Magnetic resonance imaging apparatus, magnetic resonance imaging method, and magnetic resonance imaging program

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The MRI apparatus addresses subject movement issues by estimating and adjusting imaging regions based on acquired images, reducing examination time and user burden through automated repositioning adjustments.

JP2025136587APending Publication Date: 2025-09-19CANON MEDICAL SYST CORP

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Patent Information

Application Number: JP2024035267
Authority / Receiving Office: JP · JP
Patent Type: Applications
Current Assignee / Owner
Filing Date: 2024-03-07
Publication Date: 2025-09-19

AI Technical Summary

Technical Problem

Existing magnetic resonance imaging (MRI) systems face challenges in accurately capturing the intended imaging cross section due to subject movement during scans, leading to extended examination times and user burden from repositioning and inaccurate determination of movement.

Method used

A magnetic resonance imaging apparatus that includes functions for acquiring volume and cross-sectional images, estimating subject movement, and determining whether to re-perform scans based on movement, thereby adjusting the imaging region to ensure accurate positioning without the need for additional tracking pulses or settings.

Benefits of technology

This approach reduces examination time and user burden by automatically adjusting imaging regions and preventing scans from being performed at inappropriate positions, ensuring accurate imaging without requiring additional tracking techniques.

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Abstract

To perform imaging of an imaging region set by positioning of an imaging scan.SOLUTION: A magnetic resonance imaging apparatus according to one embodiment comprises: a first acquisition unit; a setting unit; a generation unit; a second acquisition unit; an estimation unit; and a determination unit. The first acquisition unit acquires a volume image in a first scan for imaging a subject. The setting unit sets an imaging region of a second scan of the subject to be performed after the first scan by positioning based on the volume image of the first scan, and sets a reference imaging position in the volume image. The generation unit generates a first cross-sectional image corresponding to the reference imaging position from the volume image. The second acquisition unit acquires a second cross-sectional image corresponding to the reference imaging position from imaging data obtained in the imaging region of the second scan during or after the imaging of the second scan. The estimation unit estimates a degree of movement of the subject between the first scan and the second scan by comparing the first cross-sectional image and the second cross-sectional image. The determination unit determines whether or not to re-execute the second scan on the basis of the degree of movement.SELECTED DRAWING: Figure 4

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Description

[Technical Field]

[0001] The embodiments disclosed in the present specification and drawings relate to a magnetic resonance imaging apparatus, a magnetic resonance imaging method, and a magnetic resonance imaging program. [Background technology]

[0002] A magnetic resonance imaging device is an imaging device that excites the nuclear spins of a subject placed in a static magnetic field with radio frequency (RF) signals at the Larmor frequency, and generates MR images based on magnetic resonance (MR) signals generated from the subject as a result of the excitation.

[0003] When capturing MR images, the actual scan is performed after positioning the scan based on an image acquired by a scan for acquiring an image for positioning (hereinafter, sometimes referred to as a locator scan). However, if the state of the subject during the locator scan differs from the state of the subject during the actual scan due to, for example, subject movement, it may not be possible to capture the imaging cross section expected after positioning.

[0004] To address this issue, slice position correction techniques such as diaphragm tracking are known, but they require imaging settings for tracking and the application of tracking pulses. Furthermore, if the subject moves, re-imaging is possible, but a determination is required as to whether the subject has moved, and some users may not be able to make an accurate determination. Furthermore, re-imaging requires re-positioning, which extends the examination time and places a burden on the user. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-162332 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-189241 Summary of the Invention [Problem to be solved by the invention]

[0006] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to image an imaging area set by positioning an imaging scan. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0007] A magnetic resonance imaging apparatus according to one embodiment includes a first acquisition unit, a setting unit, a generation unit, a second acquisition unit, an estimation unit, and a determination unit. The first acquisition unit acquires a volume image in a first scan of a subject. The setting unit sets an imaging region for a second scan of the subject, which is performed after the first scan, by positioning based on the volume image of the first scan, and also sets a reference imaging position within the volume image. The generation unit generates a first cross-sectional image corresponding to the reference imaging position from the volume image. The second acquisition unit acquires a second cross-sectional image corresponding to the reference imaging position from imaging data obtained in the imaging region of the second scan during or after the second scan. The estimation unit estimates the degree of movement of the subject between the first and second scans by comparing the first and second cross-sectional images. The determination unit determines whether to re-perform the second scan based on the degree of movement. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an example of the overall configuration of a magnetic resonance imaging apparatus according to an embodiment; [Figure 2] FIG. 2 is a diagram for explaining the flow of an examination using a magnetic resonance imaging apparatus. [Figure 3] 1 is a schematic diagram showing an example of the configuration of a processing circuit of a magnetic resonance imaging apparatus according to a first embodiment. [Figure 4] 4 is a flowchart showing an example of the operation of the magnetic resonance imaging apparatus according to the first embodiment. [Figure 5] FIG. 10 is a diagram for explaining the degree of movement and adjustment of the imaging area of the second scan. [Figure 6] 10A and 10B are diagrams illustrating an example of a method for estimating the degree of movement. [Figure 7] 10 is a flowchart showing an example of the operation of the magnetic resonance imaging apparatus according to a modified example of the first embodiment. [Figure 8] FIG. 10 is a schematic diagram showing an example of the configuration of a processing circuit of a magnetic resonance imaging apparatus according to a second embodiment. [Figure 9] 10 is a flowchart showing an example of the operation of the magnetic resonance imaging apparatus according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of a magnetic resonance imaging apparatus, a magnetic resonance imaging method, and a magnetic resonance imaging program will be described in detail with reference to the drawings.

[0010] (Overall configuration of magnetic resonance imaging device) A magnetic resonance imaging (MRI) apparatus 1 according to an embodiment can utilize magnetic resonance imaging technology. Fig. 1 is a schematic diagram showing an example of the overall configuration of the MRI apparatus 1 according to an embodiment. The MRI apparatus 1 includes a magnet gantry 100, a control cabinet 300, an image processing device 400 such as a console, and a bed 500.

[0011] The magnet gantry 100 and the bed 500 are disposed, for example, in a shielded room called an examination room. On the other hand, the control cabinet 300 is disposed, for example, in a machine room, and the image processing device 400 is disposed, for example, in an operation room. Note that the image processing device 400 may be connected to the MRI apparatus 1 via a network and installed in a remote location away from the operation room.

[0012] The magnetic gantry 100 includes a static magnetic field magnet 10, a gradient magnetic field coil 11, and a WB (Whole Body) coil 12. The static magnetic field magnet 10 of the magnetic gantry 100 is broadly classified into a cylindrical type in which the magnet has a cylindrical magnetic structure, and an open type in which a pair of magnets are arranged above and below with an imaging space sandwiched between them. Here, an MRI apparatus 1 with a cylindrical magnetic gantry 100 will be described, but an open type MRI apparatus may also be used. Note that the open type MRI apparatus has the same configuration as the cylindrical type MRI apparatus 1, except that the static magnetic field magnet, gradient magnetic field coil, and WB coil that make up the magnetic gantry are parallel plate-shaped.

[0013] The static magnetic field magnet 10 has a roughly cylindrical shape and generates a static magnetic field within a bore into which the subject P is transported. The bore refers to the space inside the cylinder of the magnet gantry 100. The static magnetic field magnet 10 is composed of, for example, a housing for holding liquid helium, a refrigerator for cooling the liquid helium to an extremely low temperature, and a superconducting coil inside the housing. Note that the static magnetic field magnet 10 may also be composed of a permanent magnet. Below, a case where the static magnetic field magnet 10 has a superconducting coil will be described.

[0014] The static magnetic field magnet 10 incorporates a superconducting coil, which is cooled to extremely low temperatures by liquid helium. In excitation mode, the static magnetic field magnet 10 generates a static magnetic field by applying a current supplied from a static magnetic field power supply to the superconducting coil. After that, when the mode switches to persistent current mode, the static magnetic field power supply is disconnected. Once in persistent current mode, the static magnetic field magnet 10 continues to generate a static magnetic field for a long period of time, for example, for more than one year.

[0015] The gradient magnetic field coil 11 has a roughly cylindrical shape similar to the static magnetic field magnet 10, and is installed inside the static magnetic field magnet 10. The gradient magnetic field coil 11 is composed of three gradient magnetic field coils for the X-axis, Y-axis, and Z-axis. Each gradient magnetic field coil is supplied with a gradient magnetic field current (electric power) from a gradient magnetic field power supply 31 (31x for the X-axis, 31y for the Y-axis, and 31z for the Z-axis), thereby generating gradient magnetic fields in the X-axis, Y-axis, and Z-axis directions and applying them to the subject P. Here, the Z-axis direction is the direction along the static magnetic field, the Y-axis direction is the vertical direction, and the X-axis direction is the direction perpendicular to the Z-axis and Y-axis, respectively.

[0016] The WB coil 12, also called a whole-body coil, is installed in a roughly cylindrical shape inside the gradient magnetic field coil 11 so as to surround the subject P. The WB coil 12 functions as a transmitting coil. That is, the WB coil 12 transmits RF pulses to the subject P in accordance with radio frequency (RF) signals transmitted from the RF transmitter 32. Meanwhile, the WB coil 12 may also function as a receiving coil in addition to functioning as a transmitting coil that transmits RF pulses. In this case, the WB coil 12 functions as a receiving coil to receive MR signals emitted from the subject P due to excitation of atomic nuclei.

[0017] The MRI apparatus 1 may include a local coil 20 in addition to the WB coil 12. The local coil 20 is placed close to the body surface of the subject P. The local coil 20 may include a plurality of coil elements. There are several types of local coils 20, such as a head coil, a chest coil, an abdominal coil, a spine coil, and a knee coil. Note that while FIG. 1 shows a case where the local coil 20 is a chest coil, the present invention is not limited to this case.

[0018] The local coil 20 functions as a receiving coil. That is, the local coil 20 receives the above-mentioned MR signals. Note that the local coil 20 may be a transmitting / receiving coil that functions as a transmitting coil that transmits RF pulses in addition to the function as a receiving coil that receives MR signals. That is, the local coil 20 may be a dedicated transmitting coil, a dedicated receiving coil, or a dual-purpose coil.

[0019] The bed 500 includes a bed body 50 and a top board 51. The bed body 50 can move the top board 51 in the vertical and horizontal directions, and moves the subject P placed on the top board 51 to a predetermined height before imaging. Thereafter, the top board 51 is moved horizontally to move the subject P into the bore.

[0020] The control cabinet 300 includes gradient magnetic field power supplies 31 (for the X axis 31x, for the Y axis 31y, and for the Z axis 31z), an RF transmitter 32, an RF receiver 33, and a sequence controller .

[0021] The gradient magnetic field power supply 31 includes gradient magnetic field power supplies 31x, 31y, and 31z for each channel that drive coils that generate gradient magnetic fields in the X-axis direction, Y-axis direction, and Z-axis direction, respectively. The gradient magnetic field power supplies 31x, 31y, and 31z output the required current independently for each channel in response to a command from a sequence controller 34.

[0022] The RF transmitter 32 generates a high-frequency signal based on instructions from the sequence controller 34. The RF transmitter 32 transmits the generated high-frequency signal to the WB coil 12 and the local coil 20.

[0023] The MR signals received by the WB coil 12 and the local coil 20 are transmitted to the RF receiver 33. The RF receiver 33 converts the MR signals from the WB coil 12 and the local coil 20 into analog to digital (AD) signals and outputs them to a sequence controller 34. The digitally converted MR signals are sometimes called raw data.

[0024] The sequence controller 34, under the control of the image processing device 400, drives the gradient magnetic field power supply 31, the RF transmitter 32, and the RF receiver 33 to image the subject P. When raw data is received from the RF receiver 33 by imaging, the sequence controller 34 transmits the raw data to the image processing device 400.

[0025] The sequence controller 34 includes a processing circuit (not shown). This processing circuit is configured with hardware such as a processor that executes a predetermined program, an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0026] Next, we will move on to a description of the image processing device 400. The image processing device 400 includes a processing circuit 40, a memory circuit 41, a display 42, an input interface 43, and a network interface 44.

[0027] The processing circuitry 40 has a dedicated or general-purpose processor, and realizes various functions described below by reading and executing various programs, including an MRI program, stored in the storage circuitry 41 or directly incorporated in the processing circuitry 40. The processing circuitry 40 also controls the operation of the sequence controller 34 and realizes the function of generating MR images by performing imaging in accordance with a pulse sequence.

[0028] The storage circuitry 41 includes semiconductor memory elements such as RAM (Random Access Memory) and flash memory, a hard disk, an optical disk, etc. The storage circuitry 41 may also include portable media such as a USB (Universal Serial Bus) memory and a DVD (Digital Video Disk). The storage circuitry 41 stores various processing programs used in the processing circuitry 40, data required for executing the programs, and medical images.

[0029] The display 42 is configured by a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display. The display 42 displays various information under the control of the processing circuit 40. The display 42 is a display device and may also be a GUI (Graphical User Interface) that can accept various operations from the user, such as a touch panel.

[0030] The input interface 43 includes an input device that can be operated by a user and an input circuit that inputs signals from the input device. The input device can be realized by a trackball, a switch, a mouse, a keyboard, a touchpad, a touchscreen, a non-contact input device using an optical sensor, a voice input device, etc. When the user operates the input device, the input circuit generates a signal corresponding to the operation and outputs it to the processing circuit 40.

[0031] The network interface 44 includes an interface for performing communication connected to a network via a wired or wireless connection. The network interface 44 can exchange various data between the network and the storage circuitry 41, for example.

[0032] Using these components, the image processing device 400 controls the entire MRI apparatus 1. Specifically, imaging conditions and other various information and instructions are received by a user such as a medical technician operating an input interface 43, such as a mouse or keyboard. The processing circuitry 40 then causes the sequence controller 34 to execute a scan based on the input imaging conditions, while reconstructing an image based on data transmitted from the sequence controller 34. The reconstructed image is displayed on a display 42 or stored in a memory circuitry 41.

[0033] (MRI examination procedure) Here, an overview of the flow of an examination using an MRI device will be explained using Figure 2. As shown in Figure 2, in an examination using a typical MRI device, when a patient to be examined enters the examination room, he or she is placed on the tabletop, and the settings required for the imaging scan, such as coil settings and fixing the imaging area (i.e., the examination area) with pads, are performed. After the settings are made, the patient is carried into the MRI device, and the imaging scan is performed. After the imaging scan is completed, the patient is taken out of the MRI device, and post-processing is performed to remove him or her from the bed. The patient then leaves the examination room.

[0034] The process from carrying the subject into the MRI device (step S1) to carrying the subject out of the MRI device (step S10) will be described in more detail. In an examination using an MRI device, after carrying the subject into the MRI device (step S1), PAS (Programmable Anatomical Scan) selection is performed (step S2), and the scan begins (step S3). PAS selection is a function that presets an imaging protocol, such as imaging conditions, for each imaging region before the scan. Note that FIG. 2 illustrates the execution of two scans, a first scan and a second scan, as a series of examinations on the subject. However, the number of scans, imaging conditions, etc. are not limited, and any desired scans are performed depending on the diagnosis content and imaging region. Furthermore, PAS selection may be performed during multiple imaging scans performed in a series of examinations, depending on the scanning status.

[0035] After the first scan is started (step S4), an image of the first scan is output (step S5). Positioning of the second scan is performed based on the image of the first scan (step S6), and then the second scan is started (step S7). After the second scan is completed (step S8), the image of the second scan is confirmed (step S9). When it is confirmed in the image confirmation of the second scan in step S9 that an image of the position determined in step S6 has been acquired, the scan is completed and the subject is carried out of the MRI device.

[0036] However, due to subject movement, such as body movement, breathing, blood flow, or pulsation, an image at the position determined in step S6 may not be acquired. Therefore, if it is determined in step S9 during image confirmation of the second scan that an image at the position determined in step S6 has not been acquired, the second scan is retaken to acquire an image at the appropriate position. Depending on the degree of subject movement in the image of the second scan, the process may return to, for example, step S1, where the subject is being placed in the MRI apparatus, step S4, where the first scan is started, or step S6, where the second scan is positioned. In this way, retaking the image by going back a step requires repositioning, which extends the examination time and increases the user's workload. Furthermore, a user, such as a technician, may not notice that an image at the appropriate position has not been acquired in the second scan or that the subject has moved.

[0037] The MRI apparatus 1 according to the embodiment determines whether or not to re-execute the second scan during the period from the start of the second scan (step S7) to the completion of the second scan (step S8).

[0038] (First embodiment) FIG. 3 is a schematic diagram showing an example of the configuration of the processing circuitry 40 of the MRI apparatus 1 according to the first embodiment. As shown in FIG. 3, the processing circuitry 40 realizes each of the functions of a first acquisition function F1, a setting function F2, a generation function F3, a second acquisition function F4, an estimation function F5, a determination function F6, a calculation function F7, and a rescan function F8. FIG. 4 is a flowchart showing an example of the operation of the MRI apparatus 1 according to the first embodiment, or an MRI program. The functions and operations of the processing circuitry 40 in the first embodiment will be described with reference to the flowchart of FIG. 4, FIGS. 5, and 6. After the above-described steps S1 to S3, step ST10 corresponding to step S4 is started.

[0039] In step ST10, the first acquisition function F1 acquires a volume image I1 in a first scan that images the subject P. The first scan is, for example, an imaging scan for positioning that can acquire the volume image I1, such as a locator scan. The volume image I1 acquired in the first scan is used for positioning to set the imaging region for the second scan. The first scan may be any scan number in a series of examinations consisting of multiple imaging scans. Here, the volume image includes, for example, a volume image generated by a two-dimensional imaging scan of multiple slice planes and a volume image acquired by a three-dimensional imaging scan.

[0040] In step ST20, the setting function F2 sets an imaging area of the subject P to be performed after the first scan by positioning based on the volume image I1 of the first scan, and also sets a reference imaging position within the volume image I1. FIG. 5(a) shows an example of the imaging area of the second scan and the reference imaging position in the volume image I1 of the first scan. As shown in FIG. 5(a), the reference imaging position is one imaging position included in the imaging area of the second scan. Alternatively, the reference imaging position may be multiple imaging positions included in the imaging area of the second scan. The imaging area of the second scan is set by the user, for example, via the input interface 43.

[0041] In step ST30, the generation function F3 generates a first cross-sectional image I2 corresponding to the reference imaging position from the volume image I1. Fig. 5(b) is an example of the first cross-sectional image I2 corresponding to the reference imaging position set in Fig. 5(a). The first cross-sectional image I2 is, for example, an image generated by MPR (Multi Planar Reconstruction) on the volume image I1.

[0042] In step ST40, the second acquisition function F4 acquires a second cross-sectional image I3 corresponding to the reference imaging position from imaging data obtained in the imaging region of the second scan during or after the second scan. Here, Fig. 5(c) is an example of the second cross-sectional image I3 corresponding to the reference imaging position set in Fig. 5(a). The first cross-sectional image I2 in Fig. 5(b) is an image at the reference imaging position set in Fig. 5(a), whereas the second cross-sectional image I3 in Fig. 5(c) is an image at an imaging position different from the reference imaging position set in Fig. 5(a) due to movement of the subject P.

[0043] The second acquisition function F4 may acquire the second cross-sectional image I3 at a timing according to at least one of the type of sequence, the imaging conditions, and the imaging region. The second cross-sectional image I3 is an image that allows the degree of movement of the subject P to be estimated by comparing the first cross-sectional image I2 with the second cross-sectional image I3 in step ST50. The second cross-sectional image I3 may be an image with image quality and resolution that allows the shape of a specific tissue, organ, etc. that is of interest in an examination or diagnosis using the MRI apparatus 1 to be recognized. Therefore, the second cross-sectional image I3 may be reconstructed at a timing at which the image can be acquired according to the type of sequence, the imaging conditions, the imaging region, etc.

[0044] The second acquisition function F4 may also acquire one or more second cross-sectional images I3 during or after the second scan. The multiple second cross-sectional images I3 may be images for one reference imaging position or multiple reference imaging positions. For example, if multiple second cross-sectional images I3 are acquired during the second scan, the second scan is stopped when a second cross-sectional image I3 is acquired that indicates that the subject P has moved to a degree that requires reimaging, preventing the second scan from continuing at an inappropriate position. Even if the second cross-sectional image I3 is acquired after imaging, this reduces the user's burden of repositioning.

[0045] In step ST50, the estimation function F5 estimates the degree of movement of the subject P between the first and second scans by comparing the first cross-sectional image I2 with the second cross-sectional image I3. For example, as shown in FIG. 5(d), the first cross-sectional image I2 in FIG. 5(b) is compared with the second cross-sectional image I3 in FIG. 5(c), and the degree of movement of the subject P between the first and second scans can be estimated from the position of the second cross-sectional image I3, which has moved from the reference imaging position. The estimation function F5 may further estimate the degree of movement of the subject P using other information, such as a volume image of the first scan. Note that if the second cross-sectional image I3 moves within the plane of the reference imaging position, the volume image of the first scan does not need to be used.

[0046] 5 illustrates an example in which the second cross-sectional image I3 moves only in the Z-axis direction from the reference imaging position due to the movement of the subject P. Even when the second cross-sectional image I3 moves in at least one of the X-axis direction, Y-axis direction, and Z-axis direction from the reference imaging position, or when the second cross-sectional image I3 rotates from the reference imaging position relative to at least one of the X-Y plane, Y-Z plane, and Z-X plane, the degree of movement of the subject P between the first scan and the second scan can be estimated by comparing the first cross-sectional image I2 and the second cross-sectional image I3.

[0047] The estimation function F5 may estimate the degree of movement of the subject P between the first scan and the second scan based on at least one of the number and shape of predetermined structures at the reference imaging position. For example, when comparing the first cross-sectional image I2 with the second cross-sectional image I3, if the number and shape of structures such as tissues and organs are different, it is estimated that the subject P has moved. In addition to the first cross-sectional image I2, multiple MPR images of an area close to the reference imaging position with respect to the volume image I1 may be generated and compared with the second cross-sectional image I3 to estimate the degree of movement of the subject P.

[0048] The estimation function F5 may estimate the degree of movement of the subject P between the first and second scans using a learning model for shape recognition. Here, FIG. 6(a) illustrates a first cross-sectional image I2 obtained without using fat suppression, and FIG. 6(b) illustrates a second cross-sectional image I3 obtained with fat suppression. Six structures represented by regions R1, R2, R3, R4, R5, and R6 are visualized in FIG. 6(a). Meanwhile, FIG. 6(b) illustrates five structures represented by regions R1, R2, R3, R5, and R6, excluding the fat region R4, among the structures visualized in FIG. 6(a).

[0049] For example, as shown in Fig. 6(a) of a scan image using fat suppression and Fig. 6(b) of a scan image not using fat suppression, there may be a difference in the number of depicted structures such as tissues and organs. There may also be a difference in the shapes of the depicted structures such as tissues and organs. Even if there is a difference in the number and shapes of structures between the first cross-sectional image I2 and the second cross-sectional image I3, the degree of movement of the subject P between the first and second scans can be estimated by using a learning model for shape recognition.

[0050] Furthermore, the estimation function F5 may use a contrast conversion model to estimate the degree of movement of the subject P between the first scan and the second scan. For example, even if the images are acquired at the same reference imaging position, the first cross-sectional image I2 and the second cross-sectional image I3 may be images with different contrasts, such as a T1-weighted image, a T2-weighted image, a diffusion image, etc., depending on the imaging sequence and imaging conditions used in the imaging scans. In this way, even if the first cross-sectional image I2 and the second cross-sectional image I3 have different contrasts, the degree of movement of the subject P between the first scan and the second scan can be estimated by using a contrast conversion model that converts them into a predetermined contrast.

[0051] 6(c) is an image of the region surrounded by the dashed lines in FIGS. 6(a) and 6(b), which is, for example, a region of interest required for examination or diagnosis using the MRI apparatus 1. The estimation function F5 may estimate the degree of movement of the subject P between the first scan and the second scan based on the region of interest at the reference imaging position. Alternatively, the estimation function F5 may estimate the degree of movement of the subject P between the first scan and the second scan based on a specific region different from the region of interest at the reference imaging position.

[0052] In addition, the estimation function F5 may estimate the degree of movement of the subject P between the first scan and the second scan using a first k-space cross-sectional image generated from the first cross-sectional image I2 and a second k-space cross-sectional image generated from the second cross-sectional image, both of which have the same resolution.

[0053] In step ST60, the determination function F6 determines whether or not to re-perform the second scan based on the degree of movement of the subject P. If the degree of movement of the subject P is less than the first threshold (i.e., NO in step ST60), the second scan is not performed and the process ends. On the other hand, if the degree of movement of the subject P is equal to or greater than the first threshold (i.e., YES in step ST60), the process proceeds to step ST70, where the second scan is re-performed. Here, the first threshold may be defined according to the imaging region. For example, the first threshold may be set higher for the abdomen, which is prone to movement of the subject P due to breathing, than for other imaging regions.

[0054] In step ST70, the calculation function F7 calculates a correction value for adjusting the imaging region of the second scan based on the estimated degree of movement of the subject P so that the second cross-sectional image I3 is positioned at the same position as the reference imaging position.

[0055] In step ST80, the rescan function F8 adjusts the imaging area of the second scan to the correction value and re-performs the second scan. In the re-imaging of the second scan, the second scan is re-performed in the imaging area adjusted based on the estimated degree of movement of the subject P, so that an image of the imaging area set in step ST20 can be acquired.

[0056] According to the MRI apparatus 1 of the first embodiment, the degree of movement of the subject P is estimated during the second scan and a decision is made to perform reimaging, thereby preventing the second scan from being continuously performed at an inappropriate position. This shortens the examination time and reduces the burden on the subject. Furthermore, even if the user does not notice that the subject has moved or that an image of the imaging region set by the second scan positioning has not been acquired, the imaging region of the second scan is adjusted to an appropriate position and reimaging is performed. Furthermore, in this case, the adjustment of the imaging region of the second scan is performed automatically, thereby reducing the burden on the user. Furthermore, the MRI apparatus 1 of the first embodiment does not require imaging settings for tracking the diaphragm or application of pulses for tracking.

[0057] (Modification of the first embodiment) FIG. 7 is a flowchart showing an example of operation of the MRI apparatus 1 according to the modification of the first embodiment, or an MRI program. As shown in FIG. 7, the MRI apparatus 1 according to the modification of the first embodiment differs from the MRI apparatus 1 according to the first embodiment in that it determines whether to re-perform the first scan in step ST55. Other configurations and functions are substantially the same as those of the MRI apparatus 1 shown in FIGS. 1 and 3, and therefore the same configurations and functions are denoted by the same reference numerals and descriptions thereof are omitted. Furthermore, in the flowchart of FIG. 7, steps equivalent to those in the flowchart of FIG. 4 are denoted by the same reference numerals and descriptions thereof are omitted. As shown in FIG. 7, the MRI apparatus 1 according to the modification of the first embodiment proceeds to step ST55 after step ST50.

[0058] In step ST55, the determination function F6 determines whether or not to re-perform the first scan based on the degree of motion of the subject P. If the degree of motion of the subject P is equal to or greater than a second threshold value that is greater than the first threshold value (i.e., if YES in step ST55), the process proceeds to step ST90, where the first scan is re-performed. On the other hand, if the degree of motion of the subject P is less than the second threshold value (i.e., if NO in step ST55), the process proceeds to step ST60.

[0059] In step ST90, the rescan function F8 performs the first scan again. After step ST90, the processing circuit 40 proceeds to step ST10.

[0060] The MRI apparatus 1 according to the modification of the first embodiment has the same effects as the MRI apparatus 1 according to the first embodiment. Furthermore, according to the MRI apparatus 1 according to the modification of the first embodiment, even if the subject P moves in such a way that re-executing the second scan is insufficient, the imaging of the imaging region set by positioning in the second scan can be performed by re-imaging from the first scan.

[0061] (Second embodiment) The MRI apparatus 1 according to the second embodiment differs from the MRI apparatus 1 according to the first embodiment in that it includes a camera 8 that captures an image of a subject P. Other configurations are substantially the same as those of the MRI apparatus 1 according to the first embodiment, and therefore redundant explanations will be omitted.

[0062] The camera 8 includes a lens, an image sensor, an amplifier, an A / D (Analog to Digital) converter, etc. The lens is an optical element for refracting and focusing light, and may be a standard lens or a wide-angle lens with a wider angle of view than a standard lens. The image sensor captures an image of the subject via an objective optical system. The amplifier amplifies the video signal output from the image sensor. The A / D converter converts the analog video signal output from the amplifier into a digital signal. The camera 8 is connected to a processing circuit 40, and the captured optical image (i.e., camera image) is output to the processing circuit 40 as a digital signal.

[0063] The camera 8 is attached to, for example, the ceiling of the imaging room in which the MRI apparatus 1 is installed, or to a wall around the magnet gantry 100. The camera 8 captures an image of all or a part of the tabletop 51 before the subject P enters the magnet gantry 100, and acquires an optical image including the imaging region of the subject P placed on the tabletop 51. For example, the camera 8 can acquire a moving image obtained by sequentially capturing images at a predetermined frame rate as an optical image including the imaging region of the subject P.

[0064] Fig. 8 is a schematic diagram showing an example of the configuration of the processing circuitry 40 of the MRI apparatus 1 according to the second embodiment. As shown in Fig. 8, the processing circuitry 40 according to the second embodiment differs from the processing circuitry 40 according to the first embodiment in that it implements a third acquisition function F9 and a notification function F10. As the other functions are substantially the same as those of the MRI apparatus 1 according to the first embodiment shown in Fig. 3, the same functions are denoted by the same reference numerals and description thereof will be omitted.

[0065] 9 is a flowchart showing an example of operation of the MRI apparatus 1 according to the second embodiment, or an MRI program. In the flowchart of FIG. 9, steps equivalent to those in the flowchart of FIG. 4 are given the same reference numerals, and redundant explanations will be omitted. As shown in FIG. 9, in the MRI apparatus 1 according to the second embodiment, step ST5 is performed before step ST10.

[0066] In step ST5, the third acquisition function F9 acquires a camera image I4 including an imaging region of the subject P captured by the camera 8 during imaging of the first scan. After step ST5, the processing circuitry 40 proceeds to step ST10.

[0067] In step ST60, the determination function F6 determines whether or not to re-perform the second scan based on the degree of movement of the subject P. If the degree of movement of the subject P is less than the first threshold (i.e., if NO in step ST60), the second scan is not performed and the process ends. On the other hand, if the degree of movement of the subject P is equal to or greater than the first threshold (i.e., if YES in step ST60), the process proceeds to step ST75, where the second scan is re-performed.

[0068] In step ST75, the notification function F10 notifies the subject P, for example, by displaying the camera image I4. The notification function F10 may also notify the subject P of an action instruction to move to a predetermined position. The camera image I4 including the imaging part of the subject P captured during the imaging of the first scan may be displayed on a display (not shown) visible to the subject P, and an action instruction may be given to move to the same position as the camera image I4. The action instruction may also be notified by voice or the like.

[0069] Furthermore, the notification function F10 may notify the subject P of an action instruction to stay still. For example, if the movement of the subject P at the imaging site such as the knee is not so large that it requires resetting, the subject P can move or be conscious of staying still in accordance with the notified action instruction, and an image of the appropriate imaging region can be acquired in the second scan. After step ST75, the processing circuitry 40 proceeds to step ST80.

[0070] According to the MRI apparatus 1 of the second embodiment, in addition to the effects of the MRI apparatus 1 of the first embodiment and its modified example, it is possible to assist in moving the subject P in order to perform imaging of the second scan in the imaging area set by positioning.

[0071] According to the magnetic resonance imaging method and magnetic resonance imaging program according to at least one of the embodiments described above, it is possible to perform imaging of the imaging region set by positioning the imaging scan.

[0072] In the above embodiments, the term "processor" refers to circuits such as a dedicated or general-purpose CPU (Central Processing Unit), GPU (Graphics Processing Unit) or Application Specific Integrated Circuit (ASIC), for example, a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a programmable logic device such as a Field Programmable Gate Array (FPGA).

[0073] If the processor is, for example, a CPU, the processor realizes various functions by reading and executing programs stored in a memory circuit. If the processor is, for example, an ASIC, instead of storing a program in a memory circuit, the functions corresponding to the program are directly incorporated into the processor's circuit as logic circuits. In this case, the processor realizes various functions through hardware processing that reads and executes the program incorporated in the circuit. Alternatively, the processor can realize various functions by combining software processing and hardware processing.

[0074] In addition, although the above embodiment shows an example in which a single processor of a processing circuit realizes each function, a processing circuit may be configured by combining multiple independent processors, and each processor may realize each function. Furthermore, when multiple processors are provided, a memory circuit for storing programs may be provided separately for each processor, or a single memory circuit may collectively store programs corresponding to the functions of all processors.

[0075] In addition, the first acquisition function F1, setting function F2, generation function F3, second acquisition function F4, estimation function F5, judgment function F6, calculation function F7, rescanning function F8, third acquisition function F9, and notification function F10 in the description of the embodiment are examples of the first acquisition unit, setting unit, generation unit, second acquisition unit, estimation unit, judgment unit, calculation unit, rescanning unit, third acquisition unit, and notification unit, respectively, as described in the claims.

[0076] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0077] 1...Magnetic Resonance Imaging (MRI) device F1...First acquisition function F2...Setting function F3...Generation function F4...Second acquisition function F5...Estimation function F6...Determination function F7...Calculation function F8...Rescan function F9...Third acquisition function F10...Notification function

Claims

1. a first acquisition unit that acquires a volume image in a first scan that images the subject; a setting unit that sets an imaging region of a second scan of the subject to be performed after the first scan by positioning based on the volume image of the first scan, and also sets a reference imaging position within the volume image; a generating unit that generates a first cross-sectional image corresponding to the reference imaging position from the volume image; a second acquisition unit that acquires, during or after the second scan, a second cross-sectional image corresponding to the reference imaging position from imaging data obtained in an imaging region of the second scan; an estimation unit that estimates a degree of movement of the subject between the first scan and the second scan by comparing the first cross-sectional image with the second cross-sectional image; a determination unit that determines whether or not to re-perform the second scan based on the degree of movement of the subject; A magnetic resonance imaging apparatus comprising:

2. the estimation unit further estimates a degree of motion of the subject between the first scan and the second scan using the volume image of the first scan.