JP5689595B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention magnetically excites a subject's nuclear spin with a radio frequency (RF) signal of Larmor frequency, and reconstructs an image from the nuclear magnetic resonance (NMR) signal generated by this excitation. The present invention relates to a magnetic resonance imaging (MRI) apparatus, and more particularly to a magnetic resonance imaging apparatus capable of performing MRA (Magnetic Resonance Angiography) to obtain a blood flow image in synchronization with a signal representing pulsation. .

  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 an RF signal having a Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation.

  In the field of magnetic resonance imaging, MRA is known as a technique for obtaining a blood flow image. MRA that does not use a contrast agent is called non-contrast MRA. In non-contrast MRA, an FBI (Fresh Blood Imaging) method has been devised in which blood vessels are well imaged by capturing blood flow at a high flow rate pumped from the heart by performing ECG (electro cardiogram) synchronization.

  Furthermore, as a technique used together with the FBI method, an ECG-prep technique for measuring an appropriate ECG synchronization delay time has been devised. ECG-prep performs an ECG-prep scan, which is a preparation scan for determining an appropriate ECG delay time, prior to the imaging scan, and executes the imaging scan with the ECG delay time determined by the ECG-prep scan. To do. The ECG-prep scan is a scan for acquiring a plurality of ECG-prep images having different time phases by collecting data by gradually changing the delay time from the R wave of the ECG signal. By selecting an ECG-prep image in which blood vessels are appropriately depicted from a plurality of ECG-prep images obtained by this ECG-prep scan, the ECG delay time in the imaging scan can be determined.

  In addition, a technique for generating support information for determining an appropriate delay time based on a plurality of ECG-prep images obtained by an ECG-prep scan has been devised (see, for example, Patent Document 1).

  In this technology, for a region of interest (ROI) that is set arbitrarily, maximum intensity projection (MIP: maximum intensity projection) is applied to the difference image between the reference ECG-prep image and other ECG-prep images. ) Process, one MIP image is generated. Then, the MIP image is an image obtained by extracting the largest blood flow change at each position as a signal difference value.

  Next, by binarizing the MIP image using a desired threshold value, a mask image in which the pixel value of a pixel having a signal intensity equal to or higher than the threshold value is 1 and the pixel value of another pixel is 0 is generated. . Furthermore, a plurality of masked images corresponding to each time phase are generated by multiplying the ECG-prep image and the mask image in the ROI corresponding to each time phase. Then, the masked image is an image obtained by extracting a portion that is highly likely to be a blood vessel from the ROI set in the ECG-prep image.

  Next, an average value of pixel values for all the pixels in each masked image is obtained. Thereby, the representative value of the pixel value corresponding to each time phase is obtained. Then, the delay time of the ECG-prep image corresponding to the time phase in which the average value of the pixel values is the minimum and the time phase in which the average value is the maximum is determined as a delay time candidate for the imaging scan.

  In other words, blood vessel characteristics can be represented by representative values of signal values for each time phase, and the delay time from the R wave when the representative value becomes the maximum value or the minimum value can be used as a delay time candidate for the imaging scan. .

JP 2008-23317 A

  However, an appropriate delay time corresponding to the diastole exists continuously for a certain time, not instantaneously, although there are individual differences. On the other hand, in the conventional method for determining the optimum delay time, the delay time when the signal value instantaneously becomes the maximum value or the minimum value can only be used as a candidate for the imaging condition. For this reason, the operator needs to determine the appropriate time phase for data collection in the diastole by grasping the signal change for each time phase.

  Further, when collecting data by dividing it into a plurality of segments, it is necessary to adjust the number of segments so that the data can be collected in the section determined as the expansion period.

  As described above, the conventional method has a problem that it takes an operator's labor when setting the delay time or setting the imaging condition according to the delay time. It is also desirable to be able to set imaging conditions such as delay time more accurately. Furthermore, such a problem also applies to MRA synchronized with pulsations such as pulse wave synchronization.

  The present invention has been made in order to cope with such a conventional situation, and in MRA synchronized with a synchronization signal such as an ECG signal, a delay time for collecting data from a trigger such as an R wave is more easily and accurately set. An object of the present invention is to provide a magnetic resonance imaging apparatus capable of performing the above.

In order to achieve the above-described object, the magnetic resonance imaging apparatus according to the present invention performs prescan by changing the delay time from the trigger set on the signal representing pulsation to the data collection start timing. And processing for detecting a section of the change curve that can be regarded as a straight line from the change curve of the intensity of the magnetic resonance signal or the pixel value of the magnetic resonance image data for each delay time collected from the subject by the pre-scan. A delay time calculating means for detecting a stable period by processing including calculating a delay time according to the detected stable period;
Imaging scan means for generating blood flow image data by executing an imaging scan with a delay time determined based on the calculated delay time.

  In the magnetic resonance imaging apparatus according to the present invention, in the non-contrast MRA synchronized with a synchronization signal such as an ECG signal, the delay time of data collection from a trigger such as an R wave can be set more simply and accurately.

1 is a configuration diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention. The functional block diagram of the computer shown in FIG. The flowchart which shows the flow at the time of imaging the blood-flow image of a subject with the magnetic resonance imaging apparatus shown in FIG. The figure which shows the example which detected the range which can be considered as a straight line by the least square approximation from the curve showing the relative intensity | strength of the pixel value for every delay time. The table | surface which shows the relationship between the number of the delay times used as the object of approximation calculation, the value of the sample standard deviation showing the inclination of an approximate curve, and the recent degree. The figure which shows an example of the curve showing the relative intensity | strength of the representative pixel value of the PPG-prep image data for every delay time. FIG. 7 is a diagram showing an example in which points are sequentially added from three points on the relative pixel intensity curve shown in FIG. 6 to perform linear approximation. The figure which shows the example which set delay time based on the extended period detected from the curve showing the relative intensity | strength of the representative pixel value of ECG-prep image data for every delay time.

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

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

  The magnetic resonance imaging apparatus 20 includes a cylindrical static magnetic field magnet 21 that forms a static magnetic field, a shim coil 22, a gradient magnetic field coil 23, and an RF coil 24 provided inside the static magnetic field magnet 21.

  In addition, the magnetic resonance imaging apparatus 20 includes a control system 25. The control system 25 includes a static magnetic field power supply 26, a gradient magnetic field power supply 27, a shim coil power supply 28, a transmitter 29, a receiver 30, a sequence controller 31, and a computer 32. The gradient magnetic field power source 27 of the control system 25 includes an X-axis gradient magnetic field power source 27x, a Y-axis gradient magnetic field power source 27y, and a Z-axis gradient magnetic field power source 27z. In addition, the computer 32 includes an input device 33, a display device 34, an arithmetic device 35, and a storage device 36.

  The static magnetic field magnet 21 is connected to a static magnetic field power supply 26 and has a function of forming a static magnetic field in the imaging region by a current supplied from the static magnetic field power supply 26. In many cases, the static magnetic field magnet 21 is composed of a superconducting coil, and is connected to the static magnetic field power supply 26 at the time of excitation and supplied with current. It is common. In some cases, the static magnetic field magnet 21 is composed of a permanent magnet and the static magnetic field power supply 26 is not provided.

  A cylindrical shim coil 22 is coaxially provided inside the static magnetic field magnet 21. The shim coil 22 is connected to the shim coil power supply 28, and is configured such that a current is supplied from the shim coil power supply 28 to the shim coil 22 to make the static magnetic field uniform.

  The gradient magnetic field coil 23 includes an X-axis gradient magnetic field coil 23 x, a Y-axis gradient magnetic field coil 23 y, and a Z-axis gradient magnetic field coil 23 z, and is formed in a cylindrical shape inside the static magnetic field magnet 21. A bed 37 is provided inside the gradient magnetic field coil 23 as an imaging region, and the subject P is set on the bed 37. The RF coil 24 includes a whole body coil (WBC) for transmitting and receiving an RF signal built in the gantry, a bed 37 and a local coil for receiving an RF signal provided near the subject P.

  The gradient magnetic field coil 23 is connected to a gradient magnetic field power supply 27. The X-axis gradient magnetic field coil 23x, the Y-axis gradient magnetic field coil 23y, and the Z-axis gradient magnetic field coil 23z of the gradient magnetic field coil 23 are respectively an X-axis gradient magnetic field power source 27x, a Y-axis gradient magnetic field power source 27y, and a Z-axis gradient magnetic field coil 27z. It is connected to the magnetic field power supply 27z.

  The X-axis gradient magnetic field power source 27x, the Y-axis gradient magnetic field power source 27y, and the Z-axis gradient magnetic field power source 27z are supplied with currents supplied to the X-axis gradient magnetic field coil 23x, the Y-axis gradient magnetic field coil 23y, and the Z-axis gradient magnetic field coil 23z, respectively. In the imaging region, a gradient magnetic field Gx in the X-axis direction, a gradient magnetic field Gy in the Y-axis direction, and a gradient magnetic field Gz in the Z-axis direction can be formed, respectively.

  The RF coil 24 is connected to the transmitter 29 and / or the receiver 30. The transmission RF coil 24 has a function of receiving an RF signal from the transmitter 29 and transmitting it to the subject P, and the reception RF coil 24 is accompanied by excitation of the nuclear spin inside the subject P by the RF signal. It has a function of receiving the NMR signal generated in this way and giving it to the receiver 30.

  On the other hand, the sequence controller 31 of the control system 25 is connected to the gradient magnetic field power source 27, the transmitter 29, and the receiver 30. The sequence controller 31 has control information necessary for driving the gradient magnetic field power supply 27, the transmitter 29, and the receiver 30, for example, operation control information such as the intensity, application time, and application timing of the pulse current to be applied to the gradient magnetic field power supply 27. And the gradient magnetic field power source 27, the transmitter 29, and the receiver 30 are driven according to the stored predetermined sequence to drive the X-axis gradient magnetic field Gx, the Y-axis gradient magnetic field Gy, and the Z-axis gradient magnetic field. It has the function of generating Gz and RF signals.

  In addition, the sequence controller 31 is configured to receive raw data, which is complex data obtained by detection of an NMR signal and A / D (analog to digital) conversion in the receiver 30, and supply the raw data to the computer 32. The

  For this reason, the transmitter 29 is provided with a function of applying an RF signal to the RF coil 24 based on the control information received from the sequence controller 31, while the receiver 30 detects the NMR signal received from the RF coil 24. Then, by executing required signal processing and A / D conversion, a function of generating raw data that is digitized complex data and a function of supplying the generated raw data to the sequence controller 31 are provided.

  Further, the magnetic resonance imaging apparatus 20 includes an ECG unit 38 that acquires an ECG (electro cardiogram) signal of the subject P. The ECG signal acquired by the ECG unit 38 is configured to be output to the computer 32 via the sequence controller 31.

  A pulse wave synchronization (PPG: peripheral pulse gating) signal that represents pulsation as pulse wave information can be acquired instead of an ECG signal that represents pulsation as heart rate information. The PPG signal is, for example, a signal obtained by detecting a fingertip pulse wave as an optical signal. When acquiring the PPG signal, a PPG signal detection unit is provided. Hereinafter, a case where an ECG signal is acquired will be described unless otherwise specified.

  Further, the computer 32 is provided with various functions by executing the program stored in the storage device 36 of the computer 32 by the arithmetic unit 35. However, a specific circuit having various functions may be provided in the magnetic resonance imaging apparatus 20 regardless of the program.

  FIG. 2 is a functional block diagram of the computer 32 shown in FIG.

  The computer 32 functions as an imaging condition setting unit 40, a sequence controller control unit 41, a k-space database 42, and a blood flow image creation unit 43 by a program. The imaging condition setting unit 40 includes an extended period calculation unit 40A, a segment number setting unit 40B, and a delay time setting unit 40C.

  The imaging condition setting unit 40 has a function of setting imaging conditions including a pulse sequence based on instruction information from the input device 33 and providing the set imaging conditions to the sequence controller control unit 41. In particular, the imaging condition setting unit 40 has a function of setting imaging conditions for acquiring a blood flow image under ECG synchronization.

  As an imaging method for collecting a blood flow image, an FBI method for collecting blood flow image data without contrast is known. The FBI method is a non-contrast-enhanced MRA in which echo data is repeatedly collected for a plurality of heartbeats with a predetermined time delay from a trigger signal synchronized with a reference wave representing a cardiac time phase of the subject P such as an R wave. According to the FBI method, the magnetization of the transverse relaxation (T2) component of blood is recovered with the passage of a plurality of heartbeats, and a water (blood) enhanced image in which the T2 magnetization component of blood is emphasized can be obtained as a blood vessel image. Further, in the FBI method, a three-dimensional scan for collecting echo data (volume data) for a predetermined slice encoding amount is executed.

  Typical pulse sequences for acquiring a blood flow image include a FASE (fast asymmetric spin echo or fast advanced spin echo) sequence and an SSFP (steady state free precession) sequence. When imaging the heart, an FFE (fast field echo) sequence based on a segment k-space method can be used. The segment k-space method is a method in which k-space is segmented by dividing it into several regions, and k-space data is taken in sequentially for each segment.

  Furthermore, the imaging condition setting unit 40 has a function of setting imaging conditions for an ECG-prep scan, which is a pre-scan for determining an ECG synchronization delay time in an imaging scan. The ECG-prep scan is a scan for collecting a plurality of ECG-prep image data corresponding to different cardiac phases by changing a delay time from a reference wave such as an R wave of an ECG signal to a data collection start timing. The ECG-prep scan is preferably a two-dimensional (2D) scan from the viewpoint of shortening the scan time, and other imaging conditions are preferably set to be equivalent to the imaging scan.

  The expansion period calculation unit 40A has a function of obtaining a stable period as a myocardial expansion period based on ECG-prep image data or NMR signals corresponding to different delay times collected by the ECG-prep scan.

  The segment number setting unit 40B calculates the segment length and the number of segments for data collection that can be set within the extension period obtained by the extension period calculation unit 40A, and images a plurality of segments for imaging scan based on the calculation result. It has a function to set as a condition.

  The delay time setting unit 40C has a function of setting an appropriate delay time according to the extension period obtained by the extension period calculation unit 40A and / or the segment set by the segment number setting unit 40B as an imaging condition for the imaging scan. Have.

  In addition, when performing pulse wave synchronization MRA, the PPG-prep scan with different delay time from the trigger set on the PPG signal is executed, and the signal strength is based on multiple PPG-prep images with different time phases. Therefore, a stable period with little change in time is required.

  The sequence controller control unit 41 has a function of controlling driving by giving an imaging condition including a pulse sequence to the sequence controller 31 based on scan start instruction information from the input device 33. The sequence controller control unit 41 has a function of receiving raw data from the sequence controller 31 and arranging it in the k space formed in the k space database 42.

  The blood flow image creation unit 43 has a function of reconstructing image data by taking k-space data from the k-space database 42 and performing an image reconstruction process including Fourier transform (FT). It has a function of generating blood flow image data by performing necessary image processing such as difference processing and MIP processing on the obtained image data. The blood flow image creation unit 43 is configured to provide the blood flow image data for each cardiac phase collected by the ECG-prep scan to the imaging condition setting unit 40 as ECG-prep image data.

(Operation and action)
Next, the operation and action of the magnetic resonance imaging apparatus 20 will be described.

  FIG. 3 is a flowchart showing a flow when a blood flow image of the subject P is captured by the magnetic resonance imaging apparatus 20 shown in FIG.

  First, in step S1, an ECG-prep scan is executed. For this purpose, the imaging condition setting unit 40 sets imaging conditions for ECG-prep scan including a plurality of delay times.

  On the other hand, the subject P is set on the bed 37 in advance, and a static magnetic field is formed in the imaging region of the static magnetic field magnet 21 (superconducting magnet) excited by the static magnetic field power supply 26. Further, a current is supplied from the shim coil power supply 28 to the shim coil 22, and the static magnetic field formed in the imaging region is made uniform.

  When the scan start instruction is given from the input device 33 to the sequence controller control unit 41, the sequence controller control unit 41 gives the imaging conditions including the pulse sequence acquired from the imaging condition setting unit 40 to the sequence controller 31. The sequence controller 31 sets the subject P by driving the gradient magnetic field power source 27, the transmitter 29, and the receiver 30 according to the pulse sequence received from the sequence controller control unit 41 under the synchronization with the ECG signal from the ECG unit 38. A gradient magnetic field is formed in the obtained imaging region, and an RF signal is generated from the RF coil 24.

  Therefore, an NMR signal generated by nuclear magnetic resonance inside the subject P is received by the RF coil 24 and given to the receiver 30. The receiver 30 receives the NMR signal from the RF coil 24, performs necessary signal processing, and then performs A / D conversion to generate raw data that is an NMR signal of digital data. The receiver 30 gives the generated raw data to the sequence controller 31. The sequence controller 31 provides the raw data to the sequence controller control unit 41, and the sequence controller control unit 41 arranges the raw data as k-space data in the k-space formed in the k-space database 42.

  The blood flow image creation unit 43 takes in k-space data from the k-space database 42, generates blood flow image data for each delay time, and uses the generated blood flow image data as ECG-prep image data to the imaging condition setting unit 40. give.

  Next, in step S2, the expansion period calculation unit 40A obtains a stable period as the expansion period based on ECG-prep image data or NMR signals corresponding to different delay times collected by the ECG-prep scan. The extension period can be obtained by detecting a linearly changing section from a curve representing the intensity change for each delay time (time phase) of the pixel value of the ECG-prep image data or the NMR signal.

  Here, an example in which the extension period is obtained based on the pixel value of the ECG-prep image data for each delay time will be described. Similarly, the extension period can be obtained based on the NMR signal for each delay time.

  First, the representative value of the pixel value of ECG-prep image data at each delay time is obtained. The representative value can be an arbitrary value such as a total value, a maximum value, or an average value of the pixel values. The region for calculating the representative value can also be arbitrarily determined. For example, the entire ECG-prep image data may be used for calculating the representative value.

  However, from the viewpoint of reducing the data processing amount, it is desirable to extract the pixel value of the blood vessel portion of interest from the ECG-prep image data and calculate the representative value using the extracted pixel value. Therefore, for example, for ROI arbitrarily set so as to include the blood vessel of interest, difference image data between ECG-prep image data serving as a reference and other plurality of ECG-prep image data is generated. Then, difference image data turns into image data which shows the pixel value according to the variation | change_quantity of the blood flow.

  Next, one piece of MIP image data is generated by performing MIP processing on the plurality of generated difference image data. Then, the MIP image data is image data obtained by extracting the largest blood flow change at each position in the ROI as a pixel difference value.

  Next, by binarizing the MIP image data using a desired threshold value, mask image data in which the pixel value of a pixel having a pixel value equal to or greater than the threshold value is 1 and the pixel value of another pixel is 0 is generated. Is done. Then, the mask image data is image data having a pixel value of 1 at a position where the possibility of being a blood vessel is high and a pixel value of 0 at a position where the possibility of being a blood vessel is low.

  Next, a plurality of masked image data corresponding to each delay time is generated by multiplying the ECG-prep image data and the mask image data in the ROI corresponding to each delay time. Then, the masked image data is an image obtained by extracting a portion that is highly likely to be a blood vessel from the ROI set in the ECG-prep image data.

  Next, for example, an average value of pixel values for all pixels in each masked image data is obtained. Thereby, the representative value of the pixel value corresponding to each delay time is obtained. That is, a change curve F (t) of the pixel value with respect to the change of the delay time t is obtained. Then, an interval that can be regarded as a straight line from the change curve F (t) can be detected by an arbitrary method.

  FIG. 4 is a diagram illustrating an example in which a range that can be regarded as a straight line is detected by a least-square approximation from a curve representing the relative intensity of the pixel value for each delay time.

  In FIG. 4, the vertical axis indicates the relative intensity of the representative value of the pixel value, and the horizontal axis indicates the delay time from the R wave corresponding to the cardiac time phase. On the delay time-intensity curve Cecg as shown in Fig. 4, starting from the three adjacent delay times that minimize the variance, increasing the number of points to be added to the approximation calculation, and performing linear approximation by least square approximation It is possible to detect a section that can be regarded as a straight line by sequentially performing it. As a specific example, a linearly changing section can be detected according to the following algorithm.

  First, in the search range from the delay time t = Ts to t = Te, the delay time Tm when the intensity F (t) becomes the maximum value Fmax (Tm) is searched. Next, a delay time Td that minimizes the variance of the three points F (t−Δt), F (t), and F (t + Δt) in the vicinity of the delay time Tm is searched. That is, a stable time phase near the maximum pixel value is detected.

  Next, an approximate expression of a straight line is obtained by the least square method for the three points F (Td−Δt), F (Td), and F (Td + Δt) at which the variance is minimum. Next, the point F (Td-2Δt) adjacent in the negative direction is added to the three points F (Td−Δt), F (Td), F (Td + Δt) at which the variance is minimum, and the minimum 2 for the four points An approximate expression of a straight line is obtained by multiplication. Next, the point F (Td + 2Δt) adjacent in the positive direction is added to the three points F (Td−Δt), F (Td), F (Td + Δt) at which the variance is minimum, and the minimum 2 for the four points An approximate expression of a straight line is obtained by multiplication. Next, two points F (Td-2Δt) and F (Td + 2Δt) that are adjacent in both positive and negative directions are added to the three points F (Td-Δt), F (Td), and F (Td + Δt). Then, an approximate expression of a straight line is obtained for the five points by the least square method. Similarly, linear approximation is performed while sequentially adding points in the positive and negative directions.

  Then, the search is terminated when the slope of the straight line exceeds the threshold value or when the degree of straight line approximation is reduced by the test. For example, the linear approximation process can be terminated when the slope of the straight line exceeds 0.1 or when the correlation coefficient serving as an index indicating the degree of linear approximation is less than 0.9.

  In this way, it is possible to extract a straight line section in which the slope of the approximate straight line is equal to or less than the threshold and the maximum is obtained in the range where the correlation coefficient representing the degree of approximation is equal to or greater than the threshold. That is, the change curve F (t) of the relative pixel value can be separated into a stable expansion period that changes linearly and another period.

  FIG. 5 is a table showing the relationship between the number of delay times to be approximated, the slope of the approximate curve, and the value of the sample standard deviation representing the recent degree.

  As shown in FIG. 5, when linear approximation is performed with delay times of, for example, three points of 600, 700, and 800, the slope of the approximate line is 0.06 and the standard deviation of the sample is 4.38. Next, when 4-point and 5-point linear approximation is performed by adding one or both of the delay time 500 and the delay time 900, the slope and standard deviation of the recent straight line are both within the threshold. When the delay time 400 and the delay time 1000 are added, the standard deviations are 46.25 and 22.30, respectively, which are outside the threshold value. For this reason, the range of the delay time 500-900 can be extracted as the extended period.

  Similarly, in the case of pulse wave synchronous imaging, a stable period can be detected by linear approximation to a curve representing a change in the representative pixel value of PPG-prep image data for each delay time.

  FIG. 6 is a diagram showing an example of a curve representing the relative intensity of the representative pixel value of the PPG-prep image data for each delay time, and FIG. 7 shows points from three points on the relative pixel intensity curve shown in FIG. It is a figure which shows the example which performed the linear approximation by adding sequentially.

  6 and 7, the vertical axis represents the relative intensity of the representative pixel value of the PPG-prep image data, and the horizontal axis represents the delay time from the PPG trigger. A stable pulse wave signal period can be detected by performing linear approximation as shown in FIG. 7 on the delay time-intensity curve Cppg as shown in FIG.

  Next, when k-space data is collected for each segment as in cardiac imaging, the segment length and the number of segments for data collection that can be set within the expansion period obtained by the expansion period calculation unit 40A in step S3. Is calculated by the segment number setting unit 40B. That is, the segment number setting unit 40B automatically calculates a segment length that can be set with the length of the expansion period as an upper limit. Thereby, the number of data in one segment and the number of segments (number of shots) can be set as imaging conditions.

  In step S4, the delay time for imaging scan is set by the delay time setting unit 40C.

  FIG. 8 is a diagram illustrating an example in which the delay time is set based on the extended period detected from the curve representing the relative intensity of the representative pixel value of the ECG-prep image data for each delay time.

  In FIG. 8A, the vertical axis represents the relative intensity of the representative pixel value of the ECG-prep image data, and the horizontal axis represents the delay time from the R wave trigger of the ECG signal. As shown in FIG. 8A, when the extended period is detected on the delay time-intensity curve Cecg, it is possible to set an appropriate delay time according to the extended period.

  FIG. 8B shows an example of setting the delay time from the R-wave trigger to the data collection segment when collecting data in segments. As shown in FIG. 8B, for example, the delay time can be automatically set in the delay time setting unit 40C so that the center position of the segment having the length set in the segment number setting unit 40B is the center of the extension period. it can. Alternatively, the delay time can be automatically set so that the margin period from the start timing of the expansion period to the start timing of data collection becomes a desired period. The margin period can be determined in advance by experience or testing.

  On the other hand, when the data collection period is longer than the extended period as shown in FIG. 8C, the delay time from the R-wave trigger is automatically set so that the data collection timing becomes the start timing of the extended period. You can also.

  The delay time set in the delay time setting unit 40C can be used as it is as an imaging condition for an imaging scan. On the other hand, the delay time set in the delay time setting unit 40C may be displayed on the display device 34 as a candidate, and the delay time may be adjusted by operating the input device 33. For this reason, the operator can set the delay time more simply and accurately. The same applies to the segment length and the number of segments set in the segment number setting unit 40B.

  Next, in step S5, an imaging scan is executed using the set delay time as an imaging condition. That is, the imaging condition setting unit 40 sets imaging conditions for the imaging scan, and the three-dimensional scan is executed in the same flow as the ECG-prep scan.

  Next, in step S6, blood flow image data is generated based on the data collected by the imaging scan. That is, the blood flow image creation unit 43 takes in the k-space data collected by the imaging scan from the k-space database 42 and generates blood flow image data. The generated blood flow image data is displayed on the display device 34. Thus, the operator can observe a blood flow image collected in an appropriate cardiac phase.

  That is, the magnetic resonance imaging apparatus 20 as described above can more accurately and easily reduce the delay time from the trigger signal to the data collection start timing in MRA executed in synchronization with a signal representing a pulsation such as an ECG signal or a PPG signal. Thus, a stable period in which the change in signal intensity or pixel intensity is small with respect to the change in delay time is detected. Then, the delay time is automatically set so that data is collected in the detected stable period such as the expansion period.

(effect)
For this reason, according to the magnetic resonance imaging apparatus 20, it is possible to more accurately and easily determine the delay time corresponding to the optimum time phase as the data collection start timing. In addition, the delay time and the number of data collection segments according to the delay time can be set more appropriately and automatically.

DESCRIPTION OF SYMBOLS 20 Magnetic resonance imaging apparatus 21 Magnet for static magnetic field 23 Gradient magnetic field coil 24 RF coil 26 Static magnetic field power supply 27 Gradient magnetic field power supply 29 Transmitter 30 Receiver 31 Sequence controller 32 Computer 33 Input apparatus 34 Display apparatus 38 ECG unit 40 Imaging condition setting part 40A Expansion period calculation unit 40B Segment number setting unit 40C Delay time setting unit 41 Sequence controller control unit 42 k-space database 43 Blood flow image creation unit

Claims (6)

Pre-scanning means for changing the delay time from the trigger set on the signal representing the pulsation to the data collection start timing and executing the pre-scan,
Processing including processing for detecting a section of the change curve that can be regarded as a straight line from the change curve of the intensity of the magnetic resonance signal or the pixel value of the magnetic resonance image data for each delay time collected from the subject by the prescan. A delay time calculating means for detecting a stable period and calculating a delay time according to the detected stable period;
Imaging scan means for generating blood flow image data by executing an imaging scan with a delay time determined based on the calculated delay time;
A magnetic resonance imaging apparatus comprising: The magnetic field according to claim 1, further comprising segment condition calculation means for setting each segment such that each segment for collecting and collecting magnetic resonance data into a plurality of segments in the imaging scan is set within the stable period. Resonance imaging device. The magnetic resonance imaging apparatus according to claim 2, wherein the delay time calculation unit is configured to calculate a delay time according to the stable period so that the segment is in the center of the stable period. The delay time calculating unit is configured to calculate a delay time according to the stable period so that a margin period is obtained between a start timing of the stable period and a data collection start timing. Magnetic resonance imaging device. 2. The magnetism according to claim 1, wherein the delay time calculation unit is configured to detect a myocardial dilation period as the stable period and to calculate a delay time from a reference wave on an electrocardiogram signal according to the dilation period. Resonance imaging device. Pre-scanning means for changing the delay time from the trigger set on the signal representing the pulsation to the data collection start timing and executing the pre-scan,
A delay time calculating means for detecting a stable period from a magnetic resonance signal or magnetic resonance image data for each delay time collected from the subject by the pre-scan, and calculating a delay time according to the detected stable period;
Imaging scan means for generating blood flow image data by executing an imaging scan with a delay time determined based on the calculated delay time;
Segment condition calculating means for setting each segment so that each segment for collecting and collecting magnetic resonance data into a plurality of segments in the imaging scan is set within the stable period;
With
The delay time calculating means is configured to calculate a delay time according to the stable period so that the segment is in the center of the stable period.
A magnetic resonance imaging apparatus.

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