JP4253526B2 - Magnetic resonance imaging system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to magnetic resonance imaging that images the inside of a subject based on the magnetic resonance phenomenon of spins (nuclear spins), and in particular, without using a contrast agent, The present invention relates to a magnetic resonance imaging apparatus capable of collecting and presenting dynamic information.
[0002]
[Prior art]
Magnetic resonance imaging is an imaging method in which a nuclear spin of a subject placed in a static magnetic field is magnetically excited with a high-frequency signal of its Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation. .
[0003]
In the field of magnetic resonance imaging, when an blood flow image of a lung field or abdomen is obtained, clinically, MR angiography in which a contrast medium is administered to a subject and angiography is started. However, since this contrast-enhanced MR angiography method involves administration of a contrast agent, an invasive treatment is required for the subject, and above all, the burden on the patient's mental and physical strength is great. Also, the inspection cost is high. Furthermore, the contrast agent may not be administered depending on the patient's constitution.
[0004]
As an alternative to this contrast-enhanced MR angiography method, the present inventor has applied a readout gradient magnetic field pulse in the direction of blood flow indicating movement inside a subject placed in a static magnetic field, as shown in Patent Document 1. Means for acquiring an echo signal from the subject by executing a scan based on a pulse sequence including the readout gradient magnetic field pulse in a substantially aligned state, and means for generating an image from the echo signal; A readout gradient magnetic field pulse is formed by a pulse body for reading an echo signal, and an intensity-changeable phase behavior control pulse that is added to the pulse body and controls the phase behavior of the magnetization spin in the blood flow. The control pulse is formed by a dephasing pulse or a rephasing pulse for dephasing or rephasing the magnetization spin of the fluid. It is. In this scan, an optimal electrocardiographic synchronization timing is measured in advance, and the electrocardiographic synchronization scan is executed at this timing.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-200054
[Problems to be solved by the invention]
However, the scan based on the pulse sequence including the readout gradient magnetic field pulse described in Patent Document 1 described above is executed as an imaging scan, and a preparation called an ECG-prep scan is performed before this scan is executed. Because it is necessary to measure the optimal ECG synchronization timing by performing a medical scan, and the measurement takes time and effort, information on blood flow dynamics more easily and non-contrastly in the medical field It was in the present situation that it was not able to respond to the request to obtain.
[0007]
The present invention was made in order to break down the current state of the prior art, without the need to administer a contrast agent, and without the need to measure the prior ECG synchronization timing. It is an object of the present invention to provide a magnetic resonance imaging apparatus that provides fluid dynamics information such as blood flow in a subject.
[0008]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention synchronizes each of the reference waves appearing in the signal representing the cardiac time phase of the subject collected by the cardiac phase collecting means with a plurality of different delay times. In the magnetic resonance imaging apparatus including a scan unit that performs a scan based on a pulse sequence on a desired region of the subject and collects an echo signal based on magnetic resonance from the desired region, the pulse sequence includes the echo signal at a frequency A read gradient magnetic field pulse for encoding and reading out, the read gradient magnetic field pulse being added to the pulse main body and the phase behavior for controlling the phase behavior of the magnetized spin in the desired region And a plurality of delay times different from each other by the scanning means. It generates a difference image by subtracting calculating a plurality of image data based on the plurality of echo signals in the time axis direction in a plurality of time phases collected in synchronization with each of the desired region of the subject as the difference image It is characterized by comprising dynamic information providing means for providing dynamic information relating to a flowing fluid for imaging purposes.
[0009]
By appropriately adjusting the intensity of the phase behavior control pulse, the state of spin phase dispersion can be positively controlled. As a result, echo signals can be reliably collected from a fluid having a low flow velocity (such as a blood flow) or a fluid having a too high flow velocity. At the same time, since echo signals are collected at different cardiac phases, that is, by multi-face, it is possible to provide fluid dynamic information by performing appropriate processing such as differential calculation on the echo signals. As a result, since it is not necessary to perform a preparatory scan and measure the optimal ECG synchronization timing in advance, an easy-to-use MR imaging method can be provided.
[0010]
Preferably, the scanning means is configured to perform the scan so that an application direction of the readout gradient magnetic field pulse included in the pulse sequence is substantially matched with a flow direction of the fluid. In this case, for example, the phase behavior pulse is formed by a dephasing pulse or a rephasing pulse for dephasing or rephasing the magnetization spin of the fluid. It is preferable that the intensity of the phase behavior control pulse is changed according to the flow velocity of the fluid.
[0011]
Preferably, the dynamic information providing means is configured to display and display the dynamics of the fluid flow .
[0012]
For example, the pulse sequence is at least one pulse sequence selected from a pulse sequence group including a pulse sequence of a half Fourier FSE (Fast Spin Echo) method, an EPI (Echo Planar Imaging) method, and an FSE (Fast Spin Echo) method. It is a pulse sequence. The pulse sequence is composed of, for example, a pulse train responsible for two-dimensional scanning.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below.
[0014]
(First embodiment)
A first embodiment will be described with reference to FIGS.
[0015]
A schematic configuration of a magnetic resonance imaging (MRI) apparatus according to this embodiment is shown in FIG.
[0016]
(1.1) Configuration of Apparatus This magnetic resonance imaging apparatus includes a bed unit on which a subject P is placed, a static magnetic field generation unit that generates a static magnetic field, and a gradient magnetic field generation unit for adding position information to the static magnetic field. A transmission / reception unit that transmits / receives a high-frequency signal, a control / calculation unit that controls the entire system and image reconstruction, and an electrocardiogram measurement unit that measures an ECG signal as a signal representing the cardiac time phase of the subject P ing.
[0017]
The static magnetic field generation unit includes, for example, a superconducting magnet 1 and a static magnetic field power supply 2 that supplies current to the magnet 1, and an axial direction of a cylindrical opening (diagnostic space) into which the subject P is loosely inserted. (Z-axis direction) to generate a static magnetic field _{H 0.} In addition, the shim coil 14 is provided in this magnet part. The shim coil 14 is supplied with a current for homogenizing a static magnetic field from a shim coil power supply 15 under the control of a host computer to be described later. The couch portion can removably insert the top plate on which the subject P is placed into the opening of the magnet 1.
[0018]
The gradient magnetic field generator includes a gradient magnetic field coil unit 3 incorporated in the magnet 1. The gradient coil unit 3 includes three sets (types) of x, y, and z coils 3x to 3z for generating gradient magnetic fields in the X-axis direction, the Y-axis direction, and the Z-axis direction orthogonal to each other. The gradient magnetic field unit also includes a gradient magnetic field power supply 4 that supplies current to the x, y, and z coils 3x to 3z. The gradient magnetic field power supply 4 supplies a pulse current for generating gradient magnetic fields to the x, y, z coils 3x to 3z under the control of a sequencer 5 described later.
[0019]
By controlling the pulse current supplied to the x, y, z coils 3x to 3z from the gradient magnetic field power source 4, the gradient magnetic fields in the three axes (X axis, Y axis, Z axis) directions which are physical axes are synthesized. it can be arbitrarily set and change the logical axial consisting slicing direction gradient magnetic field G _S, the phase encode direction gradient magnetic field G _E, and readout direction (frequency encode direction) gradient magnetic field G _R which are orthogonal to each other. Slice direction, phase encoding direction, and gradient magnetic fields in the readout direction are superimposed on the static magnetic field H _0.
[0020]
The transmission / reception unit includes an RF coil 7 disposed in the vicinity of the subject P in the imaging space in the magnet 1, and a transmitter 8T and a receiver 8R connected to the coil 7. The transmitter 8T and the receiver 8R operate under the control of the sequencer 5 described later. 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 takes in an MR signal (high frequency signal) such as an echo signal received by the RF coil 7, and performs various signal processing such as preamplification, intermediate frequency conversion, phase detection, low frequency amplification, and filtering. After that, A / D conversion is performed to generate digital data (original data) of the MR signal.
[0021]
Further, 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, a display device 12, an input device 13, and a sound generator 16. Among these, the host computer 6 has a function of instructing the pulse sequence information to the sequencer 5 according to the stored software procedure (not shown) and supervising the operation of the entire apparatus.
[0022]
The sequencer 5 includes a CPU and a memory, stores pulse sequence information sent from the host computer 6, controls the operations of the gradient magnetic field power source 4, the transmitter 8T, and the receiver 8R according to this information, The digital data of the MR signal output from the receiver 8R is once inputted and transferred to the arithmetic unit 10. Here, the pulse sequence information is all information necessary for operating the gradient magnetic field power source 4, the transmitter 8T, and the receiver 8R according to a series of pulse sequences, for example, x, y, z coils 3x to 3z. Includes information on the intensity, application time, application timing, and the like of the pulse current applied to.
[0023]
This pulse sequence may be a two-dimensional (2D) scan or a three-dimensional scan (3D) as long as the Fourier transform method is applied. In particular, considering the length of the scan time, This embodiment is suitable for two-dimensional scanning. In addition, the pulse train forms include a fast SE (FSE) method, an EPI (Echo Planar Imaging) method, and a FASE (Fast Asymmetric SE) method (that is, an imaging method in which the fast Fourier transform method is combined with the half Fourier method). And the like are particularly suitable.
[0024]
As will be described later, these pulse sequences are executed as an electrocardiographic synchronization method based on a multi-face (a plurality of cardiac time phases), which is a part of the features of the present invention.
[0025]
More preferably, this electrocardiographic synchronization method is used in combination with a breath-holding method in which the subject holds his / her breath for several tens of seconds to 1 minute, depending on the scan time, to prevent body movement artifacts. You may make it do.
[0026]
In addition, the above-described electrocardiographic synchronization method may be executed under a parallel imaging (PI) method that has recently attracted attention as a high-speed imaging method. This parallel imaging method basically uses an array coil consisting of a plurality of RF coils (element coils) (hereinafter referred to as Phased Array Coil: PAC), a so-called multi-coil, and skips the phase encoding so that the phase encoding is performed. This is performed under the so-called sub-encoding acquisition, in which the number is reduced to a fraction of the number of RF coils of the predetermined phase encoding number required for image reconstruction. Thereby, each RF coil receives an echo signal simultaneously, and image data is produced | generated for every RF coil from these received echo signals. As a result, the FOV of the image generated for each RF coil is reduced, the scan time is shortened, and the shooting speed is increased.
[0027]
On the other hand, in an image obtained by reconstructing echo signals collected from each RF coil, folding (wrap-around or folding; also referred to as aliasing) occurs at the image end. Therefore, in the case of this parallel MR imaging method, using the fact that the sensitivities of the plurality of RF coils are individually different, a development process for unfolding each of a plurality of images obtained corresponding to each RF coil. Is performed as post-processing. For this development process, a spatial sensitivity map of the RF coil is used.
[0028]
A plurality of images subjected to this development processing are combined with the final full FOV (field of view) image. As described above, the parallel imaging method can speed up scanning (high-speed imaging), and can obtain a final image with a wide field of view, for example, the entire abdomen.
[0029]
Referring back to FIG. 1, the arithmetic unit 10 inputs digital data (also referred to as original data or raw data) output from the receiver 8R through the sequencer 5, and the k space (Fourier space or frequency space) of its internal memory. Also, the digital data is arranged on the image data, and the data is subjected to two-dimensional or three-dimensional Fourier transform for each set to reconstruct the image data in real space. In addition, the arithmetic unit can execute data composition processing and difference calculation processing (including weighted difference processing) as necessary. This synthesis processing includes processing for adding each pixel, maximum value projection (MIP) processing, and the like. As another example of the above synthesis process, the axes of a plurality of frames may be aligned in Fourier space, and the original data may be synthesized into one frame of original data. The addition processing includes simple addition processing, addition averaging processing, weighted addition processing, and the like.
[0030]
The storage unit 11 can store not only the reconstructed image data but also the image data that has been subjected to the above-described combining process and difference process. The display device 12 displays an image. Further, via the input unit 13, information regarding ECG synchronization timing setting information, scan conditions, pulse sequences, image synthesis and difference calculation desired by the operator can be input to the host computer 6.
[0031]
The voice generator 16 can issue a breath holding start message and a breath holding end message as voice when instructed by the host computer 6.
[0032]
Further, the electrocardiogram measurement unit attaches to the body surface of the subject and detects an ECG signal as an electrical signal, and performs various processing including digitization processing on the sensor signal to perform the host computer 6 and the sequencer. And an ECG unit 18 for outputting to the PC. The measurement signal from the electrocardiogram measurement unit can be used when an imaging scan based on the electrocardiogram synchronization method is executed.
[0033]
(1.2) Imaging Scan Next, the operation of the imaging scan in this embodiment will be described with reference to FIGS.
[0034]
The host computer 6 executes a predetermined main program (not shown), and as a part thereof, executes the imaging scan process shown in FIG. 2 in response to the operation information from the input device 13.
[0035]
Specifically, the host computer 6 scans conditions specified by the operator from the input device 13 (application direction of readout direction gradient magnetic field pulse, image size, type of pulse sequence corresponding to the scan region, etc.), phase behavior control pulse conditions (Types of phase control pulses (partial flow compensation (Partial FC) pulses or Partial Flow spoiling (Partial FS) pulses), intensity of phase behavior control pulses, etc.) to be added to the gradient magnetic field pulses in the readout direction, ECG Synchronization conditions (initial delay time d1, delay time increment value, number of synchronizations (number of captured images), RR interval, etc.), and image processing method information (MIP processing, difference processing, etc. In the case of difference processing, Simple difference, weighted difference processing, addition processing, etc.), and processing those information into control data, The control data is output to the sequencer 5 and the arithmetic unit 10 (step S1).
[0036]
Next, when the host computer 6 can determine that there is a notification of completion of preparation before scanning (step S2), it outputs a breath holding start command to the sound generator 14 (step S3). As a result, the voice generator 14 issues a voice message of “Please hold your breath”, so that the patient who hears it will hold his breath.
[0037]
Thereafter, the host computer 6 instructs the sequencer 5 to start an imaging scan (step S4).
[0038]
Upon receiving this imaging scan start command, the sequencer 5 executes a pulse sequence specified in advance as pulse sequence information under the electrocardiographic synchronization method based on the ECG signal.
[0039]
An example of this pulse sequence is shown in FIG. The pulse sequence shown in the figure is composed of a pulse train based on a two-dimensional FASE method. However, in this pulse train, the slice direction gradient magnetic field pulse and the phase encode direction gradient magnetic field pulse are not shown, and only the read direction gradient magnetic field pulse (RO gradient) is obtained as its original (original) waveform and phase behavior control pulse. The partial flow spoiling (Partial FS) pulse and the pulse partial flow compensation (Partial FC) pulse as the phase behavior control pulse are described in order from the bottom of the figure. The echo interval (ETS) is shortened to about 4 msec as much as possible to shorten the scanning time.
[0040]
Partial FC pulse is a pulse applied in the direction of the opposite polarity to the readout gradient magnetic field pulse (refer to the original pulse: original waveform) when the blood flow velocity is fast, and when the blood flow velocity is fast or fast An object of the present invention is to suppress the phase dispersion of the magnetization spin and to reliably capture a signal value. The Partial FS pulse is a pulse applied in the direction of the same polarity as the readout gradient magnetic field pulse (main body pulse) when the blood flow velocity is slow, and the magnetization spin when the blood flow velocity is slow or slow The purpose is to facilitate the phase dispersion of the signal so that a high signal value can be collected.
[0041]
The Partial FC pulse and Partial FS pulse are added to the back of the readout gradient magnetic field pulse (main body pulse) so that the pulse added to the head in the direction of the time axis functions as a pair with this leading pulse. The pulse has a function of compensating the spin phase controlled by the leading pulse. As described above, both partial pulses attached to the head and the rear serve the same purpose of controlling the phase behavior of the spin. Therefore, both partial pulses are referred to as phase behavior control pulses (Partial FC pulse and Partial FS pulse). .
[0042]
Note that the term “Partial” used in the present embodiment indicates that it is partial with respect to the main body pulse, and this “partial” means that the waveform area (intensity) of the main body pulse is 100. % Represents an area range greater than 0 and less than 100%. Therefore, the proportion of the waveform area of the phase behavior control pulse is specified by the operator together with the type of the pulse in the input items of the phase behavior control pulse condition in consideration of the blood flow velocity flowing through the measurement target site. .
[0043]
The waveform area of the phase behavior control pulse, that is, the intensity for controlling the spin phase is not limited to the case where the operator manually sets according to the type of the desired imaging region. The relationship is stored as a table so that the intensity of the phase behavior control pulse can be automatically set by referring to this table in response to the operator specifying a desired imaging region in the scan conditions. Also good.
[0044]
Further, as schematically shown in FIG. 3, a pulse train based on the two-dimensional FASE method is applied to a desired imaging region of the subject under the condition instructed by the operator according to the electrocardiographic synchronization condition. Specifically, a one-shot scan based on the two-dimensional FASE method is executed in synchronization with a time delayed by a delay time d1 from the peak value of the R wave first appearing in the ECG signal. As a result, the two-dimensional k-space is filled and echo data is collected (at this time, a part of the k-space where the echo data is filled by computation according to the half Fourier method after the collection is excluded). Then, after 2R-R, in synchronization with a time delayed by d2 (> d1) from the peak value of the R wave, a one-shot scan based on the two-dimensional FASE method is executed on the same slice as the previous time. Further, after 2R-R, in synchronization with the time delayed by d3 (> d2) from the peak value of the R wave, a one-shot scan based on the two-dimensional FASE method is executed on the same slice as the previous time. Similarly, the same scan is performed on the same slice while changing the delay time by a predetermined increment value.
[0045]
At this time, the initial delay time, the increment value (change width of the delay time), and the number of shots are specified by the operator according to the electrocardiographic synchronization condition. For example, the initial delay time = 100 msec, the increment value = 5 ms, and the number of shots = 30 times. In particular, the delay time increment value, that is, “dn _{+ 1− dn} ” is a very short time interval of several ms. The feature is that blood flow dynamics can be observed by setting. The RR interval is also designated in advance by the operator according to the blood flow velocity to be observed. When the blood flow velocity is relatively fast, the flow of fresh blood flow to the observation site is also fast, so that it can be set to 1R-R or 2R-R, while the blood flow velocity is relatively slow. In some cases, for example, an interval of 3R-R or more is set in order to wait for a fresh blood flow to flow into the observation site.
[0046]
Furthermore, according to this pulse sequence, the application direction of the readout magnetic gradient pulses G _R, an operator, the image pickup object of blood flow (arterial AR, vein VE) is set in advance such that substantially coincides with the direction of flow of.
[0047]
Returning to FIG. 3, when receiving a scan completion notification from the sequencer 5 (step S5), the host computer 6 outputs a breath holding release command to the sound generator 16 (step S6). Therefore, the voice generator 16 issues a voice message such as “It is fine to breathe” to the patient, and the breath holding period ends.
[0048]
An echo signal generated from the patient P is received by the RF coil 7 and sent to the receiver 8R. The receiver 8R performs various preprocessing on the echo signal and converts it into a digital quantity. This digital amount of echo data is sent to the arithmetic unit 10 through the sequencer 5, and is arranged for each line position corresponding to the phase encoding amount of the two-dimensional k-space formed by the memory.
[0049]
When the above imaging scan is completed, echo data collected in single slice / multiphase is arranged in each k-space, and further, data is satisfied by calculation under the half Fourier method. Image reconstruction is performed. As a result, real space image data of the same slice with different cardiac time phases by increment value INC (= “dn _{+ 1− dn} ”) is sequentially generated (step S7).
[0050]
When the image reconstruction is completed, the host computer 6 displays the created real space image as it is in time series as an MRA image (step S8). As a result, blood flow dynamic information can be provided to the operator to some extent.
[0051]
In addition, the host computer 6 determines whether or not to perform cine display based on the difference calculation based on the created real space image by performing an interactive exchange with the operator (step S9). When execution of cine display is decided by this determination, the host computer 6 performs calculation of the difference image and cine display (moving image display) (steps S10 and S11). These calculations may be performed by the calculation unit 10.
[0052]
When a plurality of single-slice / multi-phase images collected as described above are represented within one cardiac cycle, a conceptual diagram shown in FIG. 4 is obtained. That is, it becomes a plurality of images in which the same slice is collected in order in different cardiac phases d1, d2, d3,. For example, the increment value INC may be several ms, several tens of ms, or about 100 ms.
[0053]
As described above, the plurality of images are acquired by adding a partial FC pulse or a partial FS pulse as a phase behavior control pulse to a pulse body of a reading direction gradient magnetic field pulse. For this reason, the degree of variation (phase dispersion) of spins collected in each cardiac cycle is suppressed or promoted by the Partial FC pulse or Partial FS pulse. That is, the signal values collected in the cardiac cycle can be conceptually controlled as shown in FIG. The curve in the figure shows the change between the blood flow velocity from the systole to the diastole (in the case of a relatively high flow velocity) and the signal value collected by the FASE method. By changing the intensity of the Partial FC pulse or Partial FS pulse, the signal value curve can be controlled as shown by S1 and S2 in FIG. By appropriately setting the intensity of the Partial FC pulse or Partial FS pulse, it is possible to provide an image (MRA image) depicting blood flow while enhancing the signal value difference between different cardiac phases t1 and t2. it can.
[0054]
Therefore, when a plurality of images are subjected to a difference calculation by an appropriate method in the time axis direction (ascending order or descending order), the stationary pixel signal is erased, and the component that moves and changes the pixel signal, that is, blood flow Can be drawn. This difference calculation, for example, is based on the first or last acquired image in the time axis direction, and the remaining images are sequentially subtracted from the image along the time axis direction, so that only the blood flow dynamics are obtained. Can be drawn. The dynamics of blood flow can be dynamically provided by displaying a plurality of difference images generated by the difference calculation in a cine (moving image) manner.
[0055]
In addition, as information representing the blood flow dynamics, the blood flow velocity may be calculated from the plurality of images described above and displayed numerically or in graph form.
[0056]
As described above, according to the present embodiment, the partial FC pulse or the partial FS pulse whose intensity is adjusted is added to the gradient magnetic field pulse in the reading direction, and the scan is performed by changing the cardiac phase within one cardiac cycle. It is possible to provide information on blood flow dynamics by realizing differentiation of arteries and veins of slow blood flow and reduction of dephasing effect of fast blood flow. Therefore, it is not necessary to perform a preparatory scan for measuring the optimal ECG synchronization timing before an imaging scan as in the past, and it is possible to observe blood flow dynamics easily and quickly. it can.
[0057]
In particular, in the case of a conventional ECG-prep scan, the arteriovenous separation of a blood vessel having an ETS (echo train spacing) and a blood flow velocity suitable for each other was possible. The arteriovenous separation of blood vessels was difficult. This is because in order to prevent blur in the phase encoding direction, it is necessary to use a pulse sequence of FSE method or FASE method in which ETS is shortened as much as possible. In this case, the signals are gathered too much, and the arteriovenous separation cannot be performed. Furthermore, even in the case of blood vessels with high blood flow velocity (aortic arch, neck, etc.), even if ETS is shortened, the signal is dephased during the ETS period, so that N / 2 artifacts are likely to occur in the reconstructed image. . On the other hand, according to the present embodiment, a partial FC pulse or a partial FS pulse is added. Therefore, by adjusting the pulse intensity to an appropriate value, a change in the dephasing or rephasing of the magnetized spin is positively performed. Therefore, the flow void effect can be controlled and the problems of the ECG-prep scan can be overcome.
[0058]
Furthermore, since it is not necessary to administer a contrast medium, non-invasive imaging can be performed, and the mental and physical burden on the patient is remarkably reduced from this point. At the same time, it is freed from the troublesomeness inherent in contrast methods, such as the need to measure the timing of the contrast effect.
[0059]
The description of the embodiment is as described above, but the present invention is not limited to the configuration described in the embodiment, and those skilled in the art can appropriately change the configuration without departing from the gist described in the claims. These can be modified, and their configurations are also included in the present invention.
[0060]
【The invention's effect】
As described above , according to the magnetic resonance imaging apparatus of the present invention, it is not necessary to measure the electrocardiogram synchronization timing in advance without administering a contrast agent, and it is easier than in the past. Fluid dynamic information such as blood flow can be provided for medical diagnosis.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration example of a magnetic resonance imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic flowchart illustrating a process for an imaging scan and acquired data executed in the embodiment.
FIG. 3 is a timing chart showing an example of a pulse sequence used in the embodiment.
FIG. 4 is a diagram for explaining a difference calculation in one cardiac cycle performed to extract blood flow dynamic information.
FIG. 5 is a diagram for explaining an example of the relationship between blood flow velocity and signal intensity from systole to diastole.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnet 2 Static magnetic field power supply 3 Gradient magnetic field coil unit 4 Gradient magnetic field power supply 5 Sequencer 6 Host computer 7 RF coil 8T Transmitter 8R Receiver 10 Arithmetic unit 11 Storage unit 12 Display 13 Input device 17 ECG sensor 18 ECG unit

Claims (9)

A scan based on a pulse sequence in a desired region of the subject in synchronization with a plurality of different delay times for each of a plurality of reference waves appearing in a signal representing the cardiac time phase of the subject collected by the cardiac phase collection means In a magnetic resonance imaging apparatus comprising a scanning unit that executes echo and collects echo signals based on magnetic resonance from the desired region,
The pulse sequence includes a read gradient magnetic field pulse for frequency-encoding and reading the echo signal,
The readout gradient magnetic field pulse is formed by a pulse main body that carries out the frequency encoding, and a phase behavior control pulse that is added to the pulse main body and controls the phase behavior of the magnetization spin in the desired region. A difference image is generated by performing a difference calculation in a time axis direction on a plurality of image data based on a plurality of echo signals in a plurality of time phases collected in synchronization with a plurality of different delay times, and as the difference image, A magnetic resonance imaging apparatus comprising dynamic information providing means for providing dynamic information relating to a fluid for imaging flowing through a desired region of a subject. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus according to claim 1, wherein the scanning unit is configured to execute the scan so that an application direction of the readout gradient magnetic field pulse included in the pulse sequence is substantially matched with a fluid flow direction. The magnetic resonance imaging apparatus according to claim 1.
2. The magnetic resonance imaging apparatus according to claim 1, wherein the phase behavior pulse is formed by a dephase pulse or a rephase pulse for dephasing or rephasing a magnetization spin of a fluid. The magnetic resonance imaging apparatus according to claim 3.
A magnetic resonance imaging apparatus configured to change the intensity of the phase behavior control pulse in accordance with a velocity of the fluid flow. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus characterized in that the dynamic information providing means is configured to image and display dynamics of the fluid flow. The magnetic resonance imaging apparatus according to any one of claims 1 to 5 ,
The pulse sequence is one pulse sequence selected from a pulse sequence group including a pulse sequence of at least a half Fourier FSE (Fast Spin Echo) method, an EPI (Echo Planar Imaging) method, and an FSE (Fast Spin Echo) method. A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 6 .
2. The magnetic resonance imaging apparatus according to claim 1, wherein the pulse sequence is composed of a pulse train responsible for two-dimensional scanning. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus according to claim 1, wherein the scanning unit is configured to receive the echo signal by parallel imaging using a plurality of element coils and skipping phase encoding to receive the echo signal. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the dynamic information providing means includes display means for displaying the blood flow velocity as a numerical value or a graph as the dynamic information.

Images