JP2000005144A - Mri device and mr imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an MRA image in a non-invasive manner without administering contrast media and shorten photographing time greatly by providing a scan means for imaging executing pulse sequence for three-dimensional scan in synchronization with a signal indicating a cardiac time phase per every slice encode. SOLUTION: When a sequencer receives a command for starting image scan, it starts reading of an ECG signal and judges the predetermined n-th appearance of a peak value of R wave in the ECG signal from an ECG trigger signal synchronized with the peak value. When the predetermined n-th R wave appears, the sequencer performs the processing for waiting for a set delay time TDL. This delay time TDL is optimized to a value excelling in a draw function of its entity by increasing the intensity of an echo signal to the most when a blood stream and tissue are photographed by a scan for preparation. The sequencer executes image scan using a time when the optimum delay time TDL elapses as the optimum electrocardiographic synchronization timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to magnetic resonance imaging for imaging the inside of a subject based on the magnetic resonance phenomenon of the subject. In particular, an ECG gate (electrocardiogram) having an optimum delay time without using a contrast agent.
An MRI (magnetic resonance imaging) apparatus for MR angiography and an MRI apparatus that collects echo signals in a short imaging time by multiplying by an iogram gating and draws a blood flow.
R imaging method.

[0002] As used herein, "blood (or blood flow)" is used to mean "fluid" representing cerebrospinal fluid, blood (blood flow), and the like flowing in a subject.

[0003]

2. Description of the Related Art In magnetic resonance imaging, a nuclear spin of a subject placed in a static magnetic field is magnetically excited by a high frequency signal of the Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation. This is an imaging method.

[0004] In the field of magnetic resonance imaging, to obtain a blood flow image of a lung field or abdomen, MR angiography, which administers a contrast medium to a subject to perform angiography, is being performed clinically. However, this contrast MR angiography requires an invasive procedure because a contrast agent is administered, and above all, the mental and physical burden on the patient is great. In addition, inspection costs are high. Further, depending on the patient's constitution, the contrast agent may not be administered in some cases.

[0005] When a contrast medium cannot be administered, the only alternative method is to carry out the imaging method. As an alternative method, a time-of-flight method is used.
ght: TOF) method and phase contrast (phase)
The contrast (PC) method is known. The effect of flow in magnetic resonance imaging is caused by one of two properties of moving spins. One is
The second is that the spin simply moves its position, and the second is due to the phase shift of the transverse magnetization caused by the movement of the spin in the gradient magnetic field. Among them, the former method based on the position movement is the TOF method, and the latter method based on the phase shift is the phase contrast method.

[0006]

However, even the TOF method or the phase contrast method described above is used to obtain an MR image of a lung field or abdomen, and it is necessary to obtain a superior-inferior direction of a large blood vessel such as an aorta. In order to depict the blood flow, it is necessary to take an image perpendicular to the blood flow direction. In other words, an axial image is shot with the slice direction up and down, and when a 3D (three-dimensional) image is obtained, the number of images to be shot increases, and the entire shooting time becomes considerably long.

[0007] The present invention has been made to overcome such a state of the prior art, and one of the objects is to obtain an MRA image in a non-invasive manner without administering a contrast agent. In addition, it is to significantly reduce the imaging time.

Another object of the present invention is to enable non-invasive imaging of blood pumped from the heart without administration of a contrast agent, and to reduce the imaging time for data collection required for the imaging. It is to shorten greatly.

[0009] Still another object of the present invention is to provide a method for non-invasive imaging of arteries and veins separated without administration of a contrast medium, and for imaging necessary data for the imaging. That is to save a lot of time.

[0010] Still another object of the present invention is to improve the ability to visualize the direction of blood vessel travel in a non-invasive manner without administration of a contrast agent, and to obtain an imaging time for collecting data necessary for the visualization. Is to be greatly reduced.

[0011]

According to the MR angiography method of the present invention, since fresh blood pumped from the heart can be constantly scanned, the method is called "FBI (Fresh).
Blood Imaging) method. Specifically, the FBI method synchronizes ECG with an optimally set delay time, constantly captures a fresh, stable, high-speed blood flow that is emitted from the heart for each R-wave, and performs one slice. The repetition time TR for each encoding is set to be short so that the longitudinal magnetization of the stationary substantial part is intentionally insufficiently relaxed, and if necessary, the fat signal is inverted using an IR (inversion recovery) pulse, a fat suppression pulse, or the like. To suppress
Thus, a blood flow is drawn by performing a three-dimensional scan for suppressing the signal value from the substantial part. Thereby, a blood vessel (blood flow) can be reliably drawn even without administering a contrast agent.

The three-dimensional scan used in the present invention is a scan for imaging a volume region of a subject, and not only a scan based on a so-called three-dimensional Fourier transform method but also a plurality of slices is imaged by a two-dimensional Fourier transform method. It includes scanning based on the multi-slice method. When the present invention is implemented by the multi-slice method, the timing of synchronization with the signal representing the cardiac phase is set the same for each slice.

In particular, it is desirable to set the slice direction so that data can be acquired for each slice encode in a direction substantially parallel to the direction of travel of the blood vessel. Further, it is desirable that the phase encoding direction be matched with the traveling direction of the blood vessel. Accordingly, unlike the TOF method and the phase contrast method, the imaging time does not become long. By changing the delay time of ECG synchronization and calculating the difference between data captured twice, for example, an MRA image in which arteries and veins are separated can be provided.

Incidentally, the "short repetition time TR" referred to in the present invention is defined as MRCP (MR Cholang).
T2 such as io Pancreatography
Repetition time by FASE (Fast Asymmetric SE) method based on the conventional method when imaging a site having a long value (about 5000 ms to 8000 ms)
And it is shorter than the repetition time. The “short repetition time TR” is intended to intentionally reduce relaxation of longitudinal magnetization of spin in the stationary substantial part to an insufficient state. In comparison with the conventional method, the “short repetition time TR” in the present invention is 4 heartbeats (4R−R).
It is set as follows.

As a specific means, the MRI according to the present invention
The basic configuration of the device is a device that generates a blood flow image from the imaging region of the subject, a time phase detecting unit that collects a signal representing a cardiac phase of the subject, and a three-dimensional scan for each slice encoding. Scanning means for performing a pulse sequence in synchronization with the signal representing the cardiac phase.

[0016] Preferably, the pulse sequence includes an RF excitation pulse having a short repetition time. Further, the pulse sequence includes a slice-direction gradient magnetic field for performing data acquisition based on the slice encoding in a direction substantially parallel to the blood flow traveling direction. Further, the pulse sequence includes a phase-encoding direction gradient magnetic field that performs phase encoding in a direction substantially matching the traveling direction of the blood flow.

For example, the three-dimensional scanning pulse sequence is a pulse sequence based on a three-dimensional Fourier transform method or a multi-slice method for imaging a volume area.

Further, as an example, the time phase detecting means includes:
The ECG signal of the subject is collected as a signal representing the cardiac phase, and the imaging scan unit is a unit that executes the pulse sequence in synchronization with an R wave appearing in the ECG signal. For example, the repetition time is an interval that is four times or less the appearance cycle of the R wave.

A preparatory scan means for performing preparatory scans on the imaging region of the subject at different delay times from the R wave of the ECG signal to collect a plurality of sets of echo signals; Preparation image generating means for generating the plurality of images from the signal, wherein the imaging scanning means captures an optimum value of the delay time determined from the plurality of images, and synchronizes with the optimum delay time. Means for executing the pulse sequence of the subject.

On the other hand, preparation scanning means for performing preparatory scanning on the imaging region of the subject in each of different cardiac phases based on the signal representing the cardiac phase and collecting a plurality of sets of echo signals; Preparation image generating means for generating the plurality of images from the echo signal, wherein the scanning means for imaging captures an optimal cardiac phase among the plurality of cardiac phases determined from the plurality of images. When,
Means for executing the pulse sequence of the subject in synchronization with the time phase.

[0021] The imaging scan means may include a scan execution means for executing the pulse sequence a plurality of times while changing a synchronization timing with the signal to obtain a plurality of sets of image data. Data processing means for obtaining image data in which arteries and veins as blood flows are separated from each other may be provided. In this case, the data processing means includes a difference calculating means for adding a weight to the plurality of sets of image data and subtracting the weights from each other to obtain one set of difference image data, and the blood flow from the one set of difference image data. Generating means for generating a final image to be rendered. For example,
The generating means is a process of performing maximum intensity projection (MIP) from the set of difference image data.

Further, in each of the above-mentioned configurations, it is preferable that the apparatus further comprises breath-holding command means for instructing the subject to perform breath-holding at least while the imaging scanning means is executing the pulse sequence.

Further, in the basic configuration of the present invention, there is provided a respiratory cycle detecting means for detecting a respiratory cycle of the subject, wherein the imaging scanning means comprises a signal detected by the time phase detecting means and the respiratory cycle detecting means. May be a means for executing the pulse sequence in synchronization with the respiratory cycle detected by.

In the above-mentioned basic configuration, the time phase detecting means and the imaging scanning means may be operated in a state where a reagent is administered to the subject. For example, the reagent is a reagent that imparts a contrast effect to the blood flow of the subject. This reagent is, for example, saline or glucose. On the other hand, the reagent may be a reagent that stimulates a blood vessel of the subject. This reagent is acetic acid or a beverage containing acetic acid.

In the above basic configuration, means for obtaining a plurality of sets of MR signals by separately executing the imaging scan before and after administering a reagent to the subject, and obtaining the plurality of sets of MR signals from the plurality of sets of MR signals Means for generating a blood flow image.

In each of the above-described configurations, the pulse sequence preferably includes a pulse train formed based on the FSE method, the FASE method, or the EPI method.

On the other hand, the MR imaging method of the present invention
A method of delineating a blood flow in an imaging region of a subject, collecting a signal representing a cardiac phase of the subject, and applying a pulse sequence for a three-dimensional scan for each slice encoding to the imaging region of the subject. And executed in synchronization with a reference waveform in the signal.

For example, the pulse sequence includes an RF pulse whose repetition time is set short. Further, the pulse sequence includes a slice-direction gradient magnetic field for performing data acquisition based on the slice encoding in a direction substantially parallel to the blood flow traveling direction. Further, the pulse sequence includes a phase-encoding direction gradient magnetic field that performs phase encoding in a direction substantially coincident with the traveling direction of the blood flow.

[0029]

Embodiments of the present invention will be described below.

(First Embodiment) A first embodiment will be described with reference to FIGS.

FIG. 1 shows a schematic configuration of an MRI (magnetic resonance imaging) apparatus according to this embodiment.

This MRI apparatus comprises a bed on which a subject P is placed, a static magnetic field generator for generating a static magnetic field, a gradient magnetic field generator for adding positional information to the static magnetic field, and a transceiver for transmitting and receiving high-frequency signals. And a control / arithmetic unit for controlling the whole system and reconstructing an image, and an electrocardiographic measuring unit for measuring an ECG signal as a signal indicating a cardiac phase of the subject P.

The static magnetic field generating section includes, for example, a superconducting magnet 1 and a static magnetic field power supply 2 for supplying a current to the magnet 1, and has a cylindrical opening (diagnostic space) into which the subject P is loosely inserted. A static magnetic field H ₀ is generated in the axial direction (Z-axis direction).
Note that a shim coil 14 is provided in this magnet portion. The shim coil 14 is supplied with a current for homogenizing a static magnetic field from a shim coil power supply 15 under the control of a host computer described later. The couch part can retreatably insert the top plate on which the subject P is placed into the opening of the magnet 1.

The gradient magnetic field generator has a gradient magnetic field coil unit 3 incorporated in the magnet 1. The gradient magnetic field coil unit 3 includes three sets (types) of x, y, and z for generating gradient magnetic fields in X, Y, and Z axis directions orthogonal to each other.
The coils 3x to 3z are provided. The gradient magnetic field section also has x,
A gradient magnetic field power supply 4 for supplying a current to the y, z coils 3x to 3z is provided. The gradient magnetic field power supply 4 supplies a pulse current for generating a gradient magnetic field to the x, y, and z coils 3x to 3z under the control of a sequencer 5 described later.

The x, y, z coils 3x from the gradient magnetic field power supply 4
By controlling the pulse current supplied to ~ 3z,
The gradient magnetic fields in the three axes X, Y, and Z directions, which are physical axes, are synthesized, and the respective logics of a slice-direction gradient magnetic field Gs, a phase encoding direction gradient magnetic field Ge, and a readout direction (frequency encoding direction) gradient magnetic field Gr that are orthogonal to each other. The axial direction can be set and changed arbitrarily. Slice direction, phase encoding direction, and gradient magnetic fields in the readout direction are superimposed on the static magnetic field H _0.

The transmitting / receiving unit includes an RF coil 7 disposed near the subject P in the imaging space in the magnet 1,
And a transmitter 8T and a receiver 8R, which are connected to each other. The transmitter 8T and the receiver 8R are connected to a sequencer 5 described later.
It operates under the control of. The transmitter 8T supplies the RF coil 7 with an RF current pulse having a Larmor frequency for exciting nuclear magnetic resonance (NMR). The receiver 8R has R
The F coil 7 receives the received MR signal (high-frequency signal), performs various signal processing such as pre-amplification, intermediate frequency conversion, phase detection, low-frequency amplification, and filtering, and then performs A / D conversion. Digital data (original data) of the MR signal is generated.

The control / arithmetic unit includes a sequencer (also called a sequence controller) 5, a host computer 6, an arithmetic unit 10, a storage unit 11, and a display unit 1.
2, an input device 13 and a sound generator 16. Among them, the host computer 6 has a function of instructing the sequencer 5 with pulse sequence information by a stored software procedure (not shown) and controlling the operation of the entire apparatus.

One of the features of this MRI apparatus is that it performs scanning based on an electrocardiographic synchronization method based on a synchronization timing (cardiac phase) of a value selected in advance. Host computer 6
As shown in FIG. 2, a preparation scan (hereinafter, referred to as an ECG-prep scan) for executing a preparation pulse sequence for determining a synchronization timing in advance, and
An imaging scan (hereinafter, referred to as an imaging scan) for executing an imaging pulse sequence in ECG synchronization based on the synchronization timing is performed during execution of a main program (not shown). FIG. 3 shows an example of an ECG-prep scan execution routine, and FIG. 7 shows an example of an imaging scan execution routine based on ECG gating.
8 respectively.

The sequencer 5 has a CPU and a memory, stores the pulse sequence information sent from the host computer 6, and controls the operation of the gradient magnetic field power supply 4, the transmitter 8T, and the receiver 8R according to the information. At the same time, the digital data of the MR signal output from the receiver 8R is input once and transferred to the arithmetic unit 10. Here, the pulse sequence information is
Gradient power supply 4, according to a series of pulse sequences,
All the information necessary to operate the transmitter 8T and the receiver 8R, for example, x, y, z coils 3x to 3z
And information on the intensity of the pulse current to be applied to the device, application time, application timing, and the like.

The pulse sequence may be a two-dimensional (2D) scan or a three-dimensional scan (3D) as long as the pulse sequence is applied to the Fourier transform method. Fast SE method, E
PI (Echo Planar Imaging; echo planar imaging) method, FASE (FastAs
An ymmetric SE method (that is, an imaging method in which the fast Fourier method is combined with the half Fourier method) is preferable.

The arithmetic unit 10 inputs the digital data (original data) output from the receiver 8R through the sequencer 5, and stores the original data (raw data) in a Fourier space (also called k-space or frequency space) on its internal memory. Data (also referred to as data).
It is subjected to one-dimensional or three-dimensional Fourier transform to reconstruct image data in a real space. The arithmetic unit is configured to perform a process of synthesizing data regarding an image and a process of calculating a difference. In this synthesizing process, a process of adding image data of a plurality of frames for each corresponding pixel, a maximum value projection (M) for selecting a maximum value for each corresponding pixel among the image data of a plurality of frames.
IP) processing. As another example of the combining process, the axes of a plurality of frames may be matched in Fourier space to combine the original data with the original data of one frame. Note that the addition processing includes simple addition processing, averaging processing, weighted addition processing, and the like.

The storage unit 11 can store not only reconstructed image data but also image data that has been subjected to the above-described synthesizing processing and difference processing. The display 12 displays an image. Further, through the input device 13, parameter information for selecting a synchronization timing desired by the operator, scan conditions, pulse sequences, information relating to image synthesis and difference calculation can be input to the host computer 6.

The voice generator 16 can emit a breath-hold start and a breath-hold end message as voice when instructed by the host computer 6.

Further, the electrocardiogram measuring section is provided with an ECG sensor 17 which is attached to the body surface of the subject to detect an ECG signal as an electric signal. 6 and an ECG unit 18 for outputting to the sequencer 5. The measurement signal from the electrocardiogram measurement unit is used by the sequencer 5 when performing each of the ECG-prep scan and the electrocardiogram-synchronized imaging scan. As a result, the synchronization timing of the ECG synchronization method can be appropriately set, and an ECG-gated imaging scan based on the set synchronization timing can be performed to collect data.

Next, a process of determining a synchronization timing for an imaging scan by ECG synchronization will be described with reference to FIGS.

The host computer 6 starts executing the ECG-prep scan shown in FIG. 3 in response to a command from the input device 13 while executing a predetermined main program (not shown).

First, the host computer 6 executes the ECG-pr
Scan conditions and parameter information for executing the ep scan are read from the input device 13 (step S1 in the figure).
The scan conditions include the type of scan, pulse sequence, phase encoding direction, and the like. The parameter information includes an initial time T ₀ (here, the elapsed time from the peak value of the R wave in the ECG signal) for determining the synchronization timing (time phase) of the ECG synchronization, a step width Δt in the time increment, and the number of times. An upper limit value of the counter CNT is included, and these parameters can be arbitrarily set by the operator.

Next, the host computer 6 includes a number counter CNT for counting the number of executions of the sequence and a time increment parameter T for determining the synchronization timing.
_Inc is cleared (CNT = 0, T _inc = 0: step S2). Thereafter, the host computer 6 operates as a sound generator 16.
To cause the subject (patient) to issue a breath-hold command such as "hold breath" (step S3). This breath hold is ECG-pr
It is preferable to perform the operation in order to suppress the body movement of the subject during the execution of the ep scan. However, in some cases, the ECG-prep scan may be performed without performing the breath hold.

When the preparation is completed, the host computer 6
Sequentially executes the processing from step S4. Thereby, the process shifts to the scan execution while changing the synchronization timing of the electrocardiogram synchronization.

[0050] Specifically, the delay time _{T DL} from the peak arrival time of the R wave _is calculated by _{T DL = T 0 + T inc} ( step S4). Next, the ECG unit 18
Is read, and it is determined whether or not the peak value of the R wave in the signal has appeared (step S5). This determination process is repeated until the appearance of the R wave. When R wave appears (step S5, YES), the delay time T _DL of the time calculated in step S4 whether elapsed since the R-wave peak time is subsequently determined (step S6). This determination process is also continued until the delay time _TDL elapses.

When the delay time _TDL has elapsed from the peak time of the R wave (step S6, YES), the start of each pulse sequence is instructed to the sequencer 5 (step S6).
7: See FIG. 4). This pulse sequence is preferably
It is set to be the same as an imaging pulse sequence described later. For example, FASE (Fast Asymmetric S) in which the half Fourier method is combined with the fast SE method is used.
E) Method. Of course, this sequence has a fast SE method,
Various types such as the EPI method can be adopted. In response to this command, the sequencer 5 starts executing a pulse sequence of the type specified by the operator, so that a region of a desired part of the subject is scanned. The ECG-Prep scan may be performed by a two-dimensional (2D) scan, for example, when a main scan (imaging scan) for collecting image data is a three-dimensional (3D) method, or may be performed according to an area of the main scan. Alternatively, it may be performed by a three-dimensional scan.

After the above sequence execution start command, the operation of the counter CNT = CNT + 1 is performed (step S).
8), and a time increment parameter T _inc = ΔT ·
The calculation of CNT is performed (step S9). As a result, the count value of the number counter CNT increases by one each time the execution of the pulse sequence is instructed, and the increment parameter _Tinc for adjusting the synchronization timing increases in proportion to the count value.

Next, a predetermined period (for example, 500 to 1000 m) necessary for executing each pulse sequence is set.
(about sec) elapses (step S10). Further, it is determined whether or not the number counter CNT has reached a predetermined upper limit (step S11). When, for example, five two-dimensional images are photographed while changing the delay time _TDL to various time values in order to optimize the synchronization timing, the number counter CNT is set to five.
If the number-of-times counter CNT has not reached the upper limit value (step S11, NO), the process returns to step S5 and the above-described process is repeated. Conversely, the number counter CN
T = When the upper limit has been reached (step S11, YE
S), a command to release breath holding is issued to the sound generator 16 (step S12), and the subsequent processing is returned to the main program. The voice message for breath holding is, for example, "You can breathe."

When the above-described processing is sequentially executed, for example,
And a pulse sequence for preparation at the timing shown in FIG.
Is executed. For example, the initial time T₀= 300mse
c, time interval ΔT = 100 msec
Then, the delay time T for the first sequence_DL=
300 msec, delay time T for the second time
_DL= 400 msec, at the time of the third delay
Interval T_DL= 500 msec,…
Delay time T_DLIs adjusted. others
Therefore, when the first R wave after the breath hold command reaches the peak value,
Delay time T from the arrival time_DL(= T₀Later)
First scan IMG based on the FASE Act
_prep1Is a predetermined time (500 to 1000 msec)
Subsequently, an echo signal is collected. During this sequence
Even if the next R-wave appears at step S10 in FIG.
Is involved in this R wave appearance
Instead, the sequence continues. In other words, the same
The execution process of the sequence started in the next
Thus, the echo signal is collected.

Then, the counter CNT reaches a predetermined value.
If not reached, the processing of steps S5 to S11
Is executed again. Therefore, in the example of FIG.
When the R wave appears and reaches the peak value,
Delay time T_DL= T₀+ T _inc= 400 msec
At the time when the second scan IMG_{prep 2}
Continue for a predetermined time, and an echo signal is similarly collected. This
When the next R wave appears after the scan of
T_DL= T₀+ 2 · T_inc= 500 msec elapses
Then, the third scan IMG_prep3Is a predetermined time
Continue and echo signals are collected as well. Furthermore, this
When the next R wave appears after the scan, the delay time T
_DL= T₀+ 3 · T_inc= 600 msec elapses
And the fourth scan IMG_prep3For a predetermined time
Subsequently, echo signals are collected in the same manner. This scan
Continue the desired number of times, for example 5 times, for a total of 5 frames (sheets)
One slice of echo data is collected.

The echo data is sequentially sent to the arithmetic unit 10 via the receiver 8R and the sequencer 5. The arithmetic unit 10 reconstructs the echo data in the k space into image data in the real space by a two-dimensional Fourier transform method. This image data is stored in the storage unit 11 as MRA image data. The host computer 6 sequentially converts the MRA images into cine (C) in response to an operation signal from the input device 13, for example.
INE) Display.

FIG. 5 shows a display example of a plurality of MRA images obtained by collecting and reconstructing echo data while dynamically changing the ECG-synchronous delay signal (synchronization timing).
(A) to (e). These figures show 2D-FASE
Method (effective TE (TE _eff ) = 40 ms, echo interval (ETS) = 5 ms, number of shots = 1, slice thickness (S
T) = 40 mm, number of slices (NS) = 1, number of additions (NAQ) = 1, matrix size = 256 × 256,
FOV = 40 × 40 cm, actual scan time = 500
(approximately ms) and a phase encoding direction = vertical direction (body axis direction) in the figure, which is a view simulating an image photograph of a lung field. The blood flow as the target entity in this image is the descending aorta. Each delay time TDL in the figure, _T DL = 300 msec in (a),
(B) at _{T DL = 400msec, T DL =} 5 at (c)
00msec, _T DL = 600msec in (d),
In (e), T _DL = 700 msec.

When these cine display images are visually observed, the MRA image shown in FIG. 9E shows the strongest echo signals from the aortic flow. M of other (a) to (d)
In the case of the RA image, as compared with (e), the range in which the aortic flow is shown is a part or a short range, and the intensity of the echo signal is low due to factors such as a low blood flow speed accompanying pulsation. Is relatively low, which is close to the flow void phenomenon. That is, when obtaining an MRA image of the aortic flow in the lung field, in the case of this experiment, the state shown in FIG. 3E, that is, the delay time T _DL = 700 msec is optimal. This reveals that the synchronization timing of the ECG synchronization is a time after a delay time T _DL = 700 msec from the peak arrival time of the R wave.

Therefore, the operator can change the delay time TDL dynamically in this way to obtain a plurality of MRA images.
An optimal image, that is, an optimal delay time TDL is determined from the image by visual judgment, and processing for reflecting the parameter of the delay time in a subsequent imaging scan is performed.

Further, in the above-described ECG-prep scan, the phase encoding direction is intentionally set to a direction along the running direction of the aortic flow (body axis direction). Thereby, as compared with the case where the phase encoding direction is set to the other direction, it is possible to more clearly image without dropping or dropping the running direction (directionality) of the aortic flow,
It has excellent drawing ability. The reason will be described below.

In general, a blood flow represented by a pulmonary blood vessel or a hepatic blood vessel (portal vein) has a slightly shorter T ₂ time (T ₂ = 100 to ₂ ).
00 ms). This shorter T ₂ hour blood flow is due to CSF or synovial fluid (T ₂ > 200) where T ₂ time is longer.
0 ms), it is known that the half width of the signal is wider. This is described, for example, in the document "R. ToddC".
ons-table and John C. Gor
e, “The loss of small obj
ects in Variable TE imagi
ng: Implications for FSE,
RARE, and EPI ", Magnetic R
esonance in Medicine 28,
9-24, 1992 ". According to the document, the spread of signal values for different substances at T ₂ time is:
As shown in FIG. 6, "points spread fun"
The graph in the figure is obtained when the static magnetic field is 1.5 T, TE _{eff is} 240 ms, and the echo interval (ETS) is 12 ms, and the horizontal axis is the number of pixels on the image in the phase encoding direction. According to this, the half-width of the blood (artery) at T ₂ = 200 ms is wider than that of CSF or synovial fluid at T ₂ = 2000 ms. Is T ₂ = 20
It can be said that 0 ms of blood (artery) is equivalent to apparently wider width in the phase encoding direction per pixel than CSF or synovial fluid. Therefore, T ₂ = 200
The blood (artery) of ms indicates that the entire image is further blurred in the phase encoding direction as compared with CSF or synovial fluid.

Therefore, by making the phase encoding direction substantially coincide with the blood flow direction, the degree of the spread (blur) of the signal value of the blood in the phase encoding direction on the pixel which is short in T ₂ time is short in T ₂ time. It is possible to positively use the larger value and emphasize the blood flow direction. Therefore, as described above, when selecting an optimal MRA image (that is, an optimal delay time) for ECG synchronization, the selection is further facilitated.

Next, the operation of the imaging scan of this embodiment will be described with reference to FIGS.

The host computer 6 executes a predetermined main program (not shown), and executes a process shown in FIG. 7 in response to operation information from the input device 13 as part of the main program.

More specifically, the host computer 6 first inputs the optimum delay time TDL determined by the operator through the above-described ECG-prep scan, for example, via the input device 13 (step S20). Next, the host computer 6 scans the scan conditions (the phase encoding direction, the image size, the number of scans,
The standby time between scans, the pulse sequence according to the scan site, etc., and the information of the image processing method (addition processing or maximum intensity projection (MIP) processing, etc. In the case of addition processing,
Simple addition, averaging processing, weighted addition processing, etc.) are input, the information including the delay time _TDL is processed into control data, and the control data is output to the sequencer 5 and the arithmetic unit 10 (step S21).

Next, when it can be determined that the notification of the preparation completion before the scan has been received (step S22), step S2 is performed.
In step 3, a command to start breath holding is output to the voice generator 14 (step S23). As a result, the sound generator 14
"Hold your breath" just like G-prep scan
The patient who hears this will hold his breath (see FIG. 9).

Thereafter, the host computer 6 instructs the sequencer 5 to start an imaging scan (step S2).
4).

When receiving the instruction to start the imaging scan (step S24-1), the sequencer 5 starts reading the ECG signal (step S24-2), and
The n-th occurrence of the peak value of the R wave (reference waveform) in the signal is determined from the ECG trigger signal synchronized with the peak value (step S24-3). Here, the reason for waiting for the appearance of the R wave n times (for example, two times) is to surely estimate the time when it has shifted to breath holding. When a predetermined n-th R wave appears, performs a process of waiting for the delay time _{T DL} set (step S24-4). This delay time T
As described above, the _DL has the highest intensity of an echo signal when imaging a target blood flow or tissue by ECG-prep scan, and is optimized to a value that is excellent in depiction performance of the entity.

The sequencer 5 executes an imaging scan on the assumption that the time point at which the optimal delay time _TDL has elapsed is the optimal ECG synchronization timing (step S24).
-5). More specifically, the transmitter 8T and the gradient magnetic field power supply 4 are driven in accordance with the pulse sequence information that has already been stored. For example, the first scan based on the pulse sequence of the three-dimensional FASE method is performed as shown in FIG. It is executed in synchronization (in the figure, the illustration of the gradient magnetic field in the phase encoding direction is omitted). At this time, the phase encoding direction P
E is a designated direction, for example, as shown in FIG.
The blood flow (artery AR, vein VE) almost coincides with the flowing direction. The echo interval in this pulse sequence is reduced to about 5 msec. As a result, an echo signal is collected from the three-dimensional imaging region Rima set in the lower abdomen, for example, as shown in the figure, with a scan time of about 600 msec based on the first slice encoding amount SE1.

When the first imaging scan is completed, the sequencer 5 determines whether the final imaging scan has been completed (step S24-6).
If this determination is NO (final scan has not been completed), for example, two heartbeats (2R-R) from the R wave used for the imaging scan while monitoring the ECG signal
Then, the control waits until the shorter period elapses, and actively suppresses the recovery of the longitudinal magnetization of the spin of the stationary substantial part (step S24-7). That is, this waiting period is the repetition time TR.

This repetition time TR is set shorter than the repetition time (about 5000 ms to 8000 ms) by the FASE method when imaging by MRCP or the like. Thereby, the relaxation of the longitudinal magnetization of the spin in the stationary substantial part can be intentionally made insufficient. In comparison with the conventional method, the repetition time TR is set to four heartbeats (4R-R) or less.

As described above, after waiting for a period corresponding to, for example, 2R-R, for example, when the third R wave appears (step S24-7, YES), the sequencer 5 executes the processing in step S24-4 described above. return. Thus, when the designated delay time _TDL elapses from the ECG trigger signal synchronized with the third R-wave peak value, the second imaging scan is executed in the same manner as described above according to the next slice encode amount SE2. , the echo signals are acquired from the three-dimensional imaging region _{R ima} (step S24-4,5). Hereinafter, similarly, the final slice encoding amount SEn (for example, n
= 8) echo signals are collected.

When the final imaging scan with the slice encoding amount SEn is completed, step S24-6.
Is YES, and the sequencer 5 outputs an imaging scan completion notification to the host computer 6 (step S24-8). Thereby, the processing is returned to the host computer 6.

When the host computer 6 receives the scan completion notification from the sequencer 5 (step S25), it outputs a command to release the breath holding to the voice generator 16 (step S2).
6). Then, the voice generator 16 issues a voice message, for example, “You can breathe” to the patient,
The breath-hold period ends (see FIG. 9).

Accordingly, as schematically shown in FIG. 9, for example, imaging scans by ECG synchronization are performed n times (for example, 8 times) based on the 3D-FASE method, for example, every 2R-R.
Be executed.

The eco signal generated from the patient P is received by the RF coil 7 for each scan and sent to the receiver 8R. The receiver 8R performs various pre-processing on the echo signal and converts it into a digital amount. This digital amount of echo data is sent to the arithmetic unit 10 through the sequencer 5 and arranged in a three-dimensional k-space formed by a memory. Since the half Fourier method is employed, the data in the k space that has not been collected is obtained by calculation and is embedded in the k space. When the echo data is arranged in the entire k space in this way, a three-dimensional Fourier transform is executed, and the echo data is converted into image data in the real space. This image data is further converted into two-dimensional tomographic image data by MIP processing. This tomographic image data is stored in the storage unit 11 and displayed on the display 12.

The present inventor has taken a coronal image depicting the aorta of the abdomen to confirm the effect of the above-described configuration. The static magnetic field is O. 5T, and the pulse sequence used was a 3D-FASE sequence (TE _eff = 2
4.8 ms, ETS = 6.2 ms) and 256 × 256
Was performed with an 8-slice encoding amount every three heartbeats (3R-R), and a coronal image of the abdomen was obtained by MIP processing. The phase encoding direction was set up and down (in the direction of the patient's body axis). The ECG delay time was 600 ms.
The entire imaging time was about 23 seconds, and one breath hold was performed. As a result, excellent blood vessel visualization ability was confirmed.

As described above, by setting the repetition time TR for each one-slice encoding to be short, such as 2R-R or 3R-R, the longitudinal magnetization of the stationary substantial portion is positively insufficiently reduced and the stationary substantial portion is reduced from the substantial portion. Can be suppressed.

Furthermore, blood with a relatively high flow rate flowing for each heartbeat can be drawn by ECG synchronization. For each slice encoding, since blood flow is electrocardiographic synchronization method due to the optimum delay time T _DL which performs the scan to a stable diastolic, blood flow can be reliably capture and fresh discharged from the heart Blood can always be scanned. The present inventor described this MR angiography method as “FBI (Fr
Esh Blood Imaging) method.

A turbulent time zone that occurs immediately after the appearance of the R wave can be avoided, and a time zone in which the blood flow state is relatively stable can be selected and scanned. Thereby, the influence of the turbulent blood flow can be eliminated, and the echo signal in a stable blood flow state can be arranged in the center region of the k-space in the phase encoding direction, and the contrast of the reconstructed image can be increased.

Therefore, it is possible to provide an MR angiography which is excellent in a blood flow rendering ability.

Further, since the repetition time TR and the echo interval are set short, the phase encoding direction is made substantially coincident with the blood vessel running direction, and the slicing direction is taken before and after in the coronal direction of the patient (becoming from the front to the back). , TOF
Compared to the method of taking images perpendicular to the blood flow, such as the method,
Overall scan time is reduced. Furthermore, since the imaging range (length) in the slice direction is shortened and the number of times of application of slice encoding is reduced, the entire imaging time is significantly reduced as compared with the conventional TOF method and phase encoding method. This reduces the burden on the patient and increases the patient throughput.

Along with this, since the entire imaging (a plurality of imaging scans) can be completed within one breath holding period, the burden on the patient is significantly reduced.

Further, since there is no need to administer a contrast agent, non-invasive imaging can be performed, and the mental and physical burden on the patient is significantly reduced in this respect. At the same time, the inconvenience inherent in the contrast method, such as the need to measure the timing of the contrast effect, is released, and unlike the contrast method, repeated imaging can be performed as necessary.

Furthermore, since the phase encoding direction matches or substantially matches the running direction of the blood vessel, blurring of pixels can be positively used, and therefore, the imaging performance of the running direction of the blood vessel is excellent. I have. By changing the phase encoding direction according to the blood vessel running direction of the imaging site, various sites can be easily dealt with.

Further, since the pulse sequence of the high-speed SE system is used, the superiority in terms of susceptibility and form distortion can be naturally enjoyed.

Further, since the synchronization timing of the electrocardiogram synchronization is optimized in advance, there is almost no need to perform re-imaging, thereby reducing the operational burden on the operator and improving the patient throughput. Further, the burden on the patient is reduced or suppressed.

Further, in the case of the above-described embodiment, all the imaging scans are completed in one breath hold period. For this reason, the occurrence of body motion artifacts due to the periodic movement of the lungs and the like can be suppressed, and the occurrence of body motion artifacts due to positional displacement of the patient's body itself when performing breath-holding imaging multiple times can also be reduced. . Thereby, a high-quality image with less artifacts can be provided.

According to the present embodiment, a new composite image can be obtained from a plurality of images of echo data collected by changing the phase encoding direction. This composite image Depending on the encoding direction change control, in particular, T ₂
Excellent in the ability to visualize blood flow in a short time.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. M of this embodiment
The RI device is a further development of the configuration of the above-described embodiment, and images are taken by changing the delay time of ECG synchronization, and only a specific blood vessel is drawn by differentiating a plurality of MRA original images obtained by the imaging from each other. It is characterized by the following.

The hardware configuration of this embodiment is the same as or equivalent to that described in the first embodiment.

As schematically shown in FIG. 11, the host computer 6
Command to draw a specific blood vessel, for example, the aorta.
(Step S31), the sequencer 5 delays the ECG.
Time T _DL= Α1 (for example, 100 ms) and T_DL= Α2
(≠ α1: 500 ms, for example)
Command (steps S32 and S33). This multiple species
Delay time T_DLIs an appropriate value if their values are different
ECG-p can be set according to the type of blood vessel to be visualized.
It may be determined and stored in advance by rep scan etc.
Each time, the operator enters as part of the imaging conditions.
You may make it force.

[0093] original data more than once captured based on each the plurality of kinds of delay time T _DL, like the above, the image reconstruction operation is performed is stored in the arithmetic unit 10 (step S34). Next, the host computer 6 instructs the arithmetic unit 10 to perform a weighted difference calculation for each pixel between a plurality of sets of reconstructed image data (step 35).

Thus, for example, as schematically shown in FIG. 12, for example, the ECG delay time T _DL = 100 ms
And a set of three-dimensional image data of T _DL = 500 ms is subjected to a weighted difference operation. As shown in FIG. 3A, the ECG delay time T _DL =
If the time is shorter than 100 ms, the pumped (pulsed) blood is turbulent, causing a flow void, and the signal value of the artery AR becomes almost zero (shown black in an actual image photograph), and the vein VE Only signals are collected. In contrast,
As shown in (b), ECG delay time T _DL = 500 m
If s is an appropriate value, the signals of the artery AR and the vein VE are both collected with appropriate intensity. Therefore, the image data of FIGS. 7A and 7B are mutually weighted and differentiated for each pixel, thereby obtaining three-dimensional image data depicting only the artery AR as shown in FIG. In the case of the figure,
With respect to the image data shown in FIGS.
The difference calculation using the weighting coefficient k of “k · (a)” is performed. The weighting coefficient k is determined so that the image data of the vein VE is favorably canceled by the difference calculation.

Next, the host computer 6 executes the operation unit 1
For M.0, the MIP processing is instructed for the difference image data (step S36), and then it is displayed (step S37). As a result, an MRA image in which the artery AR is appropriately rendered is provided.

As a result, the same operation and effect as those of the first embodiment can be obtained. In addition, only the desired blood vessels can be reliably drawn.
An RA image can be provided to contribute to improvement of diagnostic performance.

Note that the above-described difference calculation in the present invention is based on two sets of three-dimensional original data (k
The spatial data) may be subjected to a difference operation, and then the reconstruction / MIP processing may be performed.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG.

The MRI apparatus of this embodiment relates to another example of the imaging scan by the electrocardiographic gating method.
It is characterized by the application of a T pulse. The FBI method according to the present invention inherits the above-described unique setting and configuration of the FBI method.

The hardware configuration and the imaging process are the same as or similar to those of the first or second embodiment.

In the present embodiment, after the delay time T _DL (synchronization timing) of the ECG synchronization method is set to an optimum value using the images collected by the ECG-prep scan,
The imaging scan shown in FIG. 13 is commanded by the sequencer 5 in the same procedure as described above. Breath-holding is also used in this imaging scan.

The train of the pulse sequence shown in FIG. 13 is synchronized with the R wave of the ECG signal for each train with a predetermined delay time _TDL . The pulse sequence for each shot (RF excitation) is a pre-sequence SQ applied first.
_pre followed by a data acquisition sequence SQ _acq
Consists of

The pre-sequence SQ _pre is composed of an MT pulse train P _MT for producing an MT effect, and the MT pulse train P
Gradient magnetic field spoiler pulse SP applied after application of _MT
S, SP _R, and a SP _E. The MT pulse train P _MT is
RF pulse P ₁ for a plurality of excitation sequentially applied as MT _{pulse, P 2, P 3, ...} , consisting of a P _n, inclined magnetic field pulse G _S slice to be applied in parallel with these MT pulse.

Slice gradient magnetic field pulse G _S The applied strength = G _S1 is applied the MT pulse is set to be off-resonance RF-excitation for imaging area of interest. As an example, selection area due to the slice gradient pulse G _S is, the imaging region (this time G _{S =} G
It is set so as to be a gapless or gap-present position different from _S2 (G _S1 ).

Each MT pulse P ₁ (P ₂ , P ₃ ,...,
P _n ) is formed, for example, by a SINC function, and the flip angle of the spin FA accompanying this pulse application is, for example, 90 °.
The strength is set so that MT pulse P ₁ , P
_{2, P 3, ..., P} n Is set to 10 as an example.

That is, in the present embodiment, instead of the conventional configuration in which one MT pulse having a large flip angle FA (for example, 500 ° to 1000 °) is applied by slice selection,
This MT pulse is divided into a plurality of MT pulses to be sequentially applied.
A pulse train configuration is adopted.

Each MT pulse P ₁ (P ₂ , P ₃ ,...,
The flip angle FA given to P _n ) is a value (preferably 90 ° to 100 °) divided so as to cause a desired MT effect in the entire MT pulse train, and the number of the flip angles FA is also equal to the entire MT pulse train. An appropriate number (5 to 10) is determined depending on the balance between the MT effect and the imaging time. The application time of each divided MT pulse is about 1300 μsec, which is a conventional slice selection MT pulse.
It is shorter than the pulse by the division.

Further, the divided MT in the MT pulse train
The time interval Δt between the pulses is set to a value that can optimize the MT effect of water / fat in a substantial part of the MT pulse application region. This time interval Δt differs depending on the measurement site,
In some cases, Δt = 0 can be set.

On the other hand, the gradient magnetic field spoiler pulses SP _S , SP _R , and SP _E inserted in three directions, ie, the slice direction, the readout direction, and the phase encode direction, are generated by the preliminary sequence S
It is used as an end spoiler in Q _{p re.} For this reason, the gradient magnetic field spoiler pulses SP _S , SP _R , S
Each P _E, dispersed in every direction spin phase after a plurality of partitioning MT pulse application, without interference of the spin phase between the pre-sequence and the data acquisition sequence, preventing the occurrence of pseudo-echo I am trying to do it.
The spoiler pulse may be applied in any one or two directions.

The data acquisition sequence SQ _acq is formed in the same manner as that of FIG.

As described above, in the pre-sequence SQ _pre , a plurality of divided MT pulses P ₁ ,..., P _n
Is used, the echo signal from the substantial part (stationary part) of the imaging region is reduced by the MT effect, and the MT generated in the blood flow (artery and / or vein) flowing into the imaging region is reduced.
The effect is reduced (reduced). That is, the apparent longitudinal relaxation T of the flowing or tumbling blood flow is based on the divided short MT pulse.
One hour is shortened, and the effect of the MT effect is reduced. On the other hand, the substantial part (stationary part) has a signal value reducing effect by the sum of a plurality of divided MT pulses, so that the effect on the imaging region is reduced. The image contrast between the inflowing blood flow (blood) and the parenchyma is significantly improved over the MT effect using a conventional single MT pulse (long application time and large flip angle).

Therefore, according to the present embodiment, in addition to the effects and advantages based on the FBI method described above, there are less artifacts, and the image contrast between the inflowing blood flow and the parenchymal part is much higher than when the conventional MT pulse is used. Improved M
An RA image can be provided.

The method of applying a plurality of divided MT pulses is not limited to the method shown in FIG. 13, but may be modified as shown in FIGS.

[0114] According to the application method shown in FIG. 14, the pulse of the plurality of partitioning MT pulse slice gradient G _S upon application of even instead of the configuration of multiple application, a plurality of partitioning M
During the application of the T pulse, the slice gradient magnetic field G _S
Is continuously applied. This gives M
The time required to the application of the T pulse train P _MT is already Te short,
The entire imaging time can also be reduced. FIG.
In the method of applying the MT pulse shown in FIG. 5, the gradient magnetic field pulse is not applied in any direction, and the divided MT pulse is applied alone. Thereby, a plurality of divided MT pulse spaces are applied non-selectively. Therefore, the divided MT pulse is applied over a wide area, and is not limited to a slice or a slab. 14 and 15, illustration of the gradient magnetic field axes in the reading direction and the phase encoding direction is omitted.

(Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIGS.

The MRI apparatus according to this embodiment is characterized in that the ECG synchronization method described above is used together with respiratory synchronization.

Therefore, as shown in FIG. 16, the MRI apparatus includes a respiratory sensor (electrode) 19 which is in contact with the chest of the subject and detects a signal proportional to the thoracic movement, and a detection signal from the sensor 19. A respiratory synchronization unit 20 that calculates respiratory curve data and outputs a synchronization signal synchronized with a desired period (for example, an expiration period) of a subject's respiratory cycle is added. The respiratory sensor and the respiratory synchronization unit may have another configuration, for example, a configuration in which the movement of the abdominal muscles is detected as an optical variable to detect a respiratory cycle, or a gas flow accompanying respiration may be detected by a rotary wing. It may be an apparatus using a configuration for detecting by (1).

The respiratory synchronization signal output from the respiratory synchronization unit 20 is sent to the sequencer 5. Sequencer 5 has E
The imaging scan described in each of the above-described embodiments is performed using both the CG signal and the respiratory synchronization signal.
Other configurations of the MRI apparatus are the same as those described above.

[0119] The sequencer 5, as shown in FIG. 17, monitors the elapse of a predetermined delay time T _k from the start, for example expiration period of the respiratory motion. When the delay time T _k has elapsed, monitoring the timing of the delay time T _DL has elapsed from R-wave of subsequent ECG signal generated. When this timing comes, a scan for each slice encoding amount is executed as described above.

In this manner, a three-dimensional scan based on the FBI method using the ECG synchronization method and the respiration synchronization method together can be executed. For this reason, in addition to the various functions and effects based on the FBI method described above, the subject does not need to hold his / her breath, so that the imaging can be performed with a reduced burden on the subject. In addition, the operational burden on the operator due to the breath holding command is reduced.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIGS.

This embodiment is characterized in that various reagents are administered to a subject, and the imaging effect of the reagent or the function of a subject stimulated by the reagent is imaged.

The reagent used in the present invention is not a conventional MR contrast agent such as Gd-DTPA, but an injection such as physiological saline and glucose, and a beverage containing acetic acid, that is, an oral administration type. It is a reagent. When the former injection is used, imaging is performed by its contrast effect. As the latter beverage, a beverage obtained by mixing acetic acid with other components so that the patient can easily drink it is suitable.

FIG. 18 shows an example of a basic sequence of an imaging method incorporating this reagent administration and a flow of image generation. This sequence is executed by the sequencer 5 and the arithmetic unit 10 under the control of the host computer 6. The execution of the scan related to this sequence and the data processing related to the image generation are the same as or equivalent to those described in the above embodiment.

[0125] initially aforementioned ECG-prep scan is performed, it is determined the optimum delay time _{T DH} in ECG gating. Thereafter, an ECG-gated imaging scan (1) before administration of the reagent is performed based on the FBI method described above. In this imaging scan (1), a breath hold command is issued.

Next, the reagent is administered to the subject. When the reagent is saline or glucose, for example, about 100 cc is administered by injection. When the reagent is a beverage containing acetic acid, for example, about 10 cc is orally administered. After this administration, wait for an appropriate time. Thereafter, the ECG-gated imaging scan (2) after the administration of the reagent is similarly performed based on the above-mentioned FBI method. This imaging scan (1) uses a breath hold method.

The pulse sequences used for the two imaging scans are both the bl of the T2 value described above.
A sequence in which the enhancement effect by the ring is obtained, for example, a three-dimensional scanning method based on the FSE method, the FASE method, the EPI method, or the like is preferable.

In addition, the TOF method or P
A configuration in which imaging is performed by the S method is also possible.

When physiological saline or glucose was injected and administered as a reagent, the blood T2 value increased, that is, T2
2 The relaxation time becomes longer, and the contrast effect is exhibited. As a result, the intensity of the echo signal detected from the blood increases, and S
NR is improved. On the other hand, when a beverage containing acetic acid is used as a reagent, the acetic acid component in the administered beverage stimulates the vascular system, particularly the portal vein (reflection), and dilates the blood vessel.
As a result, the blood flow increases, the intensity of the echo signal detected from the blood flow increases, and the SNR improves.

The echo signals generated by these imaging scans are collected by the arithmetic unit 10 via the receiver 8R and the sequencer 5, and reconstructed as three-dimensional image data (FIG. 18, steps S51a, S51).
b, S52a, S52b). Thereafter, the two sets of three-dimensional image data are subjected to difference processing for each pixel by the arithmetic unit 10 as an example (step S53). Next, the data of this difference result is displayed and stored after the MIP processing (steps S54 and S55).

On the other hand, FIG. 19 shows a flow of a sequence when a dynamic scan is performed after reagent administration. After administering the reagent or after starting the administration, imaging is performed by a three-dimensional scan of the volume area at regular intervals,
Identify the time change data in the body related to the reagent. In this three-dimensional scan, F based on a three-dimensional Fourier transform method is used.
The pulse sequence of the BI method or the multislice method of the FBI method based on the two-dimensional Fourier transform method (the same ECG synchronization delay time for each slice) is applied.

The present inventor has applied this reagent administration to the FBI method and confirmed its effect in actual experiments. In one experiment, about 150 cc of saline was injected and administered, and images of the lung field before and after the injection were imaged with a 1.5 T (static magnetic field) MRI apparatus and compared. The pulse sequence used in this experiment was a sequence of the 3D-FASE method, and its imaging parameters were TE _eff = 60 ms,
TR = 3R-R, TI = 180 ms, matrix size = 256 × 256, ETS = 5 ms, FOV = 37 cm
× 37 cm ² , resolution = 1.4 mm (RO) × 1.4 m
m (PE) / 2 mm (slice). As a result, a clear difference in signal intensity of the pulmonary artery and an improvement in the ability to depict fine blood vessels were confirmed. This is considered to be because the effect of blurring of the T2 value was reduced by the administration of the water component into the blood vessel, and the blood vessel could be drawn sharply.

In another experiment, about 20 cc of acetic acid was orally administered, and images of the thorax and abdomen before and after that were taken using a 0.5 T (static magnetic field) M image.
They were imaged on a RI device and compared. The pulse sequence used in this experiment is a sequence of the 3D-FASE method, and its imaging parameter is TE
_eff = 62ms, TR = 3R-R, TI = 140m
s, matrix size = 256 × 256, ETS = 6.
2 ms, FOV = 37 cm × 37 cm ² , resolution = 1.
4mm (RO) x 1.4mm (PE) / 2mm (sli
ce). FIGS. 20 (a) and 20 (b) schematically show these images by hand. (A) is a mimic image before administration of acetic acid, and (b) is a mimic image after administration of acetic acid. As can be seen by comparing these, it was confirmed that the image after administration showed a marked improvement in the blood vessel signal difference and the ability to visualize the vascular system as compared to the image before administration.
This is because, as described above, the acetic acid component stimulated the portal vein. In addition, this stimulus caused the blood vessels in the stomach to be drawn. Thus, it was found that the function of the blood vessel could be measured by the stimulus (reagent) to be administered.

In particular, the image after administration in FIG.
In the image before administration in FIG.
A very thin blood vessel B _thin could be confirmed. In the case of MT angio which administers the MR contrast agent Gd-DTPA, thin blood vessels such as collateral veinssels do not depend on the temporal change of the contrast effect. For this reason, if collateral circulation occurs due to stenosis in blood vessels,
Such blood circulation cannot be depicted with contrast angiography. On the other hand, according to the imaging of the FBI method of administering acetic acid according to the present invention, it can be expected that such collateral circulation can also be drawn.

Conventionally, BOLD (Blood Oxyge)
A method of performing functional MRI based on a change in T2 ^* (apparent T2 value) such as a nation level dependent method has been known. However, this method is not an imaging method that can directly observe the function of a blood vessel as an image. The present invention allows such direct observation.

Further, by using the reagent containing acetic acid as described above, the function of the blood vessel can be an object of the image. Changes in vascular function of patients with vascular dysfunction or vascular disease, which could not be described until now, can be imaged.

As one of the reagent administration methods described above,
When imaging a vascular disease site, a vasodilator or a blood pressure control reagent can be used as the reagent according to the present invention. Thus, it is possible to depict an interstitial network when there is a collateral circulation or the like due to functional MRA or stenosis before and after administration of a reagent to a patient such as a varicose vein.

By the way, Gd-DTPA-administered CE-M
In the case of the RA method, it has been reported that stenosis is underestimated (Nikki Medical Journal 17: 4; 115-124, 199).
5). As an imaging method for avoiding such underestimation, the FBI method of the present invention can be used.
That is, imaging based on the FBI method may be simply performed in a state where physiological saline is administered. Thereby, the physiological saline functions as a contrast agent, slightly increases the T2 value of blood, and reduces blurring of the T2 value.
As a result, a situation in which stenosis is underestimated can be eliminated as much as possible.

In the above embodiment, the imaging method using the reagent is performed by the FBI method. In this configuration, respiratory synchronization can be used together.

In the present invention, in the above-described pulse sequence for three-dimensional scanning, before executing the data acquisition sequence for imaging as shown in FIG.
In order to suppress the collection of MR signals from fat in the imaging region, an inversion recovery IR pulse and / or a fat suppression pulse F _sat may be applied.

The description of the present embodiment is as described above.
The present invention is not limited to the configuration described in the embodiment, and those skilled in the art can appropriately change and modify the configuration without departing from the gist of the claims. The configuration is also included in the present invention.

[0142]

As described above, according to the MR angiography of the present invention, a signal representing a cardiac phase of a subject is collected, and a pulse sequence for a three-dimensional scan is generated for each slice encoding. Since the imaging region is executed in synchronization with the reference waveform, it is possible to provide a noninvasive MRA image with high depiction ability in the direction of blood vessel travel without administration of a contrast agent. In addition, the phase encoding direction is set to a direction substantially matched to the running direction of the blood flow, including the RF excitation pulse in which the repetition time is set to be short in the pulse sequence, and the slicing direction is perpendicular to this, for example, in the longitudinal direction of the subject. This makes it possible to collect data for each slice encoding substantially parallel to the blood flow direction, so that the imaging time can be significantly reduced. In addition, an image in which arteries and veins are separated can be suitably drawn.

In addition, by executing the above-described method together with a reagent that enhances the blood contrast effect or stimulates blood vessels, it is possible to improve the S / N of a blood flow image and directly image the functions of blood vessels. it can.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an example of a configuration of an MRI apparatus according to an embodiment of the present invention.

FIG. 2 is a view for explaining a temporal relationship between an ECG-prep scan and an imaging scan based on an electrocardiographic synchronization method in the embodiment.

FIG. 3 is an exemplary flowchart illustrating the procedure of an ECG-prep scan executed by a host computer;

FIG. 4 is a timing chart showing an example of an ECG-prep scan.

FIG. 5: MRA of lung field obtained by ECG-prep scan when delay time is dynamically changed
The figure which copied the image typically.

FIG. 6 is a diagram illustrating the spread of signal values in the phase encoding direction.

FIG. 7 is a schematic flowchart illustrating a control example of an imaging scan executed by a host computer.

FIG. 8 is a schematic flowchart illustrating a control example of an imaging scan executed by a sequencer.

FIG. 9 is a rough timing chart showing the timing of an imaging scan based on the ECG gating method according to the first embodiment.

FIG. 10 is a diagram illustrating a positional relationship between a three-dimensional imaging region and each encoding direction.

FIG. 11 is a rough flowchart illustrating an outline of an imaging can process according to the second embodiment;

FIG. 12 is a view for explaining a weighted difference calculation according to the second embodiment.

FIG. 13 is a rough timing chart showing the timing of an imaging scan based on the electrocardiographic synchronization method according to the third embodiment of the present invention.

FIG. 14 is a partial timing chart showing another method of applying a divided MT pulse.

FIG. 15 is a partial timing chart showing still another method of applying a divided MT pulse.

FIG. 16 is a functional block diagram showing an example of a configuration of an MRI apparatus according to a fourth embodiment of the present invention.

FIG. 17 is a rough timing chart showing the timing of an imaging scan using both the ECG gating method and the respiration gating method in the fourth embodiment.

FIG. 18 is a view for explaining an outline of an imaging procedure and collected data processing in a fifth embodiment of the present invention.

FIG. 19 is a view for explaining an outline of an imaging procedure according to another embodiment.

FIG. 20 is a diagram schematically showing an experimental example in the fifth embodiment.

FIG. 21 is a timing chart showing another example of the pulse sequence of the present invention.

[Explanation of symbols]

 Reference Signs List 1 magnet 2 static magnetic field power supply 3 gradient magnetic field coil unit 4 gradient magnetic field power supply 5 sequencer 6 host computer 7 RF coil 8T transmitter 8R receiver 10 operation unit 11 storage unit 12 display 13 input device 16 sound generator 17 ECG sensor 18 ECG Unit 19 Respiration sensor 20 Respiration synchronization unit

Claims (25)

[Claims] 1. An MRI apparatus for generating a blood flow image from an imaging region of a subject, a time phase detecting means for acquiring a signal representing a cardiac phase of the subject;
An MRI apparatus comprising: imaging scanning means for executing a three-dimensional scanning pulse sequence for each slice encoding in synchronization with a signal representing the cardiac phase. 2. The MRI apparatus according to claim 1, wherein the three-dimensional scanning pulse sequence includes an RF excitation pulse whose repetition time is set to be short. 3. The MRI apparatus according to claim 2, wherein the pulse sequence includes a slice direction gradient magnetic field for performing data acquisition based on the slice encoding in a direction substantially parallel to a direction of travel of the blood flow. apparatus. 4. The MRI apparatus according to claim 3, wherein the pulse sequence includes a phase-encoding direction gradient magnetic field that performs phase encoding in a direction substantially matching a running direction of the blood flow. 5. The MRI apparatus according to claim 1, wherein the three-dimensional scanning pulse sequence is a pulse sequence based on a three-dimensional Fourier transform method or a multi-slice method for imaging a volume region. 6. The invention according to claim 1, wherein the time phase detecting means is means for collecting an ECG signal of the subject as a signal representing the cardiac time phase, and wherein the imaging scanning means comprises An MRI apparatus which is means for executing the pulse sequence in synchronization with an R wave appearing in an ECG signal. 7. The MRI apparatus according to claim 6, wherein the repetition time is an interval that is equal to or less than four times an appearance cycle of the R wave. 8. The apparatus according to claim 6, wherein a plurality of sets of echo signals are collected by performing a preparatory scan on the imaging region of the subject at different delay times from the R wave of the ECG signal. And a preparation image generating means for generating the plurality of images from the echo signals, wherein the imaging scanning means captures an optimum value of the delay time determined from the plurality of images. When,
Means for executing the pulse sequence of the subject in synchronization with the optimal delay time. 9. The plurality of sets of echo signals according to claim 1, wherein a preparatory scan is performed on the imaging region of the subject in each of different cardiac phases based on the signal representing the cardiac phase. And a preparation image generating means for generating the plurality of images from the echo signal, wherein the imaging scanning means includes a plurality of cardiac phases determined from the plurality of images. An MRI apparatus comprising: means for capturing an optimal cardiac phase in the apparatus; and means for executing the pulse sequence of the subject in synchronization with the phase. 10. The invention according to claim 1, wherein the scanning unit for imaging obtains a plurality of sets of image data by changing the timing of synchronization with the signal and executing the pulse sequence a plurality of times. An MRI apparatus comprising: a data processing unit that obtains image data in which the artery and vein as the blood flow are separated from each other from the plurality of sets of image data. 11. The invention according to claim 10, wherein the data processing means adds a weight to the plurality of sets of image data and makes a difference therebetween to obtain one set of difference image data; Generating means for generating a final image depicting the blood flow from a set of differential image data
I device. 12. The MRI apparatus according to claim 11, wherein the generation unit performs a maximum intensity projection (MIP) from the set of difference image data. 13. The breath according to claim 1, wherein the subject instructs the subject to perform breath holding at least while the imaging scanning unit is executing the pulse sequence. An MRI apparatus including a stop command unit. 14. The invention according to claim 1, further comprising a respiratory cycle detecting means for detecting a respiratory cycle of the subject, wherein the scanning means for imaging includes a signal detected by the time phase detecting means and the respiratory cycle. An MRI apparatus, which is means for executing the pulse sequence in synchronization with a respiratory cycle detected by the detection means. 15. The MRI apparatus according to claim 1, wherein the time phase detection unit and the imaging scanning unit are operated in a state where a reagent is administered to the subject. 16. The MRI apparatus according to claim 15, wherein the reagent is a reagent that imparts a contrast effect to a blood flow of the subject. 17. The MRI apparatus according to claim 16, wherein the reagent is physiological saline or glucose. 18. The method according to claim 15, wherein the reagent is a reagent that stimulates a blood vessel of the subject.
RI equipment. 19. The MRI according to claim 18, wherein the reagent is acetic acid or a beverage containing acetic acid.
apparatus. 20. The apparatus according to claim 1, wherein the imaging scan is executed separately before and after administering a reagent to the subject to obtain a plurality of sets of MR signals, and the plurality of sets of MR signals are provided. Means for generating a blood flow image of the subject from the MRI apparatus. 21. The invention according to claim 1, wherein the pulse sequence is an MR comprising a pulse train formed based on an FSE method, a FASE method, or an EPI method.
I device. 22. An M for depicting a blood flow in an imaging region of a subject
In the R imaging method, a signal representing a cardiac phase of the subject is collected, and a pulse sequence for a three-dimensional scan is synchronized with a reference waveform in the signal for an imaging region of the subject for each slice encoding. An MR imaging method which is performed in a state. 23. The MR imaging method according to claim 22, wherein the pulse sequence has a repetition time set to be short.
An MR imaging method including a pulse. 24. The MR imaging method according to claim 23, wherein the pulse sequence includes a gradient magnetic field in a slice direction for performing data acquisition based on the slice encoding in a direction substantially parallel to a traveling direction of the blood flow. MR imaging method. 25. The MR imaging method according to claim 24, wherein the pulse sequence includes a phase-encoding direction gradient magnetic field that performs phase encoding in a direction substantially matching a running direction of the blood flow.