Receiving Coil Device and Magnetic Resonance Imaging Device Equipped with the Same

Abstract

Provided is a technique for highly sensitively detecting the movement of the front head without reducing the workflow of the reception coil assembly before imaging. The reception coil device includes: one or more reception coils that cover the head of the subject; a base portion on which the head of the subject is placed; a holder portion to which one of the reception coils is fixed and which is supported by the base portion; and a mechanism portion that brings the reception coil fixed to the holder portion into close contact with a part of the head. Further, a detection portion for detecting a physical quantity related to the displacement of the holder portion is provided in the holder portion or the base portion. The physical quantity detected by the detection portion is sent to an MRI device used by the reception coil device.

Description

Technical Field

[0001] The present invention relates to a coil device for transmitting and receiving nuclear magnetic resonance signals used in a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus), and particularly to a receiving coil device for head imaging. Background Art

[0002] In an MRI apparatus, a high-frequency magnetic field is applied to a subject placed in a static magnetic field, and nuclear magnetic resonance (NMR) signals induced thereby are received, and an image of the subject is generated by processing the NMR signals. In the application of the high-frequency magnetic field and the reception of the NMR signals, dedicated RF coils are used. Coils of the MRI apparatus have various coil devices with different shapes depending on whether they are for transmission or reception, the direction of the static magnetic field, the width of the covered area, the shape of the imaging target site, and the like. Since the receiving coil can obtain high sensitivity by being closely arranged with the subject, receiving coils are often installed and assembled on the target site of the subject during imaging. Reducing the trouble and time during assembly and enabling the subject to maintain a closely arranged state (assemblability) without discomfort is an important issue.

[0003] On the other hand, since image degradation occurs if there is body movement of the subject during MRI imaging, it is necessary to detect body movement during imaging and eliminate the influence of the body movement. Especially in brain imaging, even when there is head movement of the same degree or slightly larger than the image resolution, the influence of this movement on the image is significant. Therefore, a technique for detecting body movement of the head during head imaging based on a receiving coil and a marker assembled on the head of the subject has been developed. For example, Patent Document 1 discloses the following technique: The receiving coil 2 is divided into a posterior head side and a face side, an airbag is arranged at the lower part of the side where the posterior head is placed, and the head movement is detected by detecting changes in the air pressure of the airbag. In addition, there is also a method of marking the nose of the subject, photographing the marker with a camera, and detecting the movement of the marker, that is, the movement of the subject's head, based on the image.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-27152 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In the shooting of the head, in most cases, the back of the head is placed downward and the face is upward for shooting. However, since the movement of the back of the head placed on the coil or its support is small, in the method described in Patent Document 1, there is a problem that the movement of the head cannot be detected with high sensitivity. Although it is also considered to arrange an airbag as disclosed in Patent Document 1 between the coil arranged on the face side and the front head of the subject, in this case, in addition to the trouble of assembling the coil, there is a trouble of arranging the airbag at an appropriate position between the coil and the subject, and the assembly work process is reduced.

[0009] In addition, the method of attaching a marker to the subject itself has problems such as the need for additional operations and a reduction in the work process, a reduction in the comfort of the subject such as an itchy nose, and the possibility of misdetecting only the movement of the nose as body movement although the head itself does not move.

[0010] An object of the present invention is to provide a technique for detecting the movement of the front head with high sensitivity without reducing the work process in the pre-shooting setting including the assembly of the receiving coil for the subject.

[0011] Means for Solving the Problem

[0012] The present invention solves the above problems by detecting the movement of a member (holder portion) that fixes a coil covering the front side of the head. The movement is detected as a physical quantity by a detection portion fixed between a base portion that supports the holder and the holder portion.

[0013] That is, the receiving coil device of the present invention includes: one or more receiving coils that cover the head of the subject; a base portion on which the head of the subject is placed; a holder portion that fixes one receiving coil and is supported by the base portion; and a mechanism portion that brings the receiving coil fixed to the holder portion into close contact with a part of the head, and also includes a detection portion that detects a physical quantity related to the displacement of the holder portion.

[0014] In the present invention, the detection portion may be composed of a combination of a marker and a camera that shoots the marker. In this case, the receiving coil device may also include one party (for example, the marker) of the combination.

[0015] In addition, the MRI device of the present invention includes the above receiving coil device as a receiving coil. When the detection portion of the receiving coil device is composed of a combination of a marker and a camera that shoots the marker, the camera can be configured to be connected to the MRI device.

[0016] Advantages of the Invention

[0017] According to the present invention, since the detection unit is fixed to the member side that supports the coil of the receiving coil device, the detection unit can be in a state of being installed on the subject only by an operation of assembling the receiving coil device to the subject, and the work process during coil assembly can be significantly improved. In addition, according to the present invention, since the operation is performed on the side opposite to the part of the subject (e.g., the posterior head) placed on the coil device (e.g., the front side), the detection sensitivity of the physical quantity is improved. Furthermore, the sense of disharmony and discomfort of the subject in the case of installing a marker on the subject can be eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. is an overall structural diagram showing an embodiment of an MRI apparatus to which the present invention is applied.

[0019] Figure 2 FIG. is a diagram showing the relationship between the transmit RF coil and the receive RF coil.

[0020] Figure 3 FIG. is a diagram showing a structural example of the receiving coil device before installing the detection unit.

[0021] Figure 4 FIG. shows Figure 3 the assembled state and the retracted state of the receiving coil device.

[0022] Figure 5 FIG. is a diagram showing the receiving coil device of Embodiment 1.

[0023] Figure 6 (A) to (C) of FIG. are diagrams showing the structures of the body movement processing units of Embodiments 1 to 3.

[0024] Figure 7 FIG. is a diagram showing the operation of the MRI apparatus including the receiving coil device of Embodiment 1.

[0025] Figure 8 FIG. is a diagram showing the arrangement of the receiving coils in a modification of Embodiment 1.

[0026] Figure 9 FIG. is a diagram showing the operation of the MRI apparatus of Embodiment 2.

[0027] Figure 10 FIG. is a diagram showing the structure of the detection unit of Embodiment 3.

[0028] Figure 11 FIG. is a diagram showing a modification of Embodiment 3.

[0029] REFERENCE SIGNS

[0030] 1: MRI apparatus, 11: static magnetic field generating device, 12: transmitting unit, 121: transmitting coil, 13: receiving unit, 131: receiving coil, 14: gradient magnetic field generating unit, 15: sequence generator, 20: computer, 21: control unit, 22: arithmetic unit, 23: body movement processing unit, 231: body movement determination unit, 232: body movement correction unit, 233: body movement amount calculation unit, 24: input device, 25: display 31: A-side coil (front-side coil), 32: P-side coil (rear-side coil), 33: neck coil, 40: receiving coil device, 41: cage portion, 42: base portion, 43: cage support portion, 45: guide portion, 50: detection unit, 51: rangefinder, 52: accelerometer, 53: pressure gauge, 55: marker, 60: camera. Detailed implementation manners

[0031] Hereinafter, with reference to the drawings, implementation manners of the receiving coil device and the MRI apparatus of the present invention will be described.

[0032] First, an implementation manner of the MRI apparatus to which the present invention is applied will be described. As Figure 1 shown, the MRI apparatus 1 includes: a static magnetic field generating device 11 that generates a static magnetic field in the space where the subject 10 is placed; a transmitting unit 12 that applies a high-frequency magnetic field pulse to the subject placed in the static magnetic field space; a receiving unit 13 that receives the nuclear magnetic resonance signal generated from the subject by the irradiation of the high-frequency magnetic field pulse; a gradient magnetic field generating unit 14 that generates a gradient magnetic field that gives position information to the nuclear magnetic resonance signal; a sequence generator 15 that causes the transmitting unit 12, the receiving unit 13, and the gradient magnetic field generating unit 14 to operate based on a given pulse sequence; a signal processing unit 16; and a computer 20 that controls the entire apparatus and performs operations such as correction and image reconstruction on the nuclear magnetic resonance signal. In addition, the signal processing unit 16 can also execute part or all of this function by the computer 20.

[0033] The static magnetic field generating device 11 includes a permanent magnet or an electromagnet such as a normal conductor or a superconductor and its driving unit, and generates a uniform static magnetic field in the imaging space where the subject is placed. In the static magnetic field magnet, according to the direction of the generated static magnetic field, there are a vertical magnetic field method, a horizontal magnetic field method, etc., and the present invention can adopt any of them. In addition, sometimes a shim coil 171 and a shim power supply 172 for maintaining the uniformity of the static magnetic field are arranged. The subject 10 is usually placed in the imaging space in a state of being placed on a couch 18 so that the imaging part is substantially aligned with the center of the static magnetic field.

[0034] The transmitting unit 12 includes a high-frequency transmitter, a high-frequency amplifier (not shown), and a transmitting RF coil (only a transmitting coil) 121. The transmitting coil 121 is disposed in the imaging space and applies a high-frequency magnetic field pulse that causes the nuclei of the atoms constituting the tissue of the subject to generate nuclear magnetic resonance. Although not limited, usually in an MRI apparatus, the nucleus targeted is a proton, and the transmitting coil is adjusted to generate a high-frequency magnetic field at the resonance frequency.

[0035] The receiving unit 13 includes a receiving RF coil (simply referred to as a receiving coil) 131 that receives the nuclear magnetic resonance signal generated from the subject, an amplifier (not shown), a quadrature detector, an A / D converter, etc. After amplifying the nuclear magnetic resonance signal received by the receiving coil 131, it is converted into digital signals in two systems and sent to the signal processing unit 16. In Figure 1 it shows a case where the transmitting coil 121 and the receiving coil 131 are respectively constituted by different coils, but there is also a case where the receiving coil also serves as the transmitting coil 121. In this case, a switch for switching transmission and reception is inserted.

[0036] In Figure 2 it shows an example of the configuration of the transmitting coil 121 and the receiving coil 131 in a horizontal magnetic field type MRI apparatus. In Figure 2 the example shown, the transmitting coil 121 is constituted by a birdcage-type RF coil sized to cover the entire subject disposed in the static magnetic field space and is connected to the transmitting unit 12. The receiving coil 131 is constituted by an array coil disposed in close contact with the examination site (here, the head) of the subject. The array coil is a coil in which a plurality of surface coils having a ring shape are arranged and are respectively connected to the receiving unit 13. In addition, in Figure 2 only two surface coils are shown, but the number and configuration of the surface coils can adopt various structures. Regarding the circuit structures of the birdcage-type coil and the multi-traction array coil, well-known structures can be adopted, and detailed descriptions are omitted in this specification, but they include circuit elements for adjusting the coil conductors and the resonance frequency. In addition, magnetic coupling prevention circuits 123 and 133 for making the other party in a non-operating state when one party is operating are inserted in the transmitting coil 121 and the receiving coil 131. The magnetic coupling prevention circuits 123 and 133 are respectively connected to the magnetic coupling prevention circuit driving device 150.

[0037] In addition, the receiving coil 131 has a support structure for supporting the receiving coil 131 and a mechanism for being in close contact with the subject in order to be assembled to the subject. Collectively including these structures and mechanisms is referred to as the receiving coil device. The MRI apparatus of the present embodiment has a detection unit 50 for detecting the body movement of the subject in this receiving coil device. The details of the receiving coil device having the detection unit 50 will be described later.

[0038] The inclined magnetic field generation unit 14 includes: three sets of inclined magnetic field coils 141 that generate inclined magnetic fields in the three axial directions of x, V, and z that are orthogonal to each other; and an inclined magnetic field power supply 142 that drives each inclined magnetic field coil 141.

[0039] Under the control of the computer 20 (control unit), the sequence generator 15 sends instructions to the transmission unit 12, the inclined magnetic field power supply 142, and the reception unit 13. Thus, based on the pulse sequence set in the sequence generator 15, high-frequency magnetic field pulses are generated, inclined magnetic field pulses from the inclined magnetic field coils 141 are generated, and nuclear magnetic resonance signals are received to collect the nuclear magnetic resonance signals required for image reconstruction. The collected nuclear magnetic resonance signals are transmitted to the computer 20 as k-space data.

[0040] The computer 20 is composed of a general-purpose computer or workstation equipped with a CPU and a memory or a GPU and a memory, and includes a control unit 21 that controls the entire device including the sequence generator 15 and an arithmetic unit 22 that performs operations such as image reconstruction using k-space data. The functions of the control unit 21 and the arithmetic unit 22 are executed by the CPU (GPU) reading a program pre-stored in a recording device or the like. The pulse sequence is one of such programs, and there are various pulse sequences according to the imaging method, and the pulse sequence to be executed is determined based on the pulse sequence selected by the user according to the imaging purpose and part and the imaging parameters set by the user.

[0041] The functions of the control unit 21 and the arithmetic unit 22 are the same as those of the control unit and the arithmetic unit provided in a known MRI device. However, the computer 20 of the present embodiment also inputs a body movement detection signal from the detection unit 50 installed in the receiving coil device, and based on the body movement detection signal, controls interruption of imaging, restart, re-measurement of NMR signals, etc., or corrects the reconstructed image to eliminate the influence of body movement based on the body movement detection signal. Therefore, in Figure 1 this, the function of the computer 20 required for this is expressed as the body movement processing unit 23.

[0042] An input device 24 for the user to input imaging conditions, instructions required for imaging, etc., a display 25 for displaying data during the processing of the computer 20, images as processing results, etc., and a storage unit such as an external storage device are connected to the computer 20. In addition, connections including wired, wireless, and via a network are provided. Further, an input port for inputting signals from an external measuring machine is provided in the computer 20, and a body movement detection signal from the detection unit 50 is obtained via the input port.

[0043] Next, an embodiment of the receiving coil device will be described. As described above, the receiving coil device includes a detection unit 50 that detects the body movement of the subject. However, since the installation position of the detection unit 50 varies depending on the type of the detection unit 50, first, the structure of the receiving coil device in a state where the detector 50 is not installed will be described. In Figure 3 An example of the head receiving coil device 40 is shown. In the following description, the left-right direction (x direction in the figure) of the subject when the receiving coil device is assembled to the subject is referred to as the left-right direction of the receiving coil device, and the direction orthogonal to the left-right direction and the body axis of the subject (front-back direction of the head: y direction in the figure) is referred to as the up-down direction.

[0044] This receiving coil device 40 is generally composed of a coil main body (receiving coil 131) and a mechanism for supporting the coil main body. In Figure 3 the example shown, as the coil main body, it includes a front-side coil (referred to as A-side coil) 31 assembled from the top of the head to the front head of the subject and a rear-side coil (referred to as P-side coil) 32 assembled to the rear head. These coils are respectively connected to the receiving unit 13 of the MRI device 1. In addition, as the mechanism for supporting the coil main body, it includes: a holder part 41 to which the A-side coil 31 is fixed; a base part 42 on which the P-side coil 32 is arranged; and a holder support part 43 that supports the holder part 41 with respect to the base part 42. Further, in Figure 3 the embodiment shown, it includes a side panel 44 for bringing the P-side coil into close contact with the side of the subject from the left and right sides of the subject.

[0045] As Figure 2 shown, the A-side coil 31 and the P-side coil 32 can be composed of a multi-array coil in which a plurality of surface coils are arranged. In each conductor loop constituting the surface coil, circuit elements such as capacitors and inductors for adjusting the reception frequency of the coil are inserted as needed, and nuclear magnetic resonance signals can be received. In addition, the A-side coil 31 and the P-side coil 32 are respectively designed in terms of the size, number, arrangement, and position of circuit elements of the surface coil according to the shape and size of the applied part. For example, the area where no conductor loop or circuit element is arranged in the A-side coil 31 covering the front side of the subject becomes the part corresponding to the eyes of the subject, and this part is made open or transparent.

[0046] In addition, in Figure 3 it is shown that, as the coil main body, the case where two coils, i.e., the A-side coil 31 and the P-side coil 32, are included is shown. However, the present invention can also be applied to a receiving coil device further including third and fourth coils such as a neck receiving coil (not shown), or a receiving coil device only including the A-side coil 31 fixed to the holder part 41.

[0047] Next, the mechanism closely related to the structure for supporting the coil main body will be described.

[0048] The base 42 is composed of a generally plate-shaped member made of non-magnetic material, and the P-side coil 32 is arranged on the upper surface, and the back of the head of the subject is placed thereon. In order to ensure the close contact between the P-side coil 32 and the subject, the base 42 may form a recessed portion on the upper surface to accommodate the back of the head, or a cushioning material such as sponge (not shown) may be arranged between the base 42 and the P-side coil 32.

[0049] The retaining frame portion 41 is composed of a thin plate-shaped member made of non-magnetic material, and the A-side coil 31 is fixed. The fixation of the coil is not particularly limited as long as it is a fixing unit that can be loaded and unloaded with screws, clips, etc., and it can also be fixed at one place or multiple places. In addition, the retaining frame portion 41 has an elongated shape that bends from the center to the left and right directions toward the base portion side, and the central part is fixed to the base portion 42 via the retaining frame support portion 43. The length of the retaining frame portion 41 in the longitudinal direction is the length that the left and right ends of the bend are slightly separated from the base portion 42. The retaining frame support portion 43 described later works, and even if the retaining frame portion 41 changes its position, it will not interfere with the base portion 42.

[0050] When the head of the subject is placed on the base 42, the holder support 43 is fixed to the base 42 so as to be located on the top side of the subject's head. Figure 4 As shown, there is a mechanism for moving the A-side coil 31 from a position (mounting position) where the A-side coil 31 is mounted to cover the front of the head of the subject to a position (retracting position) where the A-side coil 31 is retracted to the side of the top of the head of the subject. As such a mechanism, in the embodiment shown in the figure, there is a sliding portion (movable portion) 431 whose one end is fixed to the holder portion 41; and a fixing portion 432 that connects the other end of the sliding portion 431 to the base portion 42 in a step-by-step manner.

[0051] The sliding part 431 has a bent shape and is composed of an outer cylinder fixed to the cage part 41 and an inner cylinder fixed to the fixing part 432. By sliding the inner cylinder within the outer cylinder, the cage part 41 fixed along this shape to the front end of the outer cylinder and the A-side coil 31 fixed thereto can be moved between the assembly position and the retracted position. In addition, although not shown, a stopper for stopping the movement of the outer cylinder at a desired position is provided in the sliding part 431. The stopper can adopt a known structure such as a button and a hole engaged therewith. The movable range of the sliding part 431 is designed to be able to correspond to different sizes of the subject. Whether the subject has a large head size or a small head size, by operating the stopper in a state where the A-side coil 31 is in close contact with the subject by the stepwise driving force of the fixing part 432, the cage part 41 is fixed at this position as the assembly position. However, as a structure for assembling the A-side coil 31 in a close contact state, the stopper is not essential. For example, other methods such as making the frictional force between the outer cylinder and the inner cylinder greater than the stepwise driving force of the fixing part 432 can also be used.

[0052] Furthermore, in Figure 3 the embodiment, a guiding part 45 for guiding the movement of the cage part 41 is provided on the base part 42. The guiding part 45 is composed of a pair of left and right plate-like members corresponding to the left end side and the right end side of the bent cage part 41, and is respectively provided substantially perpendicular to the main plane direction of the base part 42. The left and right guiding parts 45 are arranged to be in contact with the left and right end parts of the cage part 41. Thus, the cage part 41 has a structure supported by one point fixed to the cage support part 43 and two contact points of the guiding parts 45 on both sides, and can adopt a stable structure at each position of the cage part 41, and can ensure a stable operation during movement. Furthermore, since the two points (contact points) on the left and right are not fixed to the base part 42, the movement of the cage part 41 accompanying the body movement of the subject's head can be regarded as an action integrated with the body movement, and the body movement can be detected with high precision by a detector for body movement detection described later.

[0053] In the receiving coil device 40 configured as described above, with the posterior head of the subject placed and in close contact with the P-side coil 32 on the base part 42, the cage part 41 fixing the A-side coil 31 is moved from the retracted position to the assembly position, and the A-side coil 31 is fixed to the anterior head of the subject. At this time, by utilizing the stepwise driving force of the fixing part 432, the assembly can be performed in a state of being in close contact with the subject. Therefore, the movement of the subject's head can be directly detected as the movement of the cage part 41.

[0054] Based on the structure of the receiving coil device 40 described above, hereinafter, embodiments of the detector for body movement detection will be described, and the processing of the MRI device equipped with the receiving coil device 40 of each embodiment will be described.

[0055] <Embodiment 1>

[0056] The receiving coil device of this embodiment is used as a detector 50 for body movement detection, and a rangefinder that detects changes in the distance between the end of the detection holder part and the base part is used.

[0057] Hereinafter, with reference to the drawings, the installation position of the rangefinder and the physical quantity to be measured will be described. As Figure 5 shown, a rangefinder 51 is fixedly installed near the guide part 45 of the base part 42 of the receiving coil device 40 of this embodiment. As the rangefinder, known rangefinders such as optical type, ultrasonic type, and laser type can be used, and it is connected to the MRI device via a cable (not shown). The position of the rangefinder 51 is a position where the position of the end 411 of the holder part 41 in contact with the guide part 45 can be detected. In the illustrated example, it is fixed to the base part 42 so as to be in contact with the guide part 45. The rangefinder 51 continuously measures the distance between the end 411 of the holder part 41 and the base part 42 (rangefinder 51), generates an electrical signal corresponding to the distance or its change, and transmits it to the control part 21 of the MRI device. The sampling speed at which the MRI device acquires the body movement detection signal is not particularly limited, but in the case of periodic body movement, it is preferably a period sufficiently shorter than the body movement period. In addition, although it depends on the pulse sequence, it is preferably several times or less of its repetition time TR.

[0058] The rangefinder 51 can be installed near one of the left and right guide parts 45, or can be installed on both sides. When installed on one side, the body movement in the vertical direction of the subject's head can be mainly detected. When installed on the left and right, based on the asymmetry of the left and right movements, not only the vertical movement but also the left and right movement can be detected.

[0059] The MRI device of this embodiment determines whether re-measurement is required based on the body movement signal from the rangefinder 51, and performs re-measurement according to the result. Therefore, as Figure 6 shown in (A) of, the body movement processing part 23 includes a body movement determination part 231. A threshold for determining the magnitude of body movement is preset in the body movement determination part 231. The threshold can be set by default, for example, or the user can set the allowable value of body movement according to the image resolution and the like via the input device 24 of the MRI device 1.

[0060] Next, with reference to Figure 7 the operation of the MRI device 1 that has received the body movement signal from the rangefinder 51 will be described. When imaging starts, under the control of the control part 21, the nuclear magnetic resonance signal is measured according to a given pulse sequence, and the collection of k-space data is started (S1).

[0061] The body movement processing unit 23 (body movement determination unit 21) inputs the body movement signal from the distance measuring instrument 51 simultaneously with the start of imaging, and compares the physical quantity measured by the distance measuring instrument 51, that is, the distance from the distance measuring instrument fixed to the base unit 42 to the end 411 of the holder unit 41 or the change value from the initial value with a preset threshold value (S2). For example, when the body movement determination unit 21 determines that the change value is greater than the threshold value, it sends an instruction to reshoot the k-space data obtained at the moment when this body movement signal is obtained to the control unit (S3).

[0062] The control unit 21 performs control to remeasure the k-space data at the moment when an unacceptable body movement change has occurred. In S2, when it is determined that the body movement signal is below the threshold value, the collection of k-space data continues until all the target k-space data is collected (S4), and the imaging ends.

[0063] In addition, in Figure 7 the process, the body movement is temporarily or periodically based on the premise that the position of the subject returns to the initial set position. However, in the determination step S2, when the body movement signal continuously exceeds the threshold value, it is expected that the position of the subject deviates from the initial position. Therefore, instead of reshooting a part of the k-space data, the pulse sequence can be re-executed.

[0064] In this way, according to the present embodiment, by installing the distance measuring instrument 51 as the detector 50 on the base unit 42, the coil assembly operation for the subject and the installation operation of the body movement detector can be integrated. As a result, there is no need for the operation of closely attaching or installing the detector to the subject, and the workability can be greatly improved. In addition, since the movement of a part of the holder unit assembled in close contact with the subject is detected, the movement of the subject can be substantially detected, and the body movement can be detected with high precision. Moreover, since the position of the detector 50 is far from the subject, the body movement can be detected without affecting the MRI image.

[0065] Furthermore, according to the present embodiment, by only reshooting the data obtained when there is body movement, an image that excludes the influence of body movement without significantly extending the imaging time can be obtained.

[0066] <Modification Example of Embodiment 1>

[0067] In Embodiment 1, as the detector 50 for detecting body movement, the distance measuring instrument 51 is used and the distance measuring instrument 51 is fixed to the base unit 42. However, an accelerometer 52 (Modification Example 1) or a pressure gauge 53 (Modification Example 2) can also be used as the detector 50.

[0068] In Figure 8 a structural example of the case where the accelerometer 52 or the pressure gauge 53 is used is shown.

[0069] As the accelerometer 52, without being limited thereto, an acceleration sensor using the change in capacitance or a small acceleration sensor utilizing the piezoelectric effect can be used. The accelerometer 52 is fixed to the holder portion 41 that moves integrally with the subject. Alternatively, as Figure 8 shown, it is fixed between the holder portion 41 and the guide portion 45 that is in contact with the holder portion 41. In this case, it can also be fixed to either the holder portion side or the guide portion side. Additionally, in Figure 8 , an example is shown where accelerometers 52 or pressure gauges 53 are arranged on both the left and right sides, but it can also be only either one. However, in the case of arranging them on both sides, by adding the outputs (absolute values of the change amounts) of both detectors 50, the accuracy of body momentum detection can be improved.

[0070] In such a configuration, the accelerometer 52 can mainly detect the up-and-down movement of the holder portion 41. If the holder portion 41 moves integrally with the body movement of the subject, this movement is detected as a change in capacitance or a change in resistance caused by the piezoelectric effect in the accelerometer 52.

[0071] As the pressure gauge 53, a known small strain gauge such as a semiconductor strain gauge or a capacitance-type strain gauge can be used. Similar to the accelerometer 52, it is fixedly used on either one between the holder portion 41 and the guide portion 45 that is in contact with the holder portion 41. The end of the holder portion 41 and the guide portion 45 are in contact in a state where a certain degree of pressure is applied in advance. Thus, when the holder portion 41 moves in the left-right direction along with the body movement of the subject and the pressure between the holder portion 41 and the guide portion 45 changes, it is detected by the pressure gauge 53. Thereby, the pressure gauge 53 can detect the left-right movement of the subject with high accuracy.

[0072] The accelerometer 52 and the pressure gauge 53 are connected to the MRI device 1 in the same manner as the rangefinder 51 in the first embodiment, and the detected signals are processed by the body movement processing unit 23. The content of the processing is the same as that in the first embodiment, so the description is omitted.

[0073] The effects of these modification examples are also the same as those in the first embodiment. However, not only can the up-and-down movement be detected with high accuracy, but also the left-right movement can be detected with high accuracy. Therefore, it can be suitably applied to the shooting of images that require high accuracy.

[0074] <Second Embodiment>

[0075] In the first embodiment, the case where the body movement signal from the detection unit 50 is used for determining whether to re-acquire k-space data is described. However, in this embodiment, the arithmetic unit 22 of the MRI device uses the body movement signal to correct the image during image reconstruction. Therefore, as Figure 6As shown in (B) of FIG. , the body movement processing unit 23 includes a body movement correction unit 232. Regarding methods for correcting body movement in images, various methods have been proposed in the past and any of them can be adopted. Here, as an example, the case of correcting body movement in the phase encoding direction will be described.

[0076] The phase encoding direction is determined by the pulse sequence used for imaging. Therefore, in the present embodiment, in order to accurately detect body movement in multiple directions, when using the rangefinder 51 as the detector 50, it is preferable to use a pair of rangefinders 51 on the left and right sides. Alternatively, it is also possible to simultaneously use a rangefinder 51 or an accelerometer 52 that mainly detects movement in the vertical direction and a pressure gauge 53 that mainly detects movement in the horizontal direction. For example, when a pressure gauge 53 is provided between the guiding portions 45 on the left and right sides and the cage portion 41 as one of the detectors 50, if there is horizontal body movement, the direction of the pressure change is different, so the direction of the body movement can also be known.

[0077] In Figure 9 the processing flow of the MRI apparatus according to the present embodiment is shown.

[0078] When imaging starts, under the control of the control unit 21, the nuclear magnetic resonance signal is measured according to a given pulse sequence, and the collection of k-space data is started (S11). The body movement processing unit 23 (body movement correction unit 232) simultaneously inputs the body movement signal from the detection unit 50 at the start of imaging, and uses the physical quantities measured by the detection unit 50, that is, the vertical displacement amount and the horizontal displacement amount of the end portion 411 of the cage portion 41, to calculate the displacement amount ΔY in the phase encoding direction (S12).

[0079] Next, it is determined whether the displacement amount ΔY is greater than a given threshold (S13). If it is greater than the threshold, the time point at which the body movement signal is obtained is stored in a storage unit (not shown), and the phase correction value is calculated (S14). The change amount (displacement amount ΔY) of the actual space position becomes a phase change proportional to time (Δθ = γGyΔyt: γ is the gyromagnetic ratio, Gy is the phase encoding gradient magnetic field) in the measurement space. The body movement correction unit 232 calculates the phase change Δθ in the k-space as the correction value using the displacement amount ΔY.

[0080] After the acquisition of the k-space data is completed (S16), the body movement correction unit 232 uses the calculated correction value to correct the k-space data at the time point when the body movement change is detected (S16). Then, the arithmetic unit 22 performs image reconstruction using the corrected k-space data (S17), which is the same as that of a normal MRI apparatus.

[0081] According to the present embodiment, by arranging the detector 50 at multiple positions or arranging two or more types of detectors, the accuracy of the body movement information that can be detected can be improved. As a result, the body movement information can be used afterwards to correct the image, and an image that does not cause an extension of the imaging time and excludes the influence of body movement can be obtained.

[0082] <Embodiment 3>

[0083] In Embodiment 1, an example of mounting the detector 50 on the support structure of the receiving coil device was described. However, in the present embodiment, a marker that can be detected by a camera is mounted on the support structure of the receiving coil device, and the body movement is detected based on the image of the camera in which the marker is reflected. That is, in the present embodiment, the detector is composed of the marker mounted on the support structure and the camera that captures the marker. The MRI device acquires the image signal from the camera via the input port, and calculates the body movement (amount of movement) in the body movement processing unit 23.

[0084] In Figure 10 shows an example of the arrangement of the marker 55 and the camera 60 in the present embodiment. In Figure 10 , the receiving coil device includes a holder portion 41 that fixes the receiving coil (A-side coil) 31 and a base portion 42 that supports the holder portion 41, and the marker 55 is mounted at approximately the center of the holder portion 41. However, the marker 55 is not limited to the center as long as it is in a position where it can be photographed in relation to the camera 60, and in addition, not only one but also a plurality of markers can be arranged. In addition, the material and shape of the marker 55 are not particularly limited as long as they can be identified from the image of the camera 60, and it can be either a part of the holder portion 41 or fixed to the holder portion 41 by a fixing unit such as a screw or an adhesive.

[0085] The camera 60 is fixed inside the gantry that provides the examination space for inserting the subject or outside the gantry and in a position where it can photograph the inside. In Figure 10 , one camera 60 is shown, and a plurality of cameras can also be used.

[0086] As shown in Figure 6 (C), in addition to the body movement determination unit 231, the body movement processing unit 23 of the MRI device according to the present embodiment further includes a body movement amount calculation unit 233, which inputs the image from the camera 60 and calculates the body movement amount based on the change of the marker 55. The calculation of the body movement amount, for example, extracts the marker from the image of each frame and calculates the change amount of the position of the marker in the image.

[0087] The processing flow of the MRI device in the present embodiment is the same as the flow shown in Figure 7 except for adding the above-described step of calculating the body movement amount. In Figure 7Before the determination step S2, the body momentum calculation unit 233 calculates the body momentum. Then, a portion of the k-space data is re-photographed according to the size of the body momentum, which is the same as the first embodiment.

[0088] According to this embodiment, the same effects as those of the first embodiment can be obtained, and since no equipment directly connected to the MRI apparatus is fixed to the receiving coil device side, the influence of the equipment on the image obtained by the MRI apparatus can be completely eliminated.

[0089] <Modification>

[0090] In the third embodiment, the camera 60 is used to photograph the mark 55 fixed to the holder 41, but the camera 60 may be used to photograph the mark 55 fixed to the holder 41. Figure 11 As shown, a hole 412 that is long in the vertical direction is formed at the end of the holder part 41 connected to the guide part 45, and a camera 60 is provided at a position where the end of the holder part 41 can be photographed, and the end of the guide part 45 that can be seen through the hole is photographed by the camera 60. In this case, a mark for improving recognition may be arranged at the end of the guide part 45, and lines Lmax and Lmin indicating the allowable value of the body momentum may be formed at two locations above and below the hole 412. In this way, it is possible to judge whether the body momentum from the camera image exceeds the allowable value without calculating the body momentum, and simpler control can be performed.

[0091] The embodiments of the receiving coil device and the MRI device using the receiving coil device have been described above, but the present invention is not limited to these embodiments and the drawings used in the description of the embodiments, and various changes and additions can be made. For example, in the embodiments, the configuration of the detection unit 50 is described by taking the receiving coil device of the structure shown in the figure as an example, but the detection unit 50 has a mechanism for making the receiving coil close to the subject, and any device that detects the movement of a member that moves integrally with the subject can be configured in accordance with the mechanism and the member.

Claims

1. A receiving coil device, which is a receiving coil device for a magnetic resonance imaging device, is characterized in that The receiving coil device includes: One or more receiving coils covering the head of the subject; A base portion on which the head of the subject is placed; A cage portion that fixes one of the receiving coils and is supported by the base portion; And A mechanism portion that brings the receiving coil fixed to the cage portion into close contact with a part of the head, The receiving coil device further includes a detection portion that detects a physical quantity related to the displacement of the cage portion, When the surface of the head placed on the base portion is set as the back surface and the opposite side is set as the front surface, the cage portion has a shape that bends along the side surfaces of the head, The detection portion is a rangefinder that detects the change in the distance between the end portion of the cage portion and the base portion as the physical quantity.

2. A receiving coil device, which is a receiving coil device for a magnetic resonance imaging device, is characterized in that The receiving coil device includes: One or more receiving coils covering the head of the subject; A base portion on which the head of the subject is placed; A cage portion that fixes one of the receiving coils and is supported by the base portion; And A mechanism portion that brings the receiving coil fixed to the cage portion into close contact with a part of the head, The receiving coil device further includes a detection portion that detects a physical quantity related to the displacement of the cage portion, When the surface of the head placed on the base portion is set as the back surface and the opposite side is set as the front surface, the cage portion has a shape that bends along the side surfaces of the head, The detection portion is an accelerometer that detects the movement of the end portion of the cage portion as the physical quantity.

3. The receiving coil device according to claim 1 or 2, wherein The base portion includes a guiding portion that makes surface contact with the end portion of the cage portion, The detection portion is arranged between the end portion of the cage portion and the guiding portion and is a pressure gauge that detects the change in pressure between the end portion of the cage portion and the guiding portion as the physical quantity.

4. The receiving coil device according to claim 1 or 2, wherein The cage portion has a left end portion and a right end portion corresponding to the left and right of the subject, The detection portions are respectively arranged on the left and right end sides of the cage portion.

5. The receiving coil device according to claim 1 or 2, wherein The mechanism portion includes: a movable portion fixed to the cage portion that makes the cage portion movable between an assembled position and a retracted position; and a supporting portion that supports the movable portion in a stepwise manner with respect to the base portion.

6. The receiving coil device according to claim 5, wherein The movable portion is a mechanism that slides the cage portion along the shape of the head.

7. The receiving coil device according to claim 1 or 2, wherein The cage portion is provided with a mark that can be recognized in a camera image.

8. A magnetic resonance imaging apparatus, characterized in that, It includes: A transmitting portion including a transmitting coil that applies a high-frequency magnetic field to a subject placed in a static magnetic field; A receiving portion including a receiving coil that receives a nuclear magnetic resonance signal generated from the subject; An inclined magnetic field generating portion that generates an inclined magnetic field that imparts position information to the nuclear magnetic resonance signal; A control unit that controls the transmitting unit, the inclined magnetic field generating unit, and the receiving unit; and An arithmetic unit that creates an image of the subject using the nuclear magnetic resonance signals collected under different inclined magnetic field conditions, As the receiving coil, a receiving coil device according to any one of claims 1 to 7 is provided.

9. The magnetic resonance imaging apparatus according to claim 8, wherein Based on the physical quantity detected by the detection unit, the control unit determines the inclined magnetic field condition for which the nuclear magnetic resonance signal should be reacquired, and controls the reacquisition of the nuclear magnetic resonance signal for the inclined magnetic field condition determined to require reacquisition.

10. The magnetic resonance imaging apparatus according to claim 8, wherein Based on the physical quantity detected by the detection unit, the arithmetic unit calculates a correction amount of the nuclear magnetic resonance signal and corrects the nuclear magnetic resonance signal for image reconstruction.

11. The magnetic resonance imaging apparatus according to claim 8, wherein The receiving coil is the receiving coil device according to claim 4, The arithmetic unit calculates the movement amount of the cradle using the detection results of the detection units respectively provided on both end sides of the left and right of the cradle unit.

12. The magnetic resonance imaging apparatus according to claim 8, wherein The receiving coil is the receiving coil device according to claim 7, The magnetic resonance imaging apparatus further includes a camera provided at a position where at least a part of the cradle unit including the marker can be imaged, The arithmetic unit calculates a physical quantity related to the displacement of the cradle unit using the image of the camera.

13. The magnetic resonance imaging apparatus according to claim 8, wherein The receiving coil also serves as a transmitting coil.

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