JP2007203106A - Magnetic resonance imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten examination time of the whole heart examination and reduce the burden given to an examinee. <P>SOLUTION: This MRI device for obtaining an MRI image of the examinee by an IR method for synchronous electrocardiography has a signal collection means for obtaining MR signals by setting different TIs for a plurality of slices in a region of interest of the examinee which is set in advance, an image generating means for generating the plurality of MRI images corresponding to respective TIs by reconstituting the MR signals, and an image display means for displaying the plurality of MRI images generated by the image generating means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an MRI apparatus.

Magnetic resonance imaging (MRI) excites a nuclear spin of a subject tissue placed in a static magnetic field with a high-frequency signal having the Larmor frequency, and an image is generated from the magnetic resonance signal generated by the excitation. This is an image diagnostic method to be reconstructed.

An MRI apparatus is an image diagnostic apparatus using a magnetic resonance signal detected from within a living body, and can obtain a lot of diagnostic information such as biochemical information and functional diagnostic information as well as anatomical diagnostic information. It has become indispensable in the field of diagnostic imaging. In particular, contrast-enhanced MR of the heart
I has recently made great progress and has already developed to a level widely used in clinical settings for the diagnosis of myocardial ischemia and myocardial infarction.

In diagnosis of ischemic heart disease using an MRI apparatus, an MR contrast agent (for example, Gd-
DTPA (gadolinium diethylenetriamine pentaacetic acid) was injected, and after a predetermined time, I
There is a myocardial delayed contrast method that identifies a myocardium at an infarcted site by collecting T1-weighted images using the R method (Inversion Recovery method). In myocardial infarction, the extracellular fluid distribution volume of MR contrast agent is said to be larger than that of normal myocardium due to tissue edema and damage to the myocardial cell membrane.

This Gd-based MR contrast agent is already known to have an effect of shortening the longitudinal relaxation time (T1) in MRI imaging. Therefore, a non-selective IR pulse (hereinafter referred to as IR pulse) is irradiated to the heart region of the subject to reverse the longitudinal magnetization of the myocardial tissue by 180 degrees, and the RF pulse is irradiated after a predetermined waiting time TI (inversion time: inversion time). If you take a T1-weighted image,
It is possible to emphasize and image only a portion where a short contrast medium for 1 hour exists.

Here, the waiting time TI is used to improve the contrast between the myocardial infarction and the normal myocardium.
Is a process in which the longitudinal magnetization of the nuclear spins in the myocardial infarction portion and the normal myocardium reversed by the IR pulse recovers from minus to plus based on the respective longitudinal relaxation times T1, and at the timing when the longitudinal magnetization of the normal myocardium becomes near zero. It is desirable to set. At this time, the longitudinal magnetization of the myocardial infarction portion mixed with a contrast agent having a short T1 has already been restored to a positive value, and therefore, only the myocardial infarction portion is emphasized by collecting T1-weighted images after TI. It is possible to display it as an image.

In this radiography for MRI diagnosis of ischemic heart disease, various high-speed radiography methods are introduced.
Segmented Fast Field Echo with IR pre-pulse added for R-MRI high-speed imaging
Or a high-speed imaging method called Segmented Turbo FLASH in which the k-space is divided into a plurality of segments. At this time, imaging under respiratory arrest is executed in synchronization with the electrocardiogram waveform.
The high-speed imaging MRI using this myocardial delayed imaging method is expected to be useful in the diagnosis of myocardial viability because the distribution of myocardial infarction lesions is very clearly depicted.
Sakuma, et al., “Diagnosis of ischemic heart disease by contrast-enhanced MRI”, INNERVISION (15 ・ 13) 2000 P.59-66)

However, in order to display the myocardium of the infarcted region with high contrast as described above, T
Although it is a condition to set the I time to an optimum value, this value cannot always be set constant. That is, it has been confirmed in clinical practice that the time until the longitudinal magnetization of the myocardium becomes zero varies depending on the contrast agent dose, the time after administration, the subject tissue, and the like. For this reason, in order to set the inversion time TI as the time when the signal intensity of the normal myocardium, that is, the longitudinal magnetization becomes zero, in the test imaging performed before the main imaging for each subject or for each imaging, TI
After obtaining the optimum TI from the image obtained by using the optimum TI as a parameter, IR
-Performing MRI actual photography.
FIG. 14 shows a conventional test imaging method for obtaining an optimum TI. A predetermined slice cross section for generating an MRI image is selected, and a range where TI time can be taken, for example, 200 mse.
Five types of TI are set in a range of c to 400 msec in steps of 50 msec. As the imaging method in this case, for example, “Segmented Fast Field Echo Method with IR Prepulse Added” is used.

First, as shown in FIG. 14A, an IR pulse is applied to the entire region of interest after a predetermined time Td from the R wave of the electrocardiogram waveform, and 200 msec set as the first TI time (TI1) from this IR pulse. After that, a signal is read by applying an RF pulse. However, at this time, M
The position of the slice cross section where the R signal is received is determined by three gradient magnetic fields described later.

Further, while maintaining the condition of TI = TI1 (200 msec), the MR signal is read a plurality of times (Nx times) while changing the phase encoding, and the Nx MR signal obtained at this time is reconstructed to obtain T
An MRI image is obtained when I = TI1. However, this Nx MR signal is collected over N heartbeats of M in one heartbeat period, and one MRI image is generated from this Nx (= M * N) MR signal. For example, M = 8, N = 16, and Nx = 128. The subject stops breathing during the collection period of the Nx MR signal in order to reduce the influence of the body motion on the image. Next, MRI images are collected in the same procedure even when TI = TI2 (250 msec) to TI5 (400 msec) at other TI times. An image having the lowest normal myocardial signal intensity is selected from five images obtained by setting five different TI times, and the TI time at that time is obtained. Subsequently, using the TI time, main imaging is performed in which phase encode data that is substantially the same as the phase encode number Nx is collected for each MRI image. The above Segmente
Details of the d Fast Field Echo method will be described in the embodiment of the present invention.

As described above, in the conventional setting method of the optimum TI, it is necessary to collect MR signals for each N heartbeat period in a state where breathing is stopped for each TI, and to repeat such collection for five TIs. Therefore, according to this method, not only much time is required for collecting MR signals, but also the above five breathing stops are a heavy burden on the subject.

In particular, in the examination of ischemic heart disease by MRI, since myocardial delayed contrast is usually performed in combination with myocardial perfusion imaging, cine imaging, etc., the above breath holding increases the burden on the subject and fatigue.

An object of the present invention is to shorten the examination time of the whole heart examination and reduce the burden on the subject.

In order to solve the above problems, an MRI apparatus according to the present invention according to claim 1 is an MRI apparatus that obtains an MRI image by an IR method synchronized with an electrocardiographic waveform obtained from a subject.
During a heartbeat period, signal acquisition means for acquiring MR signals by setting different TIs for a plurality of slices of the region of interest of the subject set in advance, and reconstructing the MR signals, respectively. An image generation unit that generates a plurality of MRI images corresponding to each TI and an image display unit that displays the plurality of MRI images generated by the image generation unit are provided.

The MRI apparatus of the present invention according to claim 2 is an MRI apparatus that obtains an MRI image by an IR method synchronized with an electrocardiographic waveform obtained from a subject, and has a plurality of inversion times (TI).
TI setting means for setting) and MR over a plurality of heartbeats for a predetermined slice for each TI
Signal acquisition means for continuously acquiring signals and acquiring MR signals; and a plurality of MRI corresponding to each TI by reconstructing the plurality of MR signals collected over the plurality of heartbeats.
Image generating means for generating an image, and the plurality of MRIs generated by the image generating means
An image display means for displaying an image is provided.

Furthermore, the MRI apparatus of the present invention according to claim 9 is an MRI apparatus for obtaining an MRI image by an IR method synchronized with an electrocardiographic waveform obtained from a subject, and for a predetermined slice of a region of interest of the subject. A signal collecting means for collecting MR signals by setting different TIs;
Image generating means for reconstructing the R signal to generate a plurality of MRI images corresponding to each TI, and desired TI setting means for setting a desired TI based on the plurality of MRI images; It is characterized by having.

Therefore, according to the present invention, the examination time is shortened, and the breath holding time of the subject is also shortened. For this reason, the pain given to the subject can be greatly reduced.

As described above, according to the present invention, the examination time is shortened and the breath-holding time of the subject is shortened, so that it is possible to provide an MRI apparatus that can greatly reduce the pain given to the subject.

(First embodiment)
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a schematic configuration of the entire MRI apparatus.

This MRI apparatus includes a static magnetic field generator 1 and a gradient magnetic field generator 2 that generate a magnetic field, and an RF
A transmission / reception unit 3 that transmits and receives pulse signals, a control unit 4 that controls the entire system, a high-speed calculation / storage unit 5 that performs image reconstruction and image storage, a bed 8 on which a subject 11 is placed, and an electrocardiogram measurement A unit 7, an input unit 22, and a display unit 21 are provided.

The static magnetic field generation unit 1 includes a main magnet 13 that is, for example, a superconducting magnet, and a static magnetic field power source 26 that supplies current to the main magnet 13, and forms a strong static magnetic field around the subject 11.

The gradient magnetic field generator 2 includes X, Y, and Z axis direction gradient magnetic field coils 14 that are orthogonal to each other, and a gradient magnetic field power supply 25 that supplies current to these coils.

The gradient magnetic field power supply 25 is supplied with a gradient magnetic field control signal by the sequence control circuit 24 of the control unit 4 to encode the space in which the subject 11 is placed. That is, by controlling the pulse current supplied from the gradient magnetic field power supply 25 to the X, Y, Z axis gradient magnetic field coil 14 based on this signal, the gradient magnetic fields in the X, Y, Z axis directions are synthesized and orthogonal to each other. Slice selection gradient magnetic field Gs, phase encoding gradient magnetic field Ge, and readout (frequency encoding)
It is possible to arbitrarily set the gradient magnetic field Gr. The gradient magnetic field in each direction is superimposed on the static magnetic field and applied to the subject 11.

The transmission / reception unit 3 includes an irradiation coil 15 for irradiating the subject 11 with an RF pulse, a reception coil 16 for receiving and detecting an MR signal, and a transmitter 17 connected to these coils.
And a receiver 18 is provided. However, the irradiation coil 15 and the receiving coil 16 may be separated.

The transmitter 17 is controlled by a sequence control circuit 24 described later. The irradiation coil 15 is driven by an RF pulse current having the same frequency as the magnetic resonance frequency determined by the static magnetic field strength of the main magnet 13 and modulated by the selective excitation waveform, and the subject 11 is irradiated with the RF pulse.
The receiver 18 performs A / D conversion after performing signal processing such as intermediate frequency conversion, phase detection, and filtering on the signal received as the MR signal by the receiving coil 16.

The control unit 4 includes a main control circuit 23 and a sequence control circuit 24. Main control circuit 2
Reference numeral 3 has a CPU and a memory, and has a function of controlling the entire apparatus, and in particular, a shooting start instruction signal input from the input unit 22, information on a shooting method and a pulse sequence, and image display It has a storage function for temporarily storing format information and the like, and based on such information, the sequence control circuit 24 stores pulse sequence information (for example, the gradient magnetic field coil 1).
4 and information on the intensity, application time, application timing, etc. of the pulse current applied to the irradiation coil 15. In addition, based on an image selected by the operator from a plurality of images obtained by test photographing, an optimum TI is read from the image information and stored in the internal memory.

The sequence control circuit 24 includes a CPU and a memory, stores the pulse sequence information sent from the main control circuit 23, and controls the gradient magnetic field power supply 25, the transmitter 17, and the receiver 18 in accordance with this information. In addition, an R wave is detected from the electrocardiogram waveform from the electrocardiogram measurement unit 7,
The application timing of the IR pulse, the RF wave, or the gradient magnetic field is controlled based on the R wave.

The high-speed calculation / storage unit 5 includes a high-speed calculation circuit 19 and a storage circuit 20. High-speed arithmetic circuit 1
9 is an MR signal sent from the receiver 18 via the sequence control circuit 24.
A dimensional Fourier transform is performed to reconstruct the image data (MRI image) in real space.

The storage circuit 20 stores an MR signal obtained by the MR signal memory 28 for storing the MR signal sent from the receiver 18 and the MR signal by the high-speed arithmetic circuit 19 using the MR signal. The image memory 29 is provided. The MR signal memory 28 includes a test photographing MR signal memory 51 and a main photographing MR signal memory 52 for storing the MR signal obtained by the test photographing. The receiver 18 performs intermediate frequency conversion, phase detection, and A / D. Converted M
Store the R signal.

The image memory 29 is a storage circuit for storing a reconstructed image, that is, an MRI image obtained by using the MR signal once stored in the MR signal memory 28 and subjecting it to two-dimensional Fourier transform.

The bed 8 can move the subject 11 in the body axis direction and has a structure that can be inserted into the opening of the main magnet 13.

The input unit 22 is provided with various switches, a keyboard, a mouse, and the like on the operation desk, and information related to imaging information such as a patient ID, an imaging start instruction, an imaging method, a pulse sequence, and imaging conditions, or a display method by an operator. Input an instruction to move the mechanism. The input information is sent to each unit via the main control circuit 23. On the other hand, the mouse is used as an input device for performing an interactive operation on the display on the TV monitor of the display unit 21.
It has a function of selecting an optimum image from a plurality of MRI images taken with I as a parameter.

The display unit 21 includes a TV monitor, and is obtained by reconfiguration in the high-speed calculation / storage unit 5.
The I image is displayed via the main control circuit 23.

An electrocardiogram measurement unit 7 is mounted on the body surface of the subject 11 to detect an electrocardiogram waveform,
An ECG unit 27 for converting the output of the sensor into a digital signal is provided, and the timing of a pulse sequence including irradiation of an IR pulse is set based on the R wave of the electrocardiographic waveform measured by the electrocardiogram measurement unit 7. The

Next, before explaining the imaging procedure of the embodiment of the present invention, the role of the IR method in myocardial delayed contrast imaging and the outline of the Fast-Field-Echo method to which an IR pulse is added will be described with reference to FIGS. explain.

FIG. 2 shows inversion recovery (IR). The thick arrows in FIG. 2 (a) indicate the magnetization direction and magnitude (Mo) of the nuclear spin before application of the IR pulse. When the IR pulse is irradiated onto the region of interest at t = 0, the longitudinal magnetization is It is inverted 180 degrees and has a magnitude of -Mo (FIG. 2B). This longitudinal magnetization tries to return to the original longitudinal magnetization (Mo) according to the relaxation time T1 of the tissue.

Curves 41 and 42 in FIG. 2B show longitudinal magnetization return curves in the infarcted myocardium and normal myocardium, respectively. Since the longitudinal relaxation time T1 of the myocardium at the infarcted site is shorter than that of the normal myocardium due to the injection of the contrast agent, the longitudinal magnetization of the myocardium at the infarcted site is apparent from the curve 41 as shown in FIG. Return faster than magnetization. In FIG. 2B, t = Tβ
In this case, the longitudinal magnetization in the normal myocardium becomes zero, and at this time, the longitudinal magnetization in the infarcted region has a positive value. When t> Tβ (for example, Tα), the signal from the infarcted region is larger than the signal from the normal myocardial region. Detected as a signal.

That is, in order to observe the myocardium at the infarcted region and the normal myocardium with the highest contrast, it is desirable to set t = Tβ at which the longitudinal magnetization of the normal myocardium becomes zero as the inversion time (TI).

Next, an outline of test imaging in the present embodiment to which the IR method is applied will be described with reference to FIG. FIG. 3 shows a pulse sequence for test imaging using the Fast-Field-Echo method with IR pulses, and a plurality of (5 in this embodiment) multi-frames using TI as a parameter during one heartbeat interval. Slice MRI image data is collected at high speed.

That is, after a predetermined delay time Td from the R wave of the electrocardiogram waveform shown in FIG. 3A, an IR pulse is irradiated to the region of interest of the heart by the irradiation coil 15, and after TI1 from irradiation of this IR pulse, An RF pulse for collecting MR signals of one slice cross section is applied. Similarly, an RF pulse for collecting MR signals of the second slice section to the fifth slice section is applied at t = TI2 to TI5 (FIG. 3B).

In addition, as shown in FIG. 3C, in the acquisition of MR signals in the first to fifth slice sections, MR signals for eight types of phase encoding are sequentially acquired at intervals TR (repetition time). The FIG. 3 (d) shows a Field-Echo method pulse sequence at the time of MR signal acquisition for one phase encoding performed in the TR section, (d-1) shows the irradiation timing of the IR pulse and the RF pulse, (D-2) is a slice selection gradient magnetic field Gs, (d
-3) shows the readout (frequency encoding) gradient magnetic field Gr, (d-4) shows the phase encoding gradient magnetic field Ge, and (d-5) shows the MR signal.

For example, after TI1 from the IR pulse irradiation (d-1), the first slice section is selected by the slice selection gradient magnetic field Gs (d-2), and the flip angle α with respect to this slice section is selected.
An RF pulse of ° is irradiated (d-1). When irradiation with this RF pulse is completed, TE
In order to add position information to the MR signal received from the first slice section after (echo time), gradient magnetic fields Gr and Ge in the readout direction and the phase encoding direction with respect to the first slice section are formed ( d-3, d-4). However, MR signal readout in the field-echo method is performed by inverting the readout direction gradient magnetic field Gr without applying a 180-degree RF pulse, so that data can be collected in a short time.

Based on the above imaging principle, a test imaging method in the present embodiment is shown in FIG. In the outline description of the IR pulse and fast-field-echo method in FIG. 3, the number of data in the phase encoding direction is set to 8 for simplicity of explanation, but if the data collection repetition time TR in the field echo method is 5 msec. The time required for collecting the eight phase encoded data is 40 msec, and the maximum number of phase encoded data is 8 considering the TI increase of 50 msec described later. On the other hand, the number of phase encoded data in an actual MRI image is required to be 128 or more, and it is impossible to collect these data during one heartbeat. Therefore, in the present embodiment, the segmented shooting method, that is, Segmen
Use ted Fast Field Echo. The segment in this method is 1 heartbeat (R
-R interval), and in the segmented imaging method, the collection of phase encoding data necessary to construct one image is divided into a plurality of segments.

That is, as shown in FIG. 4, 128 phase encoded data required in each of the first slice section to the fifth slice section is 16 if the number of data that can be collected in each segment is 8 for the above reason. Collected in segments. On the other hand, the memory area K-1 for the first slice section of the MR signal memory 28 in which these data are stored is also divided into 16 segments. Details of collection and storage of these phase encoded data will be described in the imaging procedure of the present embodiment described later.

Next, an MR signal collection procedure in the present embodiment will be described. The MRI imaging in this embodiment is composed of two steps: a test imaging for obtaining an optimum TI (TI0) and a main imaging performed by setting TI0 obtained by the test imaging.

First, the procedure in the test photographing will be described with reference to FIGS. 1 and 4 to 6. However, FIG. 5 is a flowchart showing the procedure of test imaging, and FIG. 6 is a diagram showing the configuration of the MR signal memory 28.

In the test shooting, the operator of the apparatus first inputs a test shooting mode start command for TI optimization from the input unit 22 (step S1). When this command is sent to the main control circuit 23, the main control circuit 23 switches the display unit 21 to a data input screen for test photographing. The operator uses the mouse or keyboard provided in the input unit 22 for this screen, the delay time Td from the R wave of the electrocardiogram waveform to the IR pulse irradiation, the number of test images (that is, the number of slice sections), Information necessary for test imaging, such as the initial value (TI1) and increment (ΔTI) of TI, or the imaging method and pulse sequence, is input (step S2).

It has already been mentioned that the optimal TI depends on various conditions, most of which are 200 ms.
It is included in the range of ec to 400 msec. Therefore, here, the initial value of TI (TI1) is set to 2
00 msec, TI increment (ΔTI) is set to 50 msec, and the number of test images is set to five.

Next, the operator attaches the ECG sensor 9 of the electrocardiogram measuring unit 7 to a predetermined part of the body surface of the subject 11, and the ECG unit 27 receives the electrocardiographic waveform signal detected at this time and converts it into a digital signal. Convert. Next, the main control circuit 23 reads the electrocardiographic waveform signal converted into a digital signal from the ECG unit 26 and displays it on the display unit 21.

After confirming on the monitor of the display unit 21 that the electrocardiogram waveform is normally obtained, the operator inputs a command for starting a test photographing on the input unit 22 (step S3).

When the main control circuit 23 receives an imaging start command from the input unit 22, the main control circuit 23 has a pulse sequence that enables five multi-slice imaging based on an imaging method that has already been set (for example, Segmented Fast Field Echo method). Information (for example, gradient magnetic field coil 14 and irradiation coil 15
Information on the intensity, application time, application timing, etc. of the pulse current applied to the
The data is sent to the sequence control circuit 24. Further, the sequence control circuit 24 stores the information in an internal storage circuit, and performs “Segmented Fast Field Echo with IR pulse” for the gradient power supply 25, the transmitter 17 and the receiver 18 in accordance with this information. Send control signal.

On the other hand, the ECG unit 27 converts the electrocardiographic waveform sent from the ECG sensor 9 into a digital signal and sends it to the sequence control circuit 24 via the main control circuit 23. The sequence control circuit 24 detects the first R wave (segment 1) from the received electrocardiogram waveform, and measures a predetermined delay time Td by a timer configured by software with reference to the R wave. Further, an IR trigger signal delayed by Td from the R wave is generated.

Based on the IR trigger signal, the sequence control circuit 24 transmits the transmitter 17 of the transmission / reception unit 3.
A control signal for IR pulse irradiation is sent to the transmitter 17, and the transmitter 17 supplies the irradiation coil 15 with an RF current pulse for exciting nuclear magnetic resonance. However, in this case, an IR pulse for exciting the entire region of interest is applied to the subject 11 without selecting a slice cross section, and this IR
The magnetization of the region of interest is reversed by 180 degrees by the pulse (step S4).

Next, after TI1 (200 msec) from the irradiation of the IR pulse, a slice cross section is set under the control of the sequence control circuit 24, and the α ° RF pulse is irradiated to the slice to collect MR signals. That is, the sequence control circuit 24 sends a control signal to the gradient magnetic field power supply 25, and the pulse current supplied to the three gradient magnetic field coils 14 by the gradient magnetic field power supply 25 after TI 1 based on the control signal from the sequence control circuit 24. Set. further,
This pulse current is supplied to the gradient magnetic field coils 14 in the X, Y, and Z directions to form a slice selection gradient magnetic field Gs1 for selecting the first slice cross section. On the other hand, the pulse sequence control circuit 24 supplies a control signal to the transmitter 17 to receive the MR signal in the first slice cross section, and sets the frequency and phase of the RF pulse supplied to the irradiation coil 15. The RF pulse current is supplied to the irradiation coil 15.

The RF pulse current has the same frequency as the magnetic resonance frequency determined by the magnetic field strength of the region of interest and is modulated with a selective excitation waveform. The transmitter 17 supplies an RF pulse current to the irradiation coil 15 so that the irradiation coil 15 irradiates the region of interest of the subject 11 with an RF pulse (step S5).

When the irradiation of the RF pulse is finished, the first gradient magnetic field coil 14 in the X, Y, and Z directions is used to add position information to the MR signal received from the first slice section.
The gradient magnetic field Gr in the readout direction with respect to the slice cross section of the first and the first in the phase encoding direction
Gradient magnetic field Ge1 is formed (step S6), and these gradient magnetic fields Gr,
The MR signal is received by the receiving coil 16 while being phase-modulated by Ge1 (
Step S7).

The receiver 18 performs signal processing such as intermediate frequency conversion, phase detection, and filtering on the MR signal supplied from the receiving coil 16, performs A / D conversion, and sends the signal to the sequence control circuit 24. The sequence control circuit 24 stores the first encoded data of the first slice section in the MR signal memory 28 (step S8).

Here, the configuration of the MR signal memory 28 is shown in FIG. The MR signal memory 28 includes a test photographing MR signal memory 51 and a main photographing MR signal memory 52. The test photographing MR signal memory 51 includes K-1 to K-1 corresponding to the first slice section to the fifth slice section. The memory area is divided into K-5. Each of these five memory areas is divided into 16 segments (SK-
1 to SK-16), each of which is composed of memory areas D-1 to D-8 in which eight phase-encoded data collected in one segment from one slice section are sequentially stored. Therefore, the first encoded data of the first slice section is D- in SK-1 in K-1.
It is saved in one area.

Next, under the control of the sequence control circuit 24, a second gradient magnetic field Ge2 in which the gradient of the gradient magnetic field in the phase encoding direction is changed by a predetermined amount ΔGe is formed by the gradient magnetic field coil 14 in the X, Y, and Z directions. MR obtained by the same procedure as in the case of the first gradient magnetic field Ge1
The signal is stored in the area K-1 / SK-1 / D-2 of the MR signal memory 28.

Hereinafter, similarly, the third gradient magnetic field Ge3 to the eighth gradient magnetic field Ge8 in the phase encoding direction are used.
As for MR signals obtained by applying the signal K-1 / SK- of the MR signal memory 28 in sequence.
Save in one area of D-3 to D-8.

Next, after TI2 (250 msec) from the irradiation of the IR pulse, the gradient magnetic field power supply 25 sets the pulse current to be supplied to the three gradient magnetic field coils 14 based on the control signal from the sequence control circuit 24, and this pulse A current is supplied to the gradient magnetic field coils 14 in the X, Y, and Z directions to form a slice selection gradient magnetic field Gs2 for selecting a second slice section adjacent to the first slice section. On the other hand, the transmitter 17 supplies an RF pulse current to the irradiation coil 15, and the irradiation coil 15 irradiates the region of interest of the subject 11 with an RF pulse.

When the irradiation with the RF pulse is completed, the gradient magnetic field coil 14 reads the gradient magnetic field Gr in the readout direction and the first gradient magnetic field Ge1 in the phase encoding direction with respect to the second slice cross section.
The MR signal is phase-modulated by these gradient magnetic fields Gr and Ge1, and is received by the receiving coil 16.

The receiver 18 performs predetermined signal processing on the MR signal, A / D converts it, and sends it to the sequence control circuit 24. The sequence control circuit 24 stores the first encoded data of the second slice section in the area K-2 / SK-1 / D-1 in the MR signal memory 28,
In the same manner, MR signals obtained when the second gradient magnetic field Ge2 to the eighth gradient magnetic field Ge8 in the phase encoding direction are applied to the MR signal memory 28 in the order of K-2 / SK-1.
In D-2 to D-8.

Furthermore, from IR pulse irradiation, TI3 (300 msec) to TI5 (400 msec)
) After that, eight phase encoding data are collected in the same procedure, and these are stored in D-1 to D-8 in SK-1 of the memory areas K-3 to K-5.

Next, the sequence control circuit 24 outputs the second R of the electrocardiographic waveform sent from the ECG sensor 9.
A wave is detected, and an IR trigger signal delayed by Td from the R wave is sent to the transmitter 17. Transmitter 17
Supplies an IR pulse current to the irradiation coil 15 in accordance with the IR trigger signal, and I is applied to the region of interest.
Apply R pulse.

In the same manner as in the case of the first R wave, the first slice section to the fifth slice section are slice selection gradient magnetic fields Gs1 to Gs5 when they are delayed from TI2 to TI5 from this IR pulse.
Selected by. Further, a phase encoding gradient magnetic field Ge9 is applied to each slice cross section.
.About.Ge16 are applied, and eight phase encoded data obtained at this time are stored in D-1 to D-8 in SK-2 of K-1 to K-5 of the MR signal memory 28, respectively.

Thereafter, the third to sixteenth R waves are similarly detected, and an IR pulse is applied to the region of interest with a delay of Td from the R waves. Further, at the time of delaying TI1 to TI5 from these IR pulses, the first slice section to the fifth slice section are set, and the phase encoding gradient magnetic fields Ge17 to Ge24, Ge25 to Ge32,. Ge121-Ge12
8 is applied. The phase encoding data obtained in this way is also stored in D-1 to D-8 of K-1 to K-5 of MR signal memory 28 and SK-3 to SK-16.

Therefore, in the memory area K-1, phase encode data D-1 to D-128 obtained in the segments 1 to 16 are arranged with respect to the first slice cross section. Similarly, in the memory regions K-2 to K-5, the phase encode data D-1 to D-128 obtained in the segments 1 to 16 are arranged for each of the second slice section to the fifth slice section. Has been.

In this way, for each MR signal arranged in the five frequency spaces (K-spaces) K-1 to K-5 of the MR signal memory 28, the high-speed arithmetic circuit 19 of the high-speed arithmetic / storage unit 5 has two. Image reconstruction by dimensional inverse Fourier transform is performed, and the five images obtained as a result are stored in the image memory 29 of the high-speed calculation / storage unit 5 (step S9). In this case, an image of the first slice section obtained by image reconstruction is obtained by TI1 (200 msec), and the second
An image of the slice cross-section is obtained by TI2 (250 msec). Similarly, the images of the third to fifth slice sections correspond to TI3 to TI5 (300 to 400 msec), and the image memory 29 in which the images of each slice section are stored is stored in the TI used for data collection. Is also stored in the accompanying memory as accompanying information.

The high-speed arithmetic circuit 19 sends a test image generation completion signal to the main control circuit 23 when the storage of the MRI image obtained in the test imaging and its accompanying information is completed. On the other hand, the main control circuit 23 receives the completion signal from the high-speed arithmetic circuit 19 and displays the test image and its accompanying information on the monitor of the display unit 21 according to a predetermined display format. In this case, a predetermined image may be sequentially selected from five MRI images having different TIs and displayed. However, by displaying all the images side by side, it becomes easy to compare the signal intensity in the normal myocardium. .

Note that the five images obtained in the present embodiment are taken in slice slices adjacent to each other and are not taken from the same part. However, since these slice sections are all set in the region of interest of the heart, it is possible to obtain the optimum TI by comparing the display sensitivity of the normal myocardium displayed in each image. .

The operator observes these displayed images, and selects an image having the weakest signal intensity of normal myocardium from these images using the mouse of the input unit 22 (step S10). Main control circuit 23
Reads the TI value associated with the selected MRI image data, temporarily stores it in a storage circuit (not shown) in the main control circuit 23, and ends the test imaging (step S11).

As described above, in the conventional test imaging, MR data is collected for one TI in one heartbeat period. In the present embodiment, data collection for five types of TI is performed in one heartbeat period. As a result, the time required for the test shooting can be shortened to 1/5.

Next, the procedure in the main photographing will be described with reference to FIGS. However, FIG. 7 is a flowchart showing the procedure of actual imaging, FIG. 8 is a method of actual imaging, and FIG. 9 is a configuration of the MR signal memory 52 for actual imaging.

Subsequent to the test imaging, the myocardial delayed contrast imaging is performed using the optimum TI (TI0). The operator inputs an imaging method, imaging conditions, display conditions, and the like at the input unit 22, and then inputs a main imaging start command for myocardial delayed contrast to start preparation for main imaging (step S21).
).

As an imaging method in this case, a multi-slice method using “Segmented Fast Field Echo with IR pulse”, which enables high-speed imaging and can clearly display the myocardium at the infarcted region by injection of a contrast agent, is selected.

The operator inputs a command for the main shooting mode from the input unit 22. When this command is sent to the main control circuit 23, the main control circuit 23 switches the display unit 21 to the data input screen for the main photographing. The operator uses the mouse and keyboard provided in the input unit 22 for this screen,
Enter the information required for the main shooting, such as the shooting method ("Segmented Fast Field Echo with IR pulse"), its pulse sequence, the number of slices and the interval. At this time, the optimum inversion time TI0 obtained by the test shooting is automatically input (step S22).
). However, input information other than TI0 may be input in advance together with test imaging conditions before the start of test imaging.

In the actual photographing in the present embodiment, the number of segments is N, and the number of phase encoding data collected in one segment is M. Therefore, the number of phase encoding data used for reconstruction of one MRI image is NxM.

When the above input work is completed, the operator confirms on the monitor of the display unit 21 that the electrocardiogram waveform is normally obtained, and inputs a command for starting the main imaging from the input unit 22 (step S23). ).

When the main control circuit 23 receives the main imaging start command from the input unit 22, the pulse sequence information of the imaging method set by the operator (the intensity of the pulse current applied to the gradient magnetic field coil 14 and the irradiation coil 15, the application time) , Information on the application timing, etc.) and sent to the sequence control circuit 24. Further, the sequence control circuit 24 stores these information in an internal storage circuit, and controls the “Segmented Fast Field Echo with IR pulse” control signal to the gradient power supply 25, the transmitter 17 and the receiver 18 according to this information. Send.

On the other hand, the ECG unit 27 converts the electrocardiographic waveform sent from the ECG sensor 9 into a digital signal and sends it to the sequence control circuit 24 via the main control circuit 23. The sequence control circuit 24 detects the first R wave from the received electrocardiogram waveform, and measures a predetermined delay time (Td) with a timer configured by software based on the R wave. Further, I delayed by Td from the R wave
An R trigger signal is generated. The sequence control circuit 24, based on this IR trigger signal,
A control signal for IR pulse irradiation is sent to the transmitter 17 of the transceiver 3. In accordance with this control signal, the transmitter 17 supplies an RF current pulse for exciting nuclear magnetic resonance to the irradiation coil 15 and applies an IR pulse to the subject 11.
Inverted by 0 degrees (step S24).

Next, the gradient magnetic field power supply 25 is connected to the sequence control circuit 24 after TI0 from the IR pulse irradiation.
Is supplied to the three gradient magnetic field coils 14 in the X, Y, and Z directions to form a slice selection gradient magnetic field Gs ′ for selecting a slice cross section. On the other hand, the pulse sequence control circuit 24 supplies a control signal to the transmitter 17 in order to receive the MR signal in the slice cross section, and the transmitter 17 supplies an RF pulse current to the irradiation coil 15 to detect the subject. The 11 regions of interest are irradiated with RF pulses (step S25).
).

When the irradiation of the RF pulse is completed, the gradient magnetic field in the readout direction with respect to the slice cross section is added by the gradient magnetic field coil 14 in the X, Y, and Z directions in order to add position information to the MR signal received from the slice cross section. Gr ′ and the first gradient magnetic field G in the phase encoding direction
e1 ′ is formed (step S26), and these gradient magnetic fields Gr ′ and Ge1 are orthogonal to each other.
The MR signal is received by the receiving coil 16 in a state subjected to phase modulation by '(step S27).

The receiver 18 performs signal processing such as intermediate frequency conversion, phase detection, and filtering on the MR signal, and then performs A / D conversion and sends the signal to the sequence control circuit 24. The sequence control circuit 24 stores the first encoded data of the first slice section in the MR signal memory 52 for main imaging of the MR signal memory 28 (step S28).

As shown in FIG. 9, the main imaging MR signal memory 52 is divided into memory areas SK′-1 to SK′-N corresponding to segments 1 to N, each of which is collected within one segment. Memory areas D'-1 to D in which M phase encoded data are sequentially stored
It is comprised by '-M. Therefore, the first encoded data is stored in the D′-1 area of SK′-1.

Next, the gradient of the gradient magnetic field Ge in the phase encoding direction is changed by a predetermined amount ΔGe ′.
MR is obtained by forming the second gradient magnetic field Ge2 ′ by the gradient magnetic field coil 14 in the X, Y, and Z directions under the control of the sequence control circuit 24 and performing the same procedure as in the case of the first gradient magnetic field Ge1 ′. The signal is stored in D′-2 of SK′-1 of the MR signal memory 28. Similarly, MR signals obtained when the third gradient magnetic field Ge3 ′ to the Mth gradient magnetic field GeM ′ in the phase encoding direction are applied in the same manner, sequentially D′-3 of SK′-1 of the MR signal memory 28. ~ D
Save to '-M.

Next, the sequence control circuit 24 detects the second R wave from the electrocardiogram waveform sent from the ECG sensor 9 via the ECG unit 27, generates an IR trigger signal delayed by Td from this R wave, and transmits it. 17 to apply an IR pulse to the region of interest. In the same manner as in the case of the first R wave, the gradient magnetic fields GeM + 1 ′ to G at the time when TI0 is delayed from this IR pulse are as follows.
M phase encode data obtained by applying e2M ′ are collected and the MR signal memory 28 is collected.
Are stored in D′-1 to D′-M of SK′-2.

Further, in the same manner for the third to N-th R waves, the region of interest is Id after Td from this R wave.
R pulse is applied, and gradient magnetic field Ge2M + 1 ′ to Ge3M ′ is TI0 after IR pulse.
, Ge3M + 1 ′ to Ge4M ′... GeM (N−1) +1 ′ to GeMN ′ are applied.
The phase encoding data obtained in this way is also SK′-3 to SK of the MR signal memory 28.
At '-N, the data is stored in each of D'-1 to D'-M. Therefore, in the MR signal memory 52 for main imaging, each M collected in the first segment to the Nth segment.
Phase encode data is stored sequentially.

Next, the high-speed arithmetic circuit 19 of the high-speed arithmetic / storage unit 5 performs image reconstruction by two-dimensional inverse Fourier transform on the MR signals arranged and stored in the main imaging MR signal memory 52 in this way. Then, the image data obtained as a result is stored in the image memory 29 of the high-speed calculation / storage unit 5 as the actual photographing image data (step S29).

When the reconstruction and storage of the MRI image obtained in the main imaging is completed, the high-speed arithmetic circuit 19 sends a signal for completion of image generation for the main imaging to the main control circuit 23. The main control circuit 23 receives the completion signal from the high-speed calculation / storage unit 5 and displays the actual captured image on the monitor of the display unit 21 according to a predetermined display format or a display format newly specified in the input unit 22. Displayed above (step S30).

In the test imaging according to the embodiment of the present invention described above, MR data at a plurality of different TIs can be collected for one IR pulse irradiation. An optimum TI (TI0) can be obtained. For this reason, not only can the examination time be shortened, but also the subject's breath-holding time can be shortened, so that the pain experienced by the subject can be greatly reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. 1 and 10 to 12.
However, FIG. 10 shows a pulse sequence of test imaging in this embodiment, and FIG. 11 is a flowchart showing the imaging procedure. In the test shooting for the purpose of optimizing the TI, it is only necessary to compare the magnitude of the signal intensity on the image, and high spatial resolution is not necessarily required. In the present embodiment, a method for obtaining the optimum TI (TI0) in a short time by performing test imaging while reducing the number of phase encodings directly related to spatial decomposition will be described.

FIG. 10 shows a pulse sequence of test imaging in the present embodiment to which an IR pulse added Segmented Fast-Field-Echo method is applied, for example, a 2-beat interval (two segments).
In, one TI is set, and MRI image data is collected at high speed. That is, FIG.
In the segment 1 shown in FIG. 4B, after a predetermined delay time Td from the R wave (R1) of the electrocardiogram waveform, an IR pulse is irradiated to the region of interest of the heart by the irradiation coil 15, and from this IR pulse irradiation, TI1 Later, an RF pulse for collecting MR signals from a predetermined slice cross section is applied. (FIG. 10 (b)).

Further, as shown in FIG. 10C, in the MR signal acquisition in this slice cross section, for example, MR signals for 32 types of phase encoding are sequentially acquired at intervals TR (repetition time). FIG. 10 (d) shows a Field-Echo method pulse sequence at the time of MR signal acquisition for one phase encoding performed in one TR section.
) Indicates the irradiation timing of the IR pulse and RF pulse, (d-2) indicates the slice selective gradient magnetic field Gs, (d-3) indicates the readout (frequency encoding) gradient magnetic field Gr, and (d-4) indicates the phase encoding gradient magnetic field. Ge and (d-5) indicate the readout timing of the MR signal.

For example, after TI1 from the irradiation of the IR pulse of (d-1), a predetermined slice section is selected by the slice selection gradient magnetic field Gs (d-2), and an RF pulse with a flip angle α ° is irradiated to this slice section. (D-1). When irradiation with this RF pulse is completed, T
In order to add position information to the MR signal received from this slice section after E (echo time), gradient magnetic fields Gr and Ge in the readout direction and the phase encoding direction with respect to the predetermined slice section are formed (d-3). D-4).

In this embodiment, the subject can hold the collection of image data at five TI values.
The following imaging conditions are set so that the number of phase-encoded data is 64, which is about a half of that during the main imaging. Therefore, as described above, phase encode data for one image is collected during two heartbeats.

In the fast-field-echo method with IR pulse addition in FIG. 10, if the number of phase-encoded data collected during one heartbeat is 32, the data collection repetition time (TR) is 5 msec.
The time required for collecting the 32 phase encode data is 160 msec, and this value is 32 msec.
It is close to the limit to handle the encoded data as data at the same TI time. That is, the number of phase encoded data 64 in the test MRI image is 2 heartbeats, that is, 2
It is necessary to collect data in one segment, and in this case, it is necessary to apply the Segmented Fast Field Echo method.

Next, the test shooting procedure in the present embodiment will be described with reference to FIGS. 1 and 10 to 12. However, FIG. 12 shows the configuration of the MR signal memory for test imaging in the present embodiment.

In the test shooting, the operator of the apparatus first inputs a test shooting mode start command for TI optimization from the input unit 22 (step S51). This command is sent to the main control circuit 23.
The main control circuit 23 switches the display unit 21 to a data input screen for test photographing. The operator uses the mouse and keyboard provided in the input unit 22 for this screen,
Enter information necessary for test imaging, such as the delay time Td from the R wave of the electrocardiogram waveform to IR pulse irradiation, the number of test images, the initial value (TI1) and increment (ΔTI) of TI, or the imaging method and pulse sequence (Step S52).

The optimum TI is empirically included in the range of 200 msec to 400 msec. Therefore, here, the initial value of TI (TI1) is 200 msec, and the increment of TI (ΔTI) is 50 msec.
The number of test images is set to 5.

Next, the operator attaches the ECG sensor 9 of the electrocardiogram measuring unit 7 to a predetermined part of the body surface of the subject 11, and the ECG unit 27 receives the electrocardiographic waveform signal detected at this time and converts it into a digital signal. Convert. Next, the main control circuit 23 reads the electrocardiographic waveform signal converted into a digital signal from the ECG unit 26 and displays it on the display unit 21.

After confirming on the monitor of the display unit 21 that the electrocardiogram waveform is normally obtained, the operator inputs a command for starting a test photographing on the input unit 22 (step S53).

When the main control circuit 23 receives an imaging start command from the input unit 22, based on the imaging method (for example, Segmented Fast Field Echo method) that has already been set, information on the pulse sequence (for example, the gradient magnetic field coil 14 and the irradiation coil). 15, and the information is sent to the sequence control circuit 24. Further, the sequence control circuit 24 stores these pieces of information in an internal storage circuit, and in accordance with this information, for the gradient magnetic field power supply 25, the transmitter 17 and the receiver 18, "Segmen with IR pulse addition" is stored.
Send control signal for “ted Fast Field Echo”.

On the other hand, the ECG unit 27 converts the electrocardiographic waveform sent from the ECG sensor 9 into a digital signal and sends it to the sequence control circuit 24 via the main control circuit 23. The sequence control circuit 24 detects the first R wave (R1) from the received electrocardiogram waveform, and measures a predetermined delay time Td by a timer configured by software with reference to the R wave. Further, an IR trigger signal delayed by Td from the R wave is generated.

Based on the IR trigger signal, the sequence control circuit 24 transmits the transmitter 17 of the transmission / reception unit 3.
A control signal for IR pulse irradiation is sent to the transmitter 17, and the transmitter 17 supplies the irradiation coil 15 with an RF current pulse for exciting nuclear magnetic resonance. However, in this case, an IR pulse for exciting the entire region of interest is applied, and the magnetization of the region of interest is inverted 180 degrees by this IR pulse (step S54).

Next, after TI1 (200 msec) from the irradiation of the IR pulse, a slice cross section is set under the control of the sequence control circuit 24, and the α ° RF pulse is irradiated to the slice to collect MR signals. That is, the sequence control circuit 24 sends a control signal to the gradient magnetic field power supply 25, and the pulse current supplied to the three gradient magnetic field coils 14 by the gradient magnetic field power supply 25 after TI 1 based on the control signal from the sequence control circuit 24. Set. further,
This pulse current is supplied to the gradient magnetic field coils 14 in the X, Y, and Z directions to form a slice selection gradient magnetic field Gs1 for selecting a predetermined slice cross section. On the other hand, the pulse sequence control circuit 24 supplies a control signal to the transmitter 17 to receive the MR signal in the slice section, and after setting the frequency and phase of the RF pulse supplied to the irradiation coil 15,
An RF pulse current is supplied to the irradiation coil 15.

The RF pulse current has the same frequency as the magnetic resonance frequency determined by the magnetic field strength of the region of interest and is modulated with a selective excitation waveform. The transmitter 17 supplies an RF pulse current to the irradiation coil 15, so that the irradiation coil 15 irradiates the region of interest of the subject 11 with an RF pulse (step S55).

When the irradiation with the RF pulse is completed, the gradient magnetic field coil 14 in the X, Y, and Z directions reads out the predetermined slice section in order to add position information to the MR signal received from the first slice section. Directional gradient magnetic field Gr and phase encoding direction first gradient magnetic field Ge1 are formed (step S56), and these gradient magnetic fields Gr,
The MR signal is received by the receiving coil 16 while being phase-modulated by Ge1 (
Step S57).

The receiver 18 performs signal processing such as intermediate frequency conversion, phase detection, and filtering on the MR signal supplied from the receiving coil 16, and then A / D-converts the signal and sends it to the sequence control circuit 24. The sequence control circuit 24 converts the first encoded data of this slice section into M
The data is stored in the R signal memory 28 (step S8).

The configuration of the MR signal memory 28 is shown in FIG. The MR signal memory 28 includes a test photographing MR signal memory 51 and a main photographing MR signal memory 52. The test photographing MR signal memory 51 includes K-1 to K-1 corresponding to the first slice section to the fifth slice section. The memory area is divided into K-5. Each of these five memory areas is divided into 10 segments (SK-1 to S).
K-10), each of which is composed of memory areas D-1 to D-32 in which 32 phase encoded data collected in one segment from one slice cross-section are sequentially stored. Therefore,
The first encoded data is stored in the area D-1 in SK-1 in K-1.

Next, under the control of the sequence control circuit 24, a second gradient magnetic field Ge2 in which the gradient of the gradient magnetic field in the phase encoding direction is changed by a predetermined amount ΔGe is formed by the gradient magnetic field coil 14 in the X, Y, and Z directions. MR obtained by the same procedure as in the case of the first gradient magnetic field Ge1
The signal is stored in K-1 / SK-1 / D-2 of the MR signal memory 28.

Hereinafter, similarly, the third gradient magnetic field Ge3 to the 32nd gradient magnetic field Ge in the phase encoding direction are used.
As for MR signals obtained when 32 is applied, K-1 / S of the MR signal memory 28 is also sequentially applied.
Store in D-3 to D-32 of K-1 region.

Next, the sequence control circuit 24 detects the second R wave (R2) of the electrocardiogram waveform and sends an IR trigger signal delayed by Td from the R wave to the transmitter 17. The transmitter 17 supplies an IR pulse current to the irradiation coil 15 according to the IR trigger signal, and applies an IR pulse to the region of interest. After TI1 (200 msec) from the irradiation of the IR pulse, the gradient magnetic field power supply 25 sets the pulse current to be supplied to the three gradient magnetic field coils 14 based on the control signal from the sequence control circuit 24, and this pulse current is set to X , Supplied to the gradient magnetic field coils 14 in the Y and Z directions to form a slice selection gradient magnetic field Gs1 for selecting a predetermined slice cross section. On the other hand, the transmitter 17 supplies an RF pulse current to the irradiation coil 15, and the irradiation coil 15 irradiates the region of interest of the subject 11 with an RF pulse.

When the irradiation of the RF pulse is completed, the gradient magnetic field coil 14 forms the gradient magnetic field Gr in the readout direction and the 33rd to 64th gradient magnetic fields Ge33 to Ge64 in the phase encoding direction with respect to the predetermined slice cross section, and these gradient magnetic fields Gr. , Ge33 to Ge64, the MR signal undergoes phase modulation and is received by the receiving coil 16.

The receiver 18 performs predetermined signal processing on the MR signal, A / D converts it, and sends it to the sequence control circuit 24. The sequence control circuit 24 stores the first encoded data of the second slice section in the D-1 to D-32 of the K-1 / SK-2 area of the MR signal memory 28. In this manner, 64 encoded data after TI1 from the IR pulse are collected in segment 1 and segment 2.

Similarly, the sequence control circuit 24 detects the third R wave (R3) and the fourth R wave (R4) of the electrocardiographic waveform sent from the ECG sensor 9, and is a time point delayed by Td from this R wave. To apply an IR pulse to the region of interest. Furthermore, TI2 (250 msec) from IR pulse irradiation
) After that, the slice cross section is set under the control of the sequence control circuit 24, and the α ° RF pulse is irradiated to the slice.

When the irradiation of the RF pulse is finished, the gradient magnetic field coil 14 reads the gradient magnetic field Gr in the readout direction and the first to 32nd gradient magnetic fields G in the phase encoding direction with respect to the predetermined slice cross section.
The el1 to Ge32 and the 33rd to 64th gradient magnetic fields Ge33 to Ge64 are formed, and the MR signal is phase-modulated by these gradient magnetic fields and received by the receiving coil 16.

The receiver 18 performs predetermined signal processing on the MR signal, A / D converts it, and sends it to the sequence control circuit 24. The sequence control circuit 24 converts the first to thirty-second and thirty-third to sixty-fourth encoded data into the D-2 to D-32 and K-2 / SK-4 areas of the K-2 / SK-3 area of the MR signal memory 28. To D-1 to D-32.

In the same manner, 64 encoded data in TI3 is obtained from segment 5 to segment 6, and TI4, segment 9 to segment 1 are obtained from segment 7 to segment 8.
At 0, 64 encoded data in the case of TI5 are obtained, and these are stored in a predetermined area of the MR signal memory 28.

In this way, for each MR signal stored in the five frequency spaces K-1 to K-5 of the MR signal memory 28, the high-speed calculation circuit 19 of the high-speed calculation / storage unit 5 performs two-dimensional inverse Fourier transform. Image reconstruction is performed, and five images obtained as a result are stored in the image memory 29 of the high-speed computation / storage unit 5 (step S59). At this time, in the image memory 29 in which the image of each slice section is stored, the TI data used for data collection is also stored in the accompanying memory as accompanying information.

The high-speed arithmetic circuit 19 sends a test image generation completion signal to the main control circuit 23 when the storage of the MRI image obtained in the test imaging and its accompanying information is completed. On the other hand, the main control circuit 23 receives the completion signal from the high-speed arithmetic circuit 19 and displays the test image and its accompanying information on the monitor of the display unit 21 according to a predetermined display format. In this case, a predetermined image may be sequentially selected from five MRI images having different TIs and displayed. However, by displaying all the images side by side, it becomes easy to compare the signal intensity in the normal myocardium. .

The operator observes these displayed images, and selects an image having the weakest signal intensity of normal myocardium from these images using the mouse of the input unit 22 (step S60). Main control circuit 23
Reads the TI value associated with the selected MRI image data, temporarily stores it in a storage circuit (not shown) in the main control circuit 23, and ends the test imaging (step S61).

Next, it is necessary to continue to perform the main photographing using the optimum TI obtained by the above procedure, but since the method and procedure are the same as those in the first embodiment, the description thereof is omitted.

According to the present embodiment described above, the time required for test imaging is further reduced as compared with the first embodiment, so that the burden on the subject is further reduced. Also, during test shooting, TI
Since the five MRI images obtained by changing the values are obtained by photographing the same slice plane, there is an advantage that image comparison when obtaining the optimum TI (TI0) becomes easy.

The specific embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be modified. For example, although the Segmented-Fast-Field-Echo method is used as the high-speed imaging method in the present embodiment, the present invention is not limited to this, and other imaging methods may be used. Also, the shooting method in the test shooting and the shooting method in the main shooting may be different, and the shooting method in the main shooting is not particularly limited. Further, the number of phase encoded data 8 in one segment, the number 16 of segments, or the number 5 of TI parameters in the test photographing of the present embodiment is not limited.

Further, when the operator determines the optimum TI (TI0), the operator may obtain a TI by observing a plurality of images having different TIs, and manually input the value using a keyboard or the like of the input unit. By selecting the image with the lowest normal myocardial signal level from among the plurality of images using a mouse or the like, the TI data attached to the selected image data is automatically recorded at the time of actual imaging. It is also possible to input as shooting conditions. The signal intensity in the normal myocardium can be quantitatively evaluated by setting a predetermined region using a mouse and calculating a histogram in the region. That is, as shown in FIG. 13, the main control circuit 23 reads out the image data obtained by the test photographing from the image memory 28 according to the operator's instruction and displays it on the display unit 21 (step S41). A histogram calculation region is set for this image using the mouse of the input unit 22 (step S42).

Next, with respect to a plurality of images obtained by test shooting, the main control circuit 23 creates a histogram using image data in the set area (step S43), and further obtains a luminance value indicating the maximum value. (Step S44). Next, the luminance value is compared between these images, the image having the lowest luminance value is selected (step S45), and the optimum TI is obtained from the TI value associated with the image (step S46). However, the above step S44 may be obtained by the operator observing the histogram, but may be obtained automatically by the CPU of the main control circuit 23, and the optimum TI is automatically obtained and set as the main photographing condition. It is also possible.

The figure which shows schematic structure of the whole MRI apparatus in the 1st and 2nd embodiment of this invention. The figure explaining inversion recovery. The figure which shows the outline | summary of the test imaging | photography in the 1st Embodiment of this invention. The figure which shows the test imaging | photography method in the 1st Embodiment of this invention. 3 is a flowchart showing a test imaging procedure in the first embodiment of the present invention. 1 is a diagram showing a configuration of a test imaging MR signal memory according to a first embodiment of the present invention. 6 is a flowchart showing a procedure of actual photographing in the first and second embodiments of the present invention. The figure which shows this imaging | photography method in the 1st and 2nd embodiment of this invention. FIG. 4 is a diagram showing a configuration of a main imaging MR signal memory according to the first and second embodiments of the present invention. The figure which shows the test imaging | photography method in the 2nd Embodiment of this invention. 9 is a flowchart showing a test imaging procedure in the second embodiment of the present invention. The figure which shows the structure of MR signal memory for test imaging | photography in the 2nd Embodiment of this invention. The flowchart which shows the selection procedure of the optimal image. The figure which shows the conventional test imaging | photography method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation part 2 ... Gradient magnetic field generation part 3 ... Transmission / reception part 4 ... Control part 5 ... Reconstruction calculation and memory | storage part 9 ... ECG sensor 10 ... Cooling system 21 ... Display part 22 ... Input part 27 ... ECG unit

Claims (9)

An MRI apparatus for obtaining an MRI image by an IR method synchronized with an electrocardiogram waveform obtained from a subject,
Signal collection means for collecting MR signals by setting different TIs for a plurality of slices of the region of interest of the subject set in advance in one heartbeat period of the electrocardiogram waveform;
Image generating means for reconstructing the MR signal and generating a plurality of MRI images corresponding to each TI;
An MRI apparatus comprising image display means for displaying the plurality of MRI images generated by the image generation means. An MRI apparatus for obtaining an MRI image by an IR method synchronized with an electrocardiogram waveform obtained from a subject,
TI setting means for setting a plurality of inversion times (TI);
Signal acquisition means for acquiring MR signals continuously by acquiring MR signals over a plurality of heartbeats for a predetermined slice for each TI;
Image generating means for reconstructing a plurality of MR signals collected over a plurality of heartbeats to generate a plurality of MRI images corresponding to each TI;
An MRI apparatus comprising image display means for displaying the plurality of MRI images generated by the image generation means. 3. The MRI apparatus according to claim 2, wherein the signal collecting means collects MR signals at each TI over two heartbeat periods. The MRI apparatus according to claim 1 or 2, wherein the signal collecting means is based on a high-speed imaging method in which a k-space is divided into a plurality of segments. The MRI apparatus according to claim 1, wherein the set TI is set in a range of 200 msec to 400 msec. The image selecting means further comprises an image selecting means, wherein the image selecting means selects a desired image by comparing image luminances at predetermined portions of a plurality of MRI images generated by the image generating means. Or the MRI apparatus of 2. The MRI apparatus according to claim 6, wherein the image selection unit obtains a histogram at a predetermined portion of the plurality of MRI images and compares the histogram values. The said signal acquisition means collects the said MR signal of different TI based on the IR pulse irradiated non-selectively with respect to the area | region containing the said several slice.
The MRI apparatus as described. An MRI apparatus for obtaining an MRI image by an IR method synchronized with an electrocardiogram waveform obtained from a subject,
Signal collecting means for collecting MR signals by setting different TIs for predetermined slices of the region of interest of the subject;
Image generating means for reconstructing the MR signal and generating a plurality of MRI images corresponding to each TI;
An MRI apparatus comprising: desired TI setting means for setting a desired TI based on the plurality of MRI images.

Images