Magnetic resonance imaging device and automatic channel selection method for multi-channel receiving coil

Abstract

To automatically select a channel for receiving a signal from an imaging part with high sensitivity in imaging using a multi-channel receiving coil.SOLUTION: A magnetic resonance imaging device collates a camera image of a subject after mounting a receiving coil and acquired before the subject is transported to an imaging position, and information specifying a position (a target position) of an imaging part of the subject, with design information of the receiving coil, selects elements of the receiving coil including the target position, and determines a coil region containing the selected elements and being activated. The target position is specified by such methods that the user specifies the target position on a camera image of the subject before mounting the receiving coil, and the user specifies the target position on a pre-scan image. The image is reconstructed using signals received by the elements in the activated coil region.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a technique for automating channel selection in a magnetic resonance imaging (hereinafter referred to as MRI) apparatus that uses a multi-channel receiving coil. [Background technology]

[0002] In an MRI device, the coil that receives the nuclear magnetic resonance signals from the subject may be an RF transmitting coil that is fixed to the device and used to irradiate a high-frequency magnetic field, but a receiving coil consisting of multiple loop coils (surface coils) that are attached in close contact with the subject's examination area is widely used because it can detect signals from the examination area with high sensitivity.

[0003] Surface coils come in various forms, combining multiple coil elements that are tailored to the shape of the area to be examined, such as the head, abdomen, and extremities. The multiple elements are connected to multiple channels of the receiver, and image reconstruction is performed using the nuclear magnetic resonance signals received by the multiple channels. Increasing the number of channels in a receiver coil generally improves image quality, so receiver coils are becoming more multi-channel. In addition, to improve the workflow of coil setting, receiver coil units with a wide sensitivity range and multiple elements have been developed, allowing multiple areas to be imaged with a single coil setting.

[0004] Furthermore, in a workflow including coil setting, it is important to position the examination area to which the receiving coil is attached at the center of the magnetic field in order to obtain good image quality, and technologies for doing so have been proposed (Patent Document 1, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-128667 A [Patent Document 2] JP 2020-141732 A Summary of the Invention [Problem to be solved by the invention]

[0006] The multi-channel receiver coil described above, which allows imaging of multiple locations at once, is attached to the subject so as to cover a wide area, for example, the subject's chest or abdomen, but even when the examination site is a portion of tissue or organs contained in the chest or abdomen, signals from all channels are processed, so there is a possibility that the image quality of the target site will be reduced due to the inclusion of unnecessary signals. Furthermore, an increase in the number of channels increases the cost of the receiving system. Therefore, in order to obtain high image quality for a specific examination site, it is necessary to select the necessary channels to generate an image.

[0007] The technology described in Patent Document 1 is a technology in which a plurality of markers are attached to a receiving coil, the marker closest to the examination site is designated, and the subject is positioned so that the marker position is at a predetermined position in the magnetic field space, and cannot solve the above-mentioned problem. Also, the technology described in Patent Document 2 is a technology in which a user designates a position of interest using a camera image, and the region of interest is moved to the center of the magnetic field to obtain a scout image, and similarly does not solve the above-mentioned problem.

[0008] In addition, when the subject is moved to the imaging space (magnetic field center), the subject to which the receiving coil is attached may be covered with a blanket, etc. In such a case, it becomes difficult to position the desired marker position or the region of interest specified using the camera image at the magnetic field center with the above-mentioned conventional technology.

[0009] The present invention aims to provide a technique for automatically selecting coil elements or a coil region consisting of multiple coil elements that are necessary and sufficient for imaging a desired examination region after a receiver coil with multiple coil elements (channels) is attached to a subject. Another objective of the present invention is to provide a technique for locating the automatically selected coil region at the center of the magnetic field, thereby enabling acquisition of a good image of the examination region. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention compares a camera image of the subject after a receiving coil is attached, acquired before the subject is transported to an imaging position, information identifying the position of the subject's imaging area (target position), and design information for the receiving coil, to select an element of the receiving coil that includes the target position, and determines a coil region to be activated that includes the selected element.

[0011] That is, the MRI apparatus of the present invention comprises an imaging unit having a multi-channel receiver that receives nuclear magnetic resonance signals generated by the subject, and a control unit that controls the imaging unit. The control unit comprises a camera image acquisition unit that acquires images from a camera arranged in the MRI apparatus, a target position identification unit that identifies a target position for imaging on the subject, and a comparison unit that compares a camera image acquired by the camera image acquisition unit, showing the subject wearing a receiving coil including multiple coil elements, with design information of the receiving coil, and determines the coil element of the receiving coil that includes the target position identified by the target position identification unit.

[0012] The design information of the receiving coil is, for example, CAD data used when designing the receiving coil, and includes design-related information such as the arrangement of elements, dimensions, receiving coil ID (type, size, etc.), information showing the relationship between the exterior and internal elements (markers, characteristic shapes, etc.) Such design information of the receiving coil is stored in the internal memory of the device or in an external storage device for each of multiple types of receiving coils.

[0013] The receiving coil is provided with information that can be seen from the outside, i.e., information that can be captured as a camera image, such as the receiving coil's ID (type, size, etc.) and information that indicates its relationship with internal elements (markers, characteristic shapes, etc.).

[0014] In addition, the automatic channel selection method for a multi-channel receiving coil of the present invention is a method for selecting coil elements of a multi-channel receiving coil used in an MRI device, and includes the steps of acquiring an image from a camera placed in the MRI device, identifying a target position in a subject, and comparing a camera image showing a subject wearing a receiving coil including multiple coil elements, the target position, and design information for the receiving coil, and determining the coil element of the receiving coil including the target position. Effect of the Invention

[0015] According to the present invention, by comparing the camera image and the target position associated with it with the design information of the receiver coil, it is possible to automatically select the element of the receiver coil that includes the target position. This makes it possible to reconstruct an image of good quality by activating only the coil area that includes the target position and eliminating signals from unnecessary elements.

[0016] Furthermore, even in a situation where the receiving coil cannot be captured by the camera due to a cover covering the receiving coil after the receiving coil is attached to the subject, the target position can be placed at the center of the magnetic field. [Brief description of the drawings]

[0017] [Figure 1] A diagram showing an overall overview of an MRI device. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 4 is a diagram showing the flow of operation of a channel selection unit. [Diagram 5] FIG. 4 is a diagram for explaining the processing of the first embodiment. [Figure 6] FIG. 13 is a diagram for explaining coil region determination according to the first modified example. [Figure 7] FIG. 11 is a diagram for explaining target position identification according to the second modification example. [Figure 8] FIG. 11 is a diagram for explaining the processing of the second embodiment. [Figure 9] FIG. 11 is a diagram for explaining the processing of the third embodiment. [Figure 10] FIG. 13 is a diagram for explaining target position identification according to Modification 3. [Figure 11] FIG. 13 is a diagram for explaining the arrangement of receiving coils and markers to which the fourth embodiment is applied. [Figure 12] 13A and 13B are diagrams for explaining correction using marker intervals arranged on a receiving coil or a fixing belt. [Figure 13] FIG. 13 is a diagram showing a modified example of the fourth embodiment in which a fixing belt is used. [Figure 14] FIG. 13 is a diagram for explaining a receiving coil to which the fifth embodiment is applied. [Figure 15] FIG. 13 is a diagram for explaining the processing of the fifth embodiment. [Figure 16] FIG. 13 is a diagram showing the processing flow of the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1, the MRI apparatus 1 includes a gantry 10 in which a static magnetic field space is formed for placing a subject therein, and a bed 105 for transporting the subject into the gantry 10. The gantry 10 and the bed 105 are placed in an examination room that is shielded from electromagnetic waves.

[0019] In the examination room, a camera 30 is installed to capture an image of a subject placed on a bed 105. A display device (not shown) for displaying images acquired by the MRI apparatus 1 is provided at the entrance of the gantry 10 or near the gantry 10, and images acquired by the camera 30 (camera images) are also displayed on this display device. The camera images are used when setting the subject at an appropriate position in the gantry 10 and when attaching a receiving coil, which will be described later, to the subject.

[0020] 1 shows an example in which cameras 30 are installed in two locations, near the entrance of the gantry 10 and on the upper part or ceiling of the examination room, the number of cameras may be one or three or more, and the installation locations may be any location that can obtain camera images required for the above-mentioned settings. Furthermore, the camera 30 may be a camera that obtains two-dimensional images, or a stereo camera that can grasp a three-dimensional position.

[0021] As shown in FIG. 2, the gantry 10 is equipped with a static magnetic field magnet 101 that generates a static magnetic field, a gradient magnetic field coil 102 that applies a magnetic field gradient to the static magnetic field space, and an RF coil 103 that generates a high frequency magnetic field.

[0022] The gradient magnetic field coil 102 includes three sets of gradient magnetic field coils that generate gradient magnetic fields in three axial directions perpendicular to each other. Each of the three sets of gradient magnetic field coils is connected to a gradient magnetic field power supply 212 and driven by power supplied from the gradient magnetic field power supply 212.

[0023] The RF coil 103 generates a high-frequency magnetic field of a magnetic resonance frequency that excites the nuclei of atoms contained in the tissue constituting the subject, and can also function as an RF receiving coil that receives a nuclear magnetic resonance signal (NMR signal) generated by the subject. In the embodiment shown in FIG. 2, a receiving-only RF coil 104 is provided in addition to the RF coil 103. The RF coil 104 is usually attached to the examination site of the subject 70. Although not shown in FIG. 1, the RF coil may be fixed to the bed. Both the RF coils 103 and 104 can function as a transmitting coil that generates a high-frequency magnetic field and a receiving coil that receives an NMR signal. Here, as an example, the RF coil 103 is a transmitting coil and the RF coil 104 is a receiving coil, and the RF coil 103 is connected to a transmitter 113 equipped with a high-frequency generator and the like, and the RF coil 104 is connected to a receiver 114 equipped with a detector, an A / D converter and the like.

[0024] In the case where the receiver 114 is a multi-channel receiver coil consisting of multiple coil elements (hereinafter simply referred to as elements), each channel is composed of multiple receivers (multiple channels) equipped with an amplifier, a detector, and an A / D converter. However, the number of channels of the receiver coil does not necessarily have to match the number of channels of the receiver, and control to switch the connection may be performed as appropriate. The output of each receiver is sent to a signal processing circuit.

[0025] The MRI apparatus 1 is equipped with a sequencer 115 that operates a gradient magnetic field power supply 112, a transmitter 113, a receiver 114, etc. according to a predetermined pulse sequence, and the sequencer 115 executes a series of operations, such as irradiating a high-frequency magnetic field pulse to a subject placed in a static magnetic field space, receiving an NMR signal from the subject, and applying a gradient magnetic field pulse to add position information to the NMR signal.

[0026] The above-described units are collectively referred to as the imaging unit 100 of the MRI apparatus 1. The MRI apparatus 1 includes a computer 20 that controls the units of the imaging unit 100 via a sequencer 115 and performs various calculations related to signals acquired by the imaging unit 100 or images reconstructed from the signals. Hereinafter, the control function of the computer 20 is referred to as the control unit 200. The computer 20 can be configured as a general-purpose computer or workstation equipped with a CPU, GPU, and memory, and the desired control and calculation can be performed by the CPU reading and executing programs required for control and calculation. Note that some of the calculations performed by the computer 20 may be performed by programmable ICs such as ASICs and FPGAs, and these hardware components are also referred to as the computer.

[0027] A UI unit 60, which is an interface with a user, and an external storage device 40 are connected to the computer 20. The UI unit 60 is equipped with a display device 50 that displays an image and a GUI acquired by the MRI apparatus 1, an input device (not shown), and the like. A display device 50A that is disposed near the gantry 10 and displays a camera image is also connected to the computer 20, and this display device 50A is capable of displaying the image acquired by the MRI apparatus 1 in addition to the camera image.

[0028] In this embodiment, the functions of the computer 20 (control unit 200) further include a function (channel selection function) of selecting a desired coil element or coil region from the multi-channel coil using a camera image acquired by the camera 30 and design information of the receiving coil. As elements for realizing this function, the computer 20 includes a camera image acquisition unit 211 that acquires a camera image captured by the camera 30, and a comparison unit 215 that compares a camera image of a receiving coil including multiple coil elements and a subject part to which the receiving coil is attached with design information of the receiving coil, and determines the elements of the receiving coil, as shown in FIG. 3.

[0029] The computer 20 further includes a target position identifying unit 213 that identifies a target position of imaging in the subject, and a collation unit 215 selects an element of the receiving coil used to image the target position or identifies a coil region including the coil element, using the camera image, design information of the receiving coil, and the target position identified by the target position identifying unit 213. These functions are collectively referred to as a channel selection unit 210.

[0030] The design information of the receiving coil may include, for example, the size, shape, and arrangement of a plurality of elements constituting the receiving coil, such as CAD data of the receiving coil, and the ID of the receiving coil (a number indicating the type, model, etc.), and may further include information that allows the positional relationship between the appearance of the receiving coil and the elements arranged inside to be grasped from the appearance. The information that allows the positional relationship between the appearance of the receiving coil and the elements arranged inside to be grasped from the appearance may be, for example, a marker or ID display unit attached to the surface of the receiving coil, or a characteristic of the shape of the receiving coil itself. In the following description, a marker is used as a representative of information that can be grasped from the appearance, but even in this case, the word "marker" is not limited and includes the above-mentioned broad information. The design information of the receiving coil is stored, for example, in the external storage device 40, and the computer 20 reads it from the external storage device 40 and the above-mentioned collation unit 215 uses it to select a coil element.

[0031] There are several methods for the target position specifying unit 213 to specify the target position, such as a method using a camera image and a method using an image acquired by an MRI device, which will be described in detail in the embodiments described later.

[0032] It should be noted that "attaching the receiving coil to the subject" does not only mean attaching the receiving coil to each part of the subject, but also includes a state in which the receiving coil is placed or exists in a fixed position relative to the subject.

[0033] According to the MRI apparatus 1 having the above configuration, the computer 20 (control unit 200) has a function of comparing the design information of the receiving coil with the camera image of the subject to which the receiving coil is attached, and selecting a predetermined channel (coil element) of the receiving coil, so that imaging is performed by driving only the channel of the coil region including the examination site, and image reconstruction is performed without using signals from channels not required for imaging, so that a reconstructed image with good image quality can be obtained. Also, since it is not necessary to provide a large number of receiving channels more than necessary as the receiver 114, the configuration of the receiver 114 can be simplified.

[0034] Specific embodiments corresponding to various receive coils and target location techniques are described below.

[0035] <Embodiment 1> In this embodiment, the receiving coil is attached so as to cover the upper surface of the imaging region of the subject, and an embodiment will be described in which the receiving coil is applied to a receiving coil with markers attached at multiple locations on the outside.

[0036] As shown in the functional block diagram of FIG. 3, the computer 20 of the MRI apparatus 1 of this embodiment includes an image processing unit 220 that reconstructs an image using the NMR signal received by the receiver 114 and performs correction and other processing using the reconstructed image, a display control unit 230 that generates display images to be displayed on the display devices 50 and 50A and controls the display, an imaging control unit 240 that controls the imaging unit 100 via the sequencer 115, and a channel selection unit 210 that selects a channel of the receiving coil.

[0037] The channel selection unit 210 includes a camera image acquisition unit 211, a target position identification unit 213, and a matching unit 215. The target position is the position of a part that is the object of imaging or the position of an axis that identifies a cross section including the part, and the target position may be identified by a point or a line, or by a shape having a predetermined area (such as a circle, a square, or the outline of a tissue).

[0038] The flow of processing in the channel selection unit 210 in the computer 20 described above is shown in Fig. 4. First, before the subject is inserted into the gantry 10, a receiving coil is attached to the subject, and the subject is laid on the bed 105. The camera image acquisition unit acquires camera images acquired by the camera 30, and the camera images are displayed on the display device 50A installed near the gantry 10 (S1).

[0039] The subject 70 and the receiving coil 104 attached to the imaging region of the subject (chest in this case) are shown in this camera image 300, as shown on the left side of Fig. 5. Markers 1041 are attached to a plurality of locations (five locations at the four corners and the center of the upper side in Fig. 5) on the surface of the receiving coil 104, and these markers 1041 are also shown in the camera image.

[0040] Meanwhile, the target position identifying unit 213 acquires the position of the target of the subject using a camera image or an MR image of the subject acquired in advance (S2). In this embodiment, as an example, a case where the position of the target is identified using a camera image (FIG. 4: dotted arrow) will be described. In this example, a medical technician or doctor (hereinafter, referred to as a user) makes a specific gesture with his / her hand to the imaging part (target) of the subject lying on the bed 105. Here, an example is shown in which the user points to the edge of the bed. In addition, a positioning laser or the like provided in the device may be used, and the method is not limited to these methods as long as the position can be shown in the camera image. In the example shown in FIG. 5, the user's hand gesture virtually constructs a line 501 perpendicular to the left and right direction of the bed, and the line 501 indicates the target position. The camera image acquired in this state allows the positional relationship between the subject, the target, and the receiving coil to be understood.

[0041] Next, the collation unit 215 collates the information obtained from the camera image, the marker position, and the target position with the design information of the receiving coil, and identifies the coil element including the target position (S3). The diagram on the right side of Fig. 5 shows the design information 400 of the receiving coil, and the collation unit 215 identifies the marker position included in this design information 400 and the corresponding marker position in the camera image 300, and then identifies the element corresponding to the line position from the positional relationship between the position of the marker 1041 in the camera image 300 and the line 501. In the illustrated example, the coil elements 1045 are arranged in an 8x6 matrix, and the elements in the second and third rows are identified as elements including the line 501 (S4).

[0042] In the above description, the user specifies the target position with the receiving coil attached, but the target position may be specified with the receiving coil not attached, and the target position specifying unit 213 may specify the target position on the camera image using the camera image in this state. The collation unit 215 may specify the target position on the camera image after the receiving coil is attached, using the target position specified in the camera image before the receiving coil is attached and the camera image 300 acquired after the receiving coil is attached to the subject at this bed position.

[0043] By using the information of the camera images before and after attachment, it is possible to grasp the element position and the target position on the image coordinates of the camera image. After that, the marker position, the target position, and the design information of the receiving coil identified on the camera image are collated to select the coil region including the target position, in the same way as when identifying the target position after the receiving coil is attached.

[0044] Furthermore, when the FOV 502 of the imaging is determined, the collation unit 215 selects an area that covers the FOV 502 as the coil area 503. Since the FOV is usually set to a value of 450 mm, 350 mm, etc. in the body axis direction as the default of the device, if the FOV position is determined so that the line 501 is the center of the FOV in the body axis direction, the coil area 503 can be selected to cover it. This makes it possible to receive NMR signals from within the FOV and its periphery, and prevents deterioration of image quality due to the reduction in elements.

[0045] Thereafter, the bed 105 is moved, the subject is inserted into the gantry 10, and the subject is positioned so that the target position is at the center of the magnetic field, and then imaging is performed (S5). For this subject positioning operation, the relative distance on the image is obtained in advance, and the necessary distance to the center of the magnetic field is calculated by linking the target coordinates with the device coordinate system, and the bed is moved by that distance.

[0046] Information on the channels in the coil region thus determined by the channel selection unit 210 is passed to the imaging control unit 250. The imaging control unit 250 activates (ON) the selected channel (S6). At this time, if necessary, control (e.g., switching) is performed to connect the selected channel to a channel of the receiver. If all elements of the receiving coil are connected to the receiver, switching is not required. Image reconstruction processing using received signals from each channel of the selected receiving coil is the same as that of a conventional MRI device, and a description thereof will be omitted here.

[0047] According to this embodiment, by comparing the camera image showing the markers attached to the receiving coil and the target position specified by the user with the design information showing the element arrangement of the receiving coil and the positional relationship between the markers, the region of the elements including the target (coil region) can be automatically specified, and only the channels within this region can be activated for imaging. This improves image quality and simplifies the receiver.

[0048] <Modification 1: Modification of the coil region> In the above embodiment, in determining the coil area, one or more elements including the target position are selected, and the area including the multiple elements and covering the FOV is determined as the coil area. However, the coil area may be determined by considering the imaging area where a predetermined image quality is guaranteed (hereinafter referred to as the imaging guaranteed area). As shown in FIG. 6 (right side), the imaging guaranteed area 600 is a device characteristic determined by the distance from the magnetic field center where the magnetic field homogeneity is maintained and the range where the linearity of the gradient magnetic field is maintained. The collation unit 215 holds such information on the imaging guaranteed area as a map, or reads it from the internal memory of the computer 20 or the external storage device 40, and performs AND between the selected channel (coil area) 503 and the imaging guaranteed area 600, and excludes elements outside the imaging guaranteed area 600 from the coil area 503 to determine the coil area.

[0049] According to this modified example, by excluding elements outside the guaranteed imaging area from the elements to be activated, it is possible to prevent degradation of image quality caused by signals from elements whose image quality is not guaranteed being used for image reconstruction. This modification is applicable not only to the first embodiment but also to each of the embodiments described below.

[0050] <Modification 2: Modification of target position identification> In the above-described first embodiment, the case has been described in which the target position identifying unit 213 identifies the target as a gesture by the user or a position pointed to by a laser, but in this modification, the matching unit 215 identifies the target using a statistical anatomical database.

[0051] Specifically, first, the user designates a target anatomical region in the computer 20. The camera image acquisition unit 211 receives information including this user designation together with the camera image. As shown in Fig. 7, the target position identification unit 213 superimposes an anatomical database 700 on the camera image 300 using a technique such as non-rigid registration, analyzes and estimates the anatomical position, and identifies the region as the target position.

[0052] Thereafter, the matching unit 215 matches the camera image (including the subject and receiving coil marker positions, and information on the identified target position) with the receiving coil design information to determine the element / coil region including the target position, as in embodiment 1.

[0053] As a method of using the anatomical database, a method of specifying the target position from examination information instead of a camera image can also be used. Normally, when imaging, information such as the examination item and examination part along with information on the subject is input to the MRI device (computer 20). The collation unit 215 determines the target part from this input information and specifies the part in the anatomical database. For example, the target part is the heart for a cardiac function examination, and the shoulder for a shoulder joint examination.

[0054] Then, the camera image is compared with the anatomical database, and the position on the camera image corresponding to the MRI image of the part identified in the anatomical database is set as the target part. According to this modification, by using the anatomical database, the target position can be identified on the camera image without anatomical knowledge, and comparison with the receiving coil design information can be easily performed.

[0055] <Embodiment 2> In this embodiment, the present invention is applied to an MRI apparatus in which a receiver coil is built into a bed on which a subject is placed. In this embodiment, as shown in Fig. 8, a marker 1051 is attached to a receiver coil built-in bed 105A, and the design information 400A of the receiver coil includes the positional relationship between the element arrangement and the marker 1051.

[0056] In this embodiment, the configuration and processing flow of the channel selection unit 210 are the same as those shown in Fig. 3 and Fig. 4. That is, the collation unit 215 collates a camera image acquired before the subject is inserted into the gantry 10, i.e., a camera image including a subject lying on a bed and a target position specified on the subject by a gesture or the like, with design information of the receiving coil, selects a channel including the target position, and determines a coil region (S1 to S4). As in the first embodiment, the coil region may be set to include the FOV. After that, only the channel of the selected coil region is turned on to perform imaging (S5, S6).

[0057] According to this embodiment, a marker is attached to the bed so that the position in the device coordinate system can be grasped. Therefore, the relationship between the marker and the target position grasped in the camera image can be used to position the selected coil region (target position) at the center of the magnetic field of the device in absolute coordinates.

[0058] <Embodiment 3> This embodiment is an embodiment in which a channel is selected for a receiving coil 104 with a marker attached to the subject, as in the first embodiment, but is characterized in that a marker 1051 is also attached to the bed. The flow of the channel selection process is the same as in the first and second embodiments, and the process of this embodiment will be described below with reference to FIG. 4 as necessary.

[0059] In this embodiment, the form or shape of the receiving coil attached to the subject is not particularly limited, but a sheet-like receiving coil 104 attached to the chest similar to that in Fig. 5 will be described as an example. The bed 105 may be a simple bed 105, or may be a bed 105A with a built-in receiving coil similar to that in the second embodiment.

[0060] First, the camera image acquisition unit 211 acquires a camera image 300 of the subject 70 lying on the bed 105A (FIG. 4: S1). As shown on the left side of FIG. 9, the camera image 300 shows the subject 70 lying on the bed 105A and the receiving coil 104 attached to the subject, as well as a plurality of markers 1041 and 1051 attached to the bed 105A and the receiving coil 104, respectively.

[0061] In this embodiment, as in the first embodiment, for example, the target position may be specified by indicating the target position with a line (not shown in FIG. 9) by a gesture (S2).

[0062] The collation unit 215 collates the positions and lines of each marker 1041 of the receiving coil 104 and each marker 1051 of the bed 105A in the camera image 300 with the design information 400 of the receiving coil 104 and the design information 400A of the receiving coil built into the bed (S3). As a result of the collation, the position of the receiving coil 104 on the bed 105A is specified from the positional relationship between each marker 1041 of the receiving coil 104 and each marker 1051 of the bed 105A in the camera image 300 and each marker 1051 of the bed 105A. Here, the receiving coil design information 400A of the receiving coil built-in bed 105A includes the positional relationship between the built-in receiving coil and the bed, and the position of the bed 105A in the device coordinate system is known, so that the receiving coil 104 and the target position (position of the line) in the device coordinate system are specified by collating the camera image 300 with the receiving coil design information 400, 400A.

[0063] When the target position is specified in the design information 400 of the receiving coil 104, the collation unit 215 selects an element including the position and determines a coil region including the selected element (S4). The coil region is determined to include the FOV determined from the target position, as in the first embodiment. Next, based on the three-dimensional FOV as shown on the right side of FIG. 9, an element on the built-in coil side is selected so as to include an area obtained by projecting the coil region onto the built-in coil side in a direction roughly perpendicular to the coil surface of the receiving coil 104 (or in the vertical direction with respect to the horizontal bed). Here, since the elements in the bed-built-in receiving coil and their arrangement and size are usually different from the receiving coil 104, the coil region of the built-in receiving coil can be selected so as to be wider than the coil region determined for the receiving coil 104, and therefore the coil region reliably included in the FOV can be selected.

[0064] Once the coil regions of the two receiving coils have been determined, the bed 105A is moved and the target is positioned at the center of the magnetic field (S5). At this time, since the target position is specified in the device coordinate system, the target can be easily positioned at the center of the magnetic field. Imaging is performed by activating elements within the selected coil regions (S6).

[0065] According to this embodiment, by placing a marker on the bed side as well, the position of the receiving coil 104 attached to the subject in the device coordinate system can be specified from the camera image, and positioning can be performed accurately. In addition, when an MRI image (for example, a pre-scan image described later) is used instead of a camera image to specify the target position, the target position can be collated with the receiving coil (selected element) position in the device coordinate system.

[0066] <Modification 3: Modification of target position identification> In the above embodiments 1 to 3, the target position identification unit 213 identifies the target position using a camera image and information on the target position designated by the user. However, the target position may be identified using a pre-scan image (MR image) acquired in advance by the MRI device.

[0067] In this case, in a pre-scan image that is normally performed to identify an imaging position, the target position identification unit 213 acquires information on the target position (a 2D image of three axes (three cross sections) or a 3D image) from an imaging region designated by a user such as a technician. Conventional MRI devices also perform a pre-scan and present a pre-scan image, and this can be used, but when the channel selection function is executed, a user instruction to perform a pre-scan and display the image may be received and executed.

[0068] FIG. 10 shows an example of a prescan image. In this example, prescan images of three planes (COR, SAG, AX) including the spinal cord are obtained, and the user specifies the target position by setting ROIs on these three planes. In such prescan images, the position on the image is associated with the position in real space (position in the device coordinate system), so by specifying the target position on the image, the target position in real space can be grasped along with the movement of the bed. In this modification, the position of the target specified by the user on such a prescan image is obtained as position information and used for subsequent matching.

[0069] Specifically, the position specified in the prescan image (position in image space) is first converted to a position in real space (position in device coordinates) and held as the target position. Then, a camera image is acquired with the receiving coil attached to the subject. The collation unit 215 collates the positions of the receiving coil and its markers included in this camera image with the design information (CAD data) of the receiving coil, and acquires the element position of the receiving coil. Next, the subject is moved to the magnetic field center of the device based on the target position information.

[0070] The collation unit 215 further obtains the position of the receiving coil in the device coordinates from the receiving coil position in the camera image. For example, in the second and third embodiments, the marker position in the camera image showing the marker attached to the bed incorporating the receiving coil can be collated with the marker position of the bed in the device coordinate system to obtain the position of the receiving coil in the device coordinates. Next, the position of the element that has moved together with the target position is determined in the device coordinate system, and the coil region including the target position is determined. In determining the coil region, the FOV is taken into consideration, or the imaging guaranteed area is also taken into consideration, as in the first embodiment and the first modified example.

[0071] According to this modification, the target position in the device coordinate system is specified from a prescan image that actually views the inside, so that the target position can be specified with higher accuracy than when the target position is specified using a camera, laser, etc., which only provides information on the appearance. Furthermore, when the subject is positioned inside the gantry, the target position can be easily positioned at the center of the magnetic field.

[0072] <Embodiment 4> Embodiments 1 to 3 are examples in which a receiving coil is provided with multiple markers that can be read by a camera, and a specific element is selected by comparing the marker position with the marker position and element arrangement contained in the design information of the receiving coil. However, this embodiment is characterized in that markers are placed at specified intervals on the receiving coil, thereby correcting the position of the markers of the receiving coil in the camera image.

[0073] The configuration of the channel selection unit 210 is the same as in the above-described embodiment, so the following will mainly describe the points that differ from the above-described embodiment with reference to FIGS.

[0074] 11 is a diagram showing a schematic camera image 300 of a subject wearing a receiving coil 104. As shown in the figure, a plurality of markers 1041 are provided at equal intervals (interval = a) on the receiving coil 104. For ease of explanation, only a portion 104A of the receiving coil 104 where five markers 1041 are provided is shown at the bottom of the figure.

[0075] The camera image 300 shows the subject, the receiving coil 104, and its marker 1041, but if the receiving coil 104 is a deformable or flexible receiving coil like a blanket, the receiving coil 104 will bend (deform) and the position of the marker 1041 will be different from when it is placed on a plane. Therefore, it cannot be directly compared with the two-dimensional design information of the receiving coil.

[0076] In this embodiment, the deformation of the receiving coil is estimated from the position of the marker 1041 of the receiving coil 104, and after correction, matching is performed. For example, as shown in FIG. 12, if the distance between the markers in the camera image 300 is "b" instead of the distance "a" in a flat state, such as between the first marker and the second marker and between the fourth marker and the fifth marker, the receiving coil 104 will be inclined at an angle θ (=cos -1 By calculating the inter-marker distance by reflecting this deformation in the inter-marker distance of the receiving coil 104, the inter-marker distance in the planar state can be obtained. Although not shown in FIG. 12, the target position of the subject is identified from a camera image or a previously acquired MR image in the same manner as in the above-described embodiment or modified example, and therefore a description thereof will be omitted here.

[0077] 11, markers are placed at predetermined intervals on the receiving coil 104, but as shown in FIG. 13, the receiving coil 104 may be fixed with a fixing belt 124, in which case markers 1241 similar to those in FIG. 11 may be placed on the fixing belt 124. By placing the markers on the fixing belt 124, even if the fixing belt 124 is placed on the marker 1041 above the receiving coil 104, the fixing belt itself has marker 1241, so that the markers can be correctly recognized. By placing the markers on what is assumed to be placed on the outermost side, the markers can be accurately recognized.

[0078] Then, the arrangement of the corrected markers 1041 or 1241, the target position, and the design information of the receiving coil 104 are compared to select a channel including the target position, and a coil region including the selected channel and FOV is determined, as in embodiment 1.

[0079] According to this embodiment, by attaching a marker to the fixing belt for fixing the receiving coil to the subject and capturing the marker in the camera image, the two-dimensional position information (inter-element distance) obtained from the camera image can be corrected for errors caused by bending of the receiving coil.

[0080] <Embodiment 5> While the first to fourth embodiments are applied to a receiving coil of a type in which the receiving coil is placed on the subject or the subject is placed on the receiving coil, the present embodiment is applied to a receiving coil of a type in which the receiving coil is folded in half or wrapped around the subject and attached to the subject. Hereinafter, the present embodiment will be described with reference to Figs. 14 to 16. In Fig. 16 showing the procedure of the present embodiment, blocks showing the same procedures as those in Fig. 4 are indicated by the same reference numerals, and description thereof will be omitted.

[0081] 14 shows a camera image 300 in which a target position is located near the upper arm end (shoulder) of a subject, and a blanket-like receiving coil 104 is folded over the subject's shoulder to surround the target position and placed on the chest and back. The camera image shows the receiving coil 104 placed on the chest and a marker 1041 attached thereto. The target position may be specified by a gesture or the like as in the first embodiment, but in this example, it is specified based on a pre-scan image (S1, S2).

[0082] When comparing the camera image 300 (marker position) with the design information of the receiving coil, the comparison unit 215 detects the turn-back line 1043 of the camera image 300 and identifies a line corresponding to the turn-back line 1043 on the design information (S31). The left side of FIG. 15 shows the turn-back line 1043 identified from the camera image, the part of the receiving coil on the chest side of the subject (the part that is not hidden), and the marker 1041. Using the position information obtained from the camera image and the target position of the camera image obtained from the information of the target position identified by the target position identification unit 213 (position information in the device coordinate system in the case of a pre-scan image), an element in a range including the target position is selected, and the coil region 503 is determined (S41). Note that the comparison between the camera image and the real space (device coordinate system) can be performed by comparing the camera image with a marker or the like whose position is determined in the device coordinate system, as described in the above modification.

[0083] Next, a folding line is determined in the design information (CAD data) 400 of the receiving coil, and an element below (hidden part) that is line-symmetrical to the selected element with respect to the folding line is selected on the CAD data (S42).

[0084] In this example, as shown on the right side of Fig. 15, it is assumed that the target positions are located at approximately equal distances on either side of the turn-back line 1043 detected in the camera image, but depending on the position of the camera, such as when the subject is thick, the distance between the turn-back line and the target position may differ between the front and back sides of the receiving coil. In this case, a correction value that takes into account the thickness of the subject may be added to the turn-back line. For example, the position detected as the turn-back line may be shifted by a predetermined amount (<thickness÷2> × any coefficient) in a direction away from the target position, and this may be used as the turn-back line.

[0085] Thereafter, the target position is moved to the center of the magnetic field, and the elements of the selected coil region are activated to perform imaging, as in other embodiments (S5, S6). Note that in the illustrated example, a case where there is one return line is shown, but this embodiment can also be applied to a case where there are return lines on the left and right, such as a type of receiving coil that is wrapped around the torso.

[0086] According to this embodiment, even in the case of a receiving coil that is mounted so that there are receiving coil portions in two or more places (front and back) on either side of the target position, an appropriate coil area can be determined for each portion and made active, thereby enabling signals from the target area to be received with high sensitivity.

[0087] <Modification 4: Modification of camera image> In the above embodiments and variants, the use of two-dimensional camera images capturing the subject before the camera is inserted into the gantry has been mainly described. However, depending on the type, function, and arrangement of the camera 30, it is possible to use camera images as described below.

[0088] For example, if the camera is equipped with a fisheye lens and a receiving coil tracking mechanism, and is installed in a position where it can photograph the condition inside the gantry bore (such as the gantry entrance or inside the bore), the camera image can capture the subject from the position where the receiving coil is attached to the subject's position until he or she is positioned at the center of the magnetic field. This makes it possible to use the camera image to perform positioning in addition to comparing it with the design information of the receiving coil.

[0089] Furthermore, if the camera has a video function, it is possible to capture the state before and after the coil is attached, and by specifying the target position before attachment and overwriting the position information of the receiving coil marker, it is possible to make it unnecessary to specify the target position using a projector, etc., and to include the target position and receiving coil position information in the camera image data. This makes it possible to match the camera image with the design information of the receiving coil without any problems, even if something is placed on the receiving coil that blocks the marker when the subject is inserted into the gantry.

[0090] Although the embodiments and modifications of the present invention have been described above, these can be combined as appropriate as long as there is no technical contradiction, and such combinations are also encompassed by the present invention. [Explanation of symbols]

[0091] 1: MRI device, 10: gantry, 20: computer, 30: camera, 40: external storage device, 50: display device, 50A: display device, 60: UI unit, 70: subject, 100: imaging unit, 104: receiving coil, 105: bed, 124: fixing belt, 200: control unit, 210: channel selection unit, 211: camera image acquisition unit, 213: target position identification unit, 215: matching unit, 230: display control unit, 240: imaging control unit, 300: camera image, 400: receiving coil design information, 501: projector light indicating target position, 502: FOV, 503: coil area, 600: imaging guaranteed area, 1041: marker, 1051: marker, 1241: marker, 1043: folding line.

Claims

1. A magnetic resonance imaging apparatus comprising: an imaging unit having a multi-channel receiver for receiving a nuclear magnetic resonance signal generated by a subject; and a control unit for controlling the imaging unit, The control unit is a camera image acquisition unit for acquiring an image from a camera disposed in the magnetic resonance imaging apparatus; a target position specifying unit for specifying a target position of the subject to be imaged; a comparison unit that compares a camera image of the subject wearing a receiver coil including a plurality of coil elements, acquired by the camera image acquisition unit, with design information of the receiver coil, and determines coil elements of the receiver coil that cover the target position identified by the target position identification unit; A magnetic resonance imaging apparatus comprising:

2. 2. The magnetic resonance imaging apparatus according to claim 1, The magnetic resonance imaging apparatus is characterized in that the target position identification unit accepts a position specified by a user using a camera image showing the subject before the receiving coil is attached, and identifies the specified position as the target position.

3. 3. The magnetic resonance imaging apparatus according to claim 2, A magnetic resonance imaging apparatus, characterized in that the target position identification unit analyzes the camera image including a position specified by a user by using an anatomical database, and identifies a predetermined portion in the anatomical database as the target position.

4. 2. The magnetic resonance imaging apparatus according to claim 1, The target position identification unit receives a position specification by a user using a pre-scan image of the subject that is acquired in advance by the imaging unit and displayed on a display device, and identifies the specified position as the target position.

5. 2. The magnetic resonance imaging apparatus according to claim 1, a marker is attached to the receiving coil, and design information of the receiving coil includes a positional relationship between the coil element and the marker; The magnetic resonance imaging apparatus according to claim 1, wherein the comparison unit compares marker positions included in the camera image with design information of the receiving coil, and determines coil elements of the receiving coil.

6. 2. The magnetic resonance imaging apparatus according to claim 1, The magnetic resonance imaging apparatus according to claim 1, wherein the comparison unit determines a coil region in which coil elements covering the target position are arranged so that the coil region includes a predetermined FOV.

7. 2. The magnetic resonance imaging apparatus according to claim 1, The magnetic resonance imaging apparatus, characterized in that the comparison unit acquires information on an imaging guaranteed area that is determined based on characteristics of a static magnetic field and a gradient magnetic field of the magnetic resonance imaging apparatus, and excludes coil elements that are not included in the imaging guaranteed area.

8. 2. The magnetic resonance imaging apparatus according to claim 1, The apparatus further includes a bed on which the subject is placed, the bed including a built-in receiving coil, the bed being provided with a marker indicating the position of the built-in receiving coil; The collation unit calculates a position of the receiving coil on a device coordinate system from a camera image showing the subject and the markers on the bed, a coil element of the receiving coil that covers the target position is determined using a coil position on the device coordinate system, a target position identified by the target position identification unit, and design information of the receiving coil.

9. 2. The magnetic resonance imaging apparatus according to claim 1, The bed further includes a bed on which the subject is placed, and a marker is provided on the bed at a position where a camera image can be acquired; a comparison unit that calculates a position of the receiving coil on an apparatus coordinate system from a camera image showing the subject wearing the receiving coil and a marker on the bed, and determines a coil element of the receiving coil that covers the target position using the coil position on the apparatus coordinate system, the target position identified by the target position identification unit, and design information of the receiving coil.

10. 10. The magnetic resonance imaging apparatus according to claim 9, 4. A magnetic resonance imaging apparatus comprising: a bed having a built-in second receiving coil; and a marker indicating a position of the built-in second receiving coil.

11. 11. The magnetic resonance imaging apparatus according to claim 10, A magnetic resonance imaging apparatus characterized in that the matching unit sets the area of ​​the second receiving coil projected in a direction perpendicular to the bed as the coil selection area, the area in which the coil elements of the receiving coil attached to the subject are located.

12. 2. The magnetic resonance imaging apparatus according to claim 1, The receiving coil is provided with markers at equal intervals; The magnetic resonance imaging device is characterized in that the comparison unit calculates the deflection of the receiving coil from the spacing of markers included in the camera image, corrects the deflection of the receiving coil, and then compares it with design information of the receiving coil to determine the coil elements of the receiving coil.

13. 2. The magnetic resonance imaging apparatus according to claim 1, the receiving coil is fixed to the subject by using a flexible belt, the flexible belt having markers at equal intervals along a longitudinal direction thereof; The magnetic resonance imaging device is characterized in that the comparison unit calculates the deflection of the receiving coil from the spacing of markers included in the camera image, corrects the deflection of the receiving coil, and then compares it with design information of the receiving coil to determine the coil elements of the receiving coil.

14. 2. The magnetic resonance imaging apparatus according to claim 1, The target position identification unit is a detection unit that detects a folding line of the receiving coil from a camera image showing the subject wearing the receiving coil; The magnetic resonance imaging device is characterized in that the matching unit identifies other coil elements of the receiving coil that are linearly symmetrical to the coil elements determined for the part of the receiving coil shown in the camera image across the folding line, and determines the coil elements and the other coil elements as the coil elements of the receiving coil.

15. 2. The magnetic resonance imaging apparatus according to claim 1, The camera is a camera equipped with any one of a fisheye lens, a subject tracking mechanism, and a video function, The magnetic resonance imaging apparatus according to claim 1, wherein the camera image acquisition unit acquires, as the camera image, information on the camera image including a temporal change or a spatial change of a subject.

16. 1. A method for selecting coil elements of a multi-channel receive coil for use in a magnetic resonance imaging device, comprising the steps of: An automatic channel selection method for a multi-channel receive coil, comprising the steps of: acquiring an image from a camera arranged on the magnetic resonance imaging device; identifying a target position in a subject on which the receive coil is attached; and comparing a camera image showing the subject wearing a receive coil including a plurality of coil elements, the target position, and design information of the receive coil, to determine a coil element of the receive coil including the target position.

17. 17. A method for automatic channel selection in a multi-channel receive coil according to claim 16, comprising the steps of: The method for automatic channel selection of a multi-channel receiving coil, wherein the step of identifying the target position includes a step of accepting a user's designation of a region in a displayed camera image, and identifying the accepted region as the target position.

18. 17. A method for automatic channel selection in a multi-channel receive coil according to claim 16, comprising the steps of: The method for automatic channel selection of a multi-channel receiving coil, wherein the step of identifying the target position includes a step of analyzing a camera image using an anatomical database, and a step of identifying one of a plurality of parts included in the anatomical database as a target part, and a step of identifying a position of the camera image corresponding to the identified target part as the target position.

Images