sequencer 5.

  This MRI apparatus measures an amount of a desired parameter among parameters related to a pulse sequence used in an imaging scan before an imaging scan for imaging, and reflects the optimum amount of the parameter in the imaging scan. It is said. Specifically, as shown in FIG. 2, the host computer 6 performs a preparation scan (hereinafter referred to as “prep. Scan”) and an imaging scan for collecting echo data for image reconstruction. prep. The scan is executed to optimize the amount of a desired parameter among a plurality of parameters related to a pulse sequence used in a subsequent imaging scan.

In this embodiment, as a plurality of parameters related to the pulse sequence,
・ Intensity of the pulse to suppress the flow void phenomenon of fluid (blood flow etc.) in the subject
-Execution TEeff time related to the behavior of the spin in the subject,
A pulse that compensates for spin transfer due to fluid flow,
-Spin reversal recovery,
-ETS time of echo signal collected from the subject,
The flip angle of the fat suppression pulse applied to suppress signal collection from the fat present in the subject,
TI time after applying fat suppression pulse,
Consider the intensity of the MT pulse that causes the MT effect that occurs in relation to the spin behavior, and the angle of the refocus pulse that reduces the MT effect. When the type of pulse sequence to be used for the imaging scan is determined in consideration of the blood flow to be imaged, the imaging region, individual differences of the subject, etc., the desired parameter is selected from the various parameters of the pulse sequence. The When this parameter is selected, prep. The scan is performed while changing the amount of the parameter multiple times. That is, data acquisition is performed a plurality of times for the imaging region of the subject (the same or almost the same region as the imaging scan) in the same cardiac phase accompanying one RF excitation. Thereby, a plurality of pieces of image data for the same imaging region are prepared and reconfigured. The operator designates, for example, an image with the highest image quality from among the reconstructed images. As a result, the designated image becomes prep. The amount of the selection parameter that was set when the image was captured by scanning is specified. As an example, the amount of the selection parameter is reflected in a subsequent imaging scan through an operator's operation. That is, among the various parameters of the pulse sequence used in the imaging scan, prep. Parameters corresponding to the parameters changed by scanning include prep. A quantity (pulse intensity, pulse angle, time, etc.) specified throughout the scan is set.

  Also, prep. For both scanning and imaging scanning, for example, a breath holding method based on voice instructions is used together.

  Note that prep. The scan is not intended for imaging itself for diagnosis of the imaging region, but is performed to optimize the desired parameters of the pulse sequence as described above. For this reason, prep. The matrix of images captured by the scan may be coarser than that of the imaging scan. When the imaging scan is a three-dimensional scan, prep. It is preferable to perform a two-dimensional scan to save scan time. Furthermore, prep. It is desirable that the types of pulse sequences used for scanning and imaging scanning are the same.

  Returning to FIG. 1, the sequencer 5 includes a CPU and a memory, stores pulse sequence information sent from the host computer 6, and in accordance with this information, the gradient magnetic field power source 4, the transmitter 8T, and the receiver 8R. Control a series of operations. Here, the pulse sequence information is all information necessary for operating the gradient magnetic field power source 4, the transmitter 8T, and the receiver 8R according to a series of pulse sequences, for example, x, y, z coils 3x to 3z. Includes information on the intensity, application time, application timing, and the like of the pulse current applied to. In addition, the sequencer 5 inputs digital data (MR signal) output from the receiver 8 </ b> R and transfers this data to the arithmetic unit 10.

  This pulse sequence may be a two-dimensional (2D) scan or a three-dimensional (3D) scan as long as the Fourier transform method can be applied. Also, the pulse train forms include SE (spin echo) method, FE (field gradient echo) method, FSE (fast SE) method, EPI (echo planar imaging) method, and Fast asymmetric SE (FASE: FSE method). A method that combines the Fourier method) can be applied.

  Further, the arithmetic unit 10 inputs the digital data of the MR signal sent from the receiver 8R via the sequencer 5, and the original data (also called raw data) to the Fourier space (also called k space or frequency space). And a two-dimensional or three-dimensional Fourier transform process for reconstructing the original data into a real space image, while performing an image data synthesis process. The Fourier transform process may be assigned to the host computer 6.

  The storage unit 11 can store not only original data and reconstructed image data, but also image data that has been subjected to various types of processing. The display device 12 displays an image. In addition, information such as the type of parameter desired by the operator, the scanning condition, the type and parameter of the pulse sequence, the desired image processing method, and the like can be input to the host computer 6 via the input unit 13.

  Moreover, the audio | voice generator 19 is provided as a breath-hold command part. This voice generator 19 can emit, for example, messages indicating the start and end of breath holding as voice when instructed by the host computer 6.

  Further, the electrocardiogram measurement unit attaches to the body surface of the patient P and detects an ECG signal as an electrical signal, and performs various processing including digitization processing on the sensor signal to perform the host computer 6 and the sequencer. And an ECG unit 18 for outputting to the PC. The measurement signal from this electrocardiogram measurement unit is prep. It is used by the host computer 6 and the sequencer 5 when executing a scan scan and an imaging scan based on the electrocardiogram synchronization method.

  Next, the overall operation of this embodiment will be described.

  At the start of imaging, the host computer 6 uses the breath holding method together with prep. Command execution of scan (see FIG. 2).

  Specifically, the host computer 6 uses prep. Scan condition and parameter information for executing the scan are read from the input device 13 (step S1 in FIG. 3). Information on these scanning conditions and parameters is arbitrarily designated by the operator in consideration of the subsequent imaging scan. Scan conditions include the type of scan, the type of pulse sequence, the phase encoding direction, and the like. The parameter information includes a delay time from the R wave for electrocardiographic synchronization and predetermined values of a plurality of parameters related to the pulse sequence.

  prep. For the scan, preferably, a two-dimensional scan pulse sequence capable of imaging a desired slice region in the imaging region is designated. As the type of sequence sequence of the pulse sequence, a sequence capable of collecting all data used for image reconstruction of one slice by one excitation is designated. Examples of such a pulse sequence include FASE method, FSE method, EPI method and the like.

  Next, the host computer 6 reads, from the input device 13, parameter designation information for changing the amount for each data collection among the plurality of parameters described above (step S2). This designation information is designated by the operator in consideration of characteristics such as the type of pulse sequence and the blood flow velocity at the imaging region.

  Next, the host computer 6 determines the type of variable parameter from the read information through the processing of steps S3 to S19 shown in FIG.

(1. prep.scan for flow void)
First, it is determined whether or not the variable parameter is the intensity of a dephase pulse related to the flow void phenomenon (step S3). When this determination is YES, a pulse sequence that is changed every time the data of the intensity of the dephase pulse is collected is set.

  FIG. 4 illustrates an outline of such a pulse sequence. The pulse sequence according to this example is a two-dimensional FASE method, and a total of four times (Acq.1 to Acq.4) of data acquisition per excitation for each data acquisition is performed using a breath holding method and an electrocardiographic synchronization method. It is designed to be executed together. With the electrocardiographic synchronization method, data collection is started each time from the R wave in the ECG wave at the same delay time, that is, at the same cardiac time phase. In addition to this, the EPI method, the FSE method, etc. may be used as the pulse sequence. However, in order to complete the data collection multiple times in a short time by using both the breath holding method and the electrocardiogram synchronization method, each time A sequence that can collect data for one slice with one excitation is desirable.

  In each data acquisition based on the pulse sequence according to the FASE method, a plurality of echoes are generated in time series with one RF excitation, and each echo is in a frequency encoding direction, that is, a readout (Read-Out) direction gradient magnetic field RO. Reading is performed together with application of (outlined portion). At this time, a dephase pulse DP (shaded portion) is added before and after the magnetic field pulse RO before and after the read direction gradient magnetic field RO in the time axis direction. The intensity of the dephasing pulse DP is changed every time data is collected. In the example of FIG. 4, the first data collection Acc. 1, the dephasing pulse DP = 0 and the second data acquisition Acc. 2, the dephasing pulse DP = small intensity and the third data collection Acc. 3, the intensity of the dephasing pulse DP = medium and the fourth data acquisition Acc. 4, the dephasing pulse DP is set to a large intensity. In FIG. 4, the phase encoding direction gradient magnetic field is not shown.

  Thus, when the variable parameter = dephase pulse DP is selected, the determinations in steps S7, S9, S11, S13, S15, S17, S19, and S21 for selecting other variable parameters are NO. For this reason, the host computer 6 uses the variable parameter = prep. The scan pulse sequence information is read out and transferred to the sequencer 5 to wait (step S21).

  Next, the host computer 6 sends prep. When the start of the scan can be determined (step S22), an instruction is sent to the sequencer 5 to instruct the breath-holding by voice (step S23), and in the same cardiac phase (ie, single phase) based on the ECG synchronization method. Prep. A scan is executed to collect echo data (step S24). After the scan, a voice message for releasing the breath hold is issued (step S25).

  This prep. By scanning, as shown in FIG. 4, data collection by four RF excitations for a total of four images is sequentially executed. Echo data for one slice is acquired by data acquisition by each RF excitation. That is, in this example, data is collected in a single slice / single phase. Note that it may be set so that data collection is performed in multi-slice / single phase for the same imaging region.

  In the data collection accompanying each RF excitation, as described above, the intensity of the dephase pulse DP applied to the gradient magnetic field RO in the readout direction is changed, and the phase dispersion (degree of dispersion) of the spin is different each time. For this reason, different spin phase dispersion is reflected in the echo data collected through the collection accompanying the four RF excitations.

  The host computer 6 is prep. When the scan is completed, image reconstruction is instructed to the arithmetic unit 10 (step S26), and these reconstructed images are displayed (steps S27 and S28). This display image is four images of the same slice. These images reflect image quality states in which the degree of phase dispersion in total of four types depending on the dephase pulse DP is changed.

  Therefore, the operator designates an image in which the blood flow image is most clearly drawn from the four displayed images via the input device 13. The designation information is read by the host computer 6 (steps S29 and S30), and then the intensity of the dephase pulse DP when the image corresponding to the designation information is collected is determined by the host computer 6 (step S31). ). Next, the intensity of the dephasing pulse DP is set as the intensity of the dephasing pulse in the pulse sequence of the subsequent imaging scan (step S32).

  For this reason, the imaging scan is performed in this manner. This is executed under various parameters and scanning conditions set by the operator, including the intensity of the dephasing pulse DP set through the scan. For example, prep. The imaging scan is executed with a pulse sequence based on the three-dimensional FASE method including the intensity of the dephase pulse DP set through the scan. Thereby, collection of echo data, image reconstruction, image processing, and image display are performed.

  Therefore, an image obtained by this imaging scan has excellent rendering ability, which is captured in an optimal dispersion state of blood flow spins and eliminates inconveniences such as a decrease in signal value due to the flow void phenomenon.

  That is, prior prep. By scanning, an appropriate flow void value (intensity ratio of the dephasing pulse to the reading gradient magnetic field pulse) in the reading direction of the imaging region can be reliably grasped, and a three-dimensional imaging scan reflecting the grasping result can be performed. .

  Note that prep. The blood flow velocity can also be measured from the signal value of the acquired data of the scan.

(2. Prep. Scan for effective TEeff time)
Returning to the processing of FIG. 3, the selection of the remaining variable parameters will be described. If NO is determined in step S3 in FIG. 3, it is determined in step S5 whether or not the variable parameter = effective TEeff time. If this determination is YES, as shown in FIG. 5, a pulse sequence is set in which the value of the effective TEeff time is changed in data collection associated with each of a plurality of RF excitations (step S6). The reason why the effective TEeff time is changed is to change the contrast of the image of the imaging region. As the pulse sequence, a pulse train based on a two-dimensional FASE method, EPI method, FSE method, or the like is preferable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the effective TEeff time is changed to 20 ms, 40 ms, 80 ms, 120 ms, 180 ms, and 240 ms.

  When this pulse sequence is executed, a plurality of images with different contrasts are displayed as the effective TEeff time is changed (steps S21 to S28). For this reason, the operator can set the effective TEeff time of the pulse sequence used in the imaging scan optimally and efficiently by designating an image having a desired contrast (steps S29 to S32).

  This prep. The T2 relaxation time can be measured by matching the readout time in the scan.

(3. Prep. Scan for flow compensation)
If NO is determined in step S5 in FIG. 3, it is determined in step S7 whether variable parameter = flow compensation pulse. If the determination is YES, as shown in FIG. 6, a pulse sequence is set in which the intensity of the flow compensation pulse is changed in data collection associated with each of a plurality of RF excitations (step S8). The flow compensation pulse is continuously added before and after the readout gradient magnetic field pulse in the time axis direction. This flow compensation pulse is used to change the intensity of the N / 2 artifact component generated in the readout frequency direction RO in the imaging region by changing its intensity. As the pulse sequence, a pulse train based on a two-dimensional FASE method, EPI method, FSE method, or the like is preferable. The example of FIG. 6 shows a pulse train based on the FASE method. The intensity of the flow compensation pulse FCP is changed in the collection of echo data accompanying a plurality of RF excitations constituting the scan. For example, this pulse sequence is executed in, for example, a single slice single phase, but may be executed in a multi slice single phase.

  When this pulse sequence is executed, a plurality of images with different N / 2 artifact components in the reading direction are displayed in accordance with the change in the intensity of the flow compensation pulse FCP (steps S21 to S28). For this reason, the operator can set the intensity of the flow compensation pulse of the pulse sequence used in the imaging scan optimally and efficiently by designating a desired image (steps S29 to S32).

(4. Prep. Scan for inversion time TI)
If NO is determined in step S7 of FIG. 3, it is determined in step S9 whether or not the variable parameter = TI time. If this determination is YES, as shown in FIG. 7, a pulse sequence in which the value of the TI time is changed in data collection associated with each of a plurality of RF excitations is set (step S10). The reason for changing the effective TI time is to change the contrast of the image of the imaging region. As the pulse sequence, a pulse train based on the FASE method, the EPI method, the FSE method, etc. in combination with a two-dimensional inversion recovery (IR) method is suitable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the TI time is changed to 100 ms, 200 ms, 300 ms, 400 ms, 500 ms, and 600 ms.

  When this pulse sequence is executed, a plurality of images with different contrasts are displayed as the TI time is changed (steps S21 to S28). Therefore, the operator can optimally and efficiently set the TI time of the pulse sequence used in the imaging scan by designating an image with a desired contrast (steps S29 to S32).

  This prep. The T1 relaxation time can be measured by matching the readout times in the scan.

(5. Prep. Scan for echo interval ETS)
If NO is determined in step S9 in FIG. 3, it is determined in step S11 whether or not variable parameter = ETS time. If this determination is YES, as shown in FIG. 8, a pulse sequence in which the value of the ETS time is changed in data collection associated with each of a plurality of RF excitations is set (step S12). The reason for changing the ETS time is to change the contrast of the image of the imaging region or the blurring in the phase encoding direction. As the pulse sequence, a pulse train based on the FASE method, the EPI method, the FSE method, etc. in combination with a two-dimensional inversion recovery (IR) method is suitable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the ETS time is changed to 5 ms, 5.5 ms, 6 ms, 6.5 ms, 7 ms, and 7.5 ms.

  When this pulse sequence is executed, a plurality of blur images with different contrast or phase encoding directions are displayed in accordance with the change of the ETS time (steps S21 to S28). Therefore, the operator can optimally and efficiently set the ETS time of the pulse sequence used in the imaging scan by designating a desired contrast or blurred image (steps S29 to S32).

  This prep. The T2 relaxation time can be measured by matching the readout time in the scan.

(6. Prep. Scan for flipping fat suppression pulses)
If NO is determined in step S11 in FIG. 3, it is determined in step S13 whether or not the variable parameter = flip angle of the fat suppression pulse FatSat. If this determination is YES, as shown in FIG. 9, a pulse sequence in which the value of the flip angle is changed in data collection associated with each of a plurality of RF excitations is set (step S14). The reason why the value of the flip angle of the fat suppression pulse FatSat is changed is to change the contrast accompanying the fat suppression of the image of the imaging region. As the pulse sequence, a pulse train based on the FASE method, the EPI method, the FSE method, etc. in combination with a two-dimensional inversion recovery (IR) method is suitable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the flip angle of the fat suppression pulse FatSat is changed to 90 °, 95 °, 100 °, 105 °, 110 °, and 120 °.

  When this pulse sequence is executed, a plurality of contrast images with different fats are displayed as the flip angle value is changed (steps S21 to S28). Therefore, the operator can optimally and efficiently set the flip angle of the fat suppression pulse FatSat of the pulse sequence used in the imaging scan by designating an image having a desired contrast (steps S29 to S32).

(7. Prep scan for TI after fat suppression)
When it is determined NO in step S13 of FIG. 3, it is determined in step S15 whether or not the inversion time TI after applying the variable parameter = fat suppression pulse FatSat. If this determination is YES, as shown in FIG. 10, a pulse sequence is set in which the value of the TI time is changed in data collection associated with each of a plurality of RF excitations (step S16). The reason for changing the value of the TI time after application of the fat suppression pulse FatSat is to change the contrast associated with the fat suppression of the image of the imaging region. As the pulse sequence, a pulse train based on a two-dimensional FASE method, EPI method, FSE method, or the like is preferable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the TI time after applying the fat suppression pulse FatSat = 10 ms, 12 ms, 14 ms, 16 ms, 18 ms, and 20 ms.

  When this pulse sequence is executed, a plurality of images having different contrasts are displayed as the TI time value is changed (steps S21 to S28). For this reason, the operator can optimally and efficiently set the TI time after applying the fat suppression pulse FatSat of the pulse sequence used in the imaging scan by designating an image with a desired contrast (steps S29 to S32).

(8. Prep.scan for MT pulse flip angle)
When it is determined NO in step S15 of FIG. 3, it is determined in step S17 whether or not the variable parameter = the flip angle of the MT pulse. If this determination is YES, as shown in FIG. 11, a pulse sequence is set in which the value of the flip angle (intensity) of the MT pulse is changed in data collection associated with each of a plurality of RF excitations (step S18). The reason for changing the value of the flip angle is to change the contrast based on the MT (Magnetization Transfer: MTC) effect of the image of the imaging region. As the pulse sequence, a pulse train based on a two-dimensional FASE method, EPI method, FSE method, or the like is preferable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the MT pulse flip angle is changed to 90 °, 95 °, 100 °, 105 °, 110 °, and 120 °.

  When this pulse sequence is executed, a plurality of images having different contrasts are displayed as the value of the flip angle of the MT pulse is changed (steps S21 to S28). For this reason, the operator can set the flip angle of the MT pulse of the pulse sequence used in the imaging scan optimally and efficiently by designating an image having a desired contrast (steps S29 to S32).

(9. prep.scan for flip angle of refocus pulse)
If NO is determined in step S17 in FIG. 3, it is determined in step S19 whether or not the variable parameter = the flip angle of the refocus pulse. If this determination is YES, as shown in FIG. 12, a pulse sequence is set in which the flip angle (intensity) value of the refocus pulse is changed in data collection associated with each of a plurality of RF excitations (step S20). The reason for changing the value of the flip angle is to change the contrast of the image of the imaging region. As the pulse sequence, a pulse train based on a two-dimensional FASE method, EPI method, FSE method, or the like is preferable. For example, one prep. In the collection of echo data associated with a total of six RF excitations constituting the scan, the flip angle Flop of the refocus pulse is changed to 180 °, 170 °, 160 °, 150 °, 140 °, and 130 °.

  When this pulse sequence is executed, a plurality of images with different contrasts are displayed as the value of the flip angle of the refocus pulse is changed (steps S21 to S28). For this reason, the operator can optimally and efficiently set the flip angle of the refocus pulse of the pulse sequence used in the imaging scan by designating an image having a desired contrast (steps S29 to S32).

  In the above-described embodiment, the variable parameter is always selected one by one and the value is variable. However, this need not necessarily be the case. An example is shown in FIG. In the figure, the flow void dephase pulse DP and the flow compensation flow compensation pulse FCP are selected together as variable parameters, and both of these values are changed, and the prep. It shows how to apply both pulses when scanning. As a result, a single prep. By scanning, a plurality of images corresponding to the plurality of times can be collected simultaneously for both the flow void and the flow compensation. This saves acquisition time while allowing the optimum intensity to be set independently for both pulses.

  In the pulse train shown in FIG. 13, the application is started from the flow compensation pulse FCP. On the contrary, the application may be started from the dephase pulse DP (in this case, the arrow shown in FIG. Represented).

  As a result, the operator does not need time and effort to estimate the flow void value based on experience or through thought and error in the field, as in the past. In other words, trial scanning performed by trial and error becomes unnecessary. As a result, the total imaging time required for one patient is reliably shortened, patient throughput is improved, and patient SAR can be suppressed. In addition, the burden on the operator is reduced as compared with the prior art.

  By the way, in each of the above-described embodiments and modifications thereof, the purpose is MR angiography (MRA) based on non-contrast imaging. However, the imaging target is not limited to only a blood vessel, and any target such as a tissue running in a fibrous form. May be.

DESCRIPTION OF SYMBOLS 1 Magnet 2 Static magnetic field power supply 3 Gradient magnetic field coil unit 4 Gradient magnetic field power supply 5 Sequencer 6 Controller 7 RF coil 8T Transmitter 8R Receiver 10 Arithmetic unit 11 Storage unit 12 Display 13 Input device 16 Sound generator 17 ECG sensor 18 ECG unit 19 Sound generator

Claims (3)

In a magnetic resonance imaging apparatus that executes an imaging scan for obtaining an MR image of a subject,
An input means for inputting designation information of a desired parameter among a plurality of parameters of a pulse sequence used in the imaging scan;
Based on the data collected by the preparation scan , among the plurality of parameters of the pulse sequence used in the imaging scan, a plurality of preparation images corresponding to a plurality of different parameter amounts for a desired parameter designated by the input means are obtained. Preparation image generating means for generating;
Imaging scan execution means for reflecting a parameter amount of a specific preparation image of the plurality of preparation images in the imaging scan and executing an imaging scan in which the parameter amount is reflected;
With
The preparatory scan is a two-dimensional scan;
The imaging scan is a three-dimensional scan based on an electrocardiogram synchronization method,
The magnetic resonance imaging apparatus according to claim 1, wherein the plurality of preparation images corresponding to the plurality of different parameter amounts are based on data obtained by performing a preparation scan with the same delay time. The desired parameter is a spin inversion time in the subject,
The pulse sequence used in the imaging scan is a pulse sequence including an IR pulse applied before an RF excitation pulse.
The magnetic resonance imaging apparatus according to claim 1. The desired parameter is the intensity of the gradient field dephasing pulse;
The pulse sequence used in the imaging scan is a pulse sequence for non-contrast MRA including the gradient magnetic field dephasing pulse.
The magnetic resonance imaging apparatus according to claim 1.

Images