JP2005305151A - Magnetic resonance imaging apparatus and method for collecting magnetic resonance signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging instrument for a non-contrast MRA which reduces the burden of a subject accompanied with the use of an ECG synchronizing technique, prevents the picture quality from lowering, and further, can prevent a patient throughput from lowering. <P>SOLUTION: The magnetic resonance imaging instrument is equipped with a first RF coil (carried in a coil unit 20) which collects a magnetic resonance signal from the subject, cardiac time phase estimation means (6 and 10) which estimate the cardiac time phase of the subject from the magnetic resonance signal collected by this first RF coil, a second RF coil (7) which collects the magnetic resonance signal from the subject based on this estimated cardiac time phase, and reorganization means (6 and 10) which reconstruct the magnetic resonance image of the subject from the magnetic resonance signal collected by this second RF coil (7). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a medical magnetic resonance imaging apparatus and a method for acquiring a magnetic resonance signal. In particular, the present invention does not use an electrocardiographic synchronization (ECG) apparatus itself, but is substantially non-contrast-enhanced MRA (under an electrocardiographic synchronization trigger scan). The present invention relates to a magnetic resonance imaging apparatus capable of performing MR Angiography) and a method of collecting magnetic resonance signals used in the apparatus.

  In magnetic resonance (MR) imaging, the 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 using the MR signal generated by this excitation. This is an imaging method. Magnetic resonance imaging devices that implement this imaging method are now an essential medical modality.

  In medical image diagnosis by magnetic resonance imaging, MRA for rendering a blood vessel image of a subject is an important imaging method. As one of the classification methods, MRA is classified into contrast MRA or non-contrast MRA depending on whether or not a contrast agent is administered to a subject.

  Contrast-enhanced MRA is an imaging method in which a contrast agent is administered to a subject and an MR scan is performed. However, in order to administer a contrast agent, an invasive treatment is required for the subject. The physical burden is heavy. Also, the inspection cost is high. Furthermore, the contrast agent may not be administered depending on the patient's constitution. For this reason, clinical non-contrast MRA is desired.

  One of the non-contrast MRA is a non-contrast MRA method that reflects a water component in blood. As a technique that falls into this category, as seen in Patent Document 1, SPEED (Swap Phase Encode Extended Data) is used to depict pulmonary blood vessels with a relatively high flow rate by using the blurring effect of T2 relaxation time of blood. And the FBI (Fresh Blood Imaging) method in which blood pumped from the heart using the ECG synchronization method is scanned in a time phase in which the blood flow velocity is relatively stable, as can be seen in Japanese Patent Application Laid-Open No. H11-133260.

Since the SPEED method and the FBI method are based on the FSE (Fast SE) method, if the influence of the movement of the subject that occurs between echoes on the data collection fluctuates greatly, a ghost is generated on the reconstructed image. It tends to occur and the image quality deteriorates. For this reason, it is important to scan in a time phase where the blood flow velocity is stable. In particular, when an artery is depicted, it is necessary to scan at a time phase in which the blood flow velocity is relatively slow (diastolic phase of the cardiac cycle). Therefore, the combined use of the ECG synchronization method is indispensable.
JP 11-338409 A JP-A-11-47115

  However, as can be seen from the above-mentioned publication, in the case of non-contrast-enhanced MRA that requires the ECG synchronization method, a plurality of electrodes for signal detection of the electrocardiogram synchronization device must be attached to the subject. Unresolved issues associated with were pointed out. In other words, the task of attaching a plurality of electrodes to the body surface of the subject is a considerable burden for the operator who prepares for magnetic resonance imaging, and the spirit that the electrodes are also attached to the patient who is the subject. And physical burden may increase. Furthermore, a signal of a gradient magnetic field for scanning may be superimposed on the ECG signal detected by this electrode, which may cause a disturbance in the waveform of the detected ECG signal. When the disturbance of the ECG waveform becomes large, it may be difficult to detect the R wave. As a result, the image quality of the reconstructed image may be reduced, and the scan time of magnetic resonance imaging will be longer than necessary due to settings and re-scanning, and patient throughput will be reduced. there were.

  Therefore, the present invention has been made in view of the unsolved problems of the non-contrast-enhanced MRA based on the above-described conventional ECG synchronization method, and reduces the burden on the subject associated with the use of the ECG synchronization method. It is an object of the present invention to provide a magnetic resonance imaging apparatus for non-contrast-enhanced MRA and a method for collecting magnetic resonance signals, which can prevent a decrease in the patient's throughput and further prevent a decrease in patient throughput.

  In order to achieve the above-described object, a magnetic resonance imaging apparatus according to an aspect of the present invention includes a first RF coil that collects magnetic resonance signals from a subject, and the magnetism collected by the first RF coil. A cardiac time phase estimating means for estimating a cardiac time phase of the subject from a resonance signal; a second RF coil for collecting a magnetic resonance signal from the subject based on the estimated cardiac time phase; Reconstructing means for reconstructing a magnetic resonance image of the subject from the magnetic resonance signals collected by the RF coil.

  According to another aspect of the present invention, there is provided a magnetic resonance imaging apparatus that collects a magnetic resonance signal from a subject and estimates a cardiac time phase of the subject from the magnetic resonance signal; A second scanning means for collecting magnetic resonance signals of a plurality of time phases of the subject based on the cardiac time phase obtained by one scanning means; and a magnetic resonance signal obtained by the second scanning means. Preparatory image generating means for generating a plurality of preparatory images, image specifying means for specifying at least one of the plurality of preparatory images, and the target image in a time phase corresponding to the specified image. And third scanning means for collecting magnetic resonance signals from the specimen.

  Furthermore, in the present invention, as one aspect thereof, the step of estimating the cardiac time phase of the subject based on the magnetic resonance signal collected from the first region of the subject using the first RF coil, and the estimation Providing the information on the cardiac phase to the means for collecting the magnetic resonance signal for imaging the second region of the subject using the second RF coil. Is done.

  According to the present invention, magnetic resonance imaging for non-contrast-enhanced MRA can reduce the burden on the subject associated with the use of the ECG synchronization method, prevent deterioration in image quality, and further prevent reduction in patient throughput. An apparatus and a method for collecting magnetic resonance signals can be provided.

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

(First embodiment)
A first embodiment of a magnetic resonance imaging apparatus and a magnetic resonance signal collection method according to the present invention will be described with reference to FIGS.

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

  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, a gradient magnetic field generation unit for adding position information to the static magnetic field, and a transmission / reception unit that transmits and receives high-frequency signals. And a control / arithmetic unit responsible for overall system control and image reconstruction.

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.

  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.

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.

  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. With this operation, 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 the MR signal (high frequency signal) received by the RF coil 7 and performs various signal processing such as preamplification, intermediate frequency conversion, phase detection, low frequency amplification, filtering, etc. Digital data (original data) of MR signal is generated by / D conversion.

  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 commanding the pulse sequence information to the sequencer 5 according to the stored software procedure (not shown) and supervising the operation of the entire apparatus.

  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.

  This pulse sequence is of a two-dimensional (2D) scan or a three-dimensional scan (3D), and the form of the pulse train is FE (gradient echo) method, FFE (fast FE) method, SE (spin). Various forms such as Echo), FSE (Fast SE), FASE (Fast Asymmetric SE), EPI (Echo Planar Imaging), etc., and pulse trains based on these techniques are implemented by the segmented method Can also be adopted.

  In addition, 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 a two-dimensional or three-dimensional k-space (Fourier space or frequency space) by its internal memory. Also, the digital data is arranged on the image data, and the data is subjected to a two-dimensional or three-dimensional Fourier transform for each set to reconstruct the image data in real space. The arithmetic unit is also capable of executing data composition processing and difference arithmetic 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.

  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 12 is used for displaying a reconstructed image, for example. Also, parameter information desired by the surgeon, scan conditions, pulse sequences, information relating to image synthesis and difference calculation, and the like can be input to the host computer 6 via the input unit 13.

  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.

  In the present embodiment, a configuration in which an ECG (electrocardiogram) measurement apparatus is actually used to obtain an ECG signal from a subject is not employed, but an imaging scan based on electrocardiographic synchronization is performed in a pseudo manner. Yes. For this purpose, it is necessary to obtain a signal or information that serves as an index for estimating the cardiac phase of the subject. As such a signal or information, in the case of the present invention, a change in blood flow velocity flowing in the ventricle (that is, a change in the phase shift amount of the spin of blood flow), a change in MR signal value obtained from the heart (ventricle), Use changes in ventricular size. In the following description, a change in blood flow velocity flowing through the ventricle is used as an index for estimating the cardiac time phase of the subject. That is, in the present embodiment, it is possible to perform imaging by an electrocardiographic synchronization method in a pseudo manner using data indicating a periodic change in the blood flow velocity.

  When imaging, the host computer 6 performs a measurement scan, a preparation scan, and an imaging scan in this order, as shown in FIG. The imaging scan includes a monitor scan.

  The measurement scan is a scan for measuring in advance the relationship with the blood flow velocity in the ventricle, which is an index of the cardiac phase of the subject, and determining the time of diastole of the cardiac cycle. In the present embodiment, velocity encoding of blood flow is performed along the long axis of the ventricle using a phase contrast method (PC) method, and changes in blood flow velocity at a desired ROI position on the long axis are continuously detected. Measurement is performed to obtain data representing changes in blood flow velocity along each cardiac time phase (ie, each timing of the cardiac cycle). From the blood flow rate change data obtained by this scan, it is discriminated which flow rate value is the systole and diastole constituting the cardiac cycle. As a result, the diastole time is specified as a time from a fixed reference position (for example, a peak value at which a waveform indicating change data repeats).

  Note that this measurement scan does not always have to be performed at the time of imaging, as long as it can be measured before imaging. However, in this embodiment, since the change of the cardiac time phase is estimated from the change of the blood flow velocity, from the viewpoint of accurately estimating the cardiac time phase of the actual subject as much as possible, the actual imaging is possible as much as possible. It is desirable to carry out immediately before.

  The preparatory scan is a scan for confirming blood flow visualization performed at a plurality of designated time phases including the diastole in the periodic change in blood flow velocity. That is, a two-dimensional scan is performed in such a plurality of time phases, and a plurality of two-dimensional images are reconstructed and displayed on the display device 12. This preparation scan includes a blood flow measurement scan by the PC method for detecting the time phase at which the scan is started.

  The reason why this preparatory scan is a two-dimensional scan is that this scan is used only to confirm the degree of blood flow. For this reason, the scanning time can be shortened by performing in two dimensions. It is desirable that the type of pulse sequence used in this preparation scan is the same as that used in the imaging scan. This is because it is possible to observe how the blood flow is depicted in a state closer to actual imaging. Furthermore, it is preferable that this preparation scan is performed on a part that includes the same part or the same desired area as a part that is imaged by an imaging scan described later.

  A plurality of images obtained by the preparatory scan are displayed on the display 12 and, for example, used for visual confirmation by the operator. For this reason, the surgeon designates from the input device 13 an image in which the blood flow to be observed is depicted with the highest contrast. As a result, the designation information is given to the host computer 6, and the host computer 6 is the one in which the designated image is collected at which value of the blood flow velocity change data (that is, at which cardiac time phase). Can be recognized. That is, the host computer 6 can hold a specific time phase in the diastole of the cardiac cycle as a setting value of the blood flow velocity through the preparation scan.

  The set value of the blood flow velocity set in this way functions as an amount corresponding to a specific delay time from, for example, the R wave as the reference wave in the ECG waveform. Therefore, by giving this set value, the imaging scan can be started at a fixed cardiac phase (ie, data collection timing) in the diastole.

  This preparation scan is not necessarily required, and the operator designates a desired value, that is, a desired blood flow velocity value from the input device 13 based on experience values and past diagnoses without executing this preparation scan. You may do it. Further, either of such designation and preparation scan may be selectable each time.

  Once prepared in this way, an imaging scan can be performed. In order to perform data collection (main scan) by an imaging scan, it is necessary to detect a desired constant cardiac phase (set value of blood flow velocity) in the diastole. In order to detect this, a monitor scan is started prior to data collection. This monitor scan is executed by velocity-encoding a pulse train based on, for example, a phase contrast (PC) method along a ventricular long axis at regular time intervals (for example, 100 msec). Thereby, the value of the blood flow velocity of the desired ROI portion in the ventricle is obtained at regular intervals. This velocity value is compared with a preset blood flow velocity setting value (that is, the data collection timing set as described above). Data collection is started when it is determined by the comparison that the two match or that they match. This data collection is performed using a three-dimensional pulse sequence.

  Next, the overall operation and effects according to the present embodiment will be described.

  Now, as shown in FIG. 2, a measurement scan and a preparation scan are executed prior to an imaging scan.

  Therefore, the host computer 6 sequentially performs the processes shown in FIG. 3 to execute the measurement scan, the preparation scan, and the imaging scan.

  First, the host computer 6 determines whether or not the operator has instructed the execution of the measurement scan based on the input information from the input device 13 (step S1). When such a command is given, predetermined pulse sequence information is given to the sequencer 5 to execute the above-described measurement scan on the subject's ventricle (step S2). Thereby, through detection of the phase shift amount of the blood flow spin, change data of the blood flow velocity at a desired position in the ventricle is obtained as shown in FIG. 4A, for example.

  Next, the host computer 6 estimates the approximate systole and diastole together with one cardiac cycle for the obtained blood flow velocity change curve (step S3). In this estimation, the RR interval calculated backward from the flow direction and heart rate indicated by the blood flow velocity data is referred to. Thus, the host computer 6 sets and stores the reference time phase (here, the timing at which the waveform shows a peak) and the time phase of the diastole in the blood flow velocity change data (step S4).

  Next, the host computer 4 determines based on the input information from the input device 13 whether or not the surgeon has instructed the execution of the preparation scan (step S5). If the determination is YES, scan conditions necessary for execution of the preparation scan such as a blood flow velocity value at the start of a plurality of preparation scans are input (step S6). At this time, the surgeon is required to specify that the execution timing of the preparation scan is also included in the expansion period.

  Thereafter, under such scanning conditions, the host computer 4 instructs the sequencer 5 to execute a preparatory scan (step S7). In order to know the arrival of the designated blood flow velocity value with this preparation scan, the blood flow velocity in the ventricle is detected by the PC method as described above. Each time the detection result indicates a designated blood flow velocity value, a preparatory scan is executed.

  Then, by the one or more preparation scans, one or more two-dimensional images for confirming the depiction of blood vessels in the ventricle are displayed on the display 12 (step S8).

  Next, the host computer 6 waits for operation information given via the input device 13 as to which of the displayed images is designated as a desired image (step S9). For this reason, the surgeon usually designates an image having the best blood flow contrast as a desired image from one or more displayed images.

  When a desired image is designated by the operator, the host computer 5 specifies and stores the blood flow velocity value when the collection of the image is instructed (step S10).

  Note that if the determination in step S5 is NO, that is, if the preparation scan is not to be executed, an input of a desired blood flow velocity value is accepted from the operator (steps S11 and S12).

  Next, the host computer 6 stands by while determining whether or not to execute an imaging scan based on the operation information passed through the operator's input device 13 (step S13). When executing an imaging scan, first, a monitor scan executed at regular intervals is started (step S14). As described above, this monitor scan is executed by obtaining the phase shift amount of the blood flow spin using the PC method and converting the phase shift amount into a blood flow velocity value.

  The host computer 6 determines whether the blood flow velocity in the ventricle detected by the monitor scan is the blood flow velocity value in the diastole set or designated in step S10 or step S11, or can be regarded as the value, or is a nearby value. Is determined (step S15). When this determination is NO, the monitor scan is executed again. Thus, the monitor scan is repeated as shown in FIG. 4B until the blood flow velocity value set through the preparation scan or the blood flow velocity value designated by the operator is obtained.

  When it is determined that the blood flow velocity value has reached the set value or a value in the vicinity thereof while repeatedly performing the monitor scan in this way, the host computer 6 causes the sequencer 5 to start data collection (main scan) (step S16). ). As a result, as shown in FIG. 4C, for example, a pulse sequence based on the three-dimensional FASE method is started, and MR signals are collected from the ventricles. Based on this MR signal, MR images of various parts such as the heart, abdomen, and lower limbs are reconstructed.

  As described above, according to the present embodiment, it is possible to solve an unsolved problem derived from the ECG synchronization method possessed by the conventional non-contrast MRA. That is, without actually using the ECG measurement device, that is, without mounting the ECG sensor on the subject, the phase shift amount of the blood flow spin obtained from the magnetic resonance signal, that is, the blood flow velocity is used as an alternative signal for ECG information. Used as Thereby, it is possible to accurately estimate the cardiac time phase in the diastole from the substitute signal. Therefore, the burden and burden on the subject associated with wearing the ECG sensor (that is, electrode) is reduced. In addition, it is possible to provide a magnetic resonance imaging apparatus for non-contrast MRA that can prevent deterioration in image quality due to attachment of an ECG sensor and further prevent deterioration in patient throughput.

  Various modifications can be made in the first embodiment described above. For example, instead of a change in blood flow velocity flowing through the ventricle (that is, a change in phase shift amount of blood flow spin) as an index or signal that can be used to estimate the cardiac time phase of the subject, the heart Changes in MR signal values obtained from (ventricle), changes in ventricular size, and the like can be used. Such signal values change periodically throughout systole and diastole, and so does the ventricle size. Therefore, by estimating the diastole from the periodic change information and setting the desired time phase of the diastole in the same manner as described above, information on the change in the MR signal value and the change in the size of the ventricle Can be substituted for the ECG signal.

(Second Embodiment)
The second embodiment of the magnetic resonance imaging apparatus of the present invention will be described with reference to FIGS.

  This second embodiment is characterized in that a cardiac unit is estimated from the intensity of MR signals collected by this coil unit using a dedicated coil unit for heart rate measurement. More specifically, in the case of the magnetic resonance imaging apparatus according to the first embodiment described above, the actual imaging region was two-dimensionally scanned by the phase contrast method as the measurement scan. A coil unit dedicated to heart rate measurement is attached to the arm (including the fingertip, wrist, and joint) of the specimen, and MR signals reflecting the heart rate are collected from the arm by this coil unit.

  FIGS. 5A to 5C show the appearance of the coil unit 20 dedicated to heart rate measurement attached to the arm. As shown in FIG. 5 (A), the coil unit 20 is formed of a non-magnetic material that has a substantially elliptic cylindrical shape as a whole, and is divided into two along the axial direction thereof. And a second coil body 20B. The first coil body 20A and the second coil body 20B are attached to the wrist of a subject from both sides, for example, and fastened with a fastener (not shown). Thus, the first and second coil bodies 20A and 20B are attached around the wrist.

  In each of the first and second coil bodies 20A and 20B, a gradient magnetic field coil 21 and a receiving RF coil 22 are embedded. 5B illustrates only the gradient magnetic field coil 21 and FIG. 5C illustrates only the RF coil 22, but the gradient coil 21 and the reception RF coil 22 are provided in both coil bodies 20A, respectively. It is desirable to provide. However, it is sufficient for the coil unit 20 to be able to detect only the MR signal from the blood flow whose flow velocity changes according to the pulsation. For this reason, it is sufficient for the gradient magnetic field coil 21 to generate a one-dimensional gradient magnetic field along the longitudinal direction of its arm portion. For this reason, the gradient coil 21 is provided only for one axis. Of course, gradient magnetic field coils in three orthogonal axes may be provided.

  Further, the coil unit to be attached to the finger (fingertip) does not have to be divided as described above. The coil unit may be mounted by inserting a finger into a cylindrical fixing structure.

  In this embodiment, an arm is selected as the heartbeat measurement site. This is because it is easy to access a blood vessel that reflects the heartbeat of the subject relatively strongly, and that the subject usually does not feel much burden when the coil unit 20 is attached to the arm portion. Furthermore, when the imaging part where the actual MRA is performed is the chest, the head, or the like, it is relatively close to the imaging part, and therefore, it is also easy to detect pulsation with higher accuracy.

  FIG. 6 shows the overall configuration of a magnetic resonance imaging apparatus that executes a measurement scan using the coil unit 20 described above. As shown in the figure, the gradient magnetic field power supply 4, the transmitter 8T, and the receiver 8R in the first embodiment described above are used for the preparation scan and the imaging scan. Furthermore, another gradient magnetic field power source 24, a transmitter 25T, and a receiver 25R that are placed under the control of the sequencer 5 are also provided. The gradient magnetic field power supply 24 is connected to the gradient magnetic field coil 21 of the coil unit 20, and the transmitter 25 T and the receiver 25 R are connected to the RF coil 22 of the coil unit 20.

  Based on the pulse sequence information from the host computer 6, the sequencer 5 includes the gradient power supply 4, the transmitter 8T, and the receiver 8R for the preparation scan and the imaging scan, as in the first embodiment. Control. On the other hand, a measurement scan instruction is issued to the gradient magnetic field power source 24, the transmitter 25T, and the receiver 25R provided therewith. Therefore, the sequencer 5 is a common device for both scans. Depending on the design, the gradient power supplies 4 and 24 are formed as one common unit, the transmitters 8T and 25T are formed as one unit, and the receivers 8R and 25R are formed as one unit. You may form as.

  As an example, this measurement scan is performed by the phase contrast (PC) method in which the flow encode pulse is applied in the gradient magnetic field direction, as described above. As a result, averaged MR signals from the signal acquisition site are acquired. This collection is performed again with the polarity of the flow encode pulse reversed, and the difference between the signal values is calculated. Therefore, MR signals reflecting changes in blood flow, particularly arterial flow, are collected sequentially in time series. As a result of this collection, a signal change curve similar to that shown in FIG. 4A is obtained, and the cardiac cycle is measured (estimated).

  Thereafter, as in the first embodiment, a preparation scan and an imaging scan are executed. As in the first embodiment, the preparatory scan is not necessarily essential.

  In particular, in the second embodiment, the measurement scan execution timing may be executed not only prior to the imaging scan but also alternately or in parallel with the imaging scan. This conceptual diagram is shown in FIGS. 7 (A) and 7 (B). As shown in FIG. 7A, by alternately executing the measurement scan and the imaging scan, the measurement scan is executed at regular intervals, and the result is reflected in the imaging scan. For example, if the measurement scan reveals that the cardiac cycle has been advanced during the imaging scan, a measure such as adjusting the timing of the imaging scan can be taken in real time. Such processing is left to the sequencer 5. Further, as shown in FIG. 7B, the measurement scan is always executed in parallel with the imaging scan, and the result of the measurement scan is reflected in the imaging scan periodically or when necessary in the imaging scan. be able to. Also in this case, the real-time property of the measurement scan can be enjoyed.

  As described above, according to the present embodiment, it is possible to obtain the same effects as those obtained in the first embodiment described above. In addition, since the measurement scan is executed by the arm portion using the dedicated coil unit 20 for heart rate measurement, the sequence processing can be simplified such that the gradient magnetic field is one-dimensional. In the case of the first embodiment, since the measurement scan is executed in two dimensions, the difference is large.

  It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying it without departing from the scope of the claims.

1 is a block diagram showing a schematic configuration of a magnetic resonance imaging apparatus according to a first embodiment of the present invention. The figure explaining the time series order of the measurement scan, preparation scan, and imaging scan which were employ | adopted in 1st Embodiment. 6 is a schematic flowchart showing processing for scanning executed by a host computer. The figure explaining the relationship between the blood flow velocity in a ventricle, a monitor scan, and data collection. The perspective view explaining the coil unit for exclusive use for the heart rate measurement used with the magnetic resonance imaging apparatus which concerns on the 2nd Embodiment of this invention. The block diagram which shows schematic structure of the magnetic resonance imaging apparatus which concerns on 2nd Embodiment. The figure explaining the execution timing of the scan for a measurement and imaging scan in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnet 2 Static magnetic field power supply 3 Gradient magnetic field coil unit (1st scanning means, 2nd scanning means, 3rd scanning means)
4 Gradient magnetic field power supply (first scanning means, second scanning means, third scanning means)
5 Sequencer (first scanning means, second scanning means, third scanning means)
6 Host computer (cardiac time phase estimation means, reconstruction means, first scanning means, second scanning means, third scanning means)
7 RF coil (first scanning means, second scanning means, third scanning means)
8T transmitter (first scanning means, second scanning means, third scanning means)
8R receiver (first scanning means, second scanning means, third scanning means)
10. Arithmetic unit (heart phase estimation means, reconstruction means, preparation image generation means)
11 Storage unit 12 Display (image designation means)
13 Input device (image designation means)
20 Dedicated coil units 20A and 20B for heart rate measurement First and second coil bodies 21 Gradient magnetic field coil 22 RF coil 24 Gradient magnetic field power supply 25T Transmitter 25R Receiver

Claims (16)

A first RF coil that collects magnetic resonance signals from the subject;
Cardiac time phase estimation means for estimating a cardiac time phase of the subject from the magnetic resonance signals collected by the first RF coil;
A second RF coil that collects magnetic resonance signals from the subject based on the estimated cardiac phase;
A magnetic resonance imaging apparatus comprising: reconstructing means for reconstructing a magnetic resonance image of the subject from the magnetic resonance signals collected by the second RF coil. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the first RF coil is provided in the vicinity of the second RF coil. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the first RF coil is disposed on a chest of the subject. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the first RF coil is disposed on an arm of the subject. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus characterized in that acquisition of the magnetic resonance signal by the first RF coil and acquisition of the magnetic resonance signal by the second RF coil are performed alternately. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus characterized in that the collection of the magnetic resonance signal by the first RF coil and the collection of the magnetic resonance signal by the second RF coil are performed in parallel. The magnetic resonance imaging apparatus according to claim 1.
The cardiac time phase estimation means includes:
Preparation image generating means for generating a plurality of preparation images from the magnetic resonance signal obtained by the first RF coil;
A magnetic resonance imaging apparatus comprising: a cardiac phase recognition unit that recognizes a temporal phase corresponding to at least one designated image among the plurality of preparation images as a cardiac phase. First scanning means for collecting a magnetic resonance signal from the subject and estimating a cardiac time phase of the subject from the magnetic resonance signal;
Second scanning means for collecting magnetic resonance signals of a plurality of time phases of the subject based on the cardiac time phase obtained by the first scanning means;
Preparation image generating means for generating a plurality of preparation images from the magnetic resonance signals obtained by the second scanning means;
Image designating means for designating at least one of the plurality of images for preparation;
And a third scanning means for collecting magnetic resonance signals from the subject in a time phase corresponding to the designated image. The magnetic resonance imaging apparatus according to claim 8.
The magnetic resonance imaging apparatus, wherein the preparation image is a two-dimensional image. The magnetic resonance imaging apparatus according to claim 9.
The magnetic resonance imaging apparatus according to claim 1, wherein the first scanning means is means for collecting the magnetic resonance signal from the chest of the subject. The magnetic resonance imaging apparatus according to claim 9.
The magnetic resonance imaging apparatus according to claim 1, wherein the first scanning unit is a unit that collects the magnetic resonance signal from an arm portion of the subject. The magnetic resonance imaging apparatus according to claim 8.
The first scanning means includes a phase shift amount based on the magnetic resonance phenomenon of a spin in the imaging region of the subject, a signal intensity based on the magnetic resonance phenomenon, and a size of a site observed in the imaging region. A magnetic resonance imaging apparatus comprising: means for estimating the cardiac phase based on any one of them. Estimating a cardiac time phase of the subject based on a magnetic resonance signal collected from the first region of the subject using the first RF coil;
Providing the information on the estimated cardiac phase to means for collecting a magnetic resonance signal for imaging the second region of the subject using a second RF coil. . The collection method according to claim 13.
The magnetic resonance signal collecting method, wherein the first region is a partial region of an arm portion including a fingertip and a wrist of the subject, and the second region is a portion other than the arm portion of the subject. The collection method according to claim 13.
The first RF coil is stored in a dedicated coil unit for estimating a cardiac time phase integrated with a gradient magnetic field coil that generates a gradient magnetic field that gives spatial position information to a static magnetic field in which the subject is placed. Resonance signal collection method. The collection method according to claim 15,
The method of collecting magnetic resonance signals, wherein the gradient coil is a gradient coil that generates a one-dimensional gradient magnetic field.

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