Projection control device, operation method of projection control device, and operation program of projection control device

Abstract

Provided are a projection control device, an operating method for the projection control device, and an operating program for the projection control device that can guide the user to the appropriate mounting position of a receiving coil unit without performing radiography when imaging the liver with an MRI device. [Solution] The projection control device is equipped with a processor, which acquires an optical image of the subject, estimates the position of the subject's liver based on the optical image, and controls the projection device to project a mark indicating the estimated liver position onto the subject as a mark indicating the position where a receiving coil unit of a magnetic resonance imaging device will be attached.

Description

[Technical Field]

[0001] The present disclosure relates to a projection control device, an operating method for a projection control device, and an operating program for a projection control device. [Background technology]

[0002] A magnetic resonance imaging (MRI) device irradiates a subject placed in an imaging region with high-frequency RF (Radio Frequency) pulses, and uses the nuclear magnetic resonance (NMR) phenomenon that occurs when this occurs to capture images that represent the physical or chemical properties of the subject, and is particularly used for medical purposes.

[0003] When an RF pulse is applied to hydrogen atoms in a subject, which are aligned in a static magnetic field, the hydrogen atoms absorb energy from the RF pulse and become excited. When the RF pulse stops, the excited hydrogen atoms attempt to return to their original aligned state, releasing the energy they absorbed in the process. This is the NMR phenomenon, and the hydrogen atoms generate a magnetic resonance signal called an FID (Free Induction Decay signal) that corresponds to the energy they release. MRI systems image the structures inside the subject based on the received FID signal. Because the FID signal is very weak, when imaging with an MRI system, a receiving coil unit that receives the FID signal is attached to a position corresponding to the area of ​​the subject that needs to be imaged. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2024-082179 Summary of the Invention [Problem to be solved by the invention]

[0005] The receiver coil unit attached to the subject is detached and carried around after each imaging session, so miniaturization is desirable. However, miniaturization narrows the coverage area of ​​the receiver coil unit, which poses a problem of narrowing the tolerance for misalignment of the receiver coil unit attachment position.

[0006] This problem is particularly pronounced when imaging the liver. The liver is an organ whose position changes relatively significantly depending on the subject's physique, making it difficult to estimate its position from outside the body. When using a small receiving coil unit, the degree of positional deviation that is tolerated by a large receiving coil unit cannot be tolerated, and the unit may end up being attached to the wrong position for the liver. If the receiving coil unit is not attached in the appropriate position, it is naturally impossible to image the target area, and re-imaging is required.

[0007] One possible solution to this problem would be to determine the position of the subject's liver by radiography before the MRI scan, but this approach has the disadvantage of complicating the device configuration and exposing the subject to radiation, making it difficult to adopt.

[0008] The technology disclosed herein provides a projection control device, an operating method for the projection control device, and an operating program for the projection control device that can guide the appropriate mounting position of a receiving coil unit without performing radiation imaging when imaging the liver with an MRI device. [Means for solving the problem]

[0009] A projection control device according to the technique of the present disclosure includes a processor, the processor acquiring an optical image of a subject, estimating a position of the subject's liver based on the optical image, By controlling the projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating the position where the receiving coil unit of the magnetic resonance imaging device is attached.

[0010] The processor may also derive the obesity level of the subject based on the optical image, and estimate the position of the liver according to the derived obesity level.

[0011] The processor may derive the degree of obesity based on a first evaluation value defined as a ratio of the length from the shoulder to the waist in the body axis direction of the subject to the body thickness.

[0012] The processor may derive the obesity level based on the first evaluation value as well as a second evaluation value defined as the ratio of the body thickness at the navel to the average body thickness of the trunk.

[0013] The processor may estimate the position of the liver of the subject using reference information that stores in advance the correspondence between the degree of obesity and the position of the liver.

[0014] The optical images may include a front image taken from the front of the subject and a side image taken from the side.

[0015] The optical images may include two front images with parallax, taken from the front of the subject.

[0016] The processor may estimate the position of the subject's liver using a machine learning model that takes the optical image as input and outputs the position of the subject's liver.

[0017] The method of operating a projection control device according to the disclosed technology is a method of operating a projection control device equipped with a processor, in which the processor acquires an optical image of a subject, estimates the position of the subject's liver based on the optical image, and controls a projection device to project a mark indicating the estimated liver position onto the subject as a mark indicating the position where a receiving coil unit of a magnetic resonance imaging device is attached.

[0018] The operating program of the projection control device according to the technology of the present disclosure is an operating program of a projection control device equipped with a processor, which causes the processor to execute processes including acquiring an optical image of the subject, estimating the position of the subject's liver based on the optical image, and controlling the projection device to project a mark indicating the estimated position of the liver onto the subject as a mark indicating the position where a receiving coil unit of a magnetic resonance imaging device should be installed. [Effects of the Invention]

[0019] According to the technology of the present disclosure, when imaging the liver with an MRI apparatus, it is possible to guide the appropriate mounting position of the receive coil unit without performing radiation imaging. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of an MRI apparatus. [Figure 2] FIG. 2 is a diagram showing an example of a state in which a receiving coil unit is attached to a subject; [Figure 3] FIG. 2 illustrates an example of the functions of a processor. [Figure 4] FIG. 10 is a diagram illustrating an example of the relationship between physique and liver position. [Figure 5] FIG. 10 is a diagram illustrating an example of reference information indicating a correspondence relationship between an obesity level and a liver position. [Figure 6] FIG. 10 is a diagram showing the relative positional relationship between the spine and the liver. [Figure 7] FIG. 10 is a diagram showing an example of a first evaluation value of obesity level. [Figure 8] 10 is a flowchart illustrating an example of an overall processing procedure of a projection process. [Figure 9] 10 is a flowchart illustrating an example of a processing procedure for deriving an obesity level. [Figure 10] FIG. 10 is a diagram showing an example of measuring spinal length from an optical image. [Figure 11] FIG. 10 is a diagram showing an example of measuring body thickness from an optical image. [Figure 12]FIG. 10 is a diagram showing an example of a state in which a liver marker is projected onto a subject. [Figure 13] FIG. 10 is a diagram for explaining a second evaluation value. [Figure 14] 10 is an example of reference information showing the relationship between the first evaluation value, the second evaluation value and the obesity degree. [Figure 15] FIG. 10 is a diagram illustrating an example of deriving an obesity level using a machine learning model. [Figure 16] FIG. 10 is a diagram illustrating an example in which a stereo camera is used. DETAILED DESCRIPTION OF THE INVENTION

[0021] [First embodiment] 1 and 2 are schematic diagrams showing an example of an MRI apparatus 10. As an example, the MRI apparatus 10 is a closed-type apparatus having a cylindrical bore 11. In addition to the bore 11, the MRI apparatus 10 includes a bed 12 and a console 13. As is well known, the bore 11 has an opening through which the subject H can enter, and the bore 11 houses a static magnetic field magnet for generating a static magnetic field, a gradient magnetic field coil for generating a gradient magnetic field, and an RF transmission coil for transmitting RF pulses. The bed 12 has a top board 12A on which the subject H can be placed in a supine position. The top board 12A can be slid horizontally to enter the opening of the bore 11. The bed 12 also has a belt 12B for fixing a receiving coil unit 16 worn by the subject H. The console 13 has a control unit 14 that controls each part of the MRI apparatus 10.

[0022] The receiving coil unit 16 receives an FID signal generated by hydrogen atoms excited by irradiation of RF pulses within the subject H. The receiving coil unit 16 is composed of multiple receiving coils and an exterior material that houses the multiple receiving coils in an array. The exterior material is flexible and curves along the body surface of the subject H. Here, the body surface refers to the outer surface of the subject H when clothed. By the exterior material curving along the body surface, it is possible to position the receiving coils close to the body surface. Conventionally, exterior materials were mainly configured to curve as a whole by movably connecting multiple hard parts made of a hard resin material, but in recent years, exterior materials made of flexible fabric have become more common. The receiving coil unit 16 of this example shown in Figures 1 and 2 is an example of a type in which the exterior material is made of flexible fabric. The receiving coil unit 16 is attached to the torso of the subject H and has, for example, a rectangular planar shape.

[0023] 2, the receiving coil unit 16 is attached by an operator OP such as a radiological technologist to a position corresponding to a region of the subject H that is to be imaged. If the region to be imaged is the liver, the receiving coil unit 16 is attached to a position corresponding to the liver. The receiving coil unit 16 is detachable from the subject H, and, as an example, is attached so as to cover the front side of the subject H in a supine position.

[0024] A receiving coil is built into the top board 12A of the bed 12, and the FID signal emitted from the back side of the subject H is received by the receiving coil in the top board 12A.

[0025] The MRI apparatus 10 further includes a projection system 21. The projection system 21 estimates the position of the liver of the subject H, and projects a mark M representing the estimated liver position onto the body surface of the subject H, as shown in FIG. 1. The projection system 21 includes optical cameras 22 and 23, a projection device 24, and a control unit 14. The control unit 14 serves as both the control unit for the MRI apparatus 10 and the control unit for the projection system 21. Of course, these control units may be configured separately.

[0026] The optical cameras 22 and 23 optically capture images of the subject H. The optical cameras 22 and 23 capture optical images of the subject H generated by, for example, visible light. The optical cameras 22 and 23 have an imaging optical system that focuses the light of the subject H, and an image sensor that outputs the focused optical image as an electrical image signal. The image sensor is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor.

[0027] The optical camera 22 captures an image of the subject H lying supine on the bed 12 from the front, and outputs a front image FV to the control unit 14 as an optical image of the subject H. The optical camera 22 is disposed, for example, on the ceiling of an imaging room in which the MRI apparatus 10 is installed.

[0028] The optical camera 23 photographs the subject H lying supine on the bed 12 from the side, and outputs a side image SV as an optical image of the subject H to the control unit 14. The optical camera 23 is disposed, for example, on a wall of the imaging room or on a stand installed on the side of the bed 12.

[0029] The projection device 24 projects projection light PL representing the mark M toward the subject H, thereby projecting the mark M onto the body surface of the subject H. The projection device 24 has a display unit that displays the mark M, and a projection optical system that projects projection light PL representing the mark M displayed on the display unit. The display unit may be, for example, a transmissive type configured by combining an LCD (Liquid Crystal Display) with a light source, or a reflective type configured by combining a DLP (Digital Light Processing) with a light source.

[0030] As shown in FIG. 3 , the control unit 14 includes a processor 31 and a storage 32. The processor 31 is configured with, for example, a central processing unit (CPU) and memory such as a random access memory (RAM), and performs projection control of the projection system 21 by executing a program loaded into the memory. The control unit 14 is an example of a "projection control device" according to the technology of the present disclosure. The storage 32 is a data storage that stores programs, setting information, reference information RF, etc., and is configured with a hard disk drive, a solid-state drive, a non-volatile memory, etc. The programs include an application program that causes the processor 31 to function as the control unit 14. This program is an example of an "operating program" according to the technology of the present disclosure.

[0031] The projection control executed by the processor 31 includes a process of estimating the position of the liver of the subject H by image analysis of the optical images of the front image FV and the side image SV acquired from the optical cameras 22 and 23, and a process of determining a projection position according to the estimated liver position and projecting a marker M at the projection position. The reference information RF stored in the storage 32 is information that the processor 31 refers to when executing the projection control. The reference information RF includes reference information RF1 that indicates the correspondence between the physique of the subject H (obesity level in the example of FIG. 3) and the liver position. The reference information RF will be described later. The marker M is, for example, an image that imitates the shape of the liver. The image used for the marker M is included in the setting information.

[0032] Figure 4 shows how the position of the liver LV changes depending on a person's physique. Regardless of height, the position of the liver LV changes along the body axis depending on the degree of obesity. Specifically, the higher the degree of obesity, the more the liver LV shifts toward the head, and the lower the degree of obesity, the more the liver LV shifts toward the feet. This is thought to be because when there is a lot of abdominal fat, the fat pushes the liver LV toward the head.

[0033] Reference information RF1 shown in FIG. 5 shows an example of the results of statistically analyzing the correspondence between such obesity levels and the position of the liver LV. Reference information RF1 classifies obesity levels into three stages, A to C, and shows the liver position for each level. The obesity levels are A, B, and C in increasing order. LPA, LPB, and LPC, which indicate the liver position, correspond to the obesity levels A, B, and C, respectively. In reference information RF1, the liver position is expressed relative to the spine.

[0034] In Figure 6, Figure 6(A) is a schematic diagram of the spine viewed from the side, and Figure 6(B) is a schematic diagram of the spine viewed from the front. Figure 6(C) shows the liver positions (LPA to LPC) in correspondence with the schematic diagram of the spine. The spine is a bony part extending along the body axis from the neck to the lower abdomen, and includes the cervical vertebrae corresponding to the neck, the thoracic vertebrae corresponding to the chest, and the lumbar vertebrae corresponding to the lower back, arranged in order from the head side. The cervical vertebrae are made up of seven blocks, from the first cervical vertebra C1 to the seventh cervical vertebra C7, arranged in order from the head side. The thoracic vertebrae are made up of 12 blocks, from the first thoracic vertebra T1 to the twelfth thoracic vertebra T12, arranged in order from the head side. The lumbar vertebrae are made up of five blocks, from the first lumbar vertebra L1 to the fifth lumbar vertebra L5, arranged in order from the head side.

[0035] Each of the liver positions LPA to LPC is set based on SL, which is the length of the spine from the seventh cervical vertebra C7 to the fifth lumbar vertebra L5. Here, SL is not the entire length of the spine, but is conveniently referred to as the spinal length, since it represents the length of a specific region of the spine. In the body axis direction, the seventh cervical vertebra C7 corresponds to the shoulder joint, and the fifth lumbar vertebra L5 corresponds to the iliac crest. In the reference information RF1 shown in FIG. 5, when the obesity level is Level A, the liver position is 2 / 7 of the spinal length SL, as viewed from the seventh cervical vertebra C7 side. This position is indicated by 2 / 7(LPA) in FIG. 6(C). Similarly, when the obesity level is Level B, the liver position is 3 / 7 of the spinal length SL, as viewed from the seventh cervical vertebra C7 side. This position is indicated by 3 / 7(LPB) in FIG. 6(C). Similarly, when the obesity level is level C, the liver position is at 4 / 7 of the 7 equal parts of the spinal length SL, as seen from the 7th cervical vertebra C7 side. This position is shown as 4 / 7(LPC) in Figure 6(C). Thus, as the obesity level increases, the liver position shifts more toward the head.

[0036] Reference information RF2 shown in FIG. 7 defines the obesity level levels A to C. As shown in reference information RF2, the levels A to C are classified based on the value of the first evaluation value V1. The first evaluation value V1 is defined as SL / Tmax. The first evaluation value V1 is an example of an evaluation value of the obesity level. As described above, SL is the spinal length from the seventh cervical vertebra C7 to the fifth lumbar vertebra L5. Tmax is the maximum value of the body thickness in the section of the spinal length SL, and will be referred to as the maximum body thickness hereinafter (see FIG. 11). In this example, the obesity level is derived from the first evaluation value V1, which is the ratio of the spinal length SL to the maximum body thickness Tmax. The spinal length SL is a value that increases with height. For the same height, the larger the value of the maximum body thickness Tmax, which is the denominator, the higher the obesity level. For the same maximum body thickness Tmax, the smaller the value of the spinal length SL, which is the numerator, the higher the obesity level. In other words, the smaller the first evaluation value V1, the higher the level of obesity. If the first evaluation value V1 is less than 1.5, the obesity level is classified as level A. If the first evaluation value V1 is 1.5 to 2.0, the obesity level is classified as level B. If the first evaluation value V1 is 2.0 or more, the obesity level is classified as level C.

[0037] The processor 31 uses such reference information RF1 and reference information RF2 to estimate the position of the liver.

[0038] The operation of the above configuration will be described below with reference to Fig. 8 to Fig. 12. Fig. 8 is a flowchart showing the overall processing procedure for projecting the liver position. Fig. 9 shows sub-steps of step S1200 incorporated in the flowchart shown in Fig. 8.

[0039] When performing imaging using the MRI apparatus 10, the operator OP first places the subject H in a supine position on the bed 12. In this state, as shown in Figures 1 and 2, the top plate 12A of the bed 12 is outside the opening of the bore 11, and the subject H has not entered the opening of the bore 11. In this state, the operator OP issues an instruction to the projection system 21 from the console 13 to execute projection processing of the liver position in order to attach the receiving coil unit 16 to the subject H.

[0040] As shown in FIG. 8, first, in step S1100, the processor 31 of the projection system 21 causes the optical cameras 22 and 23 to perform imaging and acquire optical images including a front image FV and a side image SV of the subject H on the bed 12.

[0041] In step S1200, the processor 31 derives the obesity level based on the optical image. As shown in Fig. 9, first, in step S1210, the processor 31 detects feature points PP from the front image FV. The detection of feature points PP is performed, for example, as shown in Fig. 10. For example, the processor 31 extracts the contour of the subject H from the front image FV, and detects feature points PP corresponding to the left and right shoulder joints and the left and right iliac crests using a preset pattern matching method based on the extracted contours.

[0042] The relative positional relationships between the feature point PP and each of the seventh cervical vertebra C7 and the fifth lumbar vertebra L5 are set in advance. For example, the seventh cervical vertebra C7 is located at approximately the same height as the feature points PP of the left and right shoulder joints in the body axis direction. The fifth lumbar vertebra L5 is located at approximately the same height as the feature points PP of the left and right iliac crests in the body axis direction.

[0043] In step S1220, the processor 31 detects the seventh cervical vertebra C7 and the fifth lumbar vertebra L5 from the feature point PP based on the relative positional relationship with the feature point PP. In Fig. 10, the spine is shown in the front image FV for convenience's sake to clearly show the positions of the seventh cervical vertebra C7 and the fifth lumbar vertebra L5, and of course the spine is not actually shown in the front image FV.

[0044] In step S1230, the processor 31 measures the distance between the detected seventh cervical vertebra C7 and the fifth lumbar vertebra L5 as the spinal length SL.

[0045] 9, after step S1230, the processor 31 proceeds to step S1240. In step S1240, the processor 31 measures the maximum body thickness Tmax from the side image SV.

[0046] Fig. 11 conceptually illustrates how the maximum body thickness Tmax is measured based on the lateral image SV. The processor 31 extracts the contour of the subject H from the lateral image SV and measures the distance between the upper and lower contour lines as the body thickness. The processor 31 then records the maximum body thickness value as the maximum body thickness Tmax. In Fig. 11, the lateral image SV on the left shows the subject H with a relatively low level of obesity, and the lateral image SV on the right shows the subject H with a relatively high level of obesity. The subject H with a high level of obesity on the right has a thicker overall body thickness in the trunk area and a thicker maximum body thickness Tmax than the subject H on the left.

[0047] 9, after step S1240, the processor 31 proceeds to step S1250. In step S1250, the processor 31 derives the ratio of the measured spinal length SL to the maximum body thickness Tmax as a first evaluation value V1. In step S1260, the processor 31 derives the obesity level based on the value of the derived first evaluation value V1, using the reference information RF2 shown in FIG.

[0048] 8, after step S1200, the processor 31 proceeds to step S1300. In step S1300, the processor 31 estimates liver positions LPA to LPC according to the derived obesity levels A to C, based on the reference information RF1 shown in FIG.

[0049] In step S1400, the processor 31 projects a marker M representing the estimated liver position. The relative positional relationship between the optical camera 22 and the projection device 24 is known. The distances between the optical camera 22 and the projection device 24 and the tabletop 12A on which the subject H lies supine are also known. The processor 31 can determine the distance to the body surface of the subject H onto which the marker M is projected by subtracting the body thickness of the subject H from the side image SV from the distance to the tabletop 12A. The processor 31 can also determine the body width of the subject H from the front image FV captured by the optical camera 22. Based on this information, the processor 31 derives the actual projection position on the body surface of the subject H corresponding to the estimated liver position and the projection size of the marker M. The processor 31 controls the projection device 24 based on the projection position and projection size thus determined.

[0050] 12 (see also FIG. 1), the processor 31 controls the projection device 24 in accordance with the derived projection position and projection size, thereby projecting a marker M onto a position corresponding to the liver position of the subject H on the bed 12. Then, as shown in FIG. 12 (see also FIG. 2), the operator OP determines the attachment position of the receiving coil unit 16 in the body axis direction using the marker M as a guide, and attaches the receiving coil unit 16 to the subject H. In this manner, imaging is performed by the MRI apparatus 10 with the receiving coil unit 16 attached in an appropriate position.

[0051] As described above, the projection control device according to the technique of the present disclosure, shown as the control unit 14 as an example, includes the processor 31. The processor 31 acquires optical images of the subject H (for example, a front image FV and a lateral image SV) and estimates the position of the liver of the subject H based on the optical images. The processor 31 then controls the projection device 24 to project a mark M indicating the estimated position of the liver LV onto the subject H as a mark indicating the position where the receive coil unit 16 of the MRI apparatus 10 is to be attached. This makes it possible to guide the subject H to an appropriate attachment position of the receive coil unit 16 when imaging the liver LV with the MRI apparatus 10 without performing radiography.

[0052] The liver LV has a width that changes in the body axis direction depending on the physique of the subject H, which is greater than that of other organs, making it difficult to determine from the outside. Therefore, it may be difficult to properly attach the receiving coil unit 16 to a position corresponding to the position of such a liver LV. This difficulty becomes particularly pronounced when the receiving coil unit 16 is made smaller (specifically, when the length in the body axis direction is shortened). According to the technology of the present disclosure, a mark M indicating the position of the liver LV can be projected onto the body surface of the subject H, so the operator OP can grasp the position of the liver LV at a glance. Therefore, it is easy to find an appropriate attachment position for the receiving coil unit 16.

[0053] In the above embodiment, the processor 31 derives the obesity degree of the subject H based on the optical image, and estimates the position of the liver LV according to the derived obesity degree. As shown in Fig. 4, the obesity degree and the position of the liver LV are correlated, so estimating the position of the liver according to the obesity degree is effective in improving the estimation accuracy.

[0054] Furthermore, in the above embodiment, the processor 31 derives an obesity index based on a first evaluation value V1 defined as the ratio of the length (for example, the spinal length SL) from the shoulder (for example, the shoulder joint) to the waist (for example, the iliac crest) in the body axis direction of the subject H to the body thickness (for example, the maximum body thickness Tmax), and estimates the position of the liver LV of the subject H based on the derived obesity index. Such a first evaluation value V1 is an evaluation value based on a statistical analysis of a person's physique, and therefore has high validity.

[0055] In the above embodiment, the processor 31 estimates the position of the liver LV of the subject H using reference information (for example, reference information RF1) that stores in advance the correspondence between the obesity degree and the position of the liver LV. Using the reference information RF1 may simplify the calculation process compared to using a function.

[0056] Furthermore, in the above embodiment, the optical image includes a front image FV captured from the front of the subject H and a side image SV captured from the side. This allows the obesity degree to be derived based on the body thickness measured from the side image SV as described above. Therefore, the obesity degree can be determined more accurately than when the obesity degree is derived using only information measurable from the front image FV (such as body width).

[0057] [Second embodiment] 13 and 14 is an example in which a second evaluation value V2 is used in addition to a first evaluation value V1 as an evaluation value for deriving obesity levels A to C. As shown in Fig. 14, the second evaluation value V2 is defined as Tb / Tav, where Tb is the body thickness at the navel position, Tav is, for example, the average body thickness in the section of the spine length SL, and the second evaluation value V2 is the ratio of Tb to Tav.

[0058] Even if the maximum body thickness Tmax is the same, the position of the liver LV may differ depending on factors such as muscle structure. As shown in Figure 13, in subject H in the upper row (Figure 13(A)), the body thickness Tb at the navel and the maximum body thickness Tmax coincide, whereas in subject H in the lower row (Figure 13(B)), the body thickness Tb at the navel and the maximum body thickness Tmax do not coincide, and the maximum body thickness Tmax is shifted toward the head. Subject H in Figure 13(A) shows a typical obese body type with a lot of fat, while Figure 13(B) shows the body type of an athlete with well-developed pectoral muscles, such as a hammer thrower or wrestler. In the typical obese case of Figure 13(A), the liver position shifts toward the head due to pressure from abdominal fat, as shown in Figure 4. In contrast, in a muscular case such as Figure 13(B), the pectoral muscles are thought to inhibit the shift of the liver LV toward the head, so the liver position often remains toward the abdomen rather than shifting toward the head as in Figure 13(A). Therefore, there are cases where the first evaluation value V1, which simply uses only the maximum body thickness Tmax, is not enough to distinguish between the normal obese type and the muscular type and evaluate the degree of obesity, as shown in Fig. 13. Therefore, in addition to the first evaluation value V1, the second evaluation value V2 is taken into consideration.

[0059] The reference information RF3 shown in FIG. 14 is, for example, a table in which the vertical axis is assigned the first evaluation value V1 and the horizontal axis is assigned the second evaluation value V2. This is a derivation table that derives obesity levels A to C using a matrix of the first evaluation value V1 and the second evaluation value V2. As shown in FIG. 13(A), in a typical obese body type, fat is often accumulated in the abdominal area, and the maximum body thickness Tmax is often observed near the navel. Therefore, the greater the value of the body thickness Tb at the navel relative to the average body thickness Tav, the higher the degree of obesity is evaluated. In the reference information RF3, the second evaluation value V2 is, for example, classified into three levels: less than 0.7, 0.7 to 1.2, and 1.2 or greater. The smaller the first evaluation value V1 and the larger the second evaluation value V2, the higher the degree of obesity is evaluated. In the reference information RF3, the level approaches level A as it moves toward the upper right, and level C as it moves toward the lower left.

[0060] The processor 31 estimates the liver position using such reference information RF3 and reference information RF1, thereby making it possible to evaluate the degree of obesity taking into account differences in the subject H as shown in FIG.

[0061] (Variation 1: Use of machine learning models) As shown in Fig. 15, a machine learning model 36 may be used to estimate the liver position. For example, the machine learning model 36 receives a front image FV and a side image SV as input and outputs the liver position of the subject H. The machine learning model 36 is a model trained using, for example, pairs of optical images of the front image FV and the side image SV and the liver position serving as ground truth data as training data. Alternatively, the machine learning model 36 may output each of the obesity level levels A to C instead of outputting the liver position. In this case, the processor 31 determines the liver position according to each of the obesity level levels A to C based on the reference information RF1.

[0062] (Variation 2: Use of a stereo camera) 16, optical images may be acquired using a stereo camera 41. The optical images are two front images FV_R and FV_L with parallax, which are obtained by photographing the subject H from the front. With these two front images FV_R and FV_L, depth information including the distance to the body surface of the subject H can be measured. The processor 31 performs image analysis of these front images FV_R and FV_L to, for example, measure the spine length SL, measure the maximum body thickness Tmax, and derive the first evaluation value V1. Using the stereo camera 41 in this way eliminates the need for lateral images SV.

[0063] As an example, the stereo camera 41 is an optical camera that incorporates multiple optical systems spaced apart in a single housing. Of course, two cameras each having one optical system, such as the optical camera 22, may be prepared and spaced apart to function as the stereo camera 41.

[0064] A distance measurement sensor may be used to determine the distance for measuring the body thickness of the subject H. Examples of distance measurement sensors include a LIDAR (Laser Imaging Detection and Ranging or Light Detection and Ranging) and a TOF (Time Of Flight) camera. A distance measurement sensor using ultrasound may also be used. A distance image acquired by such a distance measurement sensor may be used in addition to an optical image such as a front image FV. The distance image acquired by the LIDAR or TOF camera is included in the optical image. If the outline of the subject H can be detected in such a distance image and the spine length SL can also be measured, the distance image may be used instead of the optical image.

[0065] Furthermore, in the above embodiment, an example in which the marker M imitates the shape of a liver is shown, but the marker M is not limited to this shape. The marker M may be any marker as long as it can indicate the position of the liver, and may be, for example, a line indicating the range in the body axis direction in which the liver is located, like the dashed line shown in Fig. 4. Of course, a marker M imitating the shape of a liver is preferable because it is considered to be easier for the operator OP to intuitively recognize.

[0066] Furthermore, although the example in which the optical cameras 22 and 23 are installed is shown as being on the ceiling and wall of the imaging room, they may also be installed, for example, on the inner wall of the opening of the bore 11. However, since the receiving coil unit 16 is mounted with the top plate 12A positioned outside the opening of the bore 11, it is preferable that the optical cameras 22 and 23 be installed in a position where they can perform imaging outside the opening of the bore 11, such as on the ceiling and wall of the imaging room.

[0067] In the above embodiment, the various types of hardware listed below can be used as the hardware of the processor 31. The various types of hardware include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as a PLD (Programmable Logic Device) such as an FPGA (Field-Programmable Gate Array) whose circuit configuration can be changed after manufacture, and a dedicated electrical circuit such as an ASIC (Application Specific Integrated Circuit) that is hardware having a circuit configuration designed specifically for executing specific processing.

[0068] The various processes described above may be executed by one of these various hardware components, or may be executed by a combination of two or more hardware components of the same or different types (for example, a plurality of FPGAs, or a combination of a CPU and an FPGA). Furthermore, a plurality of processing units may be configured as a single piece of hardware. An example of configuring a plurality of processing units as a single piece of hardware is a form of using hardware that realizes the functions of an entire system including a plurality of processing units on a single IC (Integrated Circuit) chip, such as a System on Chip (SOC).

[0069] In this way, the various processing units are configured using one or more of the various hardware components described above.

[0070] Furthermore, as these various hardware structures, more specifically, electric circuits (Circuitry) combining circuit elements such as semiconductor elements can be used. do.

[0071] Furthermore, the technology of the present disclosure extends to a computer-readable storage medium (such as a USB (Universal Serial Bus) memory or a DVD (Digital Versatile Disc)-ROM (Read Only Memory)) that non-temporarily stores a program, in addition to the program that causes the processor 31 to function as a projection control device. The technology of the present disclosure can also be applied to a program and a program product.

[0072] From the above description, the technology described in the following supplementary paragraphs can be understood.

[0073] [Additional note 1] It has a processor, The processor acquires an optical image of the object; estimating a position of the subject's liver based on the optical image; By controlling the projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating the position where the receiving coil unit of the magnetic resonance imaging device is to be attached. Projection control device. [Additional note 2] The processor derives an obesity level of the subject based on the optical image; Estimate the position of the liver based on the derived obesity level Item 1. A projection control device according to claim 1. [Additional note 3] The processor derives the degree of obesity based on a first evaluation value defined as a ratio of the length from the shoulder to the waist in the body axis direction of the subject to the body thickness. Item 2. A projection control device according to claim 2. [Additional note 4] The processor derives the obesity level based on the first evaluation value and a second evaluation value defined as a ratio of the body thickness at the navel to the average body thickness of the trunk. Item 3. A projection control device according to claim 3. [Additional note 5] The processor estimates the position of the liver of the subject using reference information that stores in advance the correspondence between the obesity level and the position of the liver. Item 4. A projection control device according to any one of items 2 to 4. [Additional note 6] The optical images include a front image taken from the front of the subject and a side image taken from the side. Item 5. A projection control device according to any one of items 2 to 5. [Additional note 7] The optical image includes two frontal images with parallax, taken from the front of the subject. Item 6. A projection control device according to any one of items 2 to 6. [Additional note 8] The processor estimates the position of the subject's liver using a machine learning model that receives the optical image as an input and outputs the position of the subject's liver. 8. A projection control device according to any one of appended items 1 to 7. [Additional note 9] 1. A method of operating a projection control device having a processor, comprising: The processor acquiring an optical image of the subject; estimating a position of the subject's liver based on the optical image; By controlling the projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating the position where the receiving coil unit of the magnetic resonance imaging device is to be attached. A method for operating a projection control device. [Additional Note 10] An operating program for a projection control device having a processor, acquiring an optical image of the subject; estimating a location of the subject's liver based on the optical image; By controlling the projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating the position where a receiving coil unit of the magnetic resonance imaging device is to be installed. An operating program for a projection control device that causes a processor to execute processing including the steps of: [Additional Note 11] A magnetic resonance imaging apparatus equipped with a projection control device, The projection control device includes a processor, The processor acquires an optical image of the object; estimating a position of the subject's liver based on the optical image; By controlling the projection device, an index representing the estimated liver position is projected onto the subject as an index representing the position where the receiving coil of the magnetic resonance imaging device is to be installed. Magnetic resonance imaging device.

[0074] The above-described description and illustrations are a detailed explanation of the parts related to the technology of the present disclosure and are merely an example of the technology of the present disclosure. For example, the above description of the configuration, functions, actions, and effects is an explanation of an example of the configuration, functions, actions, and effects of the parts related to the technology of the present disclosure. Therefore, it goes without saying that unnecessary parts may be deleted, new elements may be added, or replacements may be made to the above-described description and illustrations within the scope of the gist of the technology of the present disclosure. Furthermore, to avoid confusion and facilitate understanding of the parts related to the technology of the present disclosure, the above-described description and illustrations omit explanations of common technical knowledge that do not require particular explanation to enable the implementation of the technology of the present disclosure.

[0075] In this specification, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B. Furthermore, in this specification, the same concept as "A and / or B" is also applied when three or more things are expressed connected by "and / or."

[0076] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0077] 10. Magnetic resonance imaging equipment 11 Bore 12 berths 12A Top plate 12B belt 13 Console 14 Control Unit 16 Receiving coil unit 21 Projection System 22, 23 Optical camera 24 Projection device 31 processors 32 Storage 36 Machine Learning Models 41 Stereo Camera FV, FV_R, FV_L front image H Subject C1~C7 Cervical vertebrae L1~L5 Lumbar vertebrae LPA, LPB, LPC liver position LV liver M sign OP Operator PL projection light PP Minutiae RF, RF1, RF2, RF3 Reference Information SL spine length SV side view T1~T12 Thoracic spine Tav Average body thickness Tb body thickness Tmax Maximum body thickness V1 First evaluation value V2 Second evaluation value

Claims

1. It has a processor, The processor acquires an optical image of the subject; estimating a position of the subject's liver based on the optical image; By controlling a projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating a position where a receiving coil unit of a magnetic resonance imaging device is to be attached. Projection control device.

2. The processor derives an obesity level of the subject based on the optical image; The position of the liver is estimated according to the derived obesity degree. The projection control device according to claim 1 .

3. The processor derives the obesity index based on a first evaluation value defined as a ratio of a length from a shoulder to a waist in a body axis direction of the subject to a body thickness. The projection control device according to claim 2 .

4. The processor derives the obesity index based on the first evaluation value and a second evaluation value defined as a ratio of a body thickness at the navel to an average body thickness of a trunk portion. The projection control device according to claim 3 .

5. The processor estimates the position of the liver of the subject using reference information that stores in advance a correspondence relationship between an obesity degree and the position of the liver. The projection control device according to claim 2 .

6. The optical images include a front image taken from the front of the subject and a side image taken from the side of the subject. The projection control device according to claim 2 .

7. The optical images include two front images having parallax, the front images being captured from the front of the subject. The projection control device according to claim 2 .

8. The processor estimates the position of the liver of the subject using a machine learning model that receives the optical image as an input and outputs the position of the liver of the subject. The projection control device according to claim 1 .

9. 1. A method of operating a projection control device having a processor, comprising: The processor: acquiring an optical image of the subject; estimating a position of the subject's liver based on the optical image; By controlling a projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating a position where a receiving coil unit of a magnetic resonance imaging device is to be attached. A method for operating a projection control device.

10. An operating program for a projection control device having a processor, acquiring an optical image of the subject; estimating a position of the subject's liver based on the optical image; By controlling a projection device, a mark indicating the estimated position of the liver is projected onto the subject as a mark indicating a position where a receiving coil unit of a magnetic resonance imaging device is to be installed. An operating program for a projection control device that causes the processor to execute a process including the steps of:

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