JP2010220859A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus for more easily determining an appropriate heart rate time phase and collecting data of a bloodstream image without requiring special knowledge and technique. <P>SOLUTION: The magnetic resonance imaging apparatus includes: a data collecting means for setting a delay time DELAY TIME from a reference wave R expressing the time phase of a data collection timing in imaging synchronized with a heartbeat, based on heart rate information HR or pulse wave information which is previously acquired from a subject and performing scanning SEQUENCE accompanied with the set delay time DELAY TIME, thereby collecting magnetic resonance signals; and an image generating means for generating the bloodstream image, based on the magnetic resonance signals. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention magnetically excites a subject's nuclear spin with a radio frequency (RF) signal of a Larmor frequency, and re-images the nuclear magnetic resonance (NMR) signal generated by this excitation. More particularly, the present invention relates to a magnetic resonance imaging apparatus capable of performing MRA (Magnetic Resonance Angiography) to obtain a blood flow image.

  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 that captures blood flow at a high flow rate pumped out of the heart by performing ECG (electro cardiogram) synchronization (for example, a good blood vessel) (for example, (See Patent Document 1).

  As a technique used in combination with this FBI method, a technique called ECG-prep for measuring an appropriate electrocardiographic delay time has been devised (for example, see Patent Document 1). ECG-prep performs ECG-prep scan, which is a preparatory scan for determining the appropriate ECG delay time, before the FBI scan for imaging, and FBI with the ECG delay time determined by ECG-prep scan. A scan is executed. The ECG-prep scan is a scan for acquiring a plurality of single-shot images having different time phases by collecting data by gradually changing the delay time from the R wave of the ECG signal. The ECG delay time in the FBI scan can be determined by selecting an image in which blood vessels are appropriately depicted from a plurality of images obtained by the ECG-prep scan. As a result, it is possible to depict a blood flow with a high flow velocity in a time phase with a slower flow velocity.

  Further, a technique called FBI-NAVI has been devised as a technique for selecting an optimal ECG-prep image from a plurality of ECG-prep images collected by ECG-prep scanning (see, for example, Patent Document 2).

JP-A-11-239571 JP 2008-23317 A

  However, there is a problem that it is difficult to determine a delay time in conventional electrocardiogram synchronization, that is, a time phase to be an imaging timing unless a skilled engineer refers to an ECG-prep image.

  The present invention has been made to cope with such a conventional situation, and it is possible to more easily determine an appropriate time phase and collect blood flow image data without requiring special knowledge and skill. It is an object of the present invention to provide a possible magnetic resonance imaging apparatus.

  In order to achieve the above-described object, the magnetic resonance imaging apparatus according to the present invention provides a reference representing a time phase of data collection timing in imaging synchronized with pulsation based on heartbeat information or pulse wave information acquired in advance from a subject. A data collection unit that sets a delay time from the wave and collects a magnetic resonance signal by executing a scan with the set delay time; and an image generation unit that generates a blood flow image based on the magnetic resonance signal; It is what has.

  The magnetic resonance imaging apparatus according to the present invention can collect blood flow image data by determining an appropriate time phase more easily without requiring special knowledge or skill.

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 figure explaining the determination method of the delay time in the delay time determination part shown in FIG. The figure which shows an example of the delay time preserve | saved at the delay time table shown in FIG. The flowchart which shows the procedure at the time of imaging the blood-flow image of the subject P with the magnetic resonance imaging apparatus shown in FIG.

  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.

  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, an image reconstruction unit 43, an image database 44, and a blood flow image creation unit 45 by a program. The imaging condition setting unit 40 includes a heartbeat acquisition unit 46, a delay time determination unit 47, and a delay time table 48.

  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 a pulse sequence for acquiring a blood flow image with heartbeat synchronization such as ECG synchronization or PPG synchronization using heartbeat information such as ECG signals and PPG signals. Yes.

  Examples of a technique for collecting a blood flow image include a non-contrast-enhanced MAR method that does not use a contrast agent and a contrast MRA method that is an MRA using a contrast agent. Non-contrast MAR methods include FBI method, TOF (time of flight) method, steady state free precession (SSFP) method that creates a steady state of spin, and FLOW PREP method. Therefore, a pulse sequence according to an arbitrary method among these MRA methods can be set as an imaging condition.

  The FBI method uses the SEFP (spin echo) sequence such as the FASE (fast asymmetric spin echo or fast advanced spin echo) sequence using the SSFP sequence or the half Fourier method, and the cardiac time phase of the subject P such as an R wave. Is a non-contrast-enhanced MRA that repeatedly collects echo data for each of a plurality of heartbeats with a delay of a predetermined delay time from a trigger signal synchronized with a reference wave representing. 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. In the FBI method, a three-dimensional scan for collecting echo data (volume data) for a predetermined slice encoding amount is executed.

  The TOF method is a blood vessel image acquisition method that uses the inflow effect on the cross section of blood. That is, the TOF method images a blood signal that flows into an imaging section after application of a saturation pulse. In the TOF method, scanning is performed at an earlier data collection timing using a FE (field echo) sequence, and a longitudinal relaxation (T1) weighted image is acquired as a blood vessel image.

  The Flow Prep method is a method to selectively depict an artery by applying an RF pulse according to the maximum blood flow velocity of the blood flow in the target blood vessel and performing labeling and imaging in the diastole of the myocardium. It is.

  The heart rate acquisition unit 46 of the imaging condition setting unit 40 acquires heart rate information of the subject P from the ECG unit 38 or a PPG unit (not shown), and determines a heart rate (HR) of the subject P as a delay time determination unit 47. It has a function to give to. Examples of the heartbeat information include ECG signals and PPG signals, as well as periods between adjacent reference waves on the HR itself, ECG signals, and PPG signals. When the ECG unit 38 or the PPG unit has a function of calculating HR, the heartbeat acquisition unit 46 is configured to acquire HR directly from the ECG unit 38 or PPG unit. The ECG unit 38 or the PPG unit is configured to acquire an ECG signal, a PPG signal, or a period between adjacent reference waves on these signals, and the heartbeat acquisition unit 46 calculates HR based on the ECG signal or the PPG signal. May be. For example, HR can be calculated from the R wave R-R on the ECG signal according to Equation (1).

[Equation 1]
RR = 60000ms / HR (1)

  The heart rate acquisition unit 46 may calculate or acquire a plurality of HRs, and may provide an average value of the plurality of HRs to the delay time determination unit 47 in order to improve accuracy. For example, it is possible to obtain HR about 10 times and use the average value of 10 HRs as the HR to be given to the delay time determination unit 47. In order to obtain HR with practical accuracy, it is considered that the average value may be obtained by acquiring HR from 4 to 20 times.

  The delay time determination unit 47 has a function of setting an appropriate delay time as an imaging condition from a reference wave in heartbeat synchronization imaging based on the HR acquired from the heartbeat acquisition unit 46. As a method for setting the delay time, a method for calculating the delay time from the HR using a calculation formula representing the relationship between the HR and the delay time, and a table in which the relationship between the HR and the delay time is associated in advance are prepared, There is a method of acquiring a delay time corresponding to the HR of the subject P with reference to the table.

  For example, when the myocardial systole is SD, there is a report that equation (2) is approximately established between the systole SD and HR. However, the numerical value 550 in Equation (2) may be different because there is an individual difference depending on sex and age. Therefore, the relationship between the systolic phase SD and HR may be expressed by a quadratic equation or a higher-order equation of the third or higher order.

[Equation 2]
SD = 550-2HR (2)

  Therefore, when it is desired to set the data collection timing to the diastole, the systole SD can be estimated from the equation (2), and the delay time can be set so that the data collection timing becomes the diastole. As a specific example, when HR is 60, since RR = 1000 and SD = 330 from Equation (1) and Equation (2), the delay time may be set to a period of 670 ms at least 330 ms after the R wave. It will be. That is, Expression (3) indicating the relationship between the delay time DT and HR can be determined using the function f so that Expression (2) is established.

[Equation 3]
DT = f (HR) (3)

  However, if there is an arrhythmia, R-R may become extremely short and HR may increase. In such a case, if the systolic period SD is calculated using a large HR as it is, the systolic period SD may straddle the next heartbeat. For this reason, it is desirable to calculate the systolic period SD during at least one heartbeat considered to be the minimum. Therefore, the delay time determining unit 47 can be provided with a threshold processing function for setting the upper limit value within the minimum heartbeat period when the systolic period SD exceeds the threshold corresponding to the minimum heartbeat period. In other words, the delay time DT is calculated discontinuously depending on whether or not HR exceeds the threshold, and when HR exceeds the threshold, formula (3) is determined so that the delay time DT is set to be short. be able to.

  Similarly, a relational expression between HR and diastole may be obtained in advance by an arbitrary method such as a test, and the diastole may be estimated based on a relational expression between HR and diastole. It is also possible to determine a calculation formula showing the relationship between the delay time DT and HR so that the delay time from the reference wave of the data collection timing is set to the systole.

  By the way, the imaging region of the blood flow image can also be set arbitrarily. Accordingly, it is possible to set imaging conditions for performing blood flow image imaging of the lower limbs and coronary artery imaging. However, in some cases, it is desirable to set the delay time from the reference wave at an appropriate data collection timing to a different value for each imaging region with higher accuracy, because the blood flow velocity differs for each imaging region. Therefore, a calculation formula representing the relationship between HR and delay time can be determined for each imaging region. For example, at the end portion such as the lower limb, the blood flow rate is slower than that near the heart, so that the delay time at the end portion can be set longer than the delay time near the heart.

  Furthermore, as an index representing the blood flow velocity, there is an ankle brachial index (ABI). Therefore, a calculation formula that represents the relationship between HR and delay time can be determined for each ABI value. In addition, the flow rate of the blood flow changes depending on the degree of a lesion site such as vascular stenosis. For this reason, a calculation formula representing the relationship between the HR and the delay time can be determined for each index value indicating the degree of progression of the lesion site.

  In other words, together with a calculation formula representing the relationship between HR and delay time, a correction coefficient for delay time for each imaging value, ABI value and / or index value indicating the degree of progression of the lesion site is determined, and HR and The delay time is calculated by adding or multiplying the delay time calculated based on the formula representing the relationship with the delay time by a correction coefficient for each value of the imaging site, ABI value and / or index indicating the degree of progression of the lesion site. Can be corrected.

  In addition, when setting the delay time by setting the imaging condition that sets the period from the reference wave indicating the cardiac phase such as R wave to the application time of the first RF pulse or gradient magnetic field pulse as the delay time, Depending on the sequence, it may be desirable to shift the delay time. For example, it may be desirable to set the delay time so that the data collection timing in the vicinity of the center of the k-space is not the start timing of the sequence but the desired timing in the diastole or systole. Furthermore, when performing imaging using fat suppression methods such as the STIR (short TI inversion recovery) method or CHESS (chemical shift selective) method, the delay time from the fat suppression pulse such as the STIR pulse or CHESS pulse to the 90 ° excitation pulse Need to be considered. For example, when imaging by the STIR method, it is necessary to consider an inversion time (TI) from a 180 ° IR prepulse to a 90 ° excitation pulse.

  Therefore, the delay time determination unit 47 is provided with a function of correcting the set delay time based on the delay time DTF of fat suppression pulses such as TI and the effective echo time (effective TE: effective echo time). That is, in order to provide the above functions, the delay time determination unit 47 sets the delay time DT by Equation (4), where LOCATION is the imaging region, TEeff is the execution TE, and the index value indicating the degree of progression of the lesion is INDEX. Can be configured to set. TEeff varies depending on data collection methods such as centric data collection and sequential data collection. Parameters necessary for determining the delay time can be input from the input device 33 to the delay time determining unit 47.

[Equation 4]
DT = f (HR, LOCATION, ABI, DTF, TEeff, INDEX) (4)

  If the delay time is set by the shooting condition setting method in which the period from the reference wave indicating the cardiac phase such as the R wave to the data collection timing near the center of the k-space is set as the delay time, TI etc. There is no need to consider the fat suppression pulse delay time or TEeff.

  FIG. 3 is a diagram for explaining a delay time determination method in the delay time determination unit 47 shown in FIG.

  In FIG. 3, the horizontal axis indicates the cardiac time phase. As shown in FIG. 3, by using the equations (1) and (2), it is possible to estimate the R—R, EC, and diastole DD of the ECG signal from the HR. The data collection delay time DT can be set so as not to contradict the estimated R-R, systolic SD, and diastole DD.

  For example, in the case of imaging using the FBI method, data is collected in the systolic and diastolic phases for each of multiple heartbeats using the SSFP sequence and FASE sequence, and between the data corresponding to the diastolic phase and the data corresponding to the systolic phase. By performing the difference processing, it is possible to create blood flow image data with good contrast obtained by separating the arterial artery.

  Therefore, a FASE sequence (FASEsys) for collecting data in the systolic period SD and a FASE sequence (FASEdias) for collecting data in the diastole DD are set for every plurality of heartbeats. Therefore, the delay time DTsys from the R wave of the FASE sequence (FASEsys) for data collection of systolic SD and the delay time DTdias from the R wave of the FASE sequence (FASEdias) for data collection of diastolic DD are set. Is done. That is, at the timing shifted in time by the delay time of the fat suppression pulse such as TI and TEeff so that data in the vicinity of the center of the k-space is collected at the desired timing during the systolic SD and the diastolic DD, respectively. Each delay time DTsys and DTdias can be set. The FASE sequence (FASEsys) for data collection of systolic SD and the FASE sequence (FASEdias) for data collection of diastole DD may be executed in different heartbeat periods.

  In addition, when performing ECG synchronous imaging by the TOF method, the delay time for data collection is set only to either the diastolic SD or the systolic DD. When performing ECG-synchronized imaging by the Flow Prep method, a plurality of blood flow labeling pulses are applied as preparation pulses prior to the excitation pulse. For this reason, the delay time of data collection is shifted by the echo time (TE: echo time) from the application timing of the labeling pulse to the excitation data collection timing. In the case of the Flow Prep method, the data collection timing may be only one of the systolic SD and the diastolic DD, or may be both the systolic SD and the diastolic DD.

  On the other hand, so far, the case where the delay time is set from the HR using the calculation formula has been described. However, as described above, the delay time can also be set based on the table in which the HR and the delay time are associated with each other.

  In the delay time table 48, the delay time for each range of HR values is stored in advance as a table. For example, the HR value range is divided into three ranges such as HR <50, 50 <HR <70, 70 <HR, and a different appropriate delay time is determined for each HR range to determine the delay time table 48. Can be memorized. Further, similarly to the case where the delay time is set using the calculation formula, the delay time table 48 is associated with an ABI value, an index value indicating the degree of progression of the lesion site, and / or an appropriate delay time different for each imaging site. Can be saved.

  When the delay time is set based on the table, the delay time determination unit 47 acquires the delay time corresponding to the delay time based on the information such as the ABI and the imaging part input from the input device 33. Configured as follows.

  FIG. 4 is a diagram showing an example of the delay time stored in the delay time table 48 shown in FIG.

  As shown in FIG. 4, the delay time corresponding to the value of HR corresponding to the systole (SYS) and the diastole (DIAS) is stored in the delay time table 48 for each imaging region. FIG. 4 shows an example when TI = 150 ms and TEeff = 80 ms. When there is 70% vascular stenosis, the table is created so that the delay time is set by adding 40 ms each.

  Next, other functions of the computer 32 will be described.

  The sequence controller control unit 41 has a function of performing drive control by acquiring imaging conditions including a pulse sequence from the imaging condition setting unit 40 and giving them to the sequence controller 31 when receiving scan start instruction information from the input device 33. Have. 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. For this reason, each raw data generated in the receiver 30 is stored in the k-space database 42 as k-space data.

  The image reconstruction unit 43 has a function of reconstructing image data by acquiring k-space data from the k-space database 42 and performing an image reconstruction process including Fourier transform (FT). A function of writing the received image data into the image database 44. For this reason, the image database 44 stores the image data reconstructed by the image reconstruction unit 43.

  The blood flow image creation unit 45 reads necessary image data from the image database 44 and performs display processing such as image processing such as difference processing and maximum value projection (MIP) processing. It has a function of generating flow image data and a function of displaying a blood flow image on the display device 34 by giving the generated blood flow image data to the display device 34. For example, arterial blood flow image data is extracted by performing arterial artery separation by differential processing between image data obtained from k-space data collected during diastole and image data obtained from k-space data collected during systole can do.

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

  FIG. 5 is a flowchart illustrating a procedure when a blood flow image of the subject P is captured by the magnetic resonance imaging apparatus 20 illustrated in FIG. 1, and reference numerals with numerals in the figure indicate each step of the flowchart.

  First, 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.

  Next, in step S1, HR is acquired as heart rate information. That is, the ECG signal of the subject P is acquired by the ECG unit 38. In the ECG unit 38, HR is obtained by detecting the R wave from the acquired ECG signal. The obtained HR is output from the ECG unit 38 to the computer 32 via the sequence controller 31 together with the ECG signal. Then, the heart rate acquisition unit 46 acquires HR.

  Next, in step S2, the imaging condition setting unit 40 sets MRA imaging conditions including a delay time and a pulse sequence for heart rate synchronization based on HR. The delay time is determined by referring to the relational expression representing the relationship between HR and delay time as described above in the delay time determination unit 47 and the delay time table associated with the value of HR stored in the delay time table 48. Can be set based on HR. Further, the delay time can be corrected according to the ABI, the value of the index indicating the degree of progression of the imaging site, the lesion site, the delay time of the fat suppression pulse such as TI, and / or TEeff. As a result, a pulse sequence as shown in FIG. 3 is set as an imaging condition.

  Next, in step S3, an imaging scan is executed in synchronization with an electrocardiogram accompanied by a delay time from the R wave according to the set imaging condition, and data collection is performed.

  That is, when a scan disclosure instruction is given from the input device 33 to the sequence controller control unit 41, the sequence controller control unit 41 acquires an imaging condition including an electrocardiographic synchronization delay time and a pulse sequence from the imaging condition setting unit 40. This is given to the controller 31. The sequence controller 31 drives the gradient magnetic field power source 27, the transmitter 29, and the receiver 30 under electrocardiographic synchronization in accordance with the imaging conditions received from the sequence controller control unit 41 and the ECG signal from the ECG unit 38, thereby causing the subject P to move. A gradient magnetic field is formed in the set 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 generates A / D conversion to generate raw 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.

  Here, the k-space data stored in the k-space database 42 is data collected in a timing determined by a delay time suitable for blood flow image data generation, for example, in the systole and diastole of the myocardium.

  In step S4, the image reconstruction unit 43 performs image reconstruction processing. That is, the image reconstruction unit 43 reconstructs image data by taking k-space data from the k-space database 42 and performing image reconstruction processing, and writes the image data obtained by the reconstruction to the image database 44. .

  Next, in step S <b> 5, blood flow image data is generated by the blood flow image creation unit 45, and the blood flow image is displayed on the display device 34. That is, the blood flow image creation unit 45 reads the image data from the image database 44 and performs necessary image processing to generate blood flow image data for display. Then, the generated blood flow image data for display is given to the display device 34, and the blood flow image is displayed on the display device 34. For example, arterial image data is generated by difference processing between image data corresponding to the diastole and image data corresponding to the systole.

  Therefore, the user can use the blood flow image displayed on the display device 34 based on data collected at an appropriate timing for diagnosis.

  That is, the magnetic resonance imaging apparatus 20 as described above automatically calculates the delay time from the reference wave required for the heartbeat-synchronized MRA or pulse-wave synchronization MRA to the data acquisition trigger based on heartbeat information such as HR or pulse wave information. It can be set.

(effect)
For this reason, according to the magnetic resonance imaging apparatus 20, it is possible to more easily determine an appropriate time phase and collect blood flow image data without requiring special knowledge or skill of the user. In addition, in the past, 2D multi-phase single scan such as ECG-prep scan was executed to determine the appropriate delay time from triggers such as R-wave, but such pre-scan is executed. Without delay, 3D imaging scan can be performed by determining the delay time directly from the patient information acquired from the electrocardiograph and pulse wave meter such as heart rate information or pulse wave information.

20 Magnetic Resonance Imaging Device 21 Magnet for Static Magnetic Field 22 Shim Coil 23 Gradient Magnetic Field Coil 24 RF Coil 25 Control System 26 Static Magnetic Field Power Supply 27 Gradient Magnetic Field Power Supply 28 Shim Coil Power Supply 29 Transmitter 30 Receiver 31 Sequence Controller 32 Computer 33 Input Device 34 Display Device 35 arithmetic unit 36 storage unit 37 bed 38 ECG unit 40 imaging condition setting unit 41 sequence controller control unit 42 k-space database 43 image reconstruction unit 44 image database 45 blood flow image creation unit 46 heart rate acquisition unit 47 delay time determination unit 48 delay Time table P

Claims (16)

Based on the heart rate information or pulse wave information acquired from the subject in advance, set the delay time from the reference wave that represents the time phase of the data acquisition timing in imaging synchronized with the pulsation, and execute the scan with the set delay time Data collecting means for collecting magnetic resonance signals by:
Image generating means for generating a blood flow image based on the magnetic resonance signal;
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to set the delay time based on a heart rate. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to set the delay time based on a period between adjacent R waves in an ECG signal. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to perform an electrocardiographic synchronization imaging scan. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to repeatedly collect the magnetic resonance signal for each of a plurality of heartbeats. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to collect the magnetic resonance signal using a steady free precession motion of a spin. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to set the delay time based on the heartbeat information using a calculation formula representing a relationship between the heartbeat information and the delay time. Storage means for storing a delay time for each value of the heart rate information;
The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to acquire a delay time corresponding to the heartbeat information from the storage unit. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to set a delay time according to an imaging region and a ratio of an ankle to upper arm blood pressure. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to shift the delay time based on at least one of a delay time from a fat suppression pulse to an excitation pulse and an execution echo time. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to set the delay time based on an average value of a plurality of heart rates. The data collection means is configured to estimate a systole or diastole of a myocardium based on a heart rate or an adjacent R wave, and set the delay time to be within the estimated systole or diastole The magnetic resonance imaging apparatus according to claim 1. 13. The magnetic resonance imaging apparatus according to claim 12, wherein the data collection unit is configured to set an upper limit value within the minimum heartbeat period when the systole or the diastole exceeds a threshold corresponding to the minimum heartbeat period. . The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to set a delay time according to a value of an index indicating the degree of progression of a lesion site. The data collection means is configured to perform a scan in each of the diastole and systole of the myocardium,
The magnetic resonance imaging according to claim 1, wherein the image generation unit is configured to generate the blood flow image with a difference process between data corresponding to the diastole and data corresponding to the systole. apparatus. The magnetic resonance imaging apparatus according to claim 1, wherein the data collection unit is configured to execute the three-dimensional scan by setting the delay time directly from the heartbeat information or the pulse wave information.

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