WO2017038345A1

WO2017038345A1 - Magnetic resonance imaging device and imaging sequence generating method

Info

Publication number: WO2017038345A1
Application number: PCT/JP2016/072585
Authority: WO
Inventors: 崇西原
Original assignee: 株式会社日立製作所
Priority date: 2015-08-31
Filing date: 2016-08-02
Publication date: 2017-03-09
Also published as: JP6483269B2; JPWO2017038345A1

Abstract

The objective of the present invention is to make it possible to obtain a perfusion image of tissue in which a plurality of blood vessel perfusion regions coexist, wherein the perfusion region for each blood vessel is clearly distinguished, while limiting an increase in the examination time. With respect to tissue in which a plurality of blood vessel perfusion regions coexist, in order to obtain a perfusion image in which the perfusion region for each blood vessel is clearly distinguished, two-dimensional selective excitation pulses (2DRF pulses) are used as label pulses for each blood vessel, and after the position at which each label pulse is to be applied has been determined, a delay time is determined for each blood vessel and an imaging sequence is assembled using the determined delay times. When assembling the imaging sequence, the second and subsequent label pulses to be applied are applied within the delay time of the preceding label pulse, and immediately before the corresponding data acquisition period.

Description

Magnetic resonance imaging apparatus and imaging sequence generation method

The present invention relates to a Magnetic Resonance Imaging (hereinafter referred to as MRI) apparatus, and in particular, a non-contrast perfusion that confirms a dominant region of a specific blood vessel by applying a two-dimensional selective excitation pulse (hereinafter referred to as a 2DRF pulse) as a label pulse to a plurality of locations. It relates to imaging.

Non-contrast perfusion imaging of the head using a two-dimensional selective excitation pulse (hereinafter referred to as 2DRF pulse) as a label pulse and non-contrast perfusion imaging of the liver using a label pulse of normal slice selective excitation are known. (For example, see Non-Patent Document 1 and Non-Patent Document 2).

Also, it is generally known that the T1 value changes according to the oxygen partial pressure (see, for example, Non-Patent Document 3).

As described above, conventionally, non-contrast perfusion imaging using a label pulse of slice selective excitation is performed on a tissue such as a liver that is cured by a plurality of blood vessels other than the head. This imaging has the following problems.

1) The liver, especially the vicinity of the artery, is moving due to pulsation. For this reason, this movement tends to reduce the ability to depict blood vessels and liver parenchyma.

2) The liver is cured from the two systems of hepatic artery and portal vein. Tumors are dominated by hepatic artery curing. Therefore, to determine whether or not the tumor is a tumor, it is essential to determine which region is the hepatic artery or portal vein. However, with the label pulse (IR) of slice selective excitation, it is difficult to label the hepatic artery and portal vein individually without suppressing the liver parenchyma from the anatomical arrangement. In addition, in the case where the liver parenchyma is allowed to be partially rendered and is individually labeled, a plurality of imaging operations are required, and the examination efficiency is poor.

3) In non-contrast perfusion, focus on the slight signal drop of several percent that occurs when the labeled blood reaches the perfusion region of the tissue and image it. Therefore, the time (delay time) from application of the label pulse to data acquisition is very important. However, the optimal delay time differs between the hepatic artery and portal vein, which are the hepatic blood vessels, and data cannot be acquired with the optimal Delay for both blood flows, and the perfusion may be underestimated, It is possible that the dominant region of the hepatic artery and portal vein cannot be clearly separated. Note that the optimal delay time differs between the hepatic artery and portal vein, which are factors that determine the optimal delay time, such as blood flow velocity, T1 value, and distance from the label position to the perfusion area. Because.

This applies to non-contrast perfusion imaging using an MRI device not only in the liver, but also in tissues where perfusion areas of arteries and veins are mixed, or in tissues where multiple perfusion areas of veins are to be observed separately It is a common problem.

The present invention has been made in view of the above circumstances, and a perfusion image of a tissue in which perfusion regions of a plurality of blood vessels are mixed and in which perfusion regions for each blood vessel are clearly distinguished can be obtained while suppressing an increase in examination time. The purpose is to provide the technology to obtain.

According to the present invention, regarding a tissue in which perfusion regions of a plurality of blood vessels are mixed, in order to obtain a perfusion image in which perfusion regions for each blood vessel are clearly distinguished, a two-dimensional selective excitation pulse (2DRF Pulse). Further, after determining the application position of each label pulse, a delay time is determined for each blood vessel, and an imaging sequence is assembled using the determined delay time.

In assembling the imaging sequence, the label pulse to be applied after the second is applied within the delay time of the label pulse to be applied first and immediately before the corresponding data acquisition period. At this time, the label pulse application timing is set based on the trigger for blood flow that is greatly affected by body movement.

According to the present invention, it is possible to acquire a perfusion image of a tissue in which perfusion regions of a plurality of blood vessels are mixed, in which perfusion regions for each blood vessel are clearly distinguished, while suppressing an increase in examination time.

Block diagram of the MRI apparatus of the first embodiment Functional block diagram of the control unit of the first embodiment (a) is explanatory drawing for demonstrating the imaging target of 1st embodiment, (b) is explanatory drawing for demonstrating a non-contrast perfusion sequence. Flow chart of imaging processing of the first embodiment Explanatory drawing for demonstrating the example of a reception screen of 1st embodiment (a) is explanatory drawing for demonstrating the example of a display of 1st embodiment, (b) is explanatory drawing for demonstrating the other example of a display of 1st embodiment. Flowchart of the delay time determination process of the first embodiment Flowchart of the delay time determination process of the first embodiment Explanatory drawing for demonstrating the delay time determination process of 1st embodiment. Explanatory drawing for demonstrating the sampling example of the other example of the non-orthogonal system sampling method of 1st embodiment (a) is a conventional imaging sequence example, (b) and (c) are explanatory diagrams for explaining an imaging sequence example of the present embodiment, respectively. Flowchart of imaging sequence generation processing of the first embodiment Explanatory drawing for demonstrating the example of an imaging sequence of 2nd embodiment. Flowchart of label pulse application period determination process of the second embodiment Explanatory drawing for demonstrating the label pulse application period determination process of 2nd embodiment. Explanatory drawing for demonstrating the modification of the label pulse application aspect of 2nd embodiment.

<< First Embodiment >>
Hereinafter, a first embodiment to which the present invention is applied will be described. Hereinafter, in all the drawings for explaining the embodiments of the present invention, those having the same function are basically denoted by the same reference numerals, and the repeated explanation thereof is omitted.

First, the configuration of the MRI apparatus of this embodiment will be described. FIG. 1A is a block diagram of the MRI apparatus 100 of the present embodiment. The MRI apparatus 100 of the present embodiment is an apparatus that obtains a tomographic image of the subject 101 using the NMR phenomenon. As shown in FIG. 1A, a static magnetic field generating magnet 102, a gradient magnetic field coil 103 and a gradient magnetic field power source 106, a transmission RF coil (transmission coil) 104, an RF transmission unit 107, a reception RF coil (reception coil) 105, and a signal A detection unit 108, a signal processing unit 109, a sequencer 110, a control unit 120, a display device 121, an operation unit 122, a storage device 123, and a subject 101 are mounted, and the subject 101 generates a static magnetic field. And a bed 111 to be taken in and out of the magnet 102.

The static magnetic field generating magnet 102 functions as a static magnetic field generating unit that generates a static magnetic field. The static magnetic field generating magnet 102 generates a uniform static magnetic field in the direction perpendicular to the body axis of the subject 101 in the vertical magnetic field method and in the body axis direction in the horizontal magnetic field method. A permanent magnet type, normal conducting type or superconducting type static magnetic field generating source is arranged around the.

The gradient magnetic field coil 103 and the gradient magnetic field power source 106 function as a gradient magnetic field application unit that applies a gradient magnetic field to the subject 101 arranged in a static magnetic field. The gradient magnetic field coil 103 is a coil wound in the three-axis directions of X, Y, and Z that are the real space coordinate system (stationary coordinate system) of the MRI apparatus. Each of the gradient magnetic field coils is connected to a gradient magnetic field power source 106 for driving the gradient coil and supplied with a current. Specifically, the gradient magnetic field power supply 106 of each gradient coil is driven according to a command from a sequencer 110 described later, and supplies a current to each gradient coil 103. Thereby, gradient magnetic fields Gx, Gy, and Gz are generated in the three axial directions of X, Y, and Z.

For example, when imaging a two-dimensional slice plane, a slice gradient magnetic field pulse (Gs) is applied in a direction orthogonal to the slice plane (imaging section) to set the slice plane for the subject 101. A phase encoding gradient magnetic field pulse (Gp) and a frequency encoding (leadout) gradient magnetic field pulse (Gf) are applied in the remaining two directions orthogonal to the slice plane and orthogonal to each other, and the echo signal in each direction is applied. Location information is encoded.

The transmission coil 104 and the RF transmitter 107 function as a high-frequency magnetic field transmitter that transmits a high-frequency magnetic field pulse (RF pulse) that excites the magnetization of the subject 101 at a predetermined flip angle. The transmission coil 104 is a coil that irradiates the subject 101 with an RF pulse, is connected to the RF transmission unit 107, and is supplied with an RF pulse current from the RF transmission unit 107. By irradiating the subject 101 with an RF pulse from the transmission coil 104, an NMR phenomenon is induced in the nuclear spins of the atoms constituting the biological tissue of the subject 101.

Specifically, the RF transmission unit 107 is driven according to a command from a sequencer 110 described later, amplitude-modulates and amplifies the high-frequency pulse, and supplies it to the transmission coil 104 disposed in the vicinity of the subject 101. The supplied high frequency pulse is applied to the subject 101 from the transmission coil 104.

The reception coil 105 and the signal detection unit 108 function as a signal reception unit that receives an echo signal generated by the subject 101. The reception coil 105 is a coil that receives an NMR signal (echo signal) emitted by the NMR phenomenon of the nuclear spin that constitutes the biological tissue of the subject 101, and is connected to the signal detection unit 108 to signal the received echo signal. The data is sent to the detection unit 108. The signal detection unit 108 performs detection processing of the echo signal received by the reception coil 105.

Specifically, when the echo signal of the response of the subject 101 induced by the RF pulse irradiated from the transmission coil 104 is received by the reception coil 105 disposed in the vicinity of the subject 101, the signal detection unit Sent to 108. The signal detection unit 108 amplifies the received echo signal according to a command from the sequencer 110 described later, divides the signal into two orthogonal signals by quadrature detection, and each of them is a predetermined number (for example, 128, 256, 512, etc.). ) Sampling, A / D conversion of each sampling signal is converted into a digital quantity, and sent to the signal processing unit 109 described later. Thus, the echo signal is obtained as time-series digital data (hereinafter referred to as echo data) composed of a predetermined number of sampling data.

The signal processing unit 109 performs various signal processing on the echo data, and sends the processed echo data to the control unit 120.

The sequencer 110 mainly transmits various commands for data collection necessary for the reconstruction of the tomographic image of the subject 101 to the gradient magnetic field power source 106, the RF transmission unit 107, and the signal detection unit 108. To control. Specifically, the sequencer 110 operates under the control of the control unit 120, which will be described later, and controls the gradient magnetic field power source 106, the RF transmission unit 107, and the signal detection unit 108 in accordance with the imaging sequence, and the RF pulse to the subject 101. And the application of the gradient magnetic field pulse and the detection of the echo signal from the subject 101 are repeatedly executed to collect echo data necessary for reconstruction of the image of the imaging region of the subject 101.

The control unit 120 performs control of the sequencer 110, various data processing, display of processing results, storage, and the like, and has a CPU and a memory therein. In the present embodiment, an image is reconstructed from the echo signal received by the signal receiving unit described above, and a command for controlling the operations of the gradient magnetic field applying unit, the high frequency magnetic field transmitting unit, and the signal receiving unit is given to the sequencer 110 according to the imaging sequence. give. The imaging sequence is generated by imaging parameters set by the user and a pulse sequence specified by the user.

Specifically, the control unit 120 of the present embodiment controls the sequencer 110 to execute the collection of echo data, and the collected echo data is stored in the memory based on the encoding information applied to the echo data. Store in an area corresponding to k-space. A group of echo data stored in an area corresponding to the k space of the memory is also referred to as k space data. The k-space data is subjected to processing such as signal processing and image reconstruction by Fourier transform, and the resulting image of the subject 101 is displayed on the display device 121 described later and recorded in the storage device 123. To do.

The display device 121 and the operation unit 122 are interfaces for exchanging various control information of the MRI apparatus 100, information necessary for arithmetic processing, and arithmetic processing results with the user. The MRI apparatus 100 of the present embodiment accepts input from the user via the display device 121 and the operation unit 122. The operation unit 122 is disposed in the vicinity of the display device 121, and an operator interactively controls various processes of the MRI apparatus 100 through the operation unit 122 while looking at the display device 121. For example, the display device 121 displays a reconstructed image of the subject 101 and the like. The operation unit 122 includes at least one of a trackball, a mouse, a keyboard, and the like serving as an input device.

The storage device 123 stores information necessary for the operation of the MRI apparatus 100, data being processed, and the like. For example, it is composed of an optical disk, a magnetic disk, or the like.

In FIG. 1A, the transmission coil 104 and the gradient magnetic field coil 103 are opposed to the subject 101 in the static magnetic field space of the static magnetic field generating magnet 102 into which the subject 101 is inserted, in the case of the vertical magnetic field method, If the horizontal magnetic field method is used, the object 101 is installed so as to surround it. The receiving coil 105 is installed so as to face or surround the subject 101.

Further, for example, when imaging is performed in synchronization with the periodic body movement of the subject 101, such as electrocardiogram synchronization and respiratory synchronization imaging, a body movement detection device 124 for detecting the periodic body movement of the subject 101 is further provided. You may have. The body movement detection device 124 is installed at a position of the subject 101 where the body movement to be detected can be detected. The detected body motion information is transmitted to the control unit 120.

The nuclide to be imaged by the current MRI apparatus 100 is a hydrogen nucleus (proton) that is a main constituent material of the subject 101 as widely used clinically. In the MRI 100, the information about the spatial distribution of proton density and the spatial distribution of the relaxation time of the excited state is imaged, so that the form or function of the human head, abdomen, limbs, etc. can be expressed two-dimensionally or three-dimensionally. Take an image. At this time, in MRI, an RF pulse is applied together with a gradient magnetic field in order to excite only protons in a specific region.

In this embodiment, a two-dimensional selective excitation pulse (2DRF pulse) is used as a label pulse for non-contrast perfusion imaging in which a label pulse is applied to confirm a dominant region of a specific blood vessel.

In a tissue cured by a plurality of different blood vessels, a label pulse is applied to each blood vessel, and the blood flow control region of the blood vessel is confirmed. At this time, the time from label pulse application to data acquisition (hereinafter referred to as delay time) is calculated for each blood vessel. Preferably, an optimum delay time is calculated. Then, one imaging sequence is generated using the calculated delay time. Then, imaging is executed according to the generated imaging sequence.

In order to realize this, the control unit 120 according to the present embodiment determines a delay time determination unit 130 that determines a delay time (preferably an optimal delay time) for each of a plurality of different blood vessels, as shown in FIG. 1B. An imaging sequence generation unit 140 that generates one imaging sequence using the delay time, an imaging unit 150 that obtains a perfusion image by performing imaging according to a predetermined imaging sequence including the generated imaging sequence, and a reconstructed image An image generation unit 160 that adds various types of processing and generates an image to be displayed on the display device 121, and a reception unit 170 that receives various instructions from the user.

Each function realized by the control unit 120 is realized by causing the CPU of the control unit 120 to load and execute a program stored in the storage device 123. All or some of the functions may be realized by hardware such as ASIC (Application Specific Integrated Circuit) or FPGA (field-programmable gate array). Various data used for processing of each function and various data generated during the processing are stored in the storage device 123.

Also, the control unit 120 may not realize at least one processing unit of the delay time determination unit 130, the imaging sequence generation unit 140, and the image generation unit 160. The information processing apparatus may be constructed on an information processing apparatus that is capable of transmitting / receiving data to / from the MRI apparatus 100 and independent of the MRI apparatus 100.

Note that the two-dimensional selective excitation pulse (2DRF pulse) used for the label pulse in this embodiment is an RF pulse that is applied together with a gradient magnetic field and excites a local region into a cylinder type.

Hereinafter, in the present embodiment, as shown in FIG. 2 (a), the imaging target tissue is the liver 200, and the blood vessels (observation target blood vessels) for observing the dominant region are the hepatic artery 210 that is an artery and the portal that is a vein. The case of the pulse 220 will be described as an example.

Therefore, the imaging sequence of the present embodiment obtains a first perfusion image that is a perfusion image of the imaging target tissue (liver 200) by the first blood vessel (hepatic artery 210), as shown in FIG. One non-contrast perfusion sequence 501 and a second non-contrast perfusion sequence 502 for obtaining a second perfusion image that is a perfusion image of the imaging target tissue (liver 200) by the second blood vessel (portal vein 220), Is provided. The first non-contrast perfusion sequence 501 includes a first label pulse (arterial label pulse) 510 and a first data acquisition sequence (arterial data acquisition sequence) 512. The sequence 502 includes a second label pulse (venous label pulse) 520 and a second data acquisition sequence (venous data acquisition sequence) 522.

The imaging sequence generation unit 140 of the present embodiment combines the first non-contrast perfusion sequence 501 and the second non-contrast perfusion sequence 502 to generate an imaging sequence.

The delay time determining unit 130 then applies the first delay time 511 from the application of the first label pulse 510 to the start of the first data acquisition sequence 512 and the second data acquisition sequence from the application of the second label pulse 520. Second delay times 521 until the start of 522 are respectively determined. Preferably, the delay time determination unit 130 determines a suitable or optimal first delay time 511 and second delay time 521. Hereinafter, the meaning of “optimal” includes the meaning of “preferably” or “substantially optimal”. The same applies to other embodiments.

[Imaging processing]
Details of the processing by each of the above-described units will be described along the flow of imaging processing of the present embodiment. FIG. 3 is a processing flow of the imaging processing of the present embodiment. This process starts when an instruction to start an inspection is received from the user via the receiving unit 170.

The imaging unit 150 performs pre-imaging including acquisition of a positioning image (step S1101).
In the present embodiment, as prior imaging, imaging such as shimming for correcting the magnetic field is also performed as necessary.

The reception unit 170 generates a reception screen for receiving various settings using the positioning image, displays the reception screen on the display device 121, and receives designation of an imaging range (FOV) from the user via the reception screen (step S1102). ).

Here, an example of a reception screen 300 generated by the reception unit 170 and displayed on the display device 121 is shown in FIG. As shown in the figure, the reception screen 300 includes a positioning image display area 310 and an OK button 320 that receives a setting intention. The user designates the imaging area 311 on the positioning image displayed in the positioning image display area 310. The accepting unit 170 sets the designated area as the imaging area 311.

Next, the accepting unit 170 accepts designation of label pulse application positions for the hepatic artery 210 and the portal vein 220 (step S1103). These designations are accepted via the acceptance screen 300.

As shown in FIG. 4, on the positioning image in the positioning image display area 310, the user selects the hepatic artery stack 312 as the application position of the first label pulse 510 and the portal as the application position of the second label pulse 520. Each of the pulse stacks 313 is designated so that the stack is superimposed only on the target blood vessel. For example, in order to make it easier for the user to sort the designation, the display mode of the stack designated by the user may be changed for each blood vessel. For example, the color, solid line / dotted line, etc. are changed and displayed.

Note that if there is a region that the user particularly pays attention to, for example, a region that is considered to be a tumor, the receiving unit 170 further receives designation of a region of interest (ROI) 314 (step S1104). ROI 314 is also received on the positioning image. By receiving the ROI 314, the optimum delay time can be calculated more accurately as will be described later. When there is no region of interest, the user designates the entire imaging tissue (in this case, the liver 200) as ROI 314. When the user does not designate ROI 314, the imaging target tissue may be automatically set to ROI 314.

Next, using information specified by the user (imaging region 311, hepatic artery stack 312, portal vein stack 313, region of interest 314), the delay time determination unit 130 determines each observation target blood vessel (here, hepatic artery 210 And the portal vein 220) delay time determination processing for determining the optimum delay time (hereinafter referred to as optimal delay time or optimal value) is performed (step S1105). Details of the delay time determination processing will be described later.

When the optimal delay time of each observation target blood vessel is determined, the imaging sequence generation unit 140 performs imaging sequence generation processing for generating an imaging sequence reflecting the optimal delay time (step S1106). Details of the imaging sequence generation process will also be described later.

The imaging unit 150 controls each unit according to the generated imaging sequence, performs imaging, obtains a reconstructed image, and obtains a perfusion image (a first perfusion image and a second perfusion image) from the reconstructed image (step S1107).

The perfusion image for confirming the dominant region of the blood vessel to be observed was obtained without applying the label pulse with the same imaging sequence as the image (labeled image) reconstructed from the data obtained with the imaging sequence with the label pulse applied It is generated as a difference image from an image reconstructed from data (image without label). Therefore, here, for each blood vessel, a sequence in which a label pulse is applied and a sequence in which no label pulse is applied are executed to obtain reconstructed images (labeled images and unlabeled images), respectively. And the difference of both is calculated and a perfusion image is obtained.
Note that the difference processing may be performed on raw data (k-space data) before Fourier transform.

The image generation unit 160 generates a display image to be displayed on the display device 121 from each obtained perfusion image (step S1108). Then, the generated display image is displayed on the display device 121 (step S1109), and the process ends.

Here, the display image generated in step S1108 will be described. First, an example in which the image generation unit 160 generates a display image from each perfusion image for each blood vessel to be observed and displays the display image on the display device 121 is illustrated in FIG.

In this case, the image generation unit 160, as shown in this figure, the display image 410 generated from the perfusion image by the hepatic artery 210 (first display image generated from the first perfusion image) 410 and the perfusion by the portal vein 220 An image (second display image generated from the second perfusion image) 420 is displayed side by side. At this time, the display mode of the second display image 420 may be changed from the display mode of the first display image 410.

Further, as shown in FIG. 5 (b), the image generation unit 160 may generate an image 430 in which perfusion images of the blood vessels to be observed are superimposed and display them. That is, the first display image and the second display image may be superimposed and displayed on the display device 121. In addition, at this time, it displays in the aspect which a user can identify, such as attaching | subjecting a different color for every control area | region of each blood vessel.

For example, suppose that the dominant region of the vein (portal vein) is blue and the dominant region of the artery (hepatic artery) is red. This makes it easier for the user to grasp the dominant region of each blood vessel. That is, normal liver tissue is cured in both arteries and veins. Therefore, it is displayed in purple due to the overlap of red and blue. However, if there is a tumor, it is displayed in red because it is the dominant region of the artery.

In addition, although the perfusion image etc. which attached | subjected such a color may be displayed as it is, you may display it superimposed on a normal form image. This makes it easier to understand the location of the tumor.

[Delay time determination processing]
Next, details of the delay time determination process by the delay time determination unit 130 of the present embodiment will be described. As described above, the optimum delay time varies depending on the blood flow velocity, the T1 value, the distance from the label position designated by the user to the perfusion region, and the like. Therefore, the delay time determination unit 130 according to the present embodiment is determined by applying a label pulse to a position actually designated by the user and performing imaging. Further, as described above, depending on the blood flow, it is affected by body movement such as pulsation. For this reason, imaging when determining the optimum delay time is performed using a non-orthogonal sampling method that is not easily affected by body movement.

The delay time determination unit 130 of the present embodiment efficiently updates a part of the k-space and acquires data in multiphase while suppressing the influence of body motion using a non-orthogonal sampling method for each observation target blood vessel. Then, follow the signal change and determine the optimal delay time.

Specifically, echo signals are collected using a hybrid radial method, which is one of the radial methods in the non-orthogonal sampling method. The hybrid radial method is a sequence for collecting k-space data radially in units of blades. A signal value in a predetermined area is calculated every time one blade is collected, and the blade data collection timing at which the signal value is minimum is set as the optimum delay time.

That is, the delay time determination unit 130 of the present embodiment is obtained by imaging the imaging target tissue (liver 200) by the non-orthogonal sampling method immediately after the application of the first label pulse 510 and the second label pulse 520. An optimum value (optimum delay time) is determined according to the echo data of each k-space blade.

At this time, each time the delay time determination unit 130 of the present embodiment acquires the echo data of the k-space blade, the obtained delay data is reflected to obtain a reconstructed image, and each time a reconstructed image is obtained, The signal value of the determined area is measured, the average value is calculated, and the reconstructed image having the minimum value is specified from the calculated average values. The timing at which the latest echo data of the k-space blade reflected when obtaining the reconstructed image is acquired is determined as the optimum value.

The delay time determination unit 130 measures the signal value in a predetermined region of interest (ROI 314) when the target blood vessel for which the optimal value is determined is an artery (hepatic artery 210), and determines the optimal value. When the blood vessel is a vein (portal vein 220), signal values outside the region of interest (ROI 314) or in the entire imaging region 311 are measured.

Hereinafter, the delay time determination process by the delay time determination unit 130 of the present embodiment will be described along the flow of the process. 6 and 7 are process flows of the delay time determination process of the present embodiment. FIG. 8 is a diagram for explaining the delay time determination process of the present embodiment.

First, the optimum delay time of the first blood vessel (here, hepatic artery 210) is determined.

The delay time determination unit 130 collects echo data for one slice (314 in FIG. 4) including the center of gravity of the ROI 314 in the imaging region 311 and parallel to the imaging region 311 using the hybrid radial method ( FIG. 6: Step S1201). The echo data collected for all slices for one slice is referred to as initial echo data 600 as shown in FIG. The initial echo data 600 is stored in a memory or the like.

Next, the delay time determination unit 130 applies an arterial label pulse (first label pulse) 510 to the set hepatic artery stack 312 (FIG. 6: step S1202).

Suppose here that the number of blades constituting the k space for one slice is N (N is an integer of 1 or more). FIG. 8 illustrates the case where N = 6. A counter n for counting N is initialized (FIG. 6: Step S1203), and data collection is started immediately after application of the label pulse 510 for the artery.

Then, the delay time determination unit 130 collects echo data 611 for one blade of the nth blade (FIG. 6: step S1204). Then, the echo data of the nth blade in the initial echo data 600 is replaced with newly collected echo data (step S1205), and an image is reconstructed (FIG. 6: step S1206).

The delay time determination unit 130 measures an average value (signal average value) Si1 _AV of signals in a predetermined region on the reconstructed image (FIG. 6: step S1207). Here, when the blood vessel whose optimum delay time is to be determined is an artery, the region where the signal average value is measured is ROI 314.

The measurement result is stored in association with the timing at which the echo signal of the blade is collected (elapsed time t1 _n from the application of the label pulse 510). At this time, as the position of the ROI 314, a position set by the user on the positioning image is used.

The processing from step S1204 to step S1207 is performed by using the replaced data as initial echo data 600 until the elapsed time t1 _n from the application of the label pulse 510 exceeds a predetermined time T or until the counter n becomes N. Further, it is repeated while updating the next blade (FIG. 6: Steps S1208 and 1209).

Then, the delay time determining unit 130 determines the timing t1 _{n at} which the minimum signal average value Si1 _AV is obtained as the optimum delay time Delay (A) of the hepatic artery (FIG. 6: step S1210). The reason why the timing at which the signal average value Si1 _AV is minimized is determined as the optimum delay time because the signal value is lowered by that amount when the labeled blood flows. In particular, since the tumor is cured from the artery, the signal drop of ROI 314 is large.

Subsequently, the delay time determination unit 130 determines the optimum delay time on the other side (here, the portal vein).

First, the delay time determination unit 130 applies the vein label pulse 520 to the set portal vein stack 313 (FIG. 7: step S1301). Then, the counter n is initialized (n = 1) (FIG. 7: Step S1302). Again, data collection starts immediately after application of the vein label pulse 520.

The delay time determination unit 130 collects echo data 621 for one blade of the nth blade (FIG. 7: Step S1303). Then, the echo data of the nth blade in the initial echo data 600 is replaced with newly collected echo data 621 (FIG. 7: step S1304), and an image is reconstructed (FIG. 7: step S1305).

Here, it is determined whether or not a local region considered to be a tumor is set as the ROI 314 (FIG. 7: Step S1306). The determination may be configured such that the delay time determination unit 130 automatically determines from the set size, position, etc. of the ROI 314, or may be configured so that the user inputs which is set when setting the ROI 314. Good. Further, this determination process may not be performed for each blade. For example, when the first blade is acquired, a determination is made and a flag or the like is set. In subsequent iterations, processing is performed according to the presence or absence of a flag.

When the local region is set, the average value (signal average value) Si2 _AV of the region other than the ROI 314 in the image is measured (FIG. 7: Step S1307). As mentioned above, since the veins are not supplied to the tumor, the labeled blood flows into the extratumor area of the liver. Therefore, it is an area outside the ROI 314 that the signal decreases at the timing when the labeled blood flows.

On the other hand, when the entire imaging target region (here, the liver) is set as the ROI 314, the signal average value Si2 _AV in the ROI 314, that is, the entire imaging target region is measured (FIG. 7: Step S1308).

Also in this case, the measurement result is stored in association with the timing (elapsed time t2 _n since the application of the vein label pulse 520) when the echo signal of the blade is collected.

The processing from step S1303 to step S1308 is executed by updating the blade until the elapsed time t2 _n from the application of the vein label pulse 520 exceeds a predetermined time T or until the counter n becomes N ( FIG. 7: Steps S1309 and 1310).

Then, the delay time determination unit 130 determines the timing t2 _{n at} which the minimum signal average value is obtained as the optimum delay time Delay (V) of the portal vein (FIG. 7: Step S1311), and ends the process.

In the delay time determination process, the order of determining the delay time of each blood vessel is not limited.

Further, in the delay time determination process of the present embodiment, the timing at which the signal value in the predetermined region is minimized is determined as the optimum delay time, but is not limited to this method. For example, you may comprise so that a user may designate.

In this case, for each k-space blade, the delay time determination unit 130 reconstructs an image reflecting echo data of the k-space blade and presents it to the user, and selects an image selected by the user from the presented images. The timing at which the latest echo data of the k-space blade reflected at the time of reconfiguration may be determined as the optimum value (optimum delay time).

Specifically, every time the echo data of the nth blade is collected, the delay time determination unit 130 displays a reconstructed image obtained by updating the data of the blade on the display device 121. The user confirms one or more displayed images and selects an image acquired at the timing when the signal is the lowest. The delay time determination unit 130 receives the selection and sets the timing at which the selected image is obtained as the optimum delay time.

The image displayed at this time may be the reconstructed image as it is, or may be a signal intensity ratio image with respect to the initial image obtained by reconstructing the initial echo data 600. Moreover, it is good also as a difference image with an initial image. When creating a signal intensity ratio image or a difference image, deformation or misalignment may be corrected by affine transformation or the like using the initial image as a reference. By doing so, it becomes easier to see the difference in signals.

Note that when the user makes a visual decision, the setting of ROI 314 is not necessary.

Here, every time the echo signal of the blade is acquired, the blade is replaced and the image is reconstructed, and the optimum delay time is determined using the obtained signal intensity of the predetermined area. There is no need to reconfigure.

For example, each time a blade signal is acquired, the peak intensity or integral value of the echo signal of the blade may be used, and the timing at which these values are minimized may be determined as the optimum delay time.

That is, every time the echo data of the k-space blade is acquired, the delay time determination unit 130 calculates either the peak intensity value or the integral value of the echo data as an echo value, and the k-space where the echo value is minimized You may determine the timing which acquired the echo data of a braid | blade as an optimal value.

In this case, it is not necessary to set ROI314. With this configuration, the optimum delay time can be determined more easily.

Furthermore, although the case where the hybrid radial method sequence is used as the non-orthogonal sampling method has been described as an example here, the sequence used is not limited to this.
For example, a multi-shot spiral sampling method may be used. An example of k-space sampling using the 6-shot spiral sampling method is shown in FIG.

In this case, the optimum delay time is determined by the same method as described above. That is, first, the initial echo data is collected, and then each time the echo data on one spiral locus is collected, the echo data of the locus of the initial echo data is updated, the image is reconstructed, and the signal of the predetermined area The timing at which the average value is minimized is set as the optimum delay time. Alternatively, similarly to the above, the user may specify, or the optimal delay time may be determined using the peak intensity or the integrated value of the echo signal without reconstructing the image.

[Imaging sequence generation processing]
Next, imaging sequence generation processing by the imaging sequence generation unit 140 of this embodiment will be described. FIG. 10 (a) is a diagram for explaining a conventional imaging sequence 509, and FIG. 10 (b) is a diagram for explaining an imaging sequence 500 of the present embodiment. FIG. 11 is a process flow of the imaging sequence generation process of the present embodiment.

Conventionally, when label pulses are applied to a plurality of blood vessels to obtain perfusion images, as shown in FIG. 10 (a), label pulses (510, 520) are individually applied and data acquisition sequences are performed for each blood vessel. We were performing (512, 522). For this reason, the total imaging time is significantly increased. Reference numeral 530 denotes a trigger 530 timing at the time of synchronous heartbeat imaging.

However, in the present embodiment, as shown in FIG. 10 (b), the imaging sequence 500 is generated so as to apply the label pulse for imaging one other blood vessel during the delay time for imaging one blood vessel. The total imaging time is shortened compared to the case where the individual imaging is performed.

That is, the imaging sequence generation unit 140 of the present embodiment uses the optimum value (optimum delay time) for the first delay time 511 and the second delay time 521, respectively, and during the first delay time 511, The imaging sequence 500 is generated so that the second label pulse 520 is applied immediately before the execution of the first data acquisition sequence 512 is started.

Here, since the artery (here, the hepatic artery 210) is affected by pulsation, the timing for applying the arterial label pulse (first label pulse) 510 needs to be determined in synchronization with the electrocardiogram / pulse wave. is there. On the other hand, since the vein (here, the portal vein 220) is not affected by pulsation, the application of the vein label pulse (second label pulse) 520 may be asynchronous.

Therefore, the imaging sequence generation unit 140 generates an imaging sequence so that the first label pulse 510 is applied in synchronization with a predetermined body movement. Therefore, the imaging sequence generation unit 140 first sets an arterial label pulse 510 and an arterial data acquisition sequence (first data acquisition sequence) 512.

Specifically, the imaging sequence generation unit 140 first sets the arterial label pulse 510 to be applied after a predetermined time from a predetermined trigger 530 (step S1401). Then, after applying the arterial label pulse 510, the arterial data acquisition sequence 512 is set at a timing after the optimal delay time Delay (A) 511 of the hepatic artery (step S1402).

Next, the imaging sequence generation unit 140 sets a vein label pulse 520 and a vein data acquisition sequence (second data acquisition sequence) 522.

Specifically, the imaging sequence generation unit 140 first sets a vein label pulse 520 (step S1403). Here, the venous label pulse 520 is set to be applied immediately before the start timing of the arterial data acquisition sequence 512. After the vein label pulse 520 is applied, the vein data acquisition sequence 522 is set at the timing after the optimal delay time Delay (V) 521 of the portal vein (step S1404), and the processing is terminated.

The reason why the vein label pulse 520 is set to be applied immediately before the start timing of the arterial data acquisition sequence 512 is to increase the application interval between the two

label pulses

510 and 520 as much as possible. Thereby, it is possible to suppress the influence of both

label pulses

510 and 520 from being mixed.

In addition, by setting the imaging sequence 500 in this way, the imaging time is extended as compared with the case where images are individually taken sequentially in the conventional imaging sequence 509 shown in FIG. 10 (a) while maintaining the optimum delay time. Can be suppressed.

Furthermore, the execution interval of both

data acquisition sequences

512 and 522 is also shorter than when imaging individually. Therefore, the positional shift due to the body movement between the two data acquisition sequences can be reduced as compared with the case of individually capturing images. In general, when there are a plurality of blood vessels to be observed, diagnosis is often performed by comparing perfusion images of the blood vessels. This is useful in such cases.

As described above, in accordance with the premise of the present embodiment, the imaging sequence generation method is described by taking the case where the first blood vessel is the hepatic artery (artery) 210 and the second blood vessel is the portal vein (vein) 220 as an example. did.

As described above, when the blood vessels to be observed are an artery and a vein, the configuration related to the artery is set first as described above. However, there may be a plurality of veins in the observation target blood vessel. For example, there is a case where it is desired to obtain a perfusion image by veins having different organs.

When the observation target blood vessel includes a plurality of veins having different origins, an imaging sequence is generated so that a label pulse of a non-contrast perfusion sequence with a short optimum delay time is applied first between the veins.

That is, the blood vessel sequence having the shortest delay time is set as the first non-contrast imaging sequence, and this non-contrast imaging sequence is set. Here, the first label pulse is set, the first delay time is set, and the first data acquisition sequence is set.

Next, the blood vessel sequence with the second shortest delay time is set as the second non-contrast imaging sequence, and this non-contrast imaging sequence is set. Here, the second label pulse is set immediately before the first data acquisition sequence, and the second data acquisition sequence is set after a second delay time.

Next, the second non-contrast imaging sequence is the first non-contrast imaging sequence, the blood vessel sequence with the third shortest delay time is the second non-contrast imaging sequence, and the second non-contrast imaging sequence is the same as above. Set the sequence. This is repeated to set a non-contrast imaging sequence for all veins.

For example, FIG. 10C shows a generation example of the imaging sequence 503 when one artery and two veins are blood vessels to be observed. The optimal delay time for one artery is Delay (A), the optimal delay time for the first vein is Delay (Va), the optimal delay time for the second vein is Delay (Vb), and Delay (Va) <Delay (Vb ).

As shown in the figure, first, the artery and the vein with the shortest optimal delay time among the veins (here, the first vein) are referred to as the first blood vessel and the second blood vessel, respectively. The imaging sequence is generated by the method described above.

That is, for the artery, the application timing of the arterial label pulse 510 and the execution timing of the arterial data acquisition sequence 512 are determined. As described above, the application timing of the arterial label pulse 510 is set after elapse of a predetermined time interval from the trigger 530. The arterial data acquisition sequence 512 is set after delay (A) has elapsed after the application of the arterial label pulse 510.

Next, the application timing of the first vein label pulse 520a is determined. Here, as described above, it is set immediately before the arterial data acquisition sequence 512. Then, after the delay (Va) time elapses, a first vein data acquisition sequence 522a is set.

Next, the imaging sequence 503 is generated by the above method using the first vein and the second vein as the first blood vessel and the second blood vessel. In this case, the optimum value of the first delay time is equal to or less than the optimum value of the second delay time because the label pulse of the sequence having a short delay time is generated to be applied first.

That is, the application timing of the second vein label pulse 520b is determined. Here, it is assumed to be immediately before the first vein data acquisition sequence 522a. Then, after the Delay (Vb) time has elapsed, a second vein data acquisition sequence 522b is set.

The same applies when the number of veins to be observed is 3 or more.

It should be noted that when a region where blood vessel movement due to respiration is large is a region to be imaged, respiratory synchronization is also required. In this case, the vein is also set as respiratory synchronization.

As described above, the MRI apparatus 100 of the present embodiment includes the first label pulse 510 and the first data acquisition sequence 512, and is the first perfusion image of the imaging target tissue 200 by the first blood vessel 210. A second non-contrast perfusion sequence 501 for obtaining a perfusion image, a second label pulse 520 and a second data acquisition sequence 522, and a second perfusion image of the imaging target tissue 200 by the second blood vessel 220 A second non-contrast perfusion sequence 502 for obtaining a perfusion image 420 of the first imaging sequence generator 140 for generating an imaging sequence 500 using the first non-contrast perfusion sequence 502, and the first data acquisition sequence from the application of the first label pulse 510 First delay time 511 until 512 start and second delay time 521 from the application of the second label pulse 520 to the start of the second data acquisition sequence 522, respectively. A delay time determining unit 130 for determining, and an imaging unit 150 that performs imaging according to the imaging sequence 500 and obtains the first perfusion image and the second perfusion image 420, and the imaging sequence generation unit 140 includes: Using the determined first delay time 511 and the second delay time 521, the first delay time 511 during the first delay 511 time, immediately before the execution of the first data acquisition sequence 512 is started. The imaging sequence 500 is generated so that the second label pulse 520 is applied, and the delay time determination unit 130 is configured to perform the non-orthogonal system immediately after the application of the first label pulse 510 and the second label pulse 520. The first delay time 511 and the second delay time 521 are respectively set according to echo data of each k-space blade obtained by imaging the imaging target tissue by the sampling method. Determined.

Preferably, the delay time determination unit 130 determines optimum values for the first delay time 511 and the second delay time 521, respectively.

As the first label pulse 510 and the second label pulse 520, a two-dimensional selective excitation pulse that excites a local region in a cylinder shape is used.

Thus, according to the present embodiment, a two-dimensional selective excitation pulse is used as a label pulse for suppressing a blood signal, and labeling is performed for each blood vessel to be observed. The imaging sequence is generated using the delay time determined as described above for each blood vessel to be observed, and applying a label pulse of another blood vessel during the delay time. For this reason, the imaging time can be shortened as compared with the case of executing individually.

Also, the delay time used when the imaging sequence is generated is determined by performing imaging by actually applying a label according to the label application position set by the user. Therefore, the delay time for each blood vessel can be determined with high accuracy. Since imaging is performed using the delay time determined in this way, information on the dominant region for each blood vessel can be obtained with high accuracy.

Furthermore, since the imaging used for determining the delay time uses a non-orthogonal sampling method, it is less susceptible to body movements. Further, since the hybrid radial method is used and the change in the signal value of the predetermined area is followed and determined each time the blade is updated, the delay time can be determined efficiently.

Therefore, according to the present embodiment, when performing non-contrast perfusion imaging with an MRI apparatus, information on the dominant region for each blood vessel to be observed can be efficiently and with good contrast while minimizing the extension of examination time. Obtainable. Using this information, the perfusion region of a plurality of blood vessels in the region to be imaged can be clearly separated and presented to the user.

In particular, according to the present embodiment, it is possible to suppress the extension of the examination time while improving the tissue separation ability and resolution of arterial and venous perfusion regions in abdominal organs such as the liver.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described. In the first embodiment, pulsed ASL (PASL) using one label pulse among non-contrast perfusion imaging (ASL Perfusion) is used. On the other hand, in this embodiment, among non-contrast perfusion imaging, Continuous ASL (CASL) and pseudo Continuous ASL (pCASL) that apply a label pulse for a predetermined period are used.

CASL is a technique of applying a label pulse continuously for a predetermined period, and pCASL is a technique of applying a label pulse intermittently for a predetermined period. In general, the application period is predetermined based on the blood flow velocity of the blood vessel to be applied, the T1 value, and the like.

The MRI apparatus of the present embodiment has basically the same configuration as the MRI apparatus 100 of the first embodiment. However, in the present embodiment, the CASL or pCASL method in which a high-frequency magnetic field pulse is applied continuously or intermittently for a predetermined period is used as the first label pulse 510 and the second label pulse 520.

Since the pulse used as the label pulse is different, the processing of the imaging sequence generation unit 140 is different. There is also a difference in the processing of the delay time determination unit 130. Hereinafter, the present embodiment will be described focusing on the configuration different from the first embodiment. Also in the present embodiment, a case where the imaging region is the liver 200, the observation target blood vessel is the hepatic artery (first blood vessel) 210, and the portal vein (second blood vessel) 220 will be described as an example.

As shown in FIG. 12, the imaging sequence generation unit 140 of the present embodiment basically sets the arterial label pulse 513 based on the trigger as in the first embodiment, and sets the optimum delay time Delay. (A) The arterial data acquisition sequence 512 is arranged after 511. Thereafter, the venous label pulse 623 is arranged immediately before the arterial data acquisition sequence 512, and the venous data acquisition sequence 522 is arranged after the delay (V) 521. The delay time is the time from the label pulse application end timing to the data acquisition sequence start timing.

At this time, when a CASL or pCASL type label pulse is used for the arterial label pulse 513 and the venous label pulse 523, the label pulse application period has a predetermined width. Therefore, for example, among the venous blood labeled with the label pulse 523, there is a possibility that the venous blood that has been labeled at an early stage has reached the perfusion region at the timing of obtaining the arterial data. Therefore, in the image reconstructed from the data acquired at the data acquisition timing for arteries, the signal decrease in the arterial control region and the signal decrease due to venous blood coexist, so the contrast between the arterial control region and the vein control region decreases. there is a possibility.

In order to prevent this, the imaging sequence generation unit 140 of the present embodiment sets a limit on the application period of the label pulse (second label pulse 523 in this case) to be applied after the second time. This suppresses the decrease in contrast.

For this reason, the imaging sequence generation unit 140 of the present embodiment further determines the application period of the second label pulse 523 using the suppression rate by the first label pulse 513.

Hereinafter, a method for determining the application period of the second label pulse 520 by the imaging sequence generation unit 140 according to the present embodiment will be described with reference to FIGS. Here, the case where pulses intermittently applied are used as the

label pulses

513 and 523 is exemplified.

First, the imaging sequence generation unit 140 according to the present embodiment calculates the maximum suppression rate RAmin of the arterial dominating region (here, ROI 314) based on the arterial label pulse 513 (step S2101).

The maximum suppression rate RAmin is calculated by the following equation (1) using, for example, the initial value Si1 _AV 0 of the signal average value of the ROI 314 and the minimum value Si1 _AV min.

RAmin = (Si1 _AV 0-Si1 _AV min) / Si1 _AV 0 (1)
Note that Si1 _AV 0 and Si1 _AV min use values acquired when the delay time determination unit 130 determines the first optimum delay time Delay (A) 511. Si1 _AV min is obtained by the same method as in the first embodiment. In the present embodiment, the delay time determination unit 130 obtains Si1 _AV 0 by reconstructing an image and measuring the signal intensity of the ROI 314 when the initial echo data 600 is acquired.

Next, the imaging sequence generation unit 140 uses the value acquired when the delay time determination unit 130 determines the second optimum delay time Delay (V) 521, and uses the elapsed time t from the start of application of the vein label pulse 523. A signal reduction rate RV (t) according to the above is calculated (step S2102).

The decrease rate Rv (t) is applied, for example, to the initial value Si2 _AV 0 of the signal average value of a predetermined region used when determining the optimum delay time for veins and the timing t2 _n when the _nth blade is acquired. using the the mixture was t _n signal average Si2 _AV (t _n) in (elapsed time from the start of the application of intravenous labels pulse 523) period, is calculated by the following equation (2).

RV (t _n ) = (Si2 _AV 0－Si2 _AV (t _n )) / Si2 _AV 0 (2)
In this case as well, the delay time determination unit 130 obtains Si 2 _AV 0 by reconstructing an image and measuring the signal intensity in the above-described region when the initial echo data 600 is acquired.

Then, the imaging sequence generation unit 140 determines the maximum value of the timing t _n at which Rv (t _n ) is smaller than the predetermined ratio α of RAmin as the application period TV of the venous label pulse 523 (step S2103). The ratio α may be a value less than 1.0, held by the system, or configured to be designated by the user.

Due to device limitations, the application period TV of the venous label pulse 523 is shorter than Delay (A) so that the arterial label pulse 513 and the venous label pulse 523 do not overlap in the time axis direction in the imaging sequence. To do.

However, in the case of a pCASL method label pulse in which a pulse having a short application period is applied intermittently, such a restriction need not be provided. For example, when the application periods of both pulses overlap in the time axis direction, as shown in FIG. 15, they may be applied alternately. In this case, for each pulse (beam pulse) applied intermittently, the application interval of each beam pulse is longer than the application period of one beam pulse.

Processing other than the application period determination method by the imaging sequence generation unit 140 is the same as in the first embodiment. The method for determining the optimum delay time by the delay time determination unit 130 is also the same.

As described above, the MRI apparatus of this embodiment includes the same imaging sequence generation unit 140, delay time determination unit 130, and imaging unit 150 as those of the first embodiment. The first label pulse 510 and the second label pulse 520 are high-frequency magnetic field pulses applied intermittently or continuously for a predetermined period, and the imaging sequence generation unit 140 includes the first label pulse 510 The application period of the second label pulse 520 is further determined using the suppression rate according to the above.

As described above, when performing non-contrast perfusion imaging with the MRI apparatus as in the first embodiment, the present embodiment also enables efficient and excellent contrast for each blood vessel to be observed while minimizing the extension of the examination time. Can obtain information on the dominating area. Using this information, the perfusion region of a plurality of blood vessels in the region to be imaged can be clearly separated and presented to the user.

Furthermore, even in the case of CASL or pCASL having a predetermined application period for the label pulse, a suitable or optimal application period can be determined and the reduction in contrast can be suppressed.

100 MRI apparatus, 101 subject, 102 static magnetic field generating magnet, 103 gradient magnetic field coil, 104 transmission coil, 105 reception coil, 106 gradient magnetic field power supply, 107 RF transmission unit, 108 signal detection unit, 109 signal processing unit, 110 sequencer, 111 bed, 120 control unit, 121 display device, 122 operation unit, 123 storage device, 124 body motion detection device, 130 delay time determination unit, 140 imaging sequence generation unit, 150 imaging unit, 160 image generation unit, 170 reception unit, 200 imaging target tissue (liver), 210 first blood vessel (hepatic artery), 220 second blood vessel (portal vein), 300 reception screen, 310 positioning image display area, 311 imaging area, 312 hepatic artery stack, 313 gates Pulse stack, 314 region of interest (ROI), 315 slice, 320 OK button, 410 display image, 420 display image, 430 display image, 500 imaging sequence, 501 non-contrast perfusion sequence, 502 non-construction Perfusion sequence, 503 imaging sequence, 509 imaging sequence, 510 first label pulse (arterial label pulse), 511 delay time, 512 first data acquisition sequence (arterial data acquisition sequence), 513 arterial label pulse, 520 second label pulse (venous label pulse), 520a first vein label pulse, 520b second vein label pulse, 521 delay time, 522 second data acquisition sequence (venous data acquisition sequence), 522a data acquisition sequence, 522b data acquisition sequence, 523 vein label pulse, 530 trigger, 600 initial echo data, 611 echo data, 621 echo data, 623 vein label pulse

Claims

A first non-contrast perfusion sequence that has a first label pulse and a first data acquisition sequence, and obtains a first perfusion image that is a perfusion image of a tissue to be imaged by a first blood vessel, and a second label pulse And a second data acquisition sequence, and a second non-contrast perfusion sequence for obtaining a second perfusion image that is a perfusion image of the imaging target tissue by a second blood vessel, and generating an imaging sequence A sequence generator;
A first delay time from the application of the first label pulse to the start of the first data acquisition sequence and a second delay time from the application of the second label pulse to the start of the second data acquisition sequence; A delay time determining unit for determining each,
An imaging unit that performs imaging according to the imaging sequence and obtains the first perfusion image and the second perfusion image, and
The imaging sequence generation unit generates the imaging sequence so that the second label pulse is applied immediately before the execution of the first data acquisition sequence during the first delay time,
The delay time determination unit responds to echo data of each k-space blade obtained by imaging the imaging target tissue by a non-orthogonal sampling method immediately after application of the first label pulse and the second label pulse. And determining the first delay time and the second delay time, respectively.
The magnetic resonance imaging apparatus according to claim 1,
The first blood vessel is an artery;
The magnetic resonance imaging apparatus, wherein the second blood vessel is a vein.
The magnetic resonance imaging apparatus according to claim 1,
The first blood vessel is a vein;
The magnetic resonance imaging apparatus, wherein the second blood vessel is a vein having a different organ from the first blood vessel.
The magnetic resonance imaging apparatus according to claim 2,
The magnetic resonance imaging apparatus, wherein the imaging sequence generation unit generates the imaging sequence so that the first label pulse is applied in synchronization with a predetermined body motion.
The magnetic resonance imaging apparatus according to claim 3,
The magnetic resonance imaging apparatus, wherein the first delay time is equal to or shorter than the second delay time.
The magnetic resonance imaging apparatus according to claim 1,
The delay time determination unit obtains a reconstructed image reflecting the echo data obtained every time the echo data of the k-space blade is obtained, and obtains a signal value of a predetermined region every time the reconstructed image is obtained. The first delay time and the second delay time are the timings at which the latest echo data of the k-space blade reflected when measuring and obtaining a reconstructed image in which the average value of the signal values is minimum are obtained. A magnetic resonance imaging apparatus, characterized by:
The magnetic resonance imaging apparatus according to claim 1,
The delay time determination unit reconstructs an image reflecting the echo data of the k-space blade for each k-space blade and presents it to the user, and reflects the latest image reflected when reconstructing the image selected by the user. A magnetic resonance imaging apparatus characterized in that the timing at which the echo data of the k-space blade is obtained is determined as the first delay time and the second delay time.
The magnetic resonance imaging apparatus according to claim 1,
The delay time determination unit calculates, as the echo value, one of the peak intensity value and the integral value of the echo data every time the echo data of the k space blade is acquired, and the k space where the echo value is minimized The magnetic resonance imaging apparatus characterized in that the timing at which the echo data of the blade is acquired is determined as the first delay time and the second delay time.
The magnetic resonance imaging apparatus according to claim 1,
The first label pulse and the second label pulse are high frequency magnetic field pulses applied intermittently or continuously for a predetermined period,
The imaging sequence generation unit further determines an application period of the second label pulse by using a suppression rate by the first label pulse.
The magnetic resonance imaging apparatus according to claim 1,
A magnetic resonance imaging apparatus, further comprising: an image generation unit that generates a display image from the first perfusion image and the second perfusion image and displays the display image on a display device.
The magnetic resonance imaging apparatus according to claim 10,
The image generation unit generates a first display image from the first perfusion image, and generates a second display image having a mode different from the first display image from the second perfusion image. A magnetic resonance imaging apparatus.
The magnetic resonance imaging apparatus according to claim 11,
The magnetic resonance imaging apparatus, wherein the image generation unit superimposes the first display image and the second display image on the display device.
The magnetic resonance imaging apparatus according to claim 6,
The delay time determination unit measures a signal value in a predetermined region of interest when the target blood vessel is an artery, and measures a signal value outside the region of interest or in the entire imaging region when the target blood vessel is a vein. A magnetic resonance imaging apparatus.
The magnetic resonance imaging apparatus according to claim 1,
The magnetic resonance imaging apparatus, wherein the first label pulse and the second label pulse are two-dimensional selective excitation pulses that excite a local region in a cylinder shape.
According to the first delay time from the application of the first label pulse to the start of the first data acquisition sequence and the second blood vessel in the first non-contrast perfusion sequence for obtaining a perfusion image of the imaging target tissue by the first blood vessel Determining a second delay time from the application of the second label pulse to the start of the second data acquisition sequence in the second non-contrast perfusion sequence for obtaining a perfusion image of the imaging target tissue,
Generating the imaging sequence so that the second label pulse is applied during the first delay time and immediately before starting the execution of the first data acquisition sequence;
The first delay according to the echo data of each k-space blade obtained by imaging the tissue to be imaged by the non-orthogonal sampling method immediately after the application of the first label pulse and the second label pulse. An imaging sequence generation method, wherein the time and the second delay time are respectively determined.