Magnetic resonance imaging apparatus, positioning support method, and program

Abstract

To provide a magnetic resonance imaging apparatus, a positioning support method and a program for outputting a structure in a cross section at a similar angle regardless of a subject when generating a cross-sectional image of the heart from a three dimensional image obtained by scanogram imaging.SOLUTION: A processor of a magnetic resonance imaging apparatus acquires a three dimensional image including a heart of a subject by scanogram imaging executed prior to main imaging, detects a landmark of the heart from the three dimensional image, sets a position of a cross section based on the landmark, generates a cross-sectional image appearing on the cross section from the three dimensional image, sets a horizontal direction or a vertical direction of the cross-sectional image such that the horizontal direction or the vertical direction of the cross-sectional image is parallel to a straight line obtained by projecting one axis selected from three axes forming a three dimensional orthogonal coordinate system of a real space onto the cross-sectional image, and stores the cross-sectional image in a memory.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic resonance imaging (MRI) apparatus, a positioning assistance method, and a program, and more particularly to a cross-sectional image generation technique and a positioning assistance technique that assist in setting an imaging position in a cardiac MRI examination. [Background technology]

[0002] In cardiac MRI examinations, imaging of reference slices identified based on anatomical features of the heart is performed. Reference slice images useful for diagnosis include, for example, a left ventricular short-axis view, a horizontal long-axis view, a vertical long-axis view, a four-chamber long-axis view, a two-chamber long-axis view, and a three-chamber long-axis view, and the imaging position of each slice is set according to the subject for each examination. Patent Document 1 describes a technology that supports the positioning of each reference slice.

[0003] The MRI apparatus described in Patent Document 1 includes an acquisition means for acquiring a plurality of cross-sectional image data including the heart from a subject using magnetic resonance; a reference cross-section information calculation means for calculating spatial position information of a reference cross-section of the heart based on the plurality of cross-sectional image data; a positioning means for displaying the reference cross-section image of the heart calculated from the plurality of cross-sectional image data based on the position information of the reference cross-section on a display device and positioning an imaging site for imaging via the displayed reference cross-section image of the heart; and an imaging means for imaging the imaging site set by positioning. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-110688 Summary of the Invention [Problem to be solved by the invention]

[0005] The MRI apparatus described in Patent Document 1 acquires multi-slice axial image data covering the entire heart of a subject through a preliminary scan before the actual scan, and generates three-dimensional (3D) volume image data of the heart through isotropic processing. Then, from this 3D volume image data, the positions of the apex, mitral valve, long axis, and left ventricular center are detected using a pattern matching technique, and a cross section is set based on these landmarks. Based on the cross sections thus set, a user such as a technician sets the field of view (FOV) and performs the actual scan.

[0006] The preliminary imaging corresponds to the scanogram imaging in this specification. The multi-slice axial cross-sectional image data or the 3D volume image data corresponds to the three-dimensional image in this specification.

[0007] In conventional technology, among the multiple reference cross sections used in cardiac MRI examinations, particularly the cross sections shown in (B), (E), (F), (H), and (I) of Figure 6 of Patent Document 1 (left ventricular short-axis view, horizontal long-axis view, four-chamber long-axis view, two-chamber long-axis view, and three-chamber long-axis view), the imaging cross sections are set relative to the long axis of the heart, so the angle of each of these cross sections is inclined relative to the three orthogonal axes of the body axis (see Figure 6 of Patent Document 1).

[0008] Because the shape and orientation of the heart within the body vary from person to person and from patient to patient, structures outside the heart in cross sections set based on landmarks will be oriented in different directions depending on the individual. This can cause aliasing artifacts, for example, in which structures outside the imaging field of view are reflected inside the imaging field of view. This requires the user to adjust the display angle of the cross-sectional image for each patient or change the imaging field of view settings.

[0009] The present disclosure has been made in consideration of the above circumstances, and aims to provide a magnetic resonance imaging device, a positioning assistance method, and a program that, when generating a cross-sectional image of the heart from a three-dimensional image obtained by scanogram imaging, output structures in the cross section at the same angle regardless of the subject. [Means for solving the problem]

[0010] A magnetic resonance imaging apparatus according to a first aspect of the present disclosure is a magnetic resonance imaging apparatus that includes a processor and a memory and generates an image of a subject based on nuclear magnetic resonance, wherein the processor acquires a three-dimensional image including the subject's heart by scanogram imaging performed prior to the actual imaging, detects cardiac landmarks from the three-dimensional image, sets the position of the cross section based on the landmarks, generates a cross-sectional image appearing in the cross section from the three-dimensional image, sets the horizontal or vertical direction of the cross-sectional image so that it is parallel to a line formed by projecting one axis selected from three axes forming a three-dimensional Cartesian coordinate system in real space onto the cross-sectional image, and stores the cross-sectional image in the memory.

[0011] Scanogram imaging is synonymous with preliminary imaging, positioning imaging, or prescan. The three-dimensional image obtained by scanogram imaging may be a multi-slice image consisting of multiple slice images, such as axial slices, or an isotropic three-dimensional volume image obtained by isotropic processing of the multi-slice image. The landmarks may be anatomical features such as the apex, mitral valve, tricuspid valve, or left ventricular outflow tract.

[0012] The three axes forming the three-dimensional Cartesian coordinate system in real space may be, for example, the X-axis, Y-axis, and Z-axis, which are three device axes that are coordinate axes uniquely determined in a magnetic resonance imaging device. The three device axes may form the coordinate system of a three-dimensional image obtained when a subject is imaged by scanogram imaging. The axial directions of the head-foot direction (HF direction), left-right direction (RL direction), and front-back direction (AP direction) of a subject placed in the imaging space may correspond to the directions of the three axes when the three-dimensional image is captured. One axis selected from the three axes may be determined to correspond to the cross section of interest.

[0013] According to the first aspect, the position of a cross section is determined based on landmarks detected from a three-dimensional image obtained by scanogram imaging, and a cross-sectional image is generated by cutting the three-dimensional image at the cross-sectional position. In determining the horizontal and vertical directions of this cross-sectional image (i.e., the left-right and up-down directions of the image), the processor refers to a straight line that appears on the cross-sectional image when one axis selected from the three axes of real space is projected onto the cross section (a straight line projected onto the cross-sectional image), and sets the horizontal or vertical direction of the cross-sectional image so that the straight line projected onto the cross-sectional image is parallel to the horizontal or vertical direction of the cross-sectional image.

[0014] The horizontal direction of a cross-sectional image refers to the lateral direction (left-right direction) on the image, and the vertical direction of a cross-sectional image refers to the vertical direction (up-down direction) perpendicular to the horizontal direction on the image surface. Once one of the horizontal or vertical directions of a cross-sectional image is determined, the other direction perpendicular to that direction on the same image is also determined, so setting the horizontal or vertical direction of a cross-sectional image implies setting the horizontal and vertical directions of the cross-sectional image. In this way, a cross-sectional image in which the horizontal or vertical direction of the cross-sectional image is set to match the direction of the axis in real space is stored in memory. According to the first aspect, cross-sectional images can be obtained in which the structures in the cross section are output at angles facing in the same direction, regardless of the subject.

[0015] The term "horizontal" in this specification may include the concept of approximately horizontal, which can be considered to be in a range substantially equivalent to horizontal in a technical sense. The term "vertical" may include the concept of approximately vertical, which can be considered to be in a range substantially equivalent to vertical in a technical sense. Furthermore, the term "parallel" may include the concept of approximately parallel, which can be considered to be in a range substantially equivalent to parallel in a technical sense.

[0016] The magnetic resonance imaging apparatus according to the second aspect may be configured such that, in the magnetic resonance imaging apparatus according to the first aspect, the processor rotates the cross-sectional image at an angle such that the horizontal or vertical direction of the cross-sectional image is parallel to a straight line projected onto the cross-sectional image, and stores the rotated cross-sectional image in memory.

[0017] Setting the angle by which the cross-sectional image is rotated is understood to be one aspect of setting the horizontal or vertical direction of the cross-sectional image.

[0018] The magnetic resonance imaging apparatus according to the third aspect may be the magnetic resonance imaging apparatus according to the first or second aspect, further comprising a display device, and the processor may be configured to display the cross-sectional image on the display device.

[0019] The cross-sectional images stored in the memory can be output to a display device. The cross-sectional images displayed on the display device are displayed on the screen in an orientation where the horizontal and vertical directions of the images match the horizontal (horizontal) and vertical (vertical) directions of the display screen. This allows the cross-sectional images to be displayed with the orientation of structures in the cross section aligned regardless of the subject.

[0020] A magnetic resonance imaging apparatus according to a fourth aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to third aspects, the processor generates a display image in which a frame indicating the area of ​​the imaging field of view is superimposed on the cross-sectional image.

[0021] The imaging field of view sets the imaging range for the actual imaging, and it is preferable to display a frame (imaging field of view frame) indicating the area of ​​the imaging field of view together with the cross-sectional image during positioning.

[0022] A magnetic resonance imaging apparatus according to a fifth aspect is a magnetic resonance imaging apparatus according to the fourth aspect, wherein the frame indicating the area of ​​the imaging field of view displayed on the cross-sectional image may be a rectangular frame surrounded by a pair of opposite sides parallel to the horizontal direction of the cross-sectional image and a pair of opposite sides parallel to the vertical direction of the cross-sectional image.

[0023] For example, the frame indicating the automatically set imaging field of view area can be displayed as a rectangular frame that is erected relative to the horizontal and vertical directions of the cross-sectional image.

[0024] A magnetic resonance imaging apparatus according to a sixth aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to fifth aspects, the processor detects landmarks using a first artificial intelligence model that has been trained by machine learning.

[0025] A magnetic resonance imaging apparatus according to a seventh aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to sixth aspects, the processor extracts a body surface from a three-dimensional image, sets a body axis center based on the extracted body surface, sets the center of a structure in a cross section based on the body axis center, and sets an imaging field of view for a cross-sectional image so that the center of the imaging field of view coincides with the center of the structure in the cross section.

[0026] By aligning the center of the structure in the cross section with the center of the imaging field of view, structures outside the imaging field of view that may cause artifacts can be minimized.

[0027] A magnetic resonance imaging apparatus according to an eighth aspect may be configured such that, in the magnetic resonance imaging apparatus according to the seventh aspect, the processor extracts the body surface using a second artificial intelligence model that has been trained by machine learning.

[0028] A magnetic resonance imaging apparatus according to a ninth aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to eighth aspects, the horizontal or vertical direction of the cross-sectional image is a phase encoding direction.

[0029] According to the ninth aspect, structures outside the imaging field of view can be suppressed in the phase encoding direction in which artifacts are likely to occur.

[0030] The magnetic resonance imaging apparatus of the tenth aspect may be configured such that, in the magnetic resonance imaging apparatus of any one of the first to ninth aspects, the cross sections include cross sections that can obtain at least one of a left ventricular short axis image, a horizontal long axis image, a four-chamber long axis image, a two-chamber long axis image, and a three-chamber long axis image.

[0031] The processor may generate a cross-sectional image for one of the plurality of reference cross sections used in the cardiac MRI examination, or may generate cross-sectional images for two or more of the plurality of reference cross sections. The processor is preferably configured to generate cross-sectional images for all of the plurality of reference cross sections.

[0032] The magnetic resonance imaging apparatus of the 11th aspect may be configured such that, in the magnetic resonance imaging apparatus of any one of the first to tenth aspects, the cross section is a reference cross section from which a left ventricular short axis image is obtained, and the processor rotates the cross section image at an angle such that, when the cross section includes a component in the AP direction, which is the anterior-posterior direction of the subject, the horizontal direction of the cross section image is parallel to a line formed by projecting the AP axis as one axis onto the cross section image.

[0033] A magnetic resonance imaging apparatus according to a twelfth aspect may be configured such that, in the magnetic resonance imaging apparatus according to the eleventh aspect, the processor sets the horizontal and vertical directions of the cross-sectional image to be the same as the horizontal and vertical directions of the coronal cross-sectional image when the cross-section does not include an AP direction component.

[0034] A magnetic resonance imaging apparatus according to a thirteenth aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to tenth aspects, the cross section is a reference cross section from which a horizontal long axis image is obtained, and the processor rotates the cross section image at an angle such that, when the cross section includes a component in the RL direction, which is the left-right direction of the subject, the horizontal direction of the cross section image is parallel to a line formed by projecting the RL axis as one axis onto the cross section image.

[0035] A magnetic resonance imaging apparatus according to a fourteenth aspect may be configured such that, in the magnetic resonance imaging apparatus according to the thirteenth aspect, the processor sets the horizontal and vertical directions of the cross-sectional image to be the same as the horizontal and vertical directions of the sagittal cross-sectional image when the cross-section does not include a component in the RL direction.

[0036] A magnetic resonance imaging apparatus according to a fifteenth aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to tenth aspects, the cross section is a reference cross section from which a four-chamber long axis image is obtained, and the processor rotates the cross section image at an angle such that, when the cross section includes a component in the RL direction, which is the left-right direction of the subject, the horizontal direction of the cross section image is parallel to a line formed by projecting the RL axis as one axis onto the cross section image.

[0037] A magnetic resonance imaging apparatus according to a 16th aspect may be configured such that, in the magnetic resonance imaging apparatus according to the 15th aspect, the processor sets the horizontal and vertical directions of the cross-sectional image to be the same as the horizontal and vertical directions of the sagittal cross-sectional image when the cross-section does not include a component in the RL direction.

[0038] A magnetic resonance imaging apparatus according to a seventeenth aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to tenth aspects, the cross section is a reference cross section from which a two-chamber long axis image is obtained, and the processor rotates the cross section image at an angle such that, when the cross section includes a component in the HF direction, which is the head-to-foot direction of the subject, the vertical direction of the cross section image is parallel to a line formed by projecting the HF axis as one axis onto the cross section image.

[0039] A magnetic resonance imaging apparatus according to an 18th aspect may be configured such that, in the magnetic resonance imaging apparatus according to the 17th aspect, the processor sets the horizontal and vertical directions of the cross-sectional image to be the same as the horizontal and vertical directions of the axial cross-sectional image when the cross-section does not include a component in the HF direction.

[0040] A magnetic resonance imaging apparatus according to a 19th aspect may be configured such that, in the magnetic resonance imaging apparatus according to any one of the first to tenth aspects, the cross section is a reference cross section from which a three-chamber long axis image is obtained, and the processor rotates the cross section image at an angle such that, when the cross section includes a component in the AP direction, which is the anterior-posterior direction of the subject, the vertical direction of the cross section image is parallel to a line formed by projecting the AP axis as one axis onto the cross section image.

[0041] A magnetic resonance imaging apparatus according to a 20th aspect may be configured such that, in the magnetic resonance imaging apparatus according to the 19th aspect, the processor sets the horizontal and vertical directions of the cross-sectional image to the same as the horizontal and vertical directions of the coronal cross-sectional image when the cross-section does not include an AP direction component.

[0042] A positioning assistance method according to a 21st aspect is a positioning assistance method that assists in setting an imaging position using a magnetic resonance imaging apparatus, and includes the steps of: a processor acquiring a three-dimensional image including the subject's heart by scanogram imaging performed prior to the actual imaging; detecting cardiac landmarks from the three-dimensional image; setting the position of the cross section based on the landmarks; generating a cross-sectional image that appears in the cross section from the three-dimensional image; setting the horizontal or vertical direction of the cross-sectional image so that the horizontal or vertical direction of the cross-sectional image is parallel to a line formed by projecting one axis selected from three axes that form a three-dimensional Cartesian coordinate system in real space onto the cross-sectional image; and storing the cross-sectional image in memory.

[0043] The processor may automatically execute the processing of each step according to a program, or may accept instructions input from a user for some or all of the steps and execute the processing in accordance with the accepted instructions.

[0044] The positioning assistance method according to the twenty-first aspect can be configured to include the same specific aspects as the magnetic resonance imaging apparatus according to any one of the second to twentieth aspects.

[0045] A program according to a twenty-second aspect causes a computer to execute the positioning assistance method according to the twenty-first aspect.

[0046] The program according to the twenty-second aspect may be configured to include the same specific aspects as the magnetic resonance imaging apparatus according to any one of the second to twentieth aspects.

[0047] The present disclosure also includes a non-transitory, tangible computer-readable storage medium on which a program according to the twenty-second aspect is stored. [Effects of the Invention]

[0048] According to the present disclosure, when generating a cross-sectional image of a subject's heart from a three-dimensional image obtained by scanogram imaging, a cross-sectional image can be generated in which structures within the cross section are output at a similar angle regardless of the subject. [Brief explanation of the drawings]

[0049] [Figure 1] FIG. 1 is a perspective view showing the appearance of an exemplary magnetic resonance imaging (MRI) device. [Figure 2] FIG. 2 is a diagram showing a schematic internal configuration of the MRI apparatus. [Figure 3] FIG. 3 is a block diagram showing an example of the hardware configuration of an information processing device used in an MRI apparatus. [Figure 4] FIG. 4 is an explanatory diagram of aliasing artifacts that occur due to structures outside the imaging field of view. [Figure 5] FIG. 5 shows an example of a cross-sectional image in which a structure that may cause artifacts is present outside the imaging field of view. [Figure 6] FIG. 6 is a flowchart showing an example of setting the imaging position for a left ventricular short-axis image in an MRI apparatus. [Figure 7] FIG. 7 is an explanatory diagram showing an example of the cross section cutting process in step S3 of FIG. [Figure 8] FIG. 8 is an explanatory diagram showing an example of a method for setting the center of the field of view of the left ventricular short-axis image, which is applied in steps S4 to S6 of FIG. [Figure 9] FIG. 9 is an explanatory diagram showing a cross-sectional image cut out from a 3D scanogram image before rotation. [Figure 10] FIG. 10 is an example of a cross-sectional image after rotation generated in step S7 of FIG. [Figure 11] FIG. 11 is an explanatory diagram showing an example of setting the horizontal direction of a left ventricular short-axis image when a cross section extracted from a 3D scanogram image contains an AP direction component, and shows the straight lines of each axis projected onto the cross section. [Figure 12] FIG. 12 is an explanatory diagram showing an example of setting the horizontal direction of a left ventricular short-axis image when a cross section extracted from a 3D scanogram image does not contain a component in the AP direction. [Figure 13] FIG. 13 is an explanatory diagram showing an example of a user interface when a cross-sectional display of a left ventricular short-axis image is performed. [Figure 14] FIG. 14 is a block diagram showing the functional configuration of an information processing device used in an MRI apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0050] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and accompanying drawings, components having the same functional configuration are designated by the same reference numerals, and redundant description will be omitted.

[0051] [Magnetic Resonance Imaging (MRI) Equipment Overview] 1 is a perspective view showing the exterior of an exemplary MRI apparatus 10. The MRI apparatus 10 includes a gantry 12, which is the main body of the imaging apparatus, and a bed 14. The gantry 12 has a cylindrical imaging space 18 called a bore. The gantry 12 is equipped with a static magnetic field generating magnet for generating a magnetic field in the imaging space 18, a gradient magnetic field coil, and various other coils.

[0052] The bed 14 includes a top plate 15 and legs 16 that support the top plate 15, and is disposed on the front side of the gantry 12. The top plate 15 can be moved into and out of the imaging space 18 by a drive mechanism (not shown) provided on the legs 16. The bed 14 may be configured to be fixed to the gantry 12, or may be a mobile bed (dockable bed) that can be attached to and detached from the gantry 12.

[0053] In the MRI apparatus 10, three apparatus axes are defined, which are three-dimensional Cartesian coordinate axes of a real space including an imaging space 18. The direction of each of the three apparatus axes is uniquely determined by the gantry 12 and the bed 14. In Fig. 1, the Z direction is the static magnetic field direction, the Y direction is the vertical direction, and the X direction is the direction perpendicular to the Y and Z directions.

[0054] 2 is a diagram showing a schematic internal configuration of the MRI apparatus 10. The MRI apparatus 10 includes a static magnetic field generating magnet 102, a gradient magnetic field coil 104, an RF (Radio Frequency) transmitting coil 106, a receiving coil 110, a receiver 112, a gradient magnetic field power supply 114, a high-frequency magnetic field generator 116, a sequencer 118, a control unit 120, and an operation unit 122.

[0055] The static magnetic field generating magnet 102 generates a uniform static magnetic field in the imaging space 18. The static magnetic field generating magnet 102 includes a permanent magnet type, normal conducting type, or superconducting type static magnetic field generating source. The gradient magnetic field coil 104 generates a gradient magnetic field in the imaging space 18. The gradient magnetic field coil 104 is composed of gradient magnetic field coils in the three axes of X, Y, and Z, which are the real space coordinate system (stationary coordinate system). Each gradient magnetic field coil is connected to a gradient magnetic field power supply 114 and is supplied with current. As a result, a gradient magnetic field is generated in the three axes of X, Y, and Z.

[0056] The subject 130 is placed on the top board 15 of the bed 14, and a receiving coil 110 corresponding to the examination region is attached to the subject 130. The top board 15 on which the subject 130 is placed is moved into the imaging space 18, so that the examination region of the subject 130 is positioned at the center of the static magnetic field within the imaging space 18.

[0057] The RF transmission coil 106 is a coil that irradiates a radio frequency magnetic field pulse (RF pulse) to the subject 130. The RF transmission coil 106 is connected to a radio frequency magnetic field generator 116, and is supplied with a radio frequency pulse current from the radio frequency magnetic field generator 116.

[0058] The sequencer 118 sends commands to the high frequency magnetic field generator 116 and the gradient magnetic field power supply 114 according to an imaging pulse sequence, so that appropriately amplified signals are sent to the RF transmit coil 106 and the gradient magnetic field coil 104, respectively.

[0059] The high-frequency magnetic field generator 116 is driven in accordance with instructions from the sequencer 118 to amplitude-modulate a high-frequency pulse and supply the amplified high-frequency pulse current to the RF transmitting coil 106. The RF transmitting coil 106 applies a pulsed high-frequency magnetic field (RF pulse) to the subject 130 in response to a signal from the high-frequency magnetic field generator 116. Preferably, the sequencer 118 sends an instruction to the receiving coil 110 in accordance with the imaging sequence, and turns off the receiving coil 110 when the RF pulse is applied.

[0060] Application of a high-frequency magnetic field induces a nuclear magnetic resonance (NMR) phenomenon in the spins of atoms that make up the biological tissue of the subject 130. The receiving coil 110 is a multi-channel RF coil unit that includes multiple coil elements for receiving nuclear magnetic resonance signals (NMR signals) generated in the subject 130.

[0061] The NMR signal generated from the subject 130 is detected by the receiving coil 110, amplified by a preamplifier (not shown) in the receiving coil 110, and transmitted to the receiver 112. In the receiver 112, the amplified NMR signal is subjected to AD (analog-to-digital) conversion and necessary signal processing to generate data. The generated data is transmitted to the control unit 120. This data is also called a received signal or measurement data.

[0062] A receiving-side cable (not shown) that outputs the NMR signal received by the receiving coil 110 is connected to the receiving coil 110. A receiving-side connector (not shown) is connected to an end of this receiving-side cable. The receiving-side connector is connected to a bed-side connector of a bed-side cable (not shown). The bed-side cable is connected to the control unit 120. This allows the receiving coil 110 to be communicatively connected to the control unit 120 and the sequencer 118. Note that the connection between the receiving coil 110, the control unit 120, and the sequencer 118 is not limited to a wired connection such as a cable, and wireless connection is also possible. In this case, the receiving coil 110 further includes at least an AD conversion module and a wireless communication module.

[0063] The sequencer 118 controls each component so that it operates at pre-programmed timing and intensity. A program that describes the timing and intensity of RF pulses, gradient magnetic fields, and signal reception is called a pulse sequence. Various pulse sequences are known depending on the purpose, but detailed descriptions of them will be omitted here.

[0064] The control unit 120 receives various instruction inputs from an operation unit 122 and controls each unit of the MRI apparatus 10 via a sequencer 118. The control unit 120 also performs processing such as converting the spatial frequency domain received signals from the receiver 112 into images in real space by inverse Fourier transform, thereby generating an MRI image.

[0065] The operation unit 122 includes input devices such as a mouse and a keyboard, and a display device such as a liquid crystal display, etc. The operation unit 122 functions as a user interface (UI) that allows a user such as a technician to start or stop (pause) the MRI apparatus 10, select a pulse sequence, and input imaging conditions, processing conditions, etc.

[0066] The sequencer 118 and the control unit 120 can be configured using a computer. The processing functions of the sequencer 118 and the control unit 120 may also be realized by a computer system including a plurality of computers.

[0067] [Example of hardware configuration of information processing device] 3 is a block diagram showing an example of the hardware configuration of an information processing device 200 used in the MRI apparatus 10. The information processing device 200 may be a personal computer, a workstation, or a server computer. The information processing device 200 can function as the control unit 120 and the operation unit 122 (see FIG. 2). The information processing device 200 may also function as the sequencer 118.

[0068] The information processing device 200 includes a processor 202 , a memory 204 which is a main storage device, a storage 206 which is an auxiliary storage device, an input / output interface 208 , and a bus 210 .

[0069] The processor 202 includes a CPU (Central Processing Unit). The processor 202 may include a GPU (Graphics Processing Unit). The information processing device 200 may also include one or more processors selected from the group consisting of a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), and a PLD (Programmable Logic Device).

[0070] The processor 202 is connected to a memory 204 , a storage 206 , an input / output interface 208 , an input device 212 , and a display device 214 via a bus 210 .

[0071] The memory 204 includes a random access memory (RAM). The memory 204 may also include a read only memory (ROM). The storage 206 may be, for example, a hard disk drive (HDD), a solid state drive (SSD), or a combination of these. The storage 206 may also include an external storage device such as a removable medium.

[0072] The storage device including the memory 204 and the storage 206 stores programs, data, etc. that realize various functions of the MRI apparatus 10. The processor 202 realizes various functions by executing the programs stored in the memory 204. The processor 202 comprehensively controls each part of the information processing device 200 and various devices and units provided in the MRI apparatus 10, and performs various processes.

[0073] The input / output interface 208 includes a communication interface connectable to a telecommunications line such as a local area network, a connection interface connectable to an external device, etc. As a connection interface connectable to an external device, for example, a Universal Serial Bus, a High-Definition Multimedia Interface (HDMI) (HDMI is a registered trademark), etc. can be applied.

[0074] The processor 202 communicates with various devices of the MRI apparatus 10 via an input / output interface 208, thereby transmitting and receiving necessary information.

[0075] The input device 212 is configured, for example, by a keyboard, a pointing device such as a mouse, a numeric keypad, various switch buttons, etc. The input device 212 may also include a voice input device. The input device 212 may also be a touch panel type input device that is configured integrally with the display screen of the display device 214.

[0076] The display device 214 is configured by, for example, a liquid crystal display, an organic electro-luminescence (OEL) display, a projector, or an appropriate combination of these. The display device 214 displays various information in addition to images captured by the MRI apparatus 10. The display device 214 is used as part of a UI when receiving input from the input device 212. The display device 214 is not limited to one, and a multi-display configuration having multiple display devices is also possible.

[0077] [Overview of MRI imaging procedure] A typical imaging procedure using the MRI apparatus 10 is roughly as follows.

[0078] [Step 1] An operator such as a technician uses an input device 212 such as a mouse and keyboard to set subject information, imaging region (target disease), examination protocol (imaging type, order, etc.), and other information required for the examination. The subject information includes the subject's name, subject code, etc. Some or all of this information may be manually input by the operator via the input device 212, or information stored in advance in a recording medium, etc. The operator ultimately checks the automatically set or input parameters and, if necessary, manually sets them via the input device 212.

[0079] [Step 2] The subject 130 is placed on the top board 15 of the bed 14, and the receiving coil 110 is attached to the subject 130.

[0080] [Step 3] Using a gantry operation panel or foot switch (not shown), the tabletop 15 is moved to the imaging space 18 , and the region to be examined of the subject 130 is moved to the center of the static magnetic field of the gantry 12 .

[0081] [Step 4] Scanogram imaging is performed to obtain a positioning image. In scanogram imaging, multiple slices are imaged for one or more of the axial, coronal, and sagittal planes. In the case of a cardiac MRI examination, scanogram imaging is performed in synchronization with the electrocardiogram waveform over an imaging range that covers a three-dimensional region including the heart of the subject 130, and a 3D scanogram image is obtained. Note that the slice thickness in scanogram imaging may be set to a value greater than the slice thickness in actual imaging.

[0082] [Step 5] After scanogram imaging is completed, a positioning image is reconstructed and displayed on the display device 214 of the operation unit 122. As will be described in detail later, the MRI apparatus 10 according to this embodiment is equipped with an automatic positioning function that automates the setting of the imaging position, automatically detecting cardiac landmarks from the 3D scanogram image and determining the position of the reference cross section using the landmarks. Then, a cross-sectional image extracted from the determined position of the reference cross section is presented on the display device 214.

[0083] [Step 6] The operator sets the imaging position for the actual imaging based on the cross-sectional image generated from the 3D scanogram image. In the MRI apparatus 10 according to this embodiment, the imaging position, including the slice position (cross-sectional position) to be measured in the actual imaging, is automatically calculated from the 3D scanogram image, and the recommended imaging position is presented to the operator. The operator checks the presented slice position, etc., and manually adjusts the imaging position via the input device 212 of the operation unit 122 as necessary. The operator also sets the imaging parameters to be applied to the actual imaging. Some or all of the imaging parameters may be input by a user such as a technician via the operation unit 122, or may be automatically set or input. The automatically set (automatically input) parameters are finally checked by the operator, and manually set via the input device 212 of the operation unit 122 as necessary.

[0084] [Step 7] The actual imaging is performed according to the imaging parameters and imaging positions set in this way.

[0085] [Step 8] After the actual imaging, an image is reconstructed and displayed on the display device 214 of the operation unit 122.

[0086] [Step 9] For the displayed reconstructed image, the operator sets a window value suitable for diagnosis using the input device 212 of the operation unit 122, and obtains an image to be used for diagnosis.

[0087] [Step 10] When imaging is complete, the top board 15 is removed from the imaging space 18, and the subject 130 is removed from the gantry 12. Then, the subject 130 is removed from the bed 14, and the MRI examination is completed.

[0088] The MRI apparatus 10 according to this embodiment is equipped with means for solving the problems of the prior art, particularly with respect to the output of the reconstructed image for positioning related to the operations of steps 4 to 6 among the above steps 1 to 10, and the imaging position setting support function that presents the recommended imaging position.

[0089] [Artifacts from structures outside the imaging field of view] Here, we will briefly explain artifacts, which are one of the technical challenges. Figure 4 is an explanatory diagram of aliasing artifacts that occur due to structures outside the imaging field of view. The circular area shown in the left diagram F4A of Figure 4 is a schematic representation of the internal structure to be imaged, and the rectangular area represents the imaging field of view (FOV). If a structure exists outside the imaging field of view (FOV), aliasing artifacts may occur in the output image obtained by this imaging, as shown in the right diagram F4B (right diagram F4B). Such artifacts occur more noticeably in the phase encoding direction. In the example of Figure 4, the horizontal direction (lateral direction) of the image is the phase encoding direction.

[0090] FIG. 5 is an example of a cross-sectional image in which a structure that may cause artifacts is present outside the FOV. FIG. 5 shows an example of a left ventricular short-axis image, with a rectangular frame indicating the FOV overlaid on the image. The FOV shown in FIG. 5 is an example of a default FOV, and is set as a rectangular region enclosed by a pair of opposite sides (upper and lower sides) parallel to the horizontal (lateral) direction of the cross-sectional image and a pair of opposite sides (left and right sides) parallel to the vertical (longitudinal) direction of the cross-sectional image. The term "rectangle" includes squares and rectangles. The horizontal direction of the image in FIG. 5 is the phase encoding direction.

[0091] In the left ventricular short-axis image shown in Figure 5, structures including the heart in the cross section are displayed at an angle oblique to the rectangular region of the FOV, and structures exist outside the FOV in the phase encoding direction. For this reason, aliasing artifacts may occur in the output image when actual imaging is performed with the FOV setting shown in Figure 5.

[0092] As mentioned above, the shape and orientation of the heart vary from person to person, and the body orientation from which the reference cross-sectional image is obtained also varies from person to person. Therefore, when cross-sectional images cut out from a cross-section determined based on landmarks detected from a 3D scanogram image are output to the display device 214 without particular consideration of the rotation angle (in-plane angle) of the cross-sectional image, the orientation of the cross-sectional image displayed on the screen will differ between subjects. As a result, as shown in Figure 5, structures are likely to exist outside the imaging field of view (FOV) in the phase encoding direction, and artifacts are likely to occur.

[0093] To suppress artifacts, the user needs to change the setting of the imaging field of view (FOV) or adjust the angle of the cross-sectional image relative to the imaging field of view (FOV).

[0094] This problem is not limited to the left ventricular short-axis image, but also applies to other reference cross section images such as the horizontal long-axis image, the four-chamber long-axis image, the two-chamber long-axis image, and the three-chamber long-axis image.

[0095] [Outline of the method for generating reference cross section images in the MRI device 10] In the MRI apparatus 10 according to this embodiment, the horizontal and vertical directions of cross-sectional images extracted from a 3D scanogram image are set so that the orientation of structures within each of a plurality of reference cross sections used for cardiac imaging is aligned and displayed in the same manner regardless of the subject. More specifically, the in-plane angle for rotating the cross-sectional images is set so as to minimize structures outside the field of view (FOV) in the phase encoding direction that may cause artifacts, preferably so that no structures are present outside the field of view (FOV) in the phase encoding direction, and the orientation of the cross-sectional images is aligned by the rotation process.

[0096] For example, in the case of a left ventricular short-axis view, the cross-sectional image is output at an angle such that the horizontal direction of the cross-sectional image is parallel to the line projected by the AP axis onto the cross-sectional image (see images F13A in Figures 10 and 13). This results in the cross-sectional image being displayed with the longitudinal direction of the region of the structure, including the heart, in the cross-section roughly parallel to the vertical direction of the cross-sectional image, and the region of the structure in the horizontal direction, which is the phase encoding direction, falls within the field of view (FOV). Note that in the frequency encoding direction, which is perpendicular to the phase encoding direction, structures exist outside the field of view (FOV). However, because artifacts are less likely to occur in the frequency encoding direction than in the phase encoding direction, the presence of structures outside the field of view (FOV) in the frequency encoding direction is acceptable.

[0097] [Positioning assistance method: Example of setting the imaging position for left ventricular short-axis images] A more specific example of the left ventricular short-axis image will be described below.

[0098] Fig. 6 is a flowchart showing an example of setting the imaging position of a left ventricular short-axis image in the MRI apparatus 10. The method shown in the flowchart of Fig. 6 is an example of a positioning assistance method according to the present disclosure.

[0099] In step S1, the processor 202 performs 3D scanogram imaging prior to actual imaging to obtain a 3D scanogram image including the heart of the subject 130. The 3D scanogram image may be, for example, a multi-slice image of an axial cross section including a three-dimensional region covering the entire heart of the subject 130, or may be an isotropic three-dimensional image generated by performing interpolation processing based on this multi-slice image so that data is equidistantly spaced in each of the three axial directions of the device. The 3D scanogram image is an example of a three-dimensional image in the present disclosure.

[0100] In step S2, the processor 202 detects cardiac landmarks from the acquired 3D scanogram image. Landmarks are anatomical landmarks, and include, for example, the positions of the apex of the heart, the mitral valve, the long axis, the left atrium, and the tricuspid valve. The long axis of the heart may be determined as a straight line connecting the apex of the mitral valve and the apex of the heart.

[0101] The landmark detection process may use, for example, artificial intelligence (AI). That is, the processor 202 may execute the process of detecting cardiac landmarks from the 3D scanogram image using an AI model trained by machine learning. Note that a configuration may be used in which a single AI model is used to identify and detect multiple landmarks, or a configuration may be used in which multiple AI models are used to detect different landmarks, respectively.

[0102] In step S3, the processor 202 determines the position (cross-section position) of the cross section from the 3D scanogram image using the detected landmarks. By determining the cross section, a normal line perpendicular to the cross section is determined. Then, the processor 202 cuts out the cross section from the 3D scanogram image at the determined cross-section position to generate a cross-sectional image (see FIG. 7).

[0103] In step S4, the processor 202 extracts the body surface of the subject 130 from the 3D scanogram image (see images F8A and F8B in FIG. 8). The processor 202 may execute the process of extracting the body surface using an AI model that has been trained by machine learning.

[0104] In step S5, the processor 202 calculates the center of gravity of the body surface based on the extracted body surface, and sets the center of the body axis from the center of gravity of the body surface (see image F8C in FIG. 8).

[0105] In step S6, the processor 202 calculates the center position of the structure in the cross section based on the body axis center, and sets the positional relationship between the imaging field of view and the cross section so that the center of the imaging field of view coincides with the center of the structure in the cross section (see image F8F in Figure 8).

[0106] In step S7, processor 202 sets an in-plane angle that determines the horizontal (lateral) direction and vertical (longitudinal) direction of the cross-sectional image extracted in step S3. When determining the horizontal and vertical directions of the cross-sectional image, processor 202 sets the direction of one side of either the horizontal or vertical direction of the cross-sectional image so that either the horizontal or vertical direction of the cross-sectional image is parallel to a line formed by projecting one of the three device axes (three orthogonal axes when a 3D scanogram image is captured) onto the cross-sectional image. This direction of one side is referred to as the "direction of the first side." Then, the direction of the other side of the cross-sectional image (referred to as the "direction of the second side") is set as a direction perpendicular to the direction of the first side on the plane of the cross-section.

[0107] By setting the direction of the first side, the direction of the second side perpendicular to the direction of the first side is necessarily determined. By setting the direction of the first side, an in-plane angle that determines the horizontal (lateral) direction and vertical (longitudinal) direction of the cross-sectional image extracted in step S3 is specified. Setting the direction of the first side is substantially equivalent to setting the in-plane angle of the cross-sectional image.

[0108] The three device axes are an example of three axes that form a three-dimensional Cartesian coordinate system in a real space including the imaging space 18. The three device axes when capturing a 3D scanogram image correspond to the HF axis, AP axis, and RL axis of the subject 130 on the bed 14. For example, when the subject 130 is in a supine position with his / her head first, the HF axis coincides with the Z direction, the AP axis coincides with the Y direction, and the RL axis coincides with the X direction.

[0109] In the case of a left ventricular short axis image, the processor 202 sets an in-plane angle so that the horizontal direction of the cross-sectional image is parallel to the line formed by projecting the AP axis onto the cross-sectional image, and rotates the cross-sectional image according to the set in-plane angle (see Figures 9 to 12).

[0110] In step S8, the processor 202 displays the cross-sectional image rotated according to the in-plane angle set in step S7 on the display device 214. The processor 202 automatically sets the field of view FOV for this cross-sectional image, and displays a frame indicating the area of ​​the field of view FOV (hereinafter referred to as the field of view frame) superimposed on the cross-sectional image. The "automatic setting" here may be a presentation of recommended settings proposed by automatic calculation of an automatic positioning function implemented in the MRI apparatus 10, and the final decision (establishment) of the field of view FOV may be left to the user.

[0111] The processor 202 may automatically generate a display image in which the imaging field of view frame related to the automatic setting is superimposed on the cross-sectional image, and display the image on the display device 214. The processor 202 may also receive an instruction from the user via the input device 212 regarding whether or not to display the imaging field of view frame, and switch between displaying and hiding the imaging field of view frame in accordance with the received instruction.

[0112] For example, the default setting may be set to automate the process to superimposing the imaging field of view frame on the cross-sectional image, and the user may select to change the setting to not display the imaging field of view frame.

[0113] On the screen of the display device 214, the imaging field frame is displayed together with the cross-sectional image, and the user is prompted to confirm it.

[0114] In step S9, the user checks the cross-sectional image and the imaging field of view FOV and inputs an instruction to set the imaging position or change the setting. The processor 202 accepts the instruction from the user, and if the setting is to be changed manually, provides a UI for that purpose (see FIG. 13). The processor 202 accepts instructions such as fine adjustment of the imaging position via the UI.

[0115] After the user confirms the settings in step S9, the processor 202 proceeds to step S10.

[0116] In step S10, the processor 202 executes the actual imaging under the set imaging conditions.

[0117] [Detailed explanation of step S3: concrete example of cross-section cutting process] Figure 7 is an explanatory diagram showing an example of the cross-section extraction process in step S3 of Figure 6. Images F7A and F7B shown on the left side of Figure 7 are example images of representative cross sections of a 3D scanogram image. Point P1 in image F7A is a point on the apex of the heart detected by the landmark detection process (step S2). Point P2 in image F7B is a point on the left atrium detected by the landmark detection process (step S2).

[0118] The processor 202 sets a cross section CS of the left ventricular short-axis image based on the plurality of points P1 and P2 detected by the landmark detection process.

[0119] Image F7C shown on the right side of FIG. 7 is an example of a cross-sectional image of cross section CS cut out from the 3D scanogram image.

[0120] [Detailed explanation of steps S4 to S6: Method for setting the center of the field of view for left ventricular short-axis images] FIG. 8 is an explanatory diagram showing an example of a method for setting the center of the imaging field of view of a left ventricular short-axis image. FIG. 8 shows the processing flow from step S4 to step S6 of FIG. 6 together with example images. Image F8A shown in the upper left of FIG. 8 is an example of a 3D scanogram image acquired in step S1. Image F8B shows an example in which the body surface BS is extracted from the 3D scanogram image by the processing of step S4. Processor 202 extracts the body surface BS from the 3D scanogram image using AI (see image F8B).

[0121] Image F8C shows an example in which the body axis center BC is detected by the processing in step S5. The processor 202 detects the body axis center BC from the center of gravity of the body surface BS.

[0122] Furthermore, as shown in image F8D, processor 202 determines the intersection Pc of a line Lx that passes through the body axis center BC and is parallel to the X-axis and the cross section CS extracted in step S3. As shown in image F8E, processor 202 can calculate the intersection Pc from the multiple landmarks detected in step S2.

[0123] Then, the processor 202 sets the center point of the structure in the cross section CS from the point Pc shown in the images F8D and F8E (see image F8F).

[0124] By matching the center point of the structure thus determined with the center of the imaging field of view, it is possible to minimize structures outside the imaging field of view that cause artifacts.

[0125] [Explanation of the processing content of step S7: In-plane angle setting method] 9 and 10 show examples of setting the in-plane angle of a left ventricular short-axis image. Fig. 9 shows the state of a cross-sectional image extracted from a 3D scanogram image before rotation, and Fig. 10 shows the state of the cross-sectional image after rotation by an appropriately set in-plane angle.

[0126] The cross-sectional image F9A shown in FIG. 9 is an example of a cross-section cut out from the 3D scanogram image by the processing of step S3. The cube F9B shown in the lower left of FIG. 9 represents the three-dimensional orientation of the cross-section from which the cross-sectional image F9A was cut out. In other words, assuming that the cross-section from which the cross-sectional image F9A was cut (the cross-section from which the cross-sectional image F9A appears) is parallel to the plane of FIG. 9, the cube F9B represents the orientation of the volume data of the 3D scanogram image from which this cross-section is obtained. The symbols "A," "F," and "L" attached to each face of the cube F9B represent the initials of "Anterior," "Foot," and "Left," respectively. Although not shown in FIG. 9, the face opposite the "L" face of the cube F9B is "R," the face opposite the "A" face is "P," and the face opposite the "F" face is "H."

[0127] The cube F9B indicates how the two-dimensional cross section in which the cross-sectional image F9A appears corresponds to the rotation of the 3D volume data of the original 3D scanogram image.

[0128] 9, an intersection line diagram F9C in which three lines intersect represents lines obtained by projecting each of the three axes of the device (X-axis, Y-axis, and Z-axis) onto a cross section cut out from the cross-sectional image F9A. The three axes of the device correspond to the three body axes of the subject 130. For example, when the subject 130 is in a supine position with head first, the X-axis corresponds to the RL axis, the Y-axis corresponds to the AP axis, and the Z-axis corresponds to the HF axis.

[0129] The straight lines of each axis projected onto a cross section cut out from the 3D scanogram image may be understood to be straight lines projected onto the cross section image of the RL axis, AP axis, and HF axis of cube F9B.

[0130] As shown in the cross-sectional diagram F9C, the straight lines of each axis projected onto the cross section are not parallel to the horizontal or vertical direction of the cross-sectional image F9A. In other words, before the image is rotated, none of the RL, AP, and HF directions projected onto the cross-sectional image F9A are aligned with the vertical or horizontal direction of the cross-sectional image F9A.

[0131] As explained in FIG. 5, when the cross-sectional image F9A is output at an angle as shown in FIG. 9, a structure exists outside the imaging field of view FOV in the phase encoding direction (here, the horizontal direction of the cross-sectional image F9A), which causes aliasing artifacts.

[0132] Therefore, in the MRI apparatus 10 according to this embodiment, instead of outputting the cross-sectional image F9A as shown in FIG. 9, the MRI apparatus 10 outputs the cross-sectional image F10A by setting the in-plane angle so that the left-right direction (horizontal direction) on the cross-sectional image is parallel to the line projected onto the cross-sectional image of the AP axis, as shown in FIG.

[0133] The cross-sectional image F10A shown in FIG. 10 is an example of a cross-sectional image after rotation generated by the processing of step S7, and is an example of an image displayed on the display device 214 by the cross-sectional display processing in step S8.

[0134] The cube F10B shown in the lower left of Fig. 10 represents the three-dimensional orientation of the cross section cut out from the cross-sectional image F10A, and indicates how the two-dimensional cross section in which the cross-sectional image F10A appears corresponds to the rotation of the 3D volume data of the original 3D scanogram image. The intersection line diagram F10C shown in the lower right of Fig. 10, in which three lines intersect, represents the lines projected onto the cross-sectional image cut out from the cross-sectional image F10A, each of the three axes of the device.

[0135] 10, the cross-sectional image F10A is obtained by in-plane rotating the cross-sectional image F9A in FIG. 9 so that a line projecting the Y axis (AP axis) onto the cross-sectional image is parallel to one side of the cross section in the left-right direction (the horizontal side of the cross-sectional image F10A). In the example of FIG. 10, the Y axis (AP axis) is an example of "one axis selected from three axes" in the present disclosure.

[0136] As is clear from a comparison of FIGS. 9 and 10, by rotating the pre-rotation cross-sectional image F9A counterclockwise around the normal line of the cross-section as the rotation axis, a cross-sectional image F10A as shown in FIG. 10 can be obtained.

[0137] That is, when the three axes of the device are projected onto a cross-sectional image and the cross-sectional image F9A is rotated as shown in Fig. 9, the straight lines of the three projected axes also rotate together with the cross-sectional image F9A. By rotating the image until a specific one of the three rotated axes, the Y-axis, becomes parallel to the horizontal direction of the cross-sectional image, a cross-sectional image F10A as shown in Fig. 10 is obtained.

[0138] The processor 202 also overlays an imaging field of view frame indicating the automatically set region of the imaging field of view FOV on the cross-sectional image F10A. The imaging field of view frame related to this automatic setting is displayed as an upright rectangular frame on the screen of the display device 214, as in Fig. 5. That is, the imaging field of view frame presented on the cross-sectional image F10A by the automatic positioning function of this embodiment is a rectangle surrounded by sides along the vertical and horizontal directions that coincide with the vertical and horizontal directions of the screen of the display device 214. The horizontal direction of the cross-sectional image F10A shown in Fig. 10 is the phase encoding direction.

[0139] By displaying the cross-sectional image F10A with the imaging field frame superimposed thereon, the user can confirm the setting of the imaging position on the screen of the display device 214.

[0140] Although Figures 9 and 10 show examples in which the extracted cross section includes a component in the AP direction, in the case of a left ventricular short-axis image, depending on the position of the extracted cross section, the cross section may not include a component in the AP direction.

[0141] When the extracted cross section contains an AP component, the processor 202 outputs the cross section image at an angle where the horizontal direction of the cross section image is parallel to the line where the AP axis is projected onto the cross section image, as shown in Fig. 11. On the other hand, when the extracted cross section does not contain an AP component, the processor 202 outputs the cross section image at an angle where the horizontal and vertical directions of the cross section image are set to the same horizontal and vertical directions as those of the coronal cross section, as shown in Fig. 12. That is, when the extracted cross section does not contain an AP component, the processor 202 outputs the cross section image at an angle where the horizontal direction of the cross section image is parallel to the line where the RL axis is projected onto the cross section image, and the vertical direction of the cross section image is parallel to the line where the HF axis is projected onto the cross section image.

[0142] [Specific example of steps S8 to S9: Example of cross-sectional image display and method for manually changing the imaging field of view] Figure 13 shows an example of the UI for displaying a cross-sectional view of the left ventricle short-axis image. Images F13A, F13B, and F13C shown in the upper part of Figure 13 are examples of recommended imaging positions automatically calculated based on 3D scanogram images. The bidirectional arrow A in the figure indicates the phase encoding direction.

[0143] Image F13A is the same as cross-sectional image F10A shown in Fig. 10. Image F13B is an example of an image in which the positions of multiple imaging sections set corresponding to the imaging field of view FOV are overlaid on a vertical long-axis image. Image F13C is an example of an image in which the positions of multiple imaging sections set corresponding to the imaging field of view FOV are overlaid on a horizontal long-axis image.

[0144] These multiple images F13A, F13B, and F13C may be displayed simultaneously on one screen of the display device 214, or each image may be displayed individually according to a user's selection. The MRI apparatus 10 receives an instruction to change the imaging field of view (FOV) from the input device 212. For example, the user can perform operations such as rotation, movement, or deformation by dragging the frame of the imaging field of view (FOV) overlaid on the image F13A on the screen on which the image F13A is displayed. The user can also fine-tune the imaging field of view (FOV) by specifying a rotation angle, movement amount, or deformation parameter by numerically inputting values ​​from the input device 212.

[0145] Image F13D is an example of a case where the user manually changes the angle of the imaging field of view FOV. When the user manually changes the angle of the imaging field of view FOV as in image F13D, the phase encoding direction also changes in conjunction with the angle of the imaging field of view FOV.

[0146] The user checks the imaging position settings on the screen, and if the settings are appropriate, confirms the settings and then proceeds to actual imaging. The cross-sectional image of the reference cross section for which the imaging position settings have been confirmed and information on the imaging field of view FOV are linked to the diagnostic examination image captured by the actual imaging and stored in storage 206. Storage 206 may be a storage device of an image management system such as a PACS (Picture Archiving and Communication System).

[0147] [Example of setting the horizontal or vertical direction of a cross-sectional image according to the type of reference cross section] In cardiac MRI examinations, imaging of multiple reference cross sections is usually performed in one examination. It is preferable that the processor 202 sets the horizontal or vertical direction of the cross-sectional image with reference to the device axis for at least one of the multiple reference cross sections, and preferably for all of the cross-sectional images of the multiple reference cross sections, in the same manner as in the example of the left ventricular short-axis image described above, and generates an image for display.

[0148] Preferred examples of horizontal and vertical direction settings for reference cross section images other than the left ventricular short-axis image are as follows.

[0149] [Horizontal long axis view] When generating a horizontal long axis image, if the cross section extracted from the 3D scanogram image contains a component in the RL direction, the processor 202 outputs the cross section image at an angle such that the horizontal direction of the cross section image is parallel to the line projected onto the RL axis onto the cross section image.

[0150] On the other hand, if the extracted cross section does not include an RL component, the processor 202 outputs the cross section image at an angle such that the horizontal and vertical directions of the cross section image are set to the same horizontal and vertical directions as those of the sagittal cross section image. In other words, if the extracted cross section does not include an RL component, the processor 202 outputs the cross section image at an angle such that the horizontal direction of the cross section image is parallel to the line obtained by projecting the AP axis onto the cross section image, and the vertical direction of the cross section image is parallel to the line obtained by projecting the HF axis onto the cross section image.

[0151] [In the case of a four-chamber long-axis view] When generating a four-chamber long axis image, if the cross section extracted from the 3D scanogram image contains a component in the RL direction, the processor 202 outputs the cross section image at an angle such that the horizontal direction of the cross section image is parallel to the line projected onto the RL axis onto the cross section image.

[0152] On the other hand, if the extracted cross section does not include the RL component, the processor 202 outputs the cross section image at an angle such that the horizontal and vertical directions of the cross section image are set to the same horizontal and vertical directions as those of the sagittal cross section image.

[0153] [Two-chamber long-axis view] When generating a two-chamber long axis image, if the cross section extracted from the 3D scanogram image contains a component in the HF direction (head-to-foot direction), the processor 202 outputs the cross section image at an angle such that the vertical direction of the cross section image is parallel to the line projected onto the HF axis onto the cross section image.

[0154] On the other hand, if the extracted cross section does not include an HF component, the processor 202 outputs the cross section image at an angle such that the horizontal and vertical directions of the cross section image are set to the same horizontal and vertical directions as those of the axial cross section image. In other words, if the extracted cross section does not include an HF component, the processor 202 outputs the cross section image at an angle such that the horizontal direction of the cross section image is parallel to the line obtained by projecting the RL axis onto the cross section image, and the vertical direction of the cross section image is parallel to the line obtained by projecting the AP axis onto the cross section image.

[0155] [In the case of a three-chamber long-axis view] When generating a three-chamber long axis image, if the cross section extracted from the 3D scanogram image contains an AP direction component, the processor 202 outputs the cross section image at an angle such that the horizontal direction of the cross section image is parallel to the line projecting the AP axis onto the cross section image.

[0156] On the other hand, if the extracted cross section does not contain an AP component, the processor 202 outputs the cross section image at an angle such that the horizontal and vertical directions of the cross section image are set to the same horizontal and vertical directions as those of the coronal cross section image.

[0157] [For vertical long axis images] Since the cross section of the vertical long axis image is defined as a cross section parallel to the Z direction (HF direction) of the device axis, this Z direction can be set as the vertical (longitudinal) direction of the cross section image, and rotation is not required.

[0158] [Functional configuration of information processing device 200] 14 is a block diagram showing the functional configuration of the information processing device 200. The information processing device 200 includes a scanogram image acquisition unit 220, a landmark detection unit 222, an imaging section determination unit 224, a cross-sectional image generation unit 226, an in-plane angle setting unit 228, a body surface extraction unit 230, a body axis center setting unit 232, a structure center calculation unit 234, a cross-sectional image storage unit 236, an imaging field of view setting unit 240, an imaging position setting unit 242, a display image generation unit 244, and a display control unit 246.

[0159] The scanogram image acquisition unit 220 acquires a 3D scanogram image captured by executing scanogram imaging. The landmark detection unit 222 includes a trained AI model 223 and detects cardiac landmarks from the 3D scanogram image using the AI ​​model 223. The AI ​​model 223 may be, for example, an image recognition model configured using a convolutional neural network and trained to perform an object detection task. The AI ​​model 223 is an example of a "first artificial intelligence model" in this disclosure.

[0160] The imaging section determination unit 224 determines the positions of reference cross sections as imaging sections based on the landmarks detected by the landmark detection unit 222. The imaging section determination unit 224 determines cross sections including multiple landmarks. The imaging section determination unit 224 determines the positions of, for example, the six types of reference cross sections described above.

[0161] The cross-sectional image generating unit 226 generates a cross-sectional image of the reference cross section from the 3D scanogram image. That is, the cross-sectional image generating unit 226 generates a cross-sectional image that appears on a cross section obtained by cutting the 3D scanogram image at the position of the reference cross section determined by the imaging cross section determining unit 224.

[0162] The in-plane angle setting unit 228 sets an image rotation angle that determines the horizontal or vertical direction of a cross-sectional image extracted from a 3D scanogram image. The in-plane angle setting unit 228 sets an angle for rotating the cross-sectional image, depending on the type of reference cross-section, so that the horizontal or vertical direction of the cross-sectional image is parallel to a line formed by projecting one axis selected from the three device axes onto the cross-sectional image. The in-plane angle setting unit 228 includes an image rotation unit 229 that performs image rotation processing. The image rotation unit 229 rotates the cross-sectional image by the set angle to generate a cross-sectional image whose horizontal or vertical direction is parallel to a line formed by projecting one axis selected from the three device axes onto the cross-sectional image. The cross-sectional image thus aligned in the correct orientation is stored in the cross-sectional image storage unit 236. The cross-sectional image storage unit 236 is a storage area of ​​the memory 204 and / or the storage 206.

[0163] The body surface extraction unit 230 includes a trained AI model 231, and extracts the body surface BS of the subject 130 from the 3D scanogram image using the AI ​​model 231. The AI ​​model 231 may be, for example, an image recognition model configured using a convolutional neural network and trained to perform a region classification (semantic segmentation) task. The AI ​​model 231 is an example of a "second artificial intelligence model" in this disclosure.

[0164] The body axis center setting unit 232 sets the body axis center based on the body surface extraction result by the body surface extraction unit 230. The structure center calculation unit 234 calculates the center point of the structure in the cross section based on the body axis center and the cut cross section.

[0165] Information about the center point of the structure is sent to the imaging field of view setting unit 240. The imaging field of view setting unit 240 provides a recommended imaging field of view (FOV) setting depending on the type of reference cross section. The imaging field of view setting unit 240 sets the positional relationship between the cross-sectional image and the imaging field of view so that the center of the structure in the cross section coincides with the center of the imaging field of view. The imaging field of view setting unit 240 can also accept a change in the setting of the imaging field of view via the input device 212 and change the setting of the imaging field of view in accordance with the accepted change instruction.

[0166] The imaging position setting unit 242 sets the imaging position of each slice in the main imaging based on the setting of the imaging field of view setting unit 240. The display image generation unit 244 performs processing to generate various display images to be displayed on the display device 214. The display control unit 246 generates display signals required for display output to the display device 214 and controls the display of the display device 214. The images generated by the display image generation unit 244 are displayed on the display device 214 via the display control unit 246.

[0167] [Hardware configuration of each processing unit] The hardware structure of the processing units that execute various processes, such as the scanogram image acquisition unit 220, landmark detection unit 222, imaging section determination unit 224, cross-sectional image generation unit 226, in-plane angle setting unit 228, image rotation unit 229, body surface extraction unit 230, body axis center setting unit 232, structure center calculation unit 234, imaging field of view setting unit 240, imaging position setting unit 242, display image generation unit 244, and display control unit 246 of the information processing device 200, is, for example, various processors as shown below.

[0168] Various types of processors include CPUs, which are general-purpose processors that execute programs and function as various processing units, GPUs, which are processors specialized for image processing, programmable logic devices (PLDs), such as FPGAs (Field Programmable Gate Arrays), which are processors whose circuit configuration can be changed after manufacturing, and dedicated electrical circuits, such as ASICs (Application Specific Integrated Circuits), which are processors with circuit configurations designed specifically to execute specific processes.

[0169] A single processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types. For example, a single processing unit may be configured with multiple FPGAs, or a combination of a CPU and an FPGA, or a combination of a CPU and a GPU. Alternatively, multiple processing units may be configured with a single processor. Examples of multiple processing units configured with a single processor include, first, a configuration in which a single processor is configured with a combination of one or more CPUs and software, as typified by client or server computers, and this processor functions as multiple processing units. Second, a configuration in which a processor is used to realize the functions of an entire system including multiple processing units on a single IC (Integrated Circuit) chip, as typified by a system-on-chip (SoC). In this way, the various processing units are configured with one or more of the above-mentioned various processors as a hardware structure.

[0170] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit made up of a combination of circuit elements such as semiconductor elements.

[0171] [Regarding programs that operate computers] A program that causes a computer to realize some or all of the processing functions of the information processing device 200 can be recorded on a computer-readable medium such as an optical disk, a magnetic disk, a semiconductor memory, or other tangible non-transitory information storage medium, and the program can be provided through this information storage medium.

[0172] In addition, instead of providing the program by storing it on such a tangible, non-transitory computer-readable medium, it is also possible to provide the program signal as a download service using a telecommunications line such as the Internet.

[0173] Furthermore, some or all of the processing functions of the information processing device 200 may be realized by cloud computing, and may also be provided as SaaS (Software as a Service).

[0174] [Advantages of this embodiment] The MRI apparatus 10 according to this embodiment has the following advantages.

[0175] [1] When generating a cross-sectional image of a reference cross section from a 3D scanogram image, the processor 202 sets the horizontal or vertical direction of the cross-sectional image by referring to a straight line projected onto the cross-sectional image from the axis of the device that defines the three-dimensional Cartesian coordinate system of the real space including the imaging space 18. Therefore, regardless of the subject, the structures in the cross section are displayed at the same angle on the screen of the display device 214.

[0176] [2] It is possible to output cross-sectional images at an angle that reduces structures outside the imaging field of view in the phase encoding direction, which can cause artifacts. This reduces aliasing artifacts.

[0177] [3] In particular, by aligning the center of the structure in the cross section with the center of the imaging field of view, structures outside the imaging field of view that can cause artifacts can be minimized.

[0178] [4] According to this embodiment, the position and imaging range of the cross section recommended as the imaging position for the actual scan are automatically calculated from the 3D scanogram image, and information on the automatically set FOV is provided along with the cross section image. This improves the efficiency of the work of determining the imaging position for cardiac MRI examinations.

[0179] [5] On the screen of the display device 214 that displays the cross-sectional image generated from the 3D scanogram image, a frame (imaging field of view frame) indicating the area of ​​the imaging field of view (FOV) by automatic positioning is presented as an upright rectangular frame that matches the vertical and horizontal orientation of the screen. This allows the user to easily understand the positional relationship between the imaging field of view (FOV) and the structure in the cross section.

[0180] [Variation 1] Steps S4 to S6 in FIG. 6 may be omitted.

[0181] [Variation 2] The landmark detection process in step S2 is not limited to a configuration using AI, and instead of or in combination with AI, image processing methods such as pattern recognition and feature point extraction may be applied. Similarly, the body surface extraction process in step S4 is not limited to a configuration using AI, and instead of or in combination with AI, a known method may be applied, such as extracting a region with an image density equal to or higher than a reference density as a subject region and extracting its boundary as the body surface.

[0182] [Variation 3] In the above embodiment, an example has been described in which the imaging field of view frame is automatically displayed simultaneously with the cross-sectional image in the cross-sectional display process of step S8. However, the present invention is not limited to this example. For example, the process may be automated up to the point where the cross-sectional image without the imaging field of view frame is displayed, and after the cross-sectional image is displayed, an instruction to set the imaging field of view FOV is input via the UI, and the imaging field of view frame may be displayed on the cross-sectional image.

[0183] [Variation 4] In the above-described embodiment, the horizontal direction (lateral direction) on the image when the imaging field of view FOV is set is set as the phase encoding direction as shown in Fig. 10, but the vertical direction (vertical direction) on the image can also be set as the phase encoding direction. In this case, the processor 202 sets the angle for rotating the cross-sectional image so as to minimize structures outside the imaging field of view FOV in the vertical direction, which is the phase encoding direction, preferably so that no structures exist outside the imaging field of view FOV in the phase encoding direction, and adjusts the orientation of the cross-sectional image by the rotation process.

[0184] 〔others〕 The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the technical idea of ​​the present disclosure. [Explanation of symbols]

[0185] 10 MRI machine 12 Gantry 14 berths 15 Top plate 16 Legs 18 Imaging Space 102 Static magnetic field generating magnet 104 Gradient magnetic field coil 106 RF transmit coil 110 receiving coil 112 Receiver 114 Gradient magnetic field power supply 116 High Frequency Magnetic Field Generator 118 Sequencer 120 control section 122 Operation section 130 subjects 200 Information processing device 202 processors 204 memory 206 Storage 208 Input / Output Interface 210 Bus 212 Input Device 214 Display device 220 Scanogram image acquisition unit 222 Landmark detection unit 223 AI models 224 Imaging section determination unit 226 Cross-sectional image generation unit 228 In-plane angle setting section 229 Image Rotation Unit 230 Body surface extraction part 231 AI models 232 Body axis center setting unit 234 Structure center calculation part 236 Cross-sectional image storage section 240 Imaging field setting unit 242 Imaging position setting unit 244 Display image generation unit 246 Display control unit A double arrow BC body axis center BS body surface CS cross section F4A left diagram F4B right image F7A, F7B, F7C images F8A, F8B, F8C, F8D, F8E, F8F Images F9A cross-sectional image F9B Cube F9C crossing diagram F10A cross-sectional image F10B Cube F10C cross line diagram F13A, F13B, F13C, F13D images FOV (field of view) Lx line P1 points P2 Points Pc intersection S1~S10 Steps of the positioning assistance method

Claims

1. A magnetic resonance imaging apparatus comprising a processor and a memory, and configured to generate an image of a subject based on nuclear magnetic resonance, The processor: obtaining a three-dimensional image including the heart of the subject by scanogram imaging performed prior to the main imaging; detecting landmarks of the heart from the three-dimensional image; Setting the position of the cross section based on the landmark; generating a cross-sectional image appearing on the cross section from the three-dimensional image; setting the horizontal or vertical direction of the cross-sectional image so that the horizontal or vertical direction of the cross-sectional image is parallel to a straight line obtained by projecting one axis selected from three axes forming a three-dimensional orthogonal coordinate system in real space onto the cross-sectional image; storing the cross-sectional image in the memory; Magnetic resonance imaging device.

2. The processor: rotating the cross-sectional image at an angle such that the horizontal or vertical direction of the cross-sectional image is parallel to the straight line projected onto the cross-sectional image; storing the rotated cross-sectional image in the memory; 2. The magnetic resonance imaging apparatus according to claim 1.

3. Further comprising a display device, The processor: displaying the cross-sectional image on the display device; 2. The magnetic resonance imaging apparatus according to claim 1.

4. The processor: generating a display image in which a frame indicating a region of the imaging field of view is superimposed on the cross-sectional image; 2. The magnetic resonance imaging apparatus according to claim 1.

5. the frame indicating the area of ​​the imaging field of view displayed on the cross-sectional image is a rectangular frame surrounded by a pair of opposite sides parallel to the horizontal direction of the cross-sectional image and a pair of opposite sides parallel to the vertical direction of the cross-sectional image; 5. The magnetic resonance imaging apparatus according to claim 4.

6. The processor: detecting the landmarks using a first artificial intelligence model that has been trained by machine learning; 2. The magnetic resonance imaging apparatus according to claim 1.

7. The processor: extracting a body surface from the three-dimensional image; setting a body axis center based on the extracted body surface; setting a center of a structure in the cross section based on the body axis center; setting the imaging field of view for the cross-sectional image so that the center of the imaging field of view coincides with the center of the structure in the cross-section; 2. The magnetic resonance imaging apparatus according to claim 1.

8. The processor: extracting the body surface using a second artificial intelligence model trained by machine learning; 8. The magnetic resonance imaging apparatus according to claim 7.

9. The horizontal or vertical direction of the cross-sectional image is a phase encoding direction.

2. The magnetic resonance imaging apparatus according to claim 1.

10. The slices include slices that can obtain at least one of a left ventricular short-axis image, a horizontal long-axis image, a four-chamber long-axis image, a two-chamber long-axis image, and a three-chamber long-axis image.

2. The magnetic resonance imaging apparatus according to claim 1.

11. the cross section is a reference cross section from which a left ventricular short-axis image can be obtained, The processor: When the cross section includes a component in the AP direction, which is the anterior-posterior direction of the subject, the cross section image is rotated at an angle such that the horizontal direction of the cross section image is parallel to a straight line obtained by projecting the AP axis as the one axis onto the cross section image.

2. The magnetic resonance imaging apparatus according to claim 1.

12. The processor: When the cross section does not include a component in the AP direction, the horizontal and vertical directions of the cross section image are set to be the same as the horizontal and vertical directions of the coronal cross section image.

12. The magnetic resonance imaging apparatus according to claim 11.

13. the cross section is a reference cross section for obtaining a horizontal long-axis image, The processor: When the cross section includes a component in the RL direction, which is the left-right direction of the subject, the cross section image is rotated at an angle such that the horizontal direction of the cross section image is parallel to a straight line obtained by projecting the RL axis as the one axis onto the cross section image.

2. The magnetic resonance imaging apparatus according to claim 1.

14. The processor: When the cross section does not include a component in the RL direction, the horizontal and vertical directions of the cross section image are set to be the same as the horizontal and vertical directions of the sagittal cross section image.

14. The magnetic resonance imaging apparatus according to claim 13.

15. The cross section is a reference cross section from which a four-chamber long-axis image can be obtained, The processor: When the cross section includes a component in the RL direction, which is the left-right direction of the subject, the cross section image is rotated at an angle such that the horizontal direction of the cross section image is parallel to a straight line obtained by projecting the RL axis as the one axis onto the cross section image.

2. The magnetic resonance imaging apparatus according to claim 1.

16. The processor: When the cross section does not include a component in the RL direction, the horizontal and vertical directions of the cross section image are set to be the same as the horizontal and vertical directions of the sagittal cross section image.

16. A magnetic resonance imaging apparatus according to claim 15.

17. the cross section is a reference cross section from which a two-chamber long-axis image can be obtained, The processor: When the cross section includes a component in the HF direction, which is the head-to-foot direction of the subject, the cross section image is rotated at an angle such that the vertical direction of the cross section image is parallel to a straight line obtained by projecting the HF axis as the one axis onto the cross section image.

2. The magnetic resonance imaging apparatus according to claim 1.

18. The processor: When the cross section does not include a component in the HF direction, the horizontal and vertical directions of the cross section image are set to be the same as the horizontal and vertical directions of the axial cross section image.

18. A magnetic resonance imaging apparatus according to claim 17.

19. The cross section is a reference cross section from which a three-chamber long-axis image can be obtained, The processor: When the cross section includes a component in the AP direction, which is the anterior-posterior direction of the subject, the cross section image is rotated at an angle such that the vertical direction of the cross section image is parallel to a straight line obtained by projecting the AP axis as the one axis onto the cross section image.

2. The magnetic resonance imaging apparatus according to claim 1.

20. The processor: When the cross section does not include a component in the AP direction, the horizontal and vertical directions of the cross section image are set to be the same as the horizontal and vertical directions of the coronal cross section image.

20. The magnetic resonance imaging apparatus according to claim 19.

21. A positioning support method for supporting setting of an imaging position by a magnetic resonance imaging apparatus, comprising: The processor: acquiring a three-dimensional image including the heart of the subject by scanogram imaging performed prior to the main imaging; detecting the cardiac landmarks from the three-dimensional image; setting the position of the cross section based on the landmark; generating a cross-sectional image appearing on the cross section from the three-dimensional image; setting the horizontal or vertical direction of the cross-sectional image so that the horizontal or vertical direction of the cross-sectional image is parallel to a straight line obtained by projecting one axis selected from three axes forming a three-dimensional orthogonal coordinate system in real space onto the cross-sectional image; storing the cross-sectional image in a memory; Execute the positioning assistance method.

22. A program that causes a computer to execute the positioning support method according to claim 21.

Images