JP4443918B2 - Magnetic resonance imaging apparatus and signal processing method of magnetic resonance imaging apparatus - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus and a signal processing method for a magnetic resonance imaging apparatus that obtain a rendered image of a myocardial infarction region and an extracted image of the outline of the entire myocardium in a single imaging when diagnosing myocardial infarction.

  Conventionally, a magnetic resonance imaging (MRI) apparatus 1 as shown in FIG. 12 is used as a monitoring apparatus in a medical field (see, for example, Patent Document 1).

  The MRI apparatus 1 uses the gradient magnetic field coils 3x, 3y, and 3z of the gradient magnetic field coil unit 3 in the imaging region of the subject P set inside the cylindrical static magnetic field magnet 2 that forms a static magnetic field. Nuclear magnetic field generated by excitation by forming a gradient magnetic field in the direction of the axis and Z-axis and transmitting a radio frequency (RF) signal from an RF (Radio Frequency) coil 4 to magnetically resonate nuclear spins in the subject P. This is an apparatus for reconstructing an MR image of a subject P using a resonance (NMR) signal.

  That is, a static magnetic field is previously formed in the static magnetic field magnet 2 by the static magnetic field power source 5. Further, in response to a command from the input device 6, the sequence controller control means 7 gives a sequence, which is signal control information, to the sequence controller 8. The sequence controller 8 is connected to each gradient magnetic field coil 3x, 3y, 3z according to the sequence. The transmitter 10 which gives a high frequency signal to the magnetic field power supply 9 and the RF coil 4 is controlled. For this reason, a gradient magnetic field is formed in the imaging region, and a high-frequency signal is transmitted to the subject P.

  Then, the NMR signal generated along with the excitation of the nuclear spin in the subject P is received by the RF coil 4 and given to the receiver 11 to be converted into digitized raw data. Further, the raw data is taken into the sequence controller control means 7 via the sequence controller 8, and the sequence controller control means 7 arranges the raw data in the k space (Fourier space) formed in the raw data database 12. Then, the image reconstructing means 13 performs Fourier transform on the raw data arranged in the k space and gives it to the display device 14 to display it, thereby reconstructing the image of the subject P.

  At this time, a current is supplied from the shim coil power supply 16 to the cylindrical shim coil 15 coaxially provided inside the static magnetic field magnet 2 so that the static magnetic field is made uniform.

  As a method for diagnosing myocardial infarction or ischemic heart disease using such an MRI apparatus 1, there is conventionally a myocardial delayed contrast method (Late Enhancement or Delayed Enhancement) (for example, see Non-Patent Document 1).

  In myocardial delayed contrast imaging, after injecting an MR contrast agent into a subject P, a myocardial infarction region is acquired by collecting T1-weighted images by an inversion recovery (IR) method (inversion recovery method) after a certain delay time. It is a method to specify.

  That is, in imaging by IR sequence, an IR prepulse is applied to the RF coil 4 before applying a high-frequency signal for NMR signal acquisition, and the longitudinal magnetization component in the z-axis direction of the nuclear spin is reversed. Then, an RF pulse for data acquisition is applied in the process in which longitudinal magnetization is restored by longitudinal relaxation (T1 relaxation) of nuclear spins, and an NMR signal that is an echo signal is measured.

  Here, the recovery speed from the inversion state of the longitudinal magnetization component of the nuclear spin depends only on the time constant T1 when the nuclear spin returns to the steady state by longitudinal relaxation. Therefore, by adjusting the inversion time TI (inversion recovery time) that is the time from the IR pre-pulse to the 90 ° pulse, T1 enhancement is performed using the difference of T1 in each tissue, and an image of a specific tissue is obtained. Can be obtained with emphasis.

  On the other hand, when gadolinium Gd is administered to the subject P as an MR contrast agent, the extracellular fluid distribution volume of the MR contrast agent increases from that of normal myocardium after a certain delay time due to tissue edema or myocardial cell membrane damage in the myocardial infarction region. To do. Since the MR contrast agent has the property of shortening T1, if the subject P is photographed at high speed by the IR method after the MR contrast agent is administered to the subject P, the myocardial infarction lesion may be rendered as a clear high signal area. known.

  Moreover, since IR imaging by myocardial delayed contrast imaging is performed while breathing is stopped, it is necessary to perform imaging at high speed. Therefore, conventionally, a segment k-space method (segment) in which k-space is divided into a plurality of segments, raw data for a plurality of phase encodings is collected at a time in synchronization with an electrocardiogram waveform, and an image is captured with high temporal resolution. Raw data is collected by the k-space method).

  That is, the ECG signal shown in FIG. 13 (a) obtained by the electrocardiogram (ECG) sensor 17 while breathing is stopped is given to the ECG unit 18, and is sent to the IR sequence generation means 19 via the sequence controller control means 7. Given. As shown in FIG. 13B, the IR sequence generation means 19 has an IR prepulse 20 after a certain delay time Td from the R wave of the ECG signal, and a plurality of sub-sequences after the inversion time (TI) from the IR prepulse 20. An IR sequence having a data acquisition sequence 21 composed of the sequence 21a is generated.

  At this time, the IR prepulse 20 is generated by the IR prepulse generation unit 24, while the data acquisition sequence 21 is generated by the data acquisition sequence generation unit 25 and synthesized by the IR sequence generation unit 19. The data acquisition sequence 21 includes a low frequency component collection block 22 and a high frequency component block 23.

  At this time, as shown in the graph showing the change of the longitudinal magnetization Mz with respect to the time t in FIG. 13C, the inversion time (TI) is such that the longitudinal magnetization A1 of the myocardial infarction region A1 is a positive value and the other normal myocardium. The time when the longitudinal magnetization A2 is close to zero is set, and the NMR signal from the myocardial infarction region is emphasized.

The IR sequence generation means 19 gives the IR sequence to the sequence controller 8 via the sequence controller control means 7. The sequence controller 8 controls the gradient magnetic field and the high-frequency signal according to the IR sequence, so that the myocardial infarction region image is T1-weighted and taken at high speed.
JP 2001-149341 A (refer to page 1 to page 11, FIG. 1) INNERVISION (15.3) 2000 P.I. 59-66 Diagnosis of ischemic heart disease by contrast-enhanced MRI Sakuma et al.

  Conventionally, in evaluating myocardial viability, it is important to measure the ratio of myocardial infarction area to the total myocardial volume, or what percentage of myocardial wall thickness the myocardial infarction area is recognized (wall thickness progress). Is described in “Actual Usage of Contrast Agent for MRI in the Heart Region”, “The Journal of Japan Medical Association 2002, Vol. 62, No. 12, p. 682-689”.

  The volume of the myocardial infarction region can be obtained by counting the number of voxels having a pixel value equal to or greater than a predetermined threshold in the T1-weighted image of the heart region and multiplying by the voxel volume.

  However, since the T1-weighted image is obtained with imaging parameters such that the normal myocardial pixel value is as close to 0 as possible, the boundary between the outer myocardium and the periphery can be extracted except when the fat around the myocardium is large. Often difficult.

  That is, since it is necessary to make the pixel value in the normal myocardium close to 0 and contrast between the myocardial infarction region and other regions, the intensity of the NMR signal from the normal myocardium must be made as null (no signal) as possible. For this reason, the intensity of the NMR signal from the myocardium and the surrounding lung fields is reduced to the same extent, and the boundary between the outer myocardium and the surrounding area, that is, the contour of the outer wall of the myocardium, is obtained using an image obtained by myocardial delayed imaging. It is difficult to measure the volume and wall thickness of the whole myocardium by extracting.

  In particular, when a pixel value method that automatically detects a tissue contour by detecting a change in the pixel value of an adjacent voxel by software is applied, there is a high possibility that accurate contour extraction will not be performed.

  Therefore, conventionally, when measuring the volume of myocardial infarction area or the degree of progress of wall thickness by measuring the volume of myocardium and myocardial wall thickness, myocardial delayed contrast imaging is used to extract myocardial contours. In addition to the imaging by the myocardial delay imaging method, the myocardial signal is zero in the imaging method by the pulse sequence obtained by removing the inversion pulse from the pulse sequence of the myocardial delay imaging method or the inversion time (TI) of the pulse sequence of the myocardial delay imaging method. A method is employed in which imaging is performed such that the pixel value of the myocardium is higher than the surroundings by shifting from the set value.

  As a result, imaging for extracting the outline of the myocardium is required separately from imaging of the myocardial infarction region, leading to an increase in examination time. Furthermore, the examination of ischemic heart disease by myocardial delayed imaging using the MRI apparatus 1 is usually performed in combination with imaging such as myocardial perfusion imaging and cine imaging. Such various types of imaging are usually performed while the patient who is the subject P is breathing stopped, so the patient needs to hold his / her breath multiple times in each imaging, This is an increase in labor.

  Furthermore, when the imaging is divided into a plurality of times, the respiratory stop state of the subject P is different in each imaging, so that the slice position shifts and accurate measurement becomes difficult.

  Therefore, in a cardiac examination such as an ischemic heart disease examination using the MRI apparatus 1, the entire examination time including the work of positioning the subject P and the test scan is shortened, the number of imaging is reduced, and the burden on the subject P is reduced. And improvement of measurement accuracy is desired.

  The present invention has been made to cope with such a conventional situation, and a magnetic resonance imaging apparatus and a magnetism capable of obtaining a rendered image of a myocardial infarction region and an extracted image of the outline of the entire myocardium by one imaging. It is an object of the present invention to provide a signal processing method for a resonance imaging apparatus.

In order to achieve the above object, a magnetic resonance imaging apparatus according to the present invention includes an IR prepulse generating means for generating an IR prepulse, and the longitudinal magnetization of the myocardium from the IR prepulse is near zero , as described in claim 1. and the data obtaining sequence generating means for generating data acquisition sequence after inversion time TI1 such that, as the inversion time TI1 data acquisition sequence generated by the data obtaining sequence generating means from a common IR prepulse In contrast, for the whole myocardial data for generating the whole myocardial data sequence after the inversion time TI2 such that the absolute value of the longitudinal magnetization of the myocardium becomes larger than the absolute value of the longitudinal magnetization of the myocardium after the inversion time TI1 . Sequence generating means, the IR pre-pulse, It is characterized in that a IR sequence generating means for generating an IR sequence according to the multi-echo method by combining the data acquisition sequence and myocardial entire data sequence.

In order to achieve the above object, the magnetic resonance imaging apparatus according to the present invention collects images using the inversion recovery method in synchronization with the cardiac phase of the subject as described in claim 5. In the magnetic resonance imaging apparatus, after applying an inversion recovery pulse in synchronization with the cardiac time phase of the subject, the high frequency component data of the image is collected, and the longitudinal magnetization of the myocardium is near zero Different from the first inversion recovery time and the first inversion recovery time, the absolute value of the longitudinal magnetization of the myocardium is larger than the absolute value of the longitudinal magnetization of the myocardium in the first inversion recovery time. collection means for collecting a plurality of data of low-frequency component of the image at the same slice position once in the reverse recovery time of each a plurality of different, including at least two of the inversion recovery time It is characterized in further comprising an image generating means for generating a plurality of images from the data of the data each of the low-frequency component collected in the different delay times the high frequency component.

According to the signal processing method of the magnetic resonance imaging apparatus of the present invention, in order to achieve the above-mentioned object, as described in claim 6, the longitudinal magnetization of the myocardium is determined to be near zero from the common IR prepulse by the IR method. The inversion time TI1 has a data acquisition sequence, and unlike the inversion time TI1 , the absolute value of the longitudinal magnetization of the myocardium is larger than the absolute value of the longitudinal magnetization of the myocardium after the inversion time TI1. After the inversion time TI2 such that the IR sequence by the multi-echo method having the whole myocardial data sequence is generated.

  In the magnetic resonance imaging apparatus and the signal processing method of the magnetic resonance imaging apparatus according to the present invention, the rendered image of the myocardial infarction region and the extracted image of the outline of the entire myocardium can be obtained by one imaging. It is possible to shorten the overall time, reduce the number of imaging, reduce the burden due to the subject's breathing stop, and improve the measurement accuracy due to the difference in the subject's breathing stop state.

  Embodiments of a magnetic resonance imaging apparatus and a signal processing method of the magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention.

  The magnetic resonance imaging apparatus 30 does not show a cylindrical static magnetic field magnet 31 that forms a static magnetic field, and a shim coil 32, a gradient magnetic field coil unit 33, and an RF coil 34 that are provided inside the static magnetic field magnet 31. It is built in the gantry.

  The magnetic resonance imaging apparatus 30 includes a control system 35 and an electrocardiography (ECG) measurement system 36.

  The control system 35 includes a static magnetic field power supply 37, a gradient magnetic field power supply 38, a shim coil power supply 29, a transmitter 40, a receiver 41, a sequence controller 42, and a computer 43. The gradient magnetic field power source 38 of the control system 35 includes an X-axis gradient magnetic field power source 38x, a Y-axis gradient magnetic field power source 38y, and a Z-axis gradient magnetic field power source 38z. The computer 43 includes an input device 44, a display device 45, an arithmetic device 46, and a storage device 47.

  The ECG measurement system 36 includes an ECG sensor 48 and an ECG unit 49.

  The static magnetic field magnet 31 of the magnetic resonance imaging apparatus 30 is connected to a static magnetic field power source 37 and has a function of forming a static magnetic field in the imaging region by a current supplied from the static magnetic field power source 37. A cylindrical shim coil 32 is coaxially provided inside the static magnetic field magnet 31. The shim coil 32 is connected to the shim coil power supply 29, and is configured such that a current is supplied from the shim coil power supply 29 to the shim coil 32 to make the static magnetic field uniform.

  The gradient magnetic field coil unit 33 includes an X-axis gradient magnetic field coil 33x, a Y-axis gradient magnetic field coil 33y, and a Z-axis gradient magnetic field coil 33z, and is formed in a cylindrical shape inside the static magnetic field magnet 31. A bed 50 is provided inside the gradient magnetic field coil unit 33 as an imaging region, and the subject P is set on the bed 50. The RF coil 34 may not be built in the gantry but may be provided near the bed 50 or the subject P.

  The gradient magnetic field coil unit 33 is connected to a gradient magnetic field power supply 38. The X-axis gradient magnetic field coil 33x, Y-axis gradient magnetic field coil 33y, and Z-axis gradient magnetic field coil 33z of the gradient magnetic field coil unit 33 are respectively an X-axis gradient magnetic field power supply 38x, a Y-axis gradient magnetic field power supply 38y, and a Z-axis. It is connected to the gradient magnetic field power supply 38z.

  The currents supplied from the X-axis gradient magnetic field power supply 38x, the Y-axis gradient magnetic field power supply 38y, and the Z-axis gradient magnetic field power supply 38z to the X-axis gradient magnetic field coil 33x, the Y-axis gradient magnetic field coil 33y, and the Z-axis gradient magnetic field coil 33z, respectively. In the imaging region, a gradient magnetic field Gx in the X-axis direction, a gradient magnetic field Gy in the Y-axis direction, and a gradient magnetic field Gz in the Z-axis direction can be formed, respectively.

  The RF coil 34 is connected to the transmitter 40 and the receiver 41. The RF coil 34 receives a high-frequency signal from the transmitter 40 and transmits it to the subject P, and receives an NMR signal generated by excitation by the high-frequency signal of the nuclear spin inside the subject P and receives it in the receiver 41. Has the function to give.

  On the other hand, the ECG sensor 48 of the ECG measurement system 36 is provided on the body surface of the subject P, and has a function of receiving an ECG signal and supplying it to the ECG unit 49 as an electrical signal.

  The ECG unit 49 has a function of performing various processes such as digitization on the electrical signal of the ECG signal received from the ECG sensor 48 and outputting the result to the sequence controller 42 and the computer 43.

  The sequence controller 42 of the control system 35 is connected to the gradient magnetic field power supply 38, the transmitter 40, the receiver 41, and the ECG unit 49. The sequence controller 42 has control information necessary for driving the gradient magnetic field power supply 38, the transmitter 40 and the receiver 41, for example, operation control information such as the intensity, application time, and application timing of the pulse current to be applied to the gradient magnetic field power supply 38. And the gradient magnetic field power supply 38, the transmitter 40 and the receiver 41 are driven in accordance with the stored predetermined sequence to drive the X-axis gradient magnetic field Gx, the Y-axis gradient magnetic field Gy, and the Z-axis gradient magnetic field. It has the function of generating Gz and high frequency signals.

  Further, the sequence controller 42 receives raw data which is a digitized NMR signal from the receiver 41 and receives a digitized ECG signal from the ECG unit 49 and supplies it to the computer 43. Configured.

  For this reason, the transmitter 40 is provided with a function of giving a high frequency signal to the RF coil 34 based on the control information received from the sequence controller 42, while the receiver 41 is required for the NMR signal received from the RF coil 34. A function for generating raw data that is a digitized NMR signal and a function for supplying the generated raw data to the sequence controller 42 are provided by performing the signal processing and A / D conversion.

  In addition, by executing the program stored in the storage device 47 of the computer 43 by the arithmetic device 46, the computer 43 is provided with various functions and a sequence creation system 63 is configured. However, the computer 43 may be configured by providing a specific circuit regardless of the program.

  FIG. 2 is a functional block diagram of the magnetic resonance imaging apparatus 30 shown in FIG.

  The computer 43 functions as a sequence controller control means 60, an image reconstruction means 61, and a raw data database 62 by a program.

  Furthermore, the sequence creation system 63 is configured by the sequence creation program being read and executed by the arithmetic unit 46 of the computer 43. The sequence creation system 63 includes IR prepulse generation means 64, data acquisition sequence generation means 65, whole myocardial data sequence generation means 66, IR sequence generation means 67, and data distribution means 68.

  Here, when diagnosing myocardial infarction or ischemic heart disease using the magnetic resonance imaging apparatus 30, in order to identify the myocardial infarction region, after injecting an MR contrast agent into the subject P, IR is detected after a certain delay time. Imaging by a myocardial delayed contrast method that collects T1-weighted images by a sequence is performed.

  In imaging by an IR sequence, a 180 ° pulse is applied as an IR prepulse (inversion recovery pulse) before an RF pulse for data acquisition is applied to the RF coil 4 as a high frequency signal. Then, the longitudinal magnetization component in the z-axis direction of the nuclear spin is reversed by the IR prepulse, and the longitudinal magnetization is recovered by longitudinal relaxation (T1 relaxation) that releases the energy absorbed by the excited nuclear spin to the surrounding molecules as thermal vibration energy. In the process, an RF pulse is applied, and an NMR signal that is an echo signal is measured.

  At this time, the speed of recovery from the inversion state of the longitudinal magnetization component depends only on the time constant T1 when the nuclear spin returns to the steady state by longitudinal relaxation. For this reason, by adjusting the time (inversion time) from the 180 ° pulse to the RF pulse, it is possible to obtain an image of a specific tissue by performing T1 enhancement using the difference in T1 in each tissue. .

  Here, since the Gd MR contrast agent administered to the subject P in the myocardial delayed contrast method has an effect of shortening the longitudinal relaxation time T1, it is strong from the region where the blood to which the MR contrast agent is administered is distributed. An NMR signal is generated. Therefore, when MR contrast agent is administered to the subject P and high-speed imaging is performed by the IR method, the extracellular fluid distribution volume of the MR contrast agent is normal after a certain delay time due to tissue edema or myocardial cell membrane damage in the myocardial infarction region. Since it increases compared to the myocardium, the myocardial infarction region is depicted as a high-signal region of a clear NMR signal. When the raw data obtained by the IR method is reconstructed, a T1-weighted image with a contrast enhanced according to the longitudinal relaxation time T1 of the myocardial infarction region is obtained.

  Therefore, the sequence creation system 63 has a function of generating an IR sequence for imaging by such myocardial delayed contrast imaging and giving it to the sequence controller control means 60.

  The IR prepulse generation unit 64 of the sequence creation system 63 has a function of generating an IR prepulse of the IR sequence and supplying it to the IR sequence generation unit 67. Here, the IR pre-pulse is generated in synchronization with the cardiac time phase of the ECG signal received from the ECG unit 49. That is, the IR prepulse generation means 64 is configured to receive an ECG signal from the sequence controller control means 60 and generate an IR prepulse that excites the entire imaging region after a certain delay time Td from each R wave of the ECG signal. Is done.

  The data acquisition sequence generation means 65 is a data acquisition sequence for selectively exciting a slice section of interest and receiving an NMR signal in the RF coil 4 after a certain waiting time from each IR prepulse, that is, the inversion time TI1. Are respectively generated and provided to the IR sequence generation means 67 and the data distribution means 68.

  Here, since IR imaging by myocardial delayed contrast imaging is executed under respiratory stop in synchronization with an electrocardiographic waveform, it is desired to increase the speed. Therefore, it is called Segmented FFE (fast field echo) or Segmented Turbo FLASH, which divides k-space into a plurality of segments, collects raw data for a plurality of phase encodings at a time for each segment, and captures an image with high time resolution. Raw data is collected by a segment k-space method.

  In the case of data acquisition by the segment k-space method, the data acquisition sequence is composed of a plurality of subsequences. Then, within a single segment (heartbeat) in the ECG signal, NMR signals are collected in order of phase encoding in the order called centric by each subsequence. For this reason, the subsequence on the high frequency component collection side is arranged in order from the subsequence on the low frequency component collection side in the data acquisition sequence. For this reason, the data acquisition sequence can be divided into a low-frequency component collection block and a high-frequency component collection block.

  The whole myocardial data sequence generating means 66 has a function of generating a whole myocardial data sequence after the inversion time TI2 from the IR prepulse, and a function of giving the generated whole myocardial data sequence to the IR sequence generating means 67 and the data distributing means 68. And have. In the case of data acquisition by the segment k-space method, the myocardial whole data sequence generation means 66 receives, for example, a low frequency component collection sequence composed of sub-sequences for collecting data of low frequency components by phase encoding. A function of generating as a sequence for whole myocardium data is provided.

  The low frequency component collection sequence generated as the whole myocardial data sequence by the whole myocardial data sequence generation unit 66 is included in the low frequency component collection block of the data acquisition sequence generated by the data acquisition sequence generation unit 65. It can be generated by duplicating subsequences and placing them in any order. However, each sub-sequence included in the low-frequency component collection block of the data acquisition sequence and each sub-sequence included in the low-frequency component collection sequence are not necessarily the same.

  Here, the inversion time TI2 set by the whole myocardial data sequence generation unit 66 is a time when the low frequency component collection sequence is different from the data acquisition sequence generated by the data acquisition sequence generation unit 65, for example, the data acquisition sequence. Is set longer than the inversion time TI1.

  The IR sequence generation unit 67 combines the IR prepulse, the data acquisition sequence, and the low frequency component collection sequence received from the IR prepulse generation unit 64, the data acquisition sequence generation unit 65, and the whole myocardial data sequence generation unit 66, respectively. It has a function of generating an IR sequence and a function of giving the generated IR sequence to the sequence controller control means 60.

  The data distribution unit 68 collects the low frequency components of the data acquisition sequence based on the data acquisition sequence received from the data acquisition sequence generation unit 65 and the low frequency component acquisition sequence received from the whole myocardial data sequence generation unit 66. K-space (Fourier space) for the image of the myocardial infarction region formed in the raw data database 62 by receiving the raw data collected according to the block, the high-frequency component collecting block and the low-frequency component collecting sequence from the sequence controller control means 60 ) And k-space for images of the entire myocardium.

  The data distribution unit 68 has a function of providing the image reconstruction unit 61 with identification information between raw data for acquiring images of the myocardial infarction region and raw data for acquiring images of the entire myocardium arranged in the raw data database 62. Have.

  For this reason, each raw data generated in the receiver 41 is stored in the raw data database 62. That is, in the raw data database 62, the first k space for the myocardial infarction region image is formed and the raw data for the myocardial infarction region image is arranged, while the second k for the entire myocardial image is arranged. A space is formed and raw data for an image of the entire myocardium is arranged.

  The sequence controller control means 60 has a function of controlling driving by providing the sequence controller 42 with required sequence information such as the IR sequence received from the IR sequence generation means 67 based on information from the input device 44 or other components. Have. For example, the sequence controller control means 60 gives sequence information to the sequence controller 42 so that the NMR signal can be received by the RF coil 34 in synchronization with the electrocardiogram waveform (cardiac time phase) of the ECG signal received from the ECG unit 49. Configured to be controlled.

  The image reconstruction means 61 has a function of reconstructing a tomographic image of the subject P and displaying it on the display device 45 by fetching the raw data from the raw data database 62 and performing predetermined signal processing. That is, the image reconstructing means 61 performs a two-dimensional or three-dimensional Fourier transform process on the raw data arranged in the k space of the raw data database 62 and gives it to the display device 45 to thereby convert the real space image from the raw data. Is configured to be reconfigurable.

  At this time, the image reconstruction means 61 receives identification information from the data distribution means 68 as to whether the raw data to be reconstructed is for acquiring an image of a myocardial infarction region or for acquiring an image of the entire myocardium. An image of the myocardial infarction region is reconstructed from the raw data arranged in the k space for the image of the myocardial infarction region, while an image of the entire myocardium is reconstructed from the raw data arranged in the k space for the image of the entire myocardium. Configured as follows.

  With the configuration as described above, the magnetic resonance imaging apparatus 30 as a whole collects data for generating an image by an IR sequence multiple times at different inversion times, and generates a plurality of images from each collected data. Function as image generation means.

  Next, the operation of the magnetic resonance imaging apparatus 30 will be described.

  FIG. 3 is a flowchart showing a procedure when a tomographic image of the subject P is picked up by the magnetic resonance imaging apparatus 30 shown in FIG. 1, and reference numerals with numerals in the figure indicate each step of the flowchart.

  FIG. 4 is a diagram showing an example of an IR sequence generated by the sequence creation system 63 of the magnetic resonance imaging apparatus 30 shown in FIG.

  First, in step S1, an MR contrast agent such as gadolinium Gd is injected into the subject P set in advance on the bed 50 in order to capture and identify the myocardial infarction region of the subject P by myocardial delayed imaging. After a certain delay time, the ECG measurement system 36 obtains an ECG signal of the subject P as shown in FIG. That is, the ECG sensor 48 receives the ECG signal of the subject P and supplies it as an electrical signal to the ECG unit 49. The ECG unit 49 performs various processes such as digitization processing on the electrical signal of the ECG signal and performs a sequence controller. 42 and sequence controller control means 60.

  Next, in step S2, the IR prepulse generation means 64 receives the ECG signal from the sequence controller control means 60, and IR prepulse I for reversing the longitudinal magnetization in the IR method after a certain delay time Td from the R wave of the ECG signal. Is generated. For this reason, the IR prepulse generation means 64 generates the IR prepulse I shown in FIG. Then, the IR prepulse generation means 64 gives the generated IR prepulse I to the IR sequence generation means 67.

  Next, in step S3, the data acquisition sequence generation means 65 generates a data acquisition sequence S1 for applying a high frequency signal for data acquisition to the RF coil 4 after the inversion time TI1 from the IR prepulse I.

  The data acquisition sequence S1 can be composed of an arbitrary subsequence S2 such as a single or plural SE (spin echo) sequence or FE (field echo) sequence as shown in FIG. In the case of data acquisition by Segmented FFE, which is one of the k-space methods, the data acquisition sequence S1 includes a plurality of FE sequences.

  In the case of data acquisition by Segmented FFE, in the data acquisition sequence S1, the FE sequence on the high frequency component collection side is arranged as the subsequence S2 in order from the FE sequence on the low frequency component collection side. For this reason, the data acquisition sequence S1 can be divided into a low-frequency component collection block S3 and a high-frequency component collection block S4.

  In addition, the inversion time TI1 is set to an appropriate time in order to emphasize the NMR signal from the myocardial infarction region by T1.

  FIG. 5 is a diagram showing the relationship between longitudinal magnetization and inversion time TI in the IR method.

  In FIG. 5, the vertical axis represents the longitudinal magnetization Mz, and the horizontal axis represents time t. The solid line is a curve A3 showing the temporal change in the longitudinal magnetization Mz of the nuclear spin in the component having a short longitudinal relaxation time T1, and the dotted line is the longitudinal magnetization Mz of the nuclear spin in the tissue having a long longitudinal relaxation time T1. It is curve A4 which shows the time change of.

When a 180 ° pulse is applied as an IR pre-pulse I prior to a high-frequency signal for data acquisition from the RF coil 4, the longitudinal magnetization component Mz in the z-axis direction of the nuclear spin is reversed. Then, the longitudinal magnetization Mz of tissue, the longitudinal magnetization M _IR negative value longitudinal magnetization component is inverted when the IR prepulse I is applied. Further, the longitudinal magnetization Mz of the tissue increases with time due to longitudinal relaxation and becomes a positive value again, and returns to the longitudinal magnetization M0 in the steady state before the application of the IR prepulse I. At this time, the longitudinal magnetization Mz in the structure having a short longitudinal relaxation time T1 returns to the steady state M0 earlier than the longitudinal magnetization Mz in the structure having a long longitudinal relaxation time T1. For this reason, the longitudinal magnetization Mz in the inversion time TI has a larger value in the longitudinal magnetization Mzs in the structure having a short longitudinal relaxation time T1 than in the longitudinal magnetization Mzl in the structure having a long longitudinal relaxation time T1.

  Therefore, a stronger NMR signal can be obtained from the myocardial infarction region whose longitudinal relaxation time T1 is shortened by the action of the Gd-based MR contrast agent administered to the subject P than the other myocardial regions. At this time, the contrast between the myocardial infarction region and the other myocardial regions can be enhanced by suppressing the NMR signal from the myocardial region other than the myocardial infarction region to null (no signal) as much as possible.

  Therefore, as shown in the diagram showing the temporal change in longitudinal magnetization shown in FIG. 4C, the longitudinal magnetization of the myocardial infarction region is positive, while the longitudinal magnetization of the region other than the myocardial infarction region is near zero. Is set as the inversion time TI1.

  Then, the data acquisition sequence generation unit 65 gives the generated data acquisition sequence S1 to the IR sequence generation unit 67 and the data distribution unit 68.

  Next, in step S4, the whole myocardium data sequence generation means 66 generates a low frequency component collection sequence S5 for collecting low frequency component data after the inversion time TI2 from the IR prepulse I, for example, a data acquisition sequence generation means. The sub-sequences S2 included in the low-frequency component collection block S3 in the data acquisition sequence S1 generated in 65 are arranged in an arbitrary order.

  Here, the inversion time TI2 set by the whole myocardium data sequence generation means 66 is different from the inversion time TI1, for example, longer than the inversion time TI1, and the data acquisition sequence generation means 65 generates data. It is set so as to be after the use sequence S1. As a result, as shown in FIG. 4C, the longitudinal magnetization Mz changes with time t, and at the inversion time TI2, the longitudinal magnetization A5 in the region other than the myocardial infarction region has a positive value, and the myocardial infarction. The longitudinal magnetization of the region is larger than the longitudinal magnetization A6 of the region other than the myocardial infarction region.

  Then, the data acquisition sequence generation unit 65 supplies the generated low frequency component collection sequence S5 to the IR sequence generation unit 67 and the data distribution unit 68.

  Next, in step S5, the IR sequence generation unit 67 receives the IR prepulse I, the data acquisition sequence S1 and the low level received from the IR prepulse generation unit 64, the data acquisition sequence generation unit 65, and the whole myocardial data sequence generation unit 66, respectively. By synthesizing the frequency component collection sequence S5, an IR sequence shown in FIG. 4B is generated.

  FIG. 6 is a diagram showing an example of an IR sequence generated by the magnetic resonance imaging apparatus 30 shown in FIG.

  As shown in FIG. 6, the IR sequence has a data acquisition sequence S1 after the inversion time TI1 from the IR prepulse I, and has a low frequency component collection sequence S5 after the inversion time TI2. The data acquisition sequence S1 includes a low frequency component collection block S3 and a high frequency component collection block S4.

  Further, the low-frequency component collection block S3, the high-frequency component collection block S4, and the low-frequency component collection sequence S5 of the data acquisition sequence S1 are each composed of a plurality of sub-sequences S2. FIG. 6 shows an example in which the K space is divided into eight segments, and the data acquisition sequence S1 is composed of eight subsequences S2.

  Each sub-sequence S2 is used to form a high-frequency signal S6 transmitted from the RF coil 34 to the subject P at intervals of the repetition time TR, a slice gradient magnetic field GS, a read gradient magnetic field GR, and a phase encoding gradient magnetic field GE. It consists of pulse sequences S7, S8, S9 given to the gradient magnetic field power supply 38. The example of FIG. 6 is an example in which the subsequence S2 is an FE sequence, but the subsequence S2 may be configured by other sequences.

  By such each sub-sequence S2, the echo S10 is received as an NMR signal by the RF coil 34.

  Then, the IR sequence generation means 67 gives the IR sequence generated in this way to the sequence controller control means 60.

  Next, in step S6, raw data is collected according to the IR sequence generated by the IR sequence generating means 67, and the raw data collected by the data distributing means 68 is formed in the raw data database 62 and the first k-space and the first data. Distributed in two k-spaces.

  That is, a static magnetic field is formed in the imaging region by supplying a current from the static magnetic field power source 37 to the static magnetic field magnet 31 in advance to form a static magnetic field in the imaging region and supplying a current from the shim coil power source 29 to the shim coil 32. Is made uniform.

  Then, an operation command based on the IR sequence is given from the input device 44 to the sequence controller control means 60. Therefore, the sequence controller control means 60 gives the IR sequence to the sequence controller 42. The sequence controller 42 drives the gradient magnetic field power supply 38, the transmitter 40, and the receiver 41 according to the IR sequence to thereby set an X-axis gradient magnetic field Gx, a Y-axis gradient magnetic field Gy, and a Z-axis gradient in the imaging region where the subject P is set. A magnetic field Gz is formed and a high frequency signal is generated.

  At this time, the X-axis gradient magnetic field Gx, the Y-axis gradient magnetic field Gy, and the Z-axis gradient magnetic field Gz formed by the gradient coil are mainly a phase encode (PE) gradient magnetic field, a read (RO) gradient magnetic field, and a slice (SL). ) Used as a gradient magnetic field. For this reason, regularity appears in the spin rotation direction of the nucleus inside the subject P, and the X coordinate and Y coordinate, which are two-dimensional position information in the slice formed in the Z-axis direction by the gradient magnetic field for SL, are PE The phase change amount and the frequency change amount of the spin of the nucleus inside the subject P are respectively converted by the gradient magnetic field for RO and the gradient magnetic field for RO.

  Then, a high frequency signal is given from the transmitter 40 to the RF coil 34 according to the IR sequence, and the high frequency signal is transmitted from the RF coil 34 to the subject P. That is, first, a 180 ° pulse is applied as an IR prepulse I from the RF coil 34 to the subject P. For this reason, the longitudinal magnetization of the nuclear spin of the subject P is reversed, and the longitudinal magnetization of the nuclear spin in each tissue of the subject P increases with time due to longitudinal relaxation. At this time, the longitudinal relaxation time T1 of the myocardial infarction region is shortened by the action of the Gd MR contrast agent administered to the subject P, and the longitudinal magnetization of the myocardial infarction region increases faster than other myocardial regions.

  Further, according to the data acquisition sequence S1 of the IR sequence, the longitudinal magnetization in the myocardial infarction region has a positive value, and the inversion time TI1 in which the longitudinal magnetization in the myocardial region other than the myocardial infarction region is near zero, It is transmitted from the RF coil 34 to the subject P. Therefore, the NMR signal generated by nuclear magnetic resonance in the myocardial infarction region is emphasized from the NMR signals from other myocardial regions and received by the RF coil 34.

  In addition, at the inversion time TI2 after the high-frequency signal for data acquisition is transmitted to the subject P, the high-frequency signal for low-frequency component collection is transmitted from the RF coil 34 to the subject P in accordance with the low-frequency component collection sequence S5 of the IR sequence. Sent to. At the inversion time TI2, since it is a positive value not only in the myocardial infarction region but also in other myocardial regions, a low frequency component NMR signal is received by the RF coil 34 from the entire myocardial region.

  Further, the receiver 41 receives the NMR signal from the RF coil 34 and executes various signal processing such as pre-amplification, intermediate frequency conversion, phase detection, low-frequency amplification, and filtering. And the receiver 41 produces | generates the raw data which are the NMR signals of digital data by A / D-converting an NMR signal. The receiver 41 gives the generated raw data to the sequence controller 42.

  The sequence controller 42 gives the raw data received from the receiver 41 to the sequence controller control means 60, and the sequence controller control means 60 gives the raw data to the data distribution means 68. Then, the data distribution unit 68 arranges the raw data in the k space formed in the raw data database 62.

  Here, in the raw data database 62, a first k space for reconstructing a rendered image of a myocardial infarction region and a second k space for reconstructing an extracted image of the outline of the entire myocardium are formed. Is done. The data distribution means 68 first collects the raw data collected according to the low frequency component collection block S3 and the high frequency component collection block S4 of the data acquisition sequence S1, based on the data acquisition sequence S1 received from the data acquisition sequence generation means 65. Are arranged in the first k space for the image of the myocardial infarction region.

  In addition, IR imaging by myocardial delayed contrast imaging is performed while breathing is stopped, and raw data is collected by the segment k-space method in order to speed up imaging. For this reason, the first k space and the second k space formed in the raw data database 62 are each divided into a plurality of segments, and a plurality of phase encoded raw data are synchronized at a time with the electrocardiogram waveform. Collected.

  FIG. 7 is a diagram for explaining a method of arranging raw data in the k space in IR imaging by the segment k-space method.

  In the IR imaging by the segment k-space method, the IR sequence as shown in FIG. 7B is generated by the IR sequence generator 67 based on the R wave of the ECG signal of the subject P as shown in FIG. Then, raw data is collected by the sequence controller 42.

  In other words, the IR prepulse I is generated by the IR prepulse generation means 64 so as to be after a certain delay time Td from the R wave of the ECG signal of the subject P measured by the ECG measurement system 36, and the inversion time is generated from the IR prepulse I. A data acquisition sequence generation unit 65 generates a data acquisition sequence S1 having a plurality of sub-sequences S2 such as FE sequences so as to be after TI1. Further, the myocardial whole data sequence generation means 66 generates a low frequency component collection sequence S5 having a plurality of subsequences S2 such as FE sequences so as to be after the inversion time TI2 from the IR prepulse I.

  Then, the sequence controller 42 controls the gradient magnetic field formed by the gradient magnetic field power supply 38 and the high-frequency signal transmitted from the transmitter 40 in accordance with the IR sequence as shown in FIG. Raw data is collected from each of the subsequences S2.

  On the other hand, as shown in FIG. 7C, the raw data database 62 includes a first k-space divided into a plurality of segments according to phase encoding in order to reconstruct a rendered image of the myocardial infarction region. It is formed. For example, when it is necessary to collect 128 phase-encoded raw data, it is divided into 8 segments. And between two IR prepulses I, that is, within a single segment (heartbeat) in the ECG signal, raw data corresponding to each segment in k-space is sequentially collected from each subsequence S2 of the data acquisition sequence S1. . At this time, the raw data is collected in the order of phase encoding in an order called “centric”.

  That is, in the data acquisition sequence S1, the low frequency component collection block S3 collects raw data having a small absolute value of the phase encoding amount and a low spatial frequency, that is, raw data arranged in the central portion of the k space, In the component collection block S4, raw data having a large absolute value of the phase encoding amount and a large spatial frequency, that is, raw data arranged in a portion away from the center of the k space is collected. Then, the raw data collected in the order of phase encoding by each sub-sequence S2 is arranged in order from the segment on the center side of the k space by the data distribution means 68.

  Therefore, when it is necessary to collect 128 phase-encoded raw data, according to the segment k-space method divided into 8 segments, it is possible to collect 8 phase-encoded raw data per one heartbeat. Therefore, the collection of all raw data can be completed in 128/8 = 16 heartbeats. As a result, high-speed imaging can be performed while breathing is stopped, and an image of the subject P can be obtained in which artifacts due to respiratory body movement are suppressed.

  Next, the data distribution means 68 collects according to the high frequency component collection block S4 and the low frequency component collection sequence S5 of the data acquisition sequence S1, based on the low frequency component collection sequence S5 received from the whole myocardium data sequence generation means 66. The obtained raw data is arranged in the second k space for the image of the entire myocardium.

  That is, as shown in FIG. 7D, as in the first k space, the raw data database 62 includes a plurality of segments according to phase encoding in order to reconstruct an extracted image of the contour of the entire myocardium. A second k-space divided into is formed. Then, the data distribution unit 68 outputs the raw data collected by the sub-sequence S2 included in the high-frequency component collection block S4 and the sub-sequence S2 included in the low-frequency component collection sequence S5 in the data acquisition sequence S1 to the second k Place in space.

  As a result, the raw data with a low spatial frequency collected by the sub-sequence S2 included in the low-frequency component collection sequence S5 is arranged by the data distribution means 68 in the central portion of the second k space, while the data acquisition sequence Raw data with a large spatial frequency collected by the subsequence S2 included in the high-frequency component collection block S4 in S1 is arranged in a portion away from the center of the second k-space.

  In the case of two-dimensional (2D) imaging, an image covering the entire left ventricle can be obtained by repeating the above imaging a plurality of times. Furthermore, in the case of 3D imaging in which the inspection speed is increased as compared with 2D imaging, imaging with phase encoding in the slice direction is added. In this case, the number of segment divisions in the phase encoding direction is reduced, and raw data is collected at an imaging time during which breathing can be stopped. For example, when the number of segments in the phase encoding direction is 2 and the number of slices is 10, an image of an area covering the entire left ventricle is obtained with 2 × 10 = 20 heartbeats.

  Then, the data distribution means 68 provides the image reconstruction means 61 with identification information between the raw data for acquiring the myocardial infarct region image arranged in the k space of the raw data database 62 and the raw data for acquiring the image of the entire myocardium. give.

  In step S7, the image reconstruction unit 61 receives identification information from the data distribution unit 68 that the raw data arranged in the first k space is for acquiring an image of the myocardial infarction region, and receives the raw data database. The raw data for the image of the myocardial infarction region arranged in the first k space formed in 62 is subjected to a two-dimensional or three-dimensional Fourier transform process and given to the display device 45, whereby the myocardial infarction is obtained from the raw data. Reconstruct the real space image of the region.

  Here, the raw data for the image of the myocardial infarction region arranged in the first k space is that the raw data of the entire myocardium approaches zero by the data acquisition sequence S1 corresponding to the inversion time TI1, while the myocardial infarction region Is the raw data with T1 weighted, the outline of the myocardial infarction region is drawn. That is, a contour image of the myocardial infarction region having a contrast given by the time of the inversion time TI1 is obtained.

  Next, in step S8, the image reconstruction means 61 receives identification information from the data distribution means 68 that the raw data arranged in the second k space is for image acquisition of the entire myocardium, and receives the raw data database 62. The two-dimensional or three-dimensional Fourier transform processing is performed on the raw image data for the entire myocardium arranged in the second k-space formed in FIG. Reconstruct the aerial image.

  Here, the raw data for the entire myocardium image arranged in the center portion of the second k space is positive by the longitudinal relaxation of the raw data for the entire myocardium by the low frequency component acquisition sequence S5 corresponding to the inversion time TI2. Since this is raw data collected at the time, the outline of the entire myocardium is drawn. That is, a contour image of the entire myocardium having a contrast given by the time of the inversion time TI2 is obtained.

  That is, since the signal value of the raw data from the entire myocardium is longitudinally relaxed from zero to the positive direction according to the time difference between the inversion time TI1 and the inversion time TI2, the raw data arranged in the second k space Among them, the signal value from the normal myocardium is a positive value with respect to the signal value from the surrounding lung field tissue. At this time, the inversion time TI2 depends on the length of the data acquisition sequence S1 at the inversion time TI1, but is different from the contour image of the myocardial infarction region because there is a delay of several tens to several hundreds of milliseconds. A contour image of the entire myocardium with T1 contrast can be obtained.

  The contrast of the image obtained by reconstructing the raw data is dominated by the raw data arranged in the central portion of the k space having a low spatial frequency. Therefore, at the time of the inversion time TI2 for collecting signals for the contour image of the entire myocardium, the raw data having a high spatial frequency of the high frequency component hardly contributes to the image contrast. For this reason, by arranging the raw data collected by the subsequence S2 included in the high-frequency component collection block S4 of the data acquisition sequence S1 in a portion away from the center of the second k space, the myocardial infarction region image And raw data can be shared for images of the entire myocardium.

  As a result, by collecting images having two different contrasts, an image of a myocardial infarction region in which the image value of the normal myocardium is close to 0 and an image of the entire myocardium in which the normal myocardium has a positive image value in one imaging, It is possible to extract the outline of the myocardium from the image of the entire myocardium and measure the thickness of the heart wall as well as the image of the myocardial infarction region.

  In the magnetic resonance imaging apparatus 30 as described above, since the rendered image of the myocardial infarction region and the extracted image of the outline of the entire myocardium can be obtained by one imaging, the entire examination time can be shortened and the number of imaging can be reduced. It is possible to reduce the burden caused by stopping the breathing of the subject P and improve the measurement accuracy due to the difference in the breathing stop state of the subject P.

  In other words, even if it is necessary to measure the proportion occupied by the myocardial infarction region with respect to the entire myocardium or when it is necessary to measure the proportion of the myocardial infarction region to the heart wall thickness of the myocardium, It is not necessary to separately perform image pickup for extracting. As a result, the total examination time can be shortened, the number of imaging can be reduced, and the burden caused by stopping the breathing of the subject P can be reduced.

  Conventionally, in many cases, an image of the myocardial infarction region and an image of the entire myocardium are obtained by two imaging operations in the respiratory stop state, but it is difficult to make the breathing stop position the same between the two imaging operations. For this reason, there is a possibility that the slice position is shifted between the images and accurate measurement cannot be performed. On the other hand, according to the magnetic resonance imaging apparatus 30, since an image of the myocardial infarction region and an image of the entire myocardium can be obtained by one stop of breathing, it is possible to perform a more accurate measurement while avoiding a positional shift due to the breathing stop state. Can do.

  In general, an IR sequence used in IR imaging by the segment k-space method is configured by providing a plurality of sub-sequences S2 between R waves for speeding up. There is time to provide a new subsequence S2. For this reason, even if the low frequency component collection sequence S5 is newly provided in the IR sequence, the time between R waves can be effectively utilized without affecting the number of segments in the k space.

  8 is a diagram showing a first modification of the IR sequence generated by the magnetic resonance imaging apparatus 30 shown in FIG. 1, and FIG. 9 is a second example of the IR sequence generated by the magnetic resonance imaging apparatus 30 shown in FIG. It is a figure which shows a modification.

  As shown in FIGS. 8 and 9, not only the low frequency component collection sequence S5 is generated after the data acquisition sequence S1, but also the low frequency component collection sequence S5 is generated before the data acquisition sequence S1 or data. You may produce | generate so that it may exist between the low frequency component collection block S3 and the high frequency component collection block S4 of the acquisition sequence S1. Further, three or more low-frequency component collection blocks S3 may be generated.

  FIG. 10 is a diagram showing a third modification of the IR sequence generated by the magnetic resonance imaging apparatus 30 shown in FIG.

  As shown in FIG. 10, the data acquisition sequence S1 is generated as it is as the whole myocardial data sequence S11 without dividing the data acquisition sequence S1 into the low frequency component acquisition block S3 and the high frequency component acquisition block S4. May be.

  In this case, the whole myocardial data sequence generation means 66 has a function of generating a whole myocardial data sequence S11 composed of a subsequence S2 for collecting data of all frequency components similar to the data acquisition sequence S1. Provided.

  FIG. 11 is a diagram showing a fourth modification of the IR sequence generated by the magnetic resonance imaging apparatus 30 shown in FIG.

  As shown in FIG. 11, the data acquisition sequence generation means 65 may comprise the data acquisition sequence S1 as a sub-sequence S2 that collects data for a single k space without using the segment k-space method. Good.

  In this case, the whole myocardial data sequence generation means 66 has a function of generating the whole myocardial data sequence S11 with a single sub-sequence S2 for collecting frequency component data corresponding to the data acquisition sequence S1. It is done.

1 is a configuration diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention. The functional block diagram of the magnetic resonance imaging apparatus shown in FIG. The flowchart which shows the procedure at the time of imaging the tomographic image of a subject with the magnetic resonance imaging apparatus shown in FIG. The figure which shows an example of IR sequence produced | generated by the sequence creation system of the magnetic resonance imaging apparatus shown in FIG. The figure which shows the relationship between the longitudinal magnetization and inversion time TI in IR method. FIG. 3 is a diagram showing an example of an IR sequence generated by the magnetic resonance imaging apparatus 30 shown in FIG. 1. The figure explaining the arrangement | positioning method of the raw data to k space in IR imaging by the segment k-space method. The figure which shows the 1st modification of IR sequence produced | generated by the magnetic resonance imaging apparatus 30 shown in FIG. The figure which shows the 2nd modification of IR sequence produced | generated by the magnetic resonance imaging apparatus 30 shown in FIG. The figure which shows the 3rd modification of IR sequence produced | generated by the magnetic resonance imaging apparatus 30 shown in FIG. The figure which shows the 4th modification of IR sequence produced | generated by the magnetic resonance imaging apparatus 30 shown in FIG. The block diagram of the conventional magnetic resonance imaging apparatus. The figure which shows an example of the conventional IR sequence.

Explanation of symbols

30 Magnetic Resonance Imaging Device 31 Magnet for Static Magnetic Field 32 Shim Coil 33 Gradient Magnetic Field Coil Unit 34 RF Coil 36 ECG Measurement System 37 Static Magnetic Field Power Supply 38 Gradient Magnetic Field Power Supply 39 Shim Coil Power Supply 40 Transmitter 41 Receiver 42 Sequence Controller 43 Computer 44 Input Device 45 Display device 46 Arithmetic device 47 Storage device 48 ECG sensor 49 ECG unit 50 Bed 50
60 Sequence controller control means 61 Image reconstruction means 62 Raw data database 63 Sequence creation system 64 IR prepulse generation means 65 Data acquisition sequence generation means 66 Myocardial whole data sequence generation means 67 IR sequence generation means 68 Data distribution means S1 Data acquisition Sequence S2 Subsequence S3 Low frequency component collection block S4 High frequency component collection block S5 Low frequency component collection sequence

Claims (9)

IR prepulse generation means for generating an IR (Inversion Recovery) prepulse ;
Data acquisition sequence generation means for generating a data acquisition sequence after the inversion time TI1 such that the longitudinal magnetization of the myocardium is near zero from the IR prepulse ;
Unlike the inversion time TI1 of the data acquisition sequence generated by the data acquisition sequence generation means from a common IR prepulse , the absolute value of the longitudinal magnetization of the myocardium is the absolute value of the longitudinal magnetization of the myocardium after the inversion time TI1. A myocardial whole data sequence generation means for generating a whole myocardial data sequence after an inversion time TI2 that becomes a larger value ,
IR sequence generation means for generating an IR sequence by a multi-echo method by synthesizing the IR prepulse, the data acquisition sequence and the whole myocardial data sequence ;
A magnetic resonance imaging apparatus comprising: 2. The magnetic resonance imaging apparatus according to claim 1, wherein the data acquisition sequence and the whole myocardial data sequence are each composed of a plurality of subsequences by a segment k-space method. The data acquisition sequence is composed of a plurality of subsequences by the segment k-space method, while the myocardial whole data sequence is composed of a plurality of subsequences for collecting data of low frequency components. 2. The magnetic resonance imaging apparatus according to claim 1, wherein a frequency component acquisition sequence is used. The data acquisition sequence is composed of a plurality of sub-sequences by the segment k-space method, while the whole myocardial data sequence is composed of a plurality of sub-sequences for collecting data of low frequency components. The raw data collected according to the data acquisition sequence was collected in the k-space for the myocardial infarct region image according to the high frequency component collection block of the data acquisition sequence and the low frequency component collection sequence. 2. The magnetic resonance imaging apparatus according to claim 1, further comprising data distribution means for distributing and arranging the raw data in k space for images of the entire myocardium. In a magnetic resonance imaging apparatus that collects images using an inversion recovery method in synchronization with the cardiac time phase of a subject ,
After applying an inversion recovery pulse in synchronization with the cardiac time phase of the subject, the high frequency component data of the image is collected, and a first inversion recovery time such that the longitudinal magnetization of the myocardium is near zero and At least a second reversal recovery time that is different from the first reversal recovery time and that the absolute value of the longitudinal magnetization of the myocardium is larger than the absolute value of the longitudinal magnetization of the myocardium in the first reversal recovery time. A collecting means for collecting the low frequency component data of the image at the same slice position a plurality of times in each of a plurality of different inversion recovery times including :
Image generation means for generating a plurality of images from each of the low-frequency component data collected at the different delay times and the high-frequency component data ;
A magnetic resonance imaging apparatus comprising: It has a data acquisition sequence after an inversion time TI1 in which the longitudinal magnetization of the myocardium becomes near zero from a common IR prepulse by an IR (Inversion Recovery) method. Unlike the inversion time TI1 , the absolute value of the longitudinal magnetization of the myocardium An IR sequence by a multi-echo method having a sequence for whole myocardial data is generated after an inversion time TI2 whose value is larger than the absolute value of longitudinal magnetization of the myocardium after the inversion time TI1. Signal processing method for magnetic resonance imaging apparatus. 7. The signal processing method of the magnetic resonance imaging apparatus according to claim 6, wherein each of the data acquisition sequence and the whole myocardial data sequence is composed of a plurality of subsequences by a segment k-space method. The data acquisition sequence is composed of a plurality of sub-sequences by the segment k-space method, while the whole myocardial data sequence is composed of a plurality of sub-sequences for collecting data of low frequency components. The signal processing method of the magnetic resonance imaging apparatus according to claim 6, wherein the frequency component acquisition sequence is used. The data acquisition sequence is composed of a plurality of sub-sequences by the segment k-space method, while the whole myocardial data sequence is composed of a plurality of sub-sequences for collecting data of low frequency components. The raw data collected according to the data acquisition sequence was collected in the k-space for the myocardial infarct region image according to the high frequency component collection block of the data acquisition sequence and the low frequency component collection sequence. 7. The signal processing method for a magnetic resonance imaging apparatus according to claim 6, further comprising the step of distributing and arranging the raw data in k space for images of the entire myocardium.

Images