Sensor unit, and medical imaging apparatus

Abstract

To provide a sensor unit for suppressing movement of the sensor unit caused by a subject's movement, and a medical imaging apparatus.SOLUTION: A sensor unit is fitted to a surface where a subject is mounted, detects heartbeat of the subject, and includes: an FBG sensor provided with one or more sensor elements detecting the subject's heartbeat; a fixing member which fixes a side opposite the subject in the FBG sensor and whose surface fixing the FBG sensor has prescribed rigidity; and a cover which covers the size facing the subject in the FBG sensor and has a configuration in which a cover hole is formed at a position corresponding to the sensor element on the surface facing the subject.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a sensor unit and a medical imaging device. [Background technology]

[0002] When imaging the heart with a medical imaging device such as an MRI device, the heartbeat is usually monitored and MR signals are measured in synchronization with the heartbeat. Heartbeat monitoring may also be performed when imaging hemodynamics of areas distant from the heart, such as the brain and lower limbs, using an MRI device. MRI is an abbreviation for Magnetic Resonance Imaging.

[0003] One method for monitoring heart rate is to place electrodes with conductive gel on the skin of the subject near the heart and measure the electrocardiogram waveform. Another method for monitoring heart rate is to irradiate the subject's fingertip with infrared light and measure the pulse waveform by capturing changes in blood flow that occur with the heartbeat as changes in infrared light. In both of the above methods, the peak of the electrocardiogram waveform during ventricular systole, when the subject's heart movement is greatest, and the peak of the pulse waveform are captured and used as the time trigger for measuring the MR signal.

[0004] Patent Document 1 describes an optical fiber sensor system that includes an FBG sensor and detects signals associated with pulse waves at measurement sites separately for each measurement site. FBG sensor is an abbreviation for fiber Bragg grating sensor.

[0005] In the optical fiber sensor system described in the document, an FBG sensor is attached to the skin surface of a measurement site where it is easy to detect the expansion and contraction of the arteries, such as the chest of a subject. The FBG sensor detects the slight displacement of the skin surface caused by the expansion and contraction of the arteries, thereby detecting the subject's pulse wave.

[0006] The optical fiber sensor system described in the document uses an optical fiber in which multiple FBG sensors are arranged in series when detecting pulse waves at multiple locations using FBG sensors. The multiple FBG sensors have different Bragg wavelengths. In the optical fiber sensor system, light incident on the optical fiber is a band light that includes the Bragg wavelengths of the FBG sensors, and the optical signals of each FBG sensor are separated and detected.

[0007] Patent Document 2 describes a sensing fiber including one or more optical fiber Bragg gratings. Figure 2 of the document illustrates the sensing fiber integrated into a vest. The document also exemplifies a magnetic resonance imaging system as an imaging system for imaging the inside of a subject.

[0008] Patent Document 3 describes an optical fiber type flat body sensor used in a method for detecting breathing, heartbeat, etc. with high accuracy. The optical fiber type flat body sensor described in this document has multiple filters, such as optical fiber diffraction gratings, that reflect specific wavelengths incorporated into the optical fiber. The document also describes an example of an optical fiber type flat body sensor that is installed between the pad and mattress of a bed.

[0009] Patent Document 4 describes a system that uses an FBG sensor to detect pulse waves and calculate heart rate. The document describes measuring pulse waves using an FBG sensor attached to the surface of the chest, and acquiring data using an FBG sensor with multiple sensor units. The document also describes measuring by fixing an FBG sensor to the abdomen of a pregnant woman, and measuring fetal signals from the measured waveform.

[0010] Furthermore, as a heart rate monitoring method other than electrocardiogram measurement and pulse wave measurement, a method has been proposed in which electromagnetic waves are used to measure changes in the shape of the heart and capture the peak of ventricular systole. In the heart rate monitoring method using electromagnetic waves, a heart rate monitoring antenna is installed in part of a cardiac imaging receiving coil that is placed near the heart when imaging the subject's heart, and changes in the antenna impedance due to changes in the shape of the heart when RF pulses are applied are measured. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2013 / 180085 [Patent Document 2] Special Publication No. 2014-534848 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-061306 [Patent Document 4] Japanese Patent Publication No. 2020-138022 Summary of the Invention [Problem to be solved by the invention]

[0012] However, in electrocardiogram waveform measurement, electrodes must be placed in appropriate positions by an operator while the subject is undressed. This can impose mental and time burdens on both the subject and the operator. Furthermore, in electrocardiogram waveform measurement, if the subject sweats during imaging and the electrodes come off, it becomes difficult to monitor the heart rate.

[0013] The inventions described in Patent Document 1 and Patent Document 2 have the problem of mental and time burdens on the subject and operator when installing a sensor element on the subject. Also, the invention described in Patent Document 1 has the problem of difficulty in monitoring the heart rate due to the sensor element being detached from the subject.

[0014] When measuring a subject's pulse waveform, the measurement is performed at the fingertips, which is farther from the heart than when measuring an electrocardiogram waveform, so the peak of the electrocardiogram waveform measured during ventricular systole is dulled, making the measurement of a subject's pulse waveform unsuitable for highly accurate heart rate monitoring.

[0015] Generally, when a subject is lying down, the pulse wave fluctuations at sites far from the heart, such as the fingertips, are smaller than those at sites close to the heart, such as the chest. This raises the concern that the fluctuations in the pulse waveform at the fingertips will be smaller during imaging, making it impossible to obtain the peak of the pulse waveform.

[0016] The heart rate monitoring method using electromagnetic waves has the advantage that the subject can be measured while still wearing their clothes, and that the mental and time burden on both the subject and the imaging staff is less than that of electrocardiogram measurement.Furthermore, the heart rate monitoring method using electromagnetic waves has the advantage that a heart rate monitoring sensor is placed near the heart, and the pulse waveform does not become dull to the extent that the pulse waveform peak cannot be obtained during imaging, as in the method of measuring the pulse wave at the fingertip.

[0017] On the other hand, in a heartbeat monitoring method using electromagnetic waves, when imaging hemodynamics of an imaging region distant from the heart, such as the brain or lower limbs, in synchronization with the heartbeat, the imaging region needs to be located at the center of the irradiation coil, which may result in the heartbeat monitoring antenna being located near the heart being significantly deviated from the center of the bore, making it difficult to apply a heartbeat monitoring method using electromagnetic waves.

[0018] Furthermore, the heart rate monitoring method using electromagnetic waves may have the limitation that it is difficult to monitor the heart rate with sufficient time resolution in a sequence with a long irradiation pulse interval.The heart rate monitoring method using an FBG sensor or the like that is placed on a part other than the subject's body or clothing solves the problems of the above-mentioned heart rate monitoring method using electromagnetic waves.

[0019] In a heart rate monitoring method using an FBG sensor or the like, if the FBG sensor or the like is not fixed to a rigid object such as a heavy object, the FBG sensor or the like may move in three-dimensional space due to the subject's body movements, which may cause drift in the electrocardiogram waveform.

[0020] Generally, the subject's body movements are more than 10 times larger than the skin movements that accompany the heartbeat, and during periods when the electrocardiogram waveform drifts due to the subject's body movements, it is difficult to monitor the heartbeat to capture small changes in the waveform.

[0021] In the invention described in Patent Document 2, which uses a sensing fiber attached to the subject's vest, the subject's body movements also cause the vest to move, raising concerns about the occurrence of drift in the electrocardiogram waveform. During periods when drift occurs in the electrocardiogram waveform, it is difficult to monitor the heartbeat, and when imaging the subject while synchronizing with the heartbeat using an MRI device or the like, the imaging period is extended beyond the specified imaging period.

[0022] The measured waveform output from the FBG sensor measures the reflected light from the diffraction grating. If the optical fiber connecting the diffraction grating and the interrogator, which is the propagation path of the reflected light, moves, a drift in the electrocardiogram waveform can occur, just as if the subject's body moved. During the period when a drift in the electrocardiogram waveform occurs, it is difficult to monitor the heart rate. In other words, it is preferable that the optical fiber connecting the diffraction grating and the interrogator is not subjected to vibration, pressure, etc.

[0023] When the invention described in Patent Document 3, which uses an optical fiber flat-plate upper body sensor placed between a mat and a pad placed under the subject, is applied to heart rate monitoring in an MRI device or the like, the position of the optical fiber flat-plate upper body sensor in three-dimensional space may move due to the movement of the subject's limbs, etc., which can cause unpredictable drift in the electrocardiogram waveform. During the period when drift occurs in the electrocardiogram waveform, it is difficult to monitor the heart rate.

[0024] When the invention described in Patent Document 4, which performs measurements by fixing an FBG sensor to the abdomen of a subject, is applied to heart rate monitoring in an MRI device or the like, unpredictable drifts can occur in the electrocardiogram waveform due to unpredictable movements of the subject. During the period when drifts occur in the electrocardiogram waveform, it is difficult to monitor the heart rate.

[0025] The present disclosure has been made in consideration of the above circumstances, and aims to provide a sensor unit and a medical imaging device in which movement of the sensor unit caused by movement of a subject is suppressed. [Means for solving the problem]

[0026] A sensor unit according to a first aspect of the present disclosure is a sensor unit that is attached to a surface of a bed on which a subject rests, and detects the heartbeat of the subject, and includes a fiber Bragg grating sensor having one or more sensor elements that detect the heartbeat of the subject, a fixing member that fixes the side of the fiber Bragg grating sensor opposite to the side facing the subject, and the surface to which the fiber Bragg grating sensor is fixed has a specified rigidity, and a cover that covers the side of the fiber Bragg grating sensor that faces the subject, and has a structure in which a cover hole is formed at a position corresponding to the sensor element on the surface facing the subject.

[0027] According to the sensor unit of the first aspect, the fiber Bragg grating sensor is fixed to a fixing member having a specified rigidity and is provided with a cover that covers the side facing the subject. This prevents the fiber Bragg grating sensor from moving due to the subject's movement. Meanwhile, the sensor element comes into contact with the subject through the cover hole. This allows for preferable detection of the subject's heartbeat.

[0028] The sensor unit according to the second aspect may include a contact assistant member in the sensor unit according to the first aspect, the contact assistant member being positioned on the side of the cover hole at a position corresponding to the sensor element in the fiber Bragg grating sensor, and having a shape that protrudes from the cover hole.

[0029] The sensor unit according to the third aspect is the sensor unit of the second aspect, wherein the length of the first surface of the contact auxiliary member that comes into contact with the subject is longer than the length of the second surface that comes into contact with the sensor element in the longitudinal direction of the bed on which the sensor unit is placed.

[0030] The sensor unit according to the fourth aspect may be a sensor unit according to any one of the first to third aspects, and may include a first elastic member having a specified elasticity, which is installed at a position corresponding to a sensor element in the fiber Bragg grating sensor, on the side of the fixing member.

[0031] The sensor unit according to the fifth aspect may be a sensor unit according to any one of the first to fourth aspects, and may further include a second elastic member that is attached to a fixed member, has a specified elasticity, and is thick enough to come into contact with the subject.

[0032] A sensor unit according to a sixth aspect is the sensor unit of any one of the first to fifth aspects, wherein the fixing member is installed on a bed and may also serve as a table on which the subject can rest.

[0033] A sensor unit according to a seventh aspect is the sensor unit of any one of the first to fifth aspects, wherein the fixing member has a shape that follows the shape of a surface of a table placed on a bed on which the sensor unit is placed.

[0034] A sensor unit according to an eighth aspect is the sensor unit of any one of the first to seventh aspects, wherein the cover has a shape that covers the entire length of the fiber Bragg grating sensor in the direction in which it extends.

[0035] A sensor unit according to a ninth aspect is the sensor unit of the eighth aspect, wherein the cover has a shape whose longitudinal direction is the direction in which the fiber Bragg grating sensor extends.

[0036] A sensor unit according to a tenth aspect is the sensor unit of the eighth aspect, wherein the cover may have a polygonal or circular planar shape on a surface on which the fiber Bragg grating sensor extends.

[0037] A sensor unit according to an eleventh aspect is a sensor unit according to any one of the first to tenth aspects, wherein the fiber Bragg grating sensor includes a first sensor element and a second sensor element different from the first sensor element, and the cover has a first cover hole formed at a position corresponding to the first sensor element and a second cover hole formed at a position corresponding to the second sensor element.

[0038] The sensor unit of the 12th aspect may be the sensor unit of the 11th aspect, further comprising: a first contact assistant member arranged at a position corresponding to the first sensor element in the fiber Bragg grating sensor and having a shape that protrudes from the first cover hole; and a second contact assistant member arranged at a position corresponding to the second sensor element in the fiber Bragg grating sensor and having a shape that protrudes from the second cover hole.

[0039] A sensor unit according to a thirteenth aspect may be the sensor unit of the twelfth aspect, further comprising a first fiber Bragg grating sensor having a first sensor element, and a second fiber Bragg grating sensor having a second sensor element.

[0040] A medical imaging device according to a fourteenth aspect of the present disclosure is a medical imaging device comprising: a bed on which a subject can be placed; a measurement device that measures the subject; a measurement data processing device that generates a medical image of the subject based on the measurement results of the subject; and a sensor unit that is attached to the surface of the bed on which the subject can be placed and that detects the subject's heartbeat, the sensor unit comprising: a fiber Bragg grating sensor having one or more sensor elements that detect the subject's heartbeat; a fixing member that fixes the side of the fiber Bragg grating sensor opposite to the side facing the subject, the fixing member having a specified rigidity on the surface to which the fiber Bragg grating sensor is fixed; and a cover that covers the side of the fiber Bragg grating sensor that faces the subject and has a structure in which a cover hole is formed at a position corresponding to the sensor element on the surface facing the subject.

[0041] The medical imaging device according to the fourteenth aspect of the present disclosure can achieve the same effects as the sensor unit according to the first aspect. The constituent elements of the sensor units according to the second to thirteenth aspects can be applied as constituent elements of the medical imaging device according to the other aspects.

[0042] A medical imaging device according to a 15th aspect is a medical imaging device according to the 14th aspect, which is further provided with one or more processors, and the one or more processors may select one sensor element from the plurality of sensor elements based on an image of the subject.

[0043] A medical imaging device according to a 16th aspect is a medical imaging device according to the 14th or 15th aspect, in which the fixing member is installed on a bed and may also serve as a coil unit installed on a table on which a subject rests.

[0044] A medical imaging device according to a seventeenth aspect is a medical imaging device according to the sixteenth aspect, wherein the fiber Bragg grating sensor is embedded in a plate-like member on the opposite side of the table in a housing that houses a coil provided in the coil unit. [Effects of the Invention]

[0045] According to the present disclosure, a fiber Bragg grating sensor is fixed to a fixing member having a specified rigidity and is provided with a cover that covers the side facing the subject. This prevents movement of the fiber Bragg grating sensor due to movement of the subject. Meanwhile, the sensor element contacts the subject through a hole in the cover. This allows for preferable detection of the subject's heartbeat. [Brief explanation of the drawings]

[0046] [Figure 1] FIG. 1 is a perspective view showing the appearance of an MRI apparatus. [Figure 2] FIG. 2 is a schematic diagram showing the internal configuration of the MRI apparatus. [Figure 3] FIG. 3 is an explanatory diagram of an FBG optical fiber. [Figure 4] FIG. 4 is a graph showing the detection results of the FBG optical fiber. [Figure 5] FIG. 5 is a schematic diagram of heart rate monitoring in a large subject. [Figure 6] FIG. 6 is a schematic diagram of heart rate monitoring in a small subject. [Figure 7] FIG. 7 is a schematic diagram showing a state in which the sensor unit according to the first embodiment is in use. [Figure 8] FIG. 8 is a graph showing an electrocardiogram waveform acquired using the sensor unit according to the first embodiment. [Figure 9] FIG. 9 is a graph showing the measured waveform when drift occurs. [Figure 10] FIG. 10 is a schematic diagram showing a state in which the sensor unit according to the second embodiment is in use. [Figure 11] FIG. 11 is a cross-sectional view taken along the line 11-11 in FIG. [Figure 12] FIG. 12 is a cross-sectional view taken along the line 12-12 in FIG. [Figure 13] FIG. 13 is a schematic diagram showing a state in which the sensor unit according to the third embodiment is in use. [Figure 14] FIG. 14 is a schematic diagram showing how the sensor unit is used by a subject with a small build. [Figure 15] FIG. 15 is a plan view of the load prevention cover according to the first structural example. [Figure 16] FIG. 16 is a plan view of the load prevention cover according to the second structural example. [Figure 17] FIG. 17 is a plan view of a load prevention cover according to the third structural example. [Figure 18] FIG. 18 is a plan view of a load prevention cover according to the fourth structural example. [Figure 19] FIG. 19 is a plan view of a load prevention cover according to the fifth structural example. [Figure 20] FIG. 20 is a schematic diagram showing a first example of use of an FBG optical fiber when a load prevention cover according to the fifth structural example is applied. [Figure 21] FIG. 21 is a schematic diagram showing a second use example of the FBG optical fiber when the load prevention cover according to the fifth structure example is applied. [Figure 22] FIG. 22 is a schematic diagram showing a third use example of an FBG optical fiber when a load prevention cover according to the fifth structure example is applied. [Figure 23] FIG. 23 is a schematic diagram showing a state in which the sensor unit according to the fourth embodiment is in use. [Figure 24] FIG. 24 is a graph showing a measurement waveform obtained using the sensor unit according to the fourth embodiment. [Figure 25] FIG. 25 is a schematic diagram showing a state in which the sensor unit according to the fifth embodiment is in use. [Figure 26] FIG. 26 is a schematic diagram showing a state in which the sensor unit according to the sixth embodiment is in use. [Figure 27] FIG. 27 is a schematic diagram showing a state in which the sensor unit according to the seventh embodiment is in use. DETAILED DESCRIPTION OF THE INVENTION

[0047] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description and accompanying drawings, identical components are designated by the same reference numerals, and duplicate explanations will be omitted. In addition, when multiple components are listed in the following embodiments, it can be interpreted that at least one of the multiple components is included.

[0048] [Example of MRI system configuration] FIG. 1 is a perspective view showing the exterior of an MRI apparatus. The MRI apparatus 100, which is a magnetic resonance imaging apparatus, includes a gantry 110, which is the apparatus main body, and a bed 130. The bed 130 includes a top plate 130A and is disposed on the front side of a bore 120, which is a cylindrical imaging space provided in the gantry 110. The top plate 130A can be advanced into and withdrawn from the bore 120 using a top plate driving mechanism provided in the bed 130. The top plate driving mechanism is not shown in the drawing.

[0049] The bed 130 may be configured to be fixed to the gantry 110, or may be a dockable bed, which is a movable bed that can be attached to and detached from the gantry 110. A top plate 130A provided on the bed 130 is configured to allow a sensor unit 200 to be freely attached. The sensor unit 200 is used when monitoring the heart rate of the subject. The subject is designated by the symbol Exa and is illustrated in FIG. 2 etc.

[0050] The gantry 110 is an example of a measurement device of the present disclosure, and the MRI device is an example of a medical imaging device of the present disclosure.

[0051] 2 is a schematic diagram showing the internal configuration of an MRI apparatus. The MRI apparatus 100 includes a static magnetic field generating magnet 104, a gradient magnetic field coil 106, an RF transmission coil 108, and a sensor unit 200. Note that RF is an abbreviation for Radio Frequency.

[0052] The subject Exa is placed on the top board 130A of the bed 130 and placed in the imaging space. That is, by moving the top board 130A on which the subject Exa is placed to the bore 120, the examination region of the subject Exa is moved to be positioned at the center of the static magnetic field in the bore 120. Note that the reference numeral 130A of the top board 130A is omitted in FIG. 2.

[0053] The static magnetic field generating magnet 104 generates a uniform static magnetic field in the imaging space. The static magnetic field generating magnet 104 includes a permanent magnet type, a resistive conducting type, or a superconducting type static magnetic field generating source. The gradient magnetic field coil 106 generates a gradient magnetic field in the imaging space. The gradient magnetic field coil 106 is composed of gradient magnetic field coils in the three axes of X, Y, and Z, which are real space coordinate systems and stationary coordinate systems. Each gradient magnetic field coil is connected to a gradient magnetic field power supply 116 and is supplied with current. As a result, gradient magnetic fields are generated in the three axes of X, Y, and Z.

[0054] The RF transmission coil 108 is a coil that irradiates a radio frequency magnetic field pulse to the subject Exa. The radio frequency magnetic field pulse may also be referred to as an RF pulse. The RF transmission coil 108 is connected to a radio frequency magnetic field generator 112, and a radio frequency pulse current is supplied to the RF transmission coil 108. The radio frequency magnetic field generator 112 is driven in accordance with instructions from a sequencer 118 to amplitude-modulate the radio frequency pulse and supply the amplified radio frequency pulse to the RF transmission coil 108.

[0055] The sequencer 118 sends commands to the radio frequency magnetic field generator 112 and the gradient magnetic field power supply 116 according to the imaging pulse sequence, causing them to generate a radio frequency magnetic field and a gradient magnetic field, respectively. The generated radio frequency magnetic field is applied to the subject Exa as a pulsed radio frequency magnetic field via the RF transmission coil 108. This induces a nuclear magnetic resonance phenomenon in the spins of atoms that make up the biological tissue of the subject Exa. Note that nuclear magnetic resonance may be referred to as NMR, an abbreviation of nuclear magnetic resonance.

[0056] The MRI apparatus 100 includes a receiving coil unit. The receiving coil unit is a coil that receives echo signals emitted due to the NMR phenomenon of the spins of atoms that constitute the biological tissue of the subject Exa. The echo signals may also be referred to as NMR signals.

[0057] In Figure 2, the receiving coil unit is not shown. The receiving coil unit may be a blanket type that is applied to imaging of the chest and abdomen. Different receiving coil units may be applied depending on the examination area. For example, receiving coil units for imaging various areas such as the head, spine, abdomen, legs, and arms can be used. One or more receiving coil units may be used in a single imaging session, and multiple receiving coil units may be used simultaneously to image different areas. Note that the receiving coil unit may sometimes be simply called a receiving coil. The NMR signal generated from the subject Exa is received using the receiving coil unit and detected using the receiver 114.

[0058] The nuclear magnetic resonance frequency used as a detection reference in the receiver 114 is set by the sequencer 118. The nuclear magnetic resonance frequency may be referred to as a detection reference frequency. The sequencer 118 controls each component so that pre-programmed timing and intensity are applied. A program that describes the timing and intensity of RF pulses, gradient magnetic fields, and signal reception is called a pulse sequence. Various pulse sequences are known depending on the purpose, but a detailed description thereof will be omitted here.

[0059] The control unit 140 controls the operation of the MRI apparatus 100 via the sequencer 118, receives signals detected by the receiver 114, and performs various signal processing such as image reconstruction.

[0060] The receiver 114 applies a set detection reference frequency, performs quadrature phase detection on the echo signal, which is an analog wave, converts it into raw data, and then transmits it to the control unit 140. This raw data is also called an echo signal or measurement data.

[0061] The sensor unit 200 detects the heartbeat of the subject Exa. The sensor unit 200 outputs a detection signal of the heartbeat of the subject Exa via the interrogator 220. The sequencer 118 monitors the heartbeat of the subject Exa based on the heartbeat detection signal transmitted from the interrogator 220, and performs imaging of the subject Exa.

[0062] The control unit 140 can be configured using a computer. The computer applied to the control unit 140 may be a personal computer or a workstation. That is, the control unit 140 includes one or more processors and one or more memories, and the one or more processors execute a program containing one or more instructions stored in the one or more memories to realize various functions of the MRI apparatus 100.

[0063] The control unit 140 receives various instruction inputs from the operation unit 150, controls each unit of the MRI apparatus 100, and performs processes such as converting the echo signals in the spatial frequency domain received via the sequencer 118 into images in real space by inverse Fourier transform, thereby generating MRI images. The control unit 140 is an example of a measurement data processing device that generates medical images of a subject based on the measurement results of the subject.

[0064] The operation unit 150 includes a mouse, a keyboard, etc., and functions as part of a GUI that accepts input from an operator using a display operation window on a display (not shown). That is, the operation unit 150 and the display function as a GUI that allows the operator to start, stop, or pause the MRI apparatus 100, select a pulse sequence, and input imaging conditions and processing conditions. Note that GUI is an abbreviation for Graphical User Interface.

[0065] [FBG Optical Fiber Overview] Fig. 3 is an explanatory diagram of an FBG optical fiber. The sensor unit 200 shown in Fig. 1 etc. includes an FBG optical fiber 202. The FBG optical fiber 202 is an optical fiber device in which a periodic refractive index change is formed in a core portion 202B of an optical fiber 202A. The refractive index change acts as a diffraction grating 204, and only light of a Bragg wavelength λ that satisfies the Bragg reflection condition based on the period of the diffraction grating 204 is reflected. When the refractive index of the core is n and the grating period is Λ, the Bragg wavelength λ is expressed as λ = 2 × n × Λ.

[0066] The diffraction grating 204 may be referred to as a fiber Bragg grating, which may be abbreviated as FBG, which is an English abbreviation of Fiber Bragg Grating.

[0067] The FBG optical fiber 202 is connected to an interrogator 220 shown in Figure 2. The interrogator 220 functions as a light source device that inputs incident light to the FBG optical fiber 202, and also functions as a sensor that analyzes the light reflected by the diffraction grating 204.

[0068] Figure 4 is a graph showing the detection results of the FBG optical fiber. Figure 4 shows a measured waveform acquired as an electrical signal synchronized with the subject's heartbeat. The horizontal axis of the graph shown in Figure 4 represents time, and the vertical axis represents signal intensity.

[0069] The MRI apparatus 100 measures the light reflected from the diffraction grating 204 placed near the subject's heart, and acquires an electrical signal that represents the strain of the FBG optical fiber 202 associated with the movement of the skin synchronized with the subject's heartbeat. The peak Pe of the waveform shown in Fig. 4 corresponds to the ventricular systole, and the MRI apparatus 100 uses the peak Pe of the waveform as a trigger for imaging.

[0070] The FBG optical fiber 202 can detect not only pressure changes but also temperature changes. The MRI apparatus 100 has a particular problem in that the temperature inside the gantry 110 rises due to heat generation from the gradient magnetic field coil 106 and the RF transmit coil 108 during imaging. The MRI apparatus 100 includes an FBG optical fiber for temperature detection, and may detect the temperature inside the gantry 110 using the FBG optical fiber 202 for temperature detection and correct the electrical signal representing the distortion of the FBG optical fiber 202.

[0071] Furthermore, the FBG optical fiber 202 used for monitoring the heartbeat may include an FBG optical fiber 202 having a plurality of diffraction gratings, and a diffraction grating 204 located away from the subject's heart may be used to detect the temperature inside the gantry 110 and correct the electrical signal representing the distortion of the FBG optical fiber 202. This allows the MRI apparatus 100 to acquire a measurement waveform representing the time change of the detection signal synchronized with the heartbeat of the subject with high accuracy.

[0072] The FBG optical fiber 202 may include a plurality of diffraction gratings 204. The sensor unit 200 may automatically estimate the position of the diffraction grating 204 that is closest to the heart of the subject Exa from among the plurality of diffraction gratings 204, based on an image captured by the gantry camera. That is, the control unit 140 of the MRI apparatus 100 may acquire an image of the subject Exa captured using the gantry camera, analyze the image of the subject Exa, and estimate the position of the heart of the subject Exa. The control unit 140 may notify information about the position of the diffraction grating 204 that is closest to the position of the heart of the subject Exa.

[0073] Fig. 5 is a schematic diagram of heart rate monitoring in a large-sized subject. Fig. 6 is a schematic diagram of heart rate monitoring in a small-sized subject. Fig. 5 schematically illustrates a state in which a large-sized subject Exa1 is laid on a mat 134 on a table 132. Similarly, Fig. 6 schematically illustrates a state in which a small-sized subject Exa2 is laid on a mat 134 on the table 132.

[0074] The FBG optical fiber 202 shown in Fig. 5 is placed on the back side of the subject Exa1 when the subject Exa1 is lying on his back. The same applies to the FBG optical fiber 202 shown in Fig. 6.

[0075] The FBG optical fiber 202 shown in FIGS. 5 and 6 includes a plurality of diffraction gratings 204, namely, a diffraction grating 204A, a diffraction grating 204B, a diffraction grating 204C, a diffraction grating 204D, and a diffraction grating 204E.

[0076] 5, the grating 204C is estimated as the grating 204 closest to the heart. The grating 204A is estimated as the grating 204 closest to the heart for the large-sized subject Exa1 shown in FIG. 6.

[0077] [Sensor unit according to the first embodiment] Fig. 7 is a schematic diagram showing a state in which the sensor unit according to the first embodiment is in use. Fig. 7 shows a cross section taken along the 7-7 cross section line shown in Fig. 5. For convenience of illustration, the cross section line is omitted from Fig. 7 as appropriate.

[0078] 7 includes an FBG optical fiber 202, a diffraction grating 204, a weight-bearing cover 206, and a heart rate transmitter 208. The FBG optical fiber 202 is connected to an interrogator 220 via an optical fiber 210. The optical fiber 210 functions as a propagation path for incident light and a propagation path for reflected light between the FBG optical fiber 202 and the interrogator 220.

[0079] The y direction and z direction shown in FIG. 7 are directions in a three-dimensional Cartesian coordinate system applied to the three-dimensional space in which the MRI apparatus 100 is installed. The y direction is an axis perpendicular to the surface on which the MRI apparatus 100 is installed. The y direction may be the vertical direction. The z direction may be parallel to the surface on which the MRI apparatus 100 is installed and parallel to the longitudinal direction of the table 132. The x direction, not shown in FIG. 7, is perpendicular to the y direction and the z direction and may be parallel to the short-side direction of the table 132.

[0080] The FBG optical fiber 202 is installed on the upper surface 132A of the table 132 of the MRI apparatus 100. That is, the side of the FBG optical fiber 202 opposite to the side facing the subject Exa is fixed to a hard object having a specified rigidity. This prevents the FBG optical fiber 202 from moving from the fixed position in three-dimensional space, thereby suppressing drift of the measurement waveform.

[0081] The heartbeat of the subject Exa applies a small strain of about several micrometers to several hundred micrometers in the y direction to the FBG optical fiber 202. The FBG optical fiber 202 detects the small strain as the heartbeat. The sensor unit 200 outputs a measurement waveform that represents the time change in the heartbeat as the detection result of the FBG optical fiber 202.

[0082] On the other hand, the FBG optical fiber 202, which is not fixed and moves in three-dimensional space, moves by several hundred micrometers to several millimeters in the x and z directions when the subject Exa makes unpredictable movements such as moving his or her arms and legs, causing the measured waveform to drift.

[0083] The sensor unit 200 is adapted to have a structure that suppresses weight applied to the FBG optical fiber 202 and the optical fiber 210 due to the subject's movement. That is, the FBG optical fiber 202 and the optical fiber 210 are covered on the side facing the subject Exa with a weight prevention cover 206. This suppresses drift of the measurement waveform due to unpredictable movements of the subject's limbs, etc.

[0084] A material having a specified rigidity is applied to the load prevention cover 206. An example of the material of the load prevention cover 206 is a synthetic resin such as plastic. The rigidity of the load prevention cover 206 may be equal to or less than the rigidity of the upper surface 132A of the table 132.

[0085] The load prevention cover 206 has a structure that covers the entire length of the FBG optical fiber 202 in the direction in which the FBG optical fiber 202 extends. The load prevention cover 206 may have a structure that covers a part of or the entire length of the optical fiber 210 that is connected to the FBG optical fiber 202 in the direction in which the FBG optical fiber 202 extends.

[0086] The heartbeat propagating device 208 is placed at a position where one surface 208A contacts the lower part of the heart Ha on the back side of the subject Exa, and the other surface 208B contacts the diffraction grating 204 of the FBG optical fiber 202. The weight protection cover 206 has a cover hole 206A formed therein that penetrates in the y direction relative to the position where the heartbeat propagating device 208 is placed.

[0087] The heartbeat transmitting device 208 transmits with high sensitivity the movement of the subject Exa synchronized with the heartbeat of the subject Exa, which is the object of measurement, to the diffraction grating 204 of the FBG optical fiber 202. This makes it possible to monitor the heartbeat of the subject Exa while the subject Exa remains fully clothed.

[0088] With respect to the position in the y direction relative to the upper surface 132A of the table 132, the position of the surface of the heartbeat transmitting device 208 that comes into contact with the subject Exa is higher than the position of one surface 206B of the weight-transmitting cover 206. In other words, the heartbeat transmitting device 208 has a structure in which one surface 208A protrudes in the y direction from the cover hole 206A that penetrates the weight-transmitting cover 206.

[0089] The heart rate transmitting device 208 is made of a material that is softer than the weight protection cover 206. An example of a material that can be used for the heart rate transmitting device 208 is rubber. The rigidity of the heart rate transmitting device 208 may be less than the rigidity of the weight protection cover 206.

[0090] 7 has a shape in which the length of the surface in contact with the subject Exa is the same as the length of the surface in contact with the diffraction grating 204 in the z direction. The length of the heartbeat propagating device 208 in the z direction may be the same as or longer than the length of the diffraction grating 204. Here, the term "same" in this specification is not limited to an embodiment in which the two are completely identical, but may include a substantially same object that is different but can achieve the same operational effect.

[0091] The table 132 is an example of a fixing member that also serves as a table on which a subject can stand, as disclosed herein. The FBG optical fiber 202 is an example of a fiber Bragg grating sensor, as disclosed herein. The diffraction grating 204 is an example of one or more sensor elements, as disclosed herein. The weight-preventing cover 206 is an example of a cover, as disclosed herein. The heartbeat transmitting device 208 is an example of a contact assisting member, as disclosed herein.

[0092] Fig. 8 is a graph showing an electrocardiogram waveform acquired using the sensor unit according to the first embodiment. The horizontal axis of the graph shown in Fig. 8 represents time, and the vertical axis represents signal strength. The signal strength is normalized.

[0093] The measured waveform shown in Figure 8 is a long-period waveform synchronized with breathing and having a period of approximately 6 seconds, and a short-period waveform synchronized with the heartbeat superimposed on it. The long-period waveform can be separated and removed from the measured waveform using a frequency filter.

[0094] The MR signal is measured while synchronizing with the heartbeat based on the heartbeat waveform extracted from the measured waveform, thereby capturing still images of each time phase of the subject Exa's heartbeat.

[0095] Figure 9 is a graph showing the measured waveform when drift occurs. Figure 9 shows an example of drift in the measured waveform of an unfixed FBG optical fiber. The horizontal axis of the graph shown in Figure 9 is time, and the vertical axis is signal intensity. The signal intensity is normalized.

[0096] If the position of the unfixed FBG optical fiber 202 or the like changes at the timing indicated by the arrow, a drift occurs in the measured waveform as shown in Fig. 9. If a drift occurs in the measured waveform, it becomes difficult to measure the heart rate for several seconds until zero correction is completed at the position where the FBG optical fiber 202 or the like has stopped.

[0097] [Sensor unit according to the second embodiment] 10 is a schematic diagram showing the state of use of the sensor unit according to the second embodiment. The following mainly describes the differences from sensor unit 200 according to the first embodiment.

[0098] The sensor unit 200A according to the second embodiment has a detachable structure that allows it to be attached to and detached from the table 132. There is a need to detach the sensor unit 200A when not performing heartbeat-synchronized imaging in the MRI apparatus 100. Therefore, the sensor unit 200A includes a rigid member 214 having a shape that follows the shape of the upper surface 132A of the table 132, and is configured to be detachable from the table 132 freely.

[0099] That is, in the sensor unit 200A, the FBG optical fiber 202 is fixed to one surface 214A of the rigid member 214. In the sensor unit 200A, the other surface 214B of the rigid member 214 is fixed to the upper surface 132A of the table 132, and the sensor unit 200A is integrated with the table 132. This provides the same effect as when the FBG optical fiber 202 is fixed to the upper surface 132A of the table 132.

[0100] Sensor unit 200A also includes mat 212 and neck rest 216. Mat 212 and neck rest 216 are placed on one surface 214A of rigid member 214.

[0101] The mat 212 and the neck rest 216 have a structure in which the height in the y direction is constant relative to one surface 214A of the rigid member 214. The mat 212 and the neck rest 216 may be made of a material that elastically deforms when the subject Exa is placed on them.

[0102] The mat 212 is placed at a position corresponding to the position of the torso of the subject Exa in the z direction, and the neck rest 216 is placed at a position corresponding to the position of the neck of the subject Exa in the z direction.

[0103] The mat 212 is made of a material having a rigidity less than that of the heartbeat transmitting device 208. The mat 212 may be made of a material that elastically deforms when the subject Exa is placed on it. The neck rest 216 may be made of the same material as the mat 212.

[0104] The mat 212 and the neck rest 216 have a structure in which the height in the y direction is constant relative to one surface 214A of the rigid member 214. In other words, the surface of the mat 212 that comes into contact with the subject Exa and the surface of the neck rest 216 that comes into contact with the subject Exa are planes that are parallel to one surface 214A of the rigid member 214.

[0105] With respect to the position in the y direction with one surface 214A of the rigid member 214 as the reference, the position of the surface of the mat 212 that comes into contact with the subject Exa is higher than the position of one surface 206B of the weight protection cover 206.

[0106] Furthermore, with respect to the position in the y direction with respect to one surface 214A of the rigid member 214 as the reference, the position of one surface 208A of the heartbeat transmitting device 208 is higher than the position of the surface of the mat 212 that comes into contact with the subject Exa.

[0107] Furthermore, the sensor unit 200A includes a buffer member 218. The buffer member 218 is located at a position where the diffraction grating 204 is formed, and is installed between the FBG optical fiber 202 and the rigid member 214. Fig. 10 illustrates the buffer member 218 embedded in the rigid member 214.

[0108] Fig. 11 is a cross-sectional view taken along the line 11-11 in Fig. 10. Fig. 11 schematically illustrates an example structure at the position of the diffraction grating 204 of the FBG optical fiber 202 illustrated in Fig. 10.

[0109] Mats 212 are placed on both sides of the FBG optical fiber 202 in the x direction. The mats 212 have through holes 212A formed in the positions on the xy plane that correspond to the positions of the diffraction gratings 204. That is, one surface 208A of the heartbeat transmitting device 208 protrudes from the mats 212. This allows the one surface 208A of the heartbeat transmitting device 208 to be reliably brought into contact with the subject Exa.

[0110] Figure 12 is a cross-sectional view taken along the line 12-12 in Figure 10. Figure 12 schematically illustrates an example structure of the FBG optical fiber 202 shown in Figure 10 at a position where the diffraction grating 204 is not formed. Mats 212 are installed on both sides of the FBG optical fiber 202 in the x direction, and a mat 212 is also installed on the upper side of the load prevention cover 206.

[0111] That is, in the position where the diffraction grating 204 is not formed, the weight-bearing protection cover 206 is covered with the mat 212. This prevents the weight-bearing protection cover 206 from coming into contact with the subject Exa, alleviating the hard feeling that the subject Exa feels on the back, and allowing the subject Exa to relax.

[0112] The sensor unit 200A further includes a buffer member 218. The buffer member 218 is placed at a position between the diffraction grating 204 and the rigid member 214. The provision of the buffer member 218 reduces the stiff feeling felt on the back of the subject Exa, allowing the subject Exa to relax. The buffer member 218 may be bonded to the FBG optical fiber 202 at the position of the diffraction grating 204. The rigid member 214 may have a through-hole, a recess, or the like formed in accordance with the shape of the buffer member 218 at the position where the buffer member 218 is placed.

[0113] Rigid member 214 is an example of a fixing member of the present disclosure. Cushioning member 218 is an example of a first elastic member having a specified elasticity of the present disclosure. Mat 212 is an example of a second elastic member of the present disclosure.

[0114] [Sensor unit according to the third embodiment] 13 is a schematic diagram showing the use state of the sensor unit according to the third embodiment. The following mainly describes the differences from the sensor unit 200 according to the first embodiment. The sensor unit 200B according to the second embodiment includes a heartbeat transmitting device 230 that has a different structure from the heartbeat transmitting device 208 shown in FIG.

[0115] The heartbeat transmitting device 230 includes a subject contact portion 230A that contacts the subject Exa1, etc., and a fiber contact portion 230B that contacts the diffraction grating 204. The area of ​​a first surface 231A of the subject contact portion 230A that contacts the subject Exa1, etc., is larger than the area of ​​a second surface 231B of the fiber contact portion 230B that contacts the diffraction grating 204. Specifically, the length of the subject contact portion 230A in the z direction extends from the position of the heart Ha of the larger subject Exa1 to the position of the heart Ha of the smaller subject Exa2. The z direction is an example of the longitudinal direction of the bed of the present disclosure.

[0116] 14 is a schematic diagram showing the state of use of the sensor unit on a small-sized subject. The sensor unit 200B can bring the subject contact portion 230A of the heartbeat transmission device 230 into contact with a position on the back of the subject Exa2, which corresponds to the position of the heart Ha, even for the small-sized subject Exa2.

[0117] This allows variations in the position of the heart Ha from a small subject Exa2 to a large subject Exa1 to be accommodated using a single diffraction grating 204, thereby improving the workflow.

[0118] [Example of weight prevention cover structure] [First structure example] 15 is a plan view of a load prevention cover according to the first structural example. The load prevention cover 2061 shown in the drawing has a rod-like structure extending in the z direction, which is the longitudinal direction of the table 132.

[0119] The weight protection cover 2061 according to the first structural example is less susceptible to the influence of the movements of the limbs of the subject Exa. Note that Fig. 15 illustrates an FBG optical fiber 202 having one diffraction grating 204. The same applies to Figs. 16 and 17.

[0120] [Second structure example] 16 is a plan view of a load prevention cover according to the second structural example. The load prevention cover 2062 shown in the drawing has a rod-like structure extending in the x-direction, which is the short side direction of the table 132.

[0121] The weight prevention cover 2062 according to the second structural example allows most of the optical fiber 210 connected to the FBG optical fiber 202 to be installed at the edge of the table 132 where the weight of the subject Exa is not applied, and the length of the weight prevention cover 2062 in the z direction can be made relatively short.

[0122] [Third structure example] Fig. 17 is a plan view of a load prevention cover according to a third structural example. The load prevention cover 2063 shown in the figure has a planar structure with specified lengths in the x and z directions. Fig. 17 shows a load prevention cover 2063 whose planar shape in the xz plane is square, but the planar shape in the xz plane of the load prevention cover 2063 may be a quadrangle such as a rectangle or a parallelogram, a polygon such as a regular polygon, a circle, an ellipse, etc.

[0123] The size of the weight protection cover 2063 may be any size as long as it is large enough to cover the FBG optical fiber 202 and the optical fiber 210 in the area where the subject Exa is placed.

[0124] Like the load prevention cover 2062 according to the second structural example, the load prevention cover 2063 according to the third structural example allows most of the optical fiber 210 to be installed at the edge of the table 132, and the length of the load prevention cover 2062 in the z direction can be made relatively short.

[0125] 15 to 17 show cover hole 206A whose planar shape in the xz plane is square, but the planar shape of cover hole 206A in the xz plane may be a quadrilateral such as a rectangle or a parallelogram, or may be a polygon, circle, ellipse, etc.

[0126] [Fourth structure example] Fig. 18 is a plan view of a load prevention cover according to the fourth structural example. Note that the FBG optical fiber 202, the optical fiber 210, the interrogator 220, etc. are omitted from the drawing. The same applies to Fig. 19.

[0127] 18 has a plurality of cover holes 206A formed along the z direction. The positions of the plurality of cover holes 206A in the xz plane correspond to the positions of the plurality of diffraction gratings 204 formed in the FBG optical fiber 202 in the xz plane.

[0128] In the sensor unit 200 having the weight protection cover 2064 in which a plurality of cover holes 206A are formed corresponding to the respective positions of the plurality of diffraction gratings 204, the diffraction grating 204 closest to the position of the heart Ha of the subject Exa is selected, and the heartbeat transmitting device 208 is attached to the selected diffraction grating 204. In Fig. 18, the cover hole 206A corresponding to the selected diffraction grating 204 is indicated by dot hatching.

[0129] The position of the heart Ha of the subject Exa can be determined based on the analysis results of an image obtained by imaging the subject Exa using a camera Ca such as a gantry camera.

[0130] In the sensor unit 200 equipped with the weight prevention cover 2064 according to the fourth structural example, the heartbeat of the subject Exa is transmitted with high sensitivity to the diffraction grating 204. Furthermore, the weight caused by the movement of the subject Exa is not transmitted to the diffraction grating 204 corresponding to the cover hole 206A to which the heartbeat transmitting device 208 is not attached, and therefore, drift of the detected waveform caused by unpredictable movement of the subject Exa is suppressed.

[0131] 10 is used as a reference position, it is possible to cover variations in the position of the heart Ha from a small subject Exa2 to a large subject Exa1. For example, if five cover holes 206A are formed with an arrangement pitch of 5 centimeters in the z direction, it is possible to accommodate subjects Exa having heights ranging from 1.2 meters to 2.0 meters.

[0132] [Fifth structure example] 19 is a plan view of a load prevention cover according to the fifth structural example. A load prevention cover 2065 according to the fifth structural example has a plurality of cover holes 206A formed along both the x direction and the z direction.

[0133] In the sensor unit 200 equipped with the weight protection cover 2065, the diffraction grating 204 closest to the position of the heart Ha of the subject Exa is selected, and the heartbeat propagating device 208 is attached to the selected diffraction grating 204. In Fig. 19, the cover hole 206A corresponding to the selected diffraction grating 204 is hatched with dots.

[0134] The sensor unit 200 including the weight prevention cover 2065 can obtain the same effects as the sensor unit 200 including the weight prevention cover 2064 according to the fourth structural example. Furthermore, the sensor unit 200 including the weight prevention cover 2065 has a wider range of options for the diffraction grating 204 compared to the sensor unit 200 including the weight prevention cover 2064 according to the fourth structural example.

[0135] [Example of FBG optical fiber use] 20 is a schematic diagram showing a first example of use of an FBG optical fiber when a load prevention cover according to the fifth structural example is applied. A load prevention cover 2065 in which a plurality of cover holes 206A are formed two-dimensionally is used for a plurality of FBG optical fibers 202.

[0136] Fig. 20 shows an aspect in which five FBG optical fibers 202 extending in the z direction are installed along the x direction. Note that the optical fibers 210, the interrogator 220, etc. are not shown in Fig. 20. The same applies to Figs. 21 and 22.

[0137] 21 is a schematic diagram showing a second use example of an FBG optical fiber when the load prevention cover according to the fifth structural example is applied, in which five FBG optical fibers 202 extending in the x direction are installed along the z direction.

[0138] 22 is a schematic diagram showing a third use example of an FBG optical fiber when a load prevention cover according to the fifth structural example is applied. The figure shows an aspect in which nine FBG optical fibers 202 extending in oblique directions intersecting with each of the x and z directions are installed along a direction perpendicular to the direction in which the FBG optical fibers 202 extend.

[0139] [Sensor unit according to the fourth embodiment] 23 is a schematic diagram showing a state in which a sensor unit according to the fourth embodiment is in use. The sensor unit 200C shown in the figure includes an FBG optical fiber 2021 having a first diffraction grating 2041 and a second diffraction grating 2042. A first heartbeat propagating element 2081 is attached to the first diffraction grating 2041. A second heartbeat propagating element 2082 is attached to the second diffraction grating 2042. An optical fiber 210 is connected to the FBG optical fiber 2021 on the side of the second diffraction grating 2042.

[0140] The weight protection cover 206 is formed with cover holes 2061A corresponding to the positions and sizes of the first heartbeat carrier 2081 and the second heartbeat carrier 2082. The cover holes 2061A may include a plurality of individual cover holes, such as a first cover hole corresponding to the first heartbeat carrier 2081 and a second cover hole corresponding to the second heartbeat carrier 2082. The first heartbeat carrier 2081 is an example of a first contact assisting member of the present disclosure, and the second heartbeat carrier 2082 is an example of a second contact assisting member.

[0141] The second heartbeat transmitting device 2082, which is close to the heart Ha of the subject Exa, transmits the heartbeat of the subject Exa with high sensitivity to the second diffraction grating 2042. The first heartbeat transmitting device 2081, which is farther from the heart Ha of the subject Exa, is less affected by the heartbeat of the subject Exa than the second heartbeat transmitting device 2082, and transmits the respiration of the subject Exa with high sensitivity to the first diffraction grating 2041.

[0142] In addition, the FBG optical fiber 2021 does not transmit the movement of the subject Exa caused by breathing, which is more than 10 times larger than the movement of the subject Exa caused by heartbeat, to the second diffraction grating 2042 and the reflected light propagation path of the second diffraction grating 2042 of the optical fiber 210.

[0143] On the other hand, when the first diffraction grating 2041 is positioned on the optical fiber 210 side of the second diffraction grating 2042, the effect of heartbeat on the first diffraction grating 2041 is small, and the movement of the subject Exa caused by breathing is propagated to the first diffraction grating 2041 with high sensitivity, but this affects the propagation of reflected light from the second diffraction grating 2042.

[0144] The distance between the first heartbeat transmitting device 2081 and the second heartbeat transmitting device 2082 can be determined based on the propagation of the movement of the subject Exa caused by the heartbeat and the propagation of the movement of the subject Exa caused by breathing. For example, when the distance between the first heartbeat transmitting device 2081 and the second heartbeat transmitting device 2082 is set to 8.0 centimeters, the above-mentioned effect can be obtained.

[0145] The first diffraction grating 2041 is an example of a first sensor element of the present disclosure, and the second diffraction grating 2042 is an example of a second sensor element.

[0146] Fig. 24 is a graph showing a measurement waveform acquired using the sensor unit according to the fourth embodiment. The horizontal axis of the graph shown in Fig. 24 represents time, and the vertical axis represents signal strength. The signal strength is normalized.

[0147] The waveform shown in FIG. 24 is derived as the difference between the measured waveform obtained as the output of the second diffraction grating 2042, in which the heartbeat and breathing are superimposed, and the breathing waveform obtained as the output of the first diffraction grating 2041.

[0148] The sensor unit 200C extracts with high accuracy a heartbeat waveform in which the influence of respiration is minimized from a measurement waveform in which the heartbeat and respiration are superimposed and obtained as the output of the second diffraction grating 2042, without using a frequency filter.

[0149] [Sensor unit according to the fifth embodiment] 25 is a schematic diagram showing a state in which a sensor unit according to the fifth embodiment is used. The sensor unit 200D according to the fifth embodiment includes a first FBG optical fiber 2023 and a second FBG optical fiber 2024 as multiple systems of FBG optical fibers 202. A first diffraction grating 2043 is formed in the first FBG optical fiber 2023, and a second diffraction grating 2044 is formed in the second FBG optical fiber 2024.

[0150] The sensor unit 200D includes a first heartbeat propagating device 2083 and a second heartbeat propagating device 2084. The first heartbeat propagating device 2083 is located directly below the heart Ha of the subject Exa in the z direction, at the position of the first diffraction grating 2043. The second heartbeat propagating device 2084 is located closer to the lower limbs than the first heartbeat propagating device 2083 in the z direction, at the position of the second diffraction grating 2044. For example, the second heartbeat propagating device 2084 is located 8 centimeters away from the first heartbeat propagating device 2083 in the z direction.

[0151] The sensor unit 200D includes a first weight prevention cover 2067 and a second weight prevention cover 2068. The first weight prevention cover 2067 is installed in a position where it covers the first FBG optical fiber 2023. The second weight prevention cover 2068 is installed in a position where it covers the second FBG optical fiber 2024.

[0152] The first FBG optical fiber 2023 is connected to the first interrogator 2201 via the first optical fiber 2101. The first interrogator 2201 outputs incident light to the first FBG optical fiber 2023 and acquires the reflected light from the first diffraction grating 2043.

[0153] The second FBG optical fiber 2024 is connected to the second interrogator 2202 via the second optical fiber 2102. The second interrogator 2202 outputs incident light to the second FBG optical fiber 2024 and acquires the reflected light from the second diffraction grating 2044.

[0154] The sensor unit 200D acquires a measurement waveform in which the heartbeat and respiration are superimposed from the first interrogator 2201, and acquires a measurement waveform of respiration from the second interrogator 2202. The MRI apparatus 100 derives the measurement waveform of the heartbeat as the difference between the measurement waveform in which the heartbeat and respiration are superimposed and the measurement waveform of respiration.

[0155] The sensor unit 200D extracts with high accuracy a heartbeat waveform in which the influence of respiration is minimized from a measurement waveform in which the heartbeat and respiration are superimposed and obtained as the output of the first diffraction grating 2043, without using a frequency filter.

[0156] In this embodiment, the sensor unit 200D is exemplified as having two systems of FBG optical fibers 202, but the sensor unit 200D may be provided with three or more systems of FBG optical fibers 202. This allows the target heart rate to be extracted with high accuracy from the measured waveform in which multiple components are superimposed.

[0157] The first FBG optical fiber 2023 is an example of a first fiber Bragg grating sensor of the present disclosure, and the second FBG optical fiber 2024 is an example of a second fiber Bragg grating sensor. The first diffraction grating 2043 is an example of a first sensor element of the present disclosure, and the second diffraction grating 2044 is an example of a second sensor element.

[0158] [Sensor unit according to the sixth embodiment] 26 is a schematic diagram showing a state in which a sensor unit according to the sixth embodiment is used. The sensor unit 200E shown in the figure is placed on the upper surface 132A of a table 132, and an FBG optical fiber 202 is fixed to the upper surface 300A of a spine coil unit 300. This prevents the FBG optical fiber 202 from moving in three-dimensional space.

[0159] The spine coil unit 300 includes a plurality of RF coils housed in a housing 301, electrical wiring corresponding to each of the plurality of RF coils, etc. An upper surface 300A of the spine coil unit 300 is the surface of the housing 301 of the spine coil unit 300 opposite to the table 132.

[0160] 7, the sensor unit 200E has a heartbeat transmitting device 208 placed on the back of the subject Exa at a position directly below the heart Ha. This allows the heartbeat of the subject Exa to be transmitted to the diffraction grating 204 via the heartbeat transmitting device 208 with high sensitivity.

[0161] Furthermore, in the sensor unit 200E, the FBG optical fiber 202 is covered with a load prevention cover 206 on the upper surface 300A of the spine coil unit 300. This suppresses drift of the measurement waveform caused by unpredictable movements of the subject Exa.

[0162] The sensor unit 200E includes a connector 302 that connects and disconnects the FBG optical fiber 202 installed on the upper surface 300A of the spine coil unit 300 to and from the optical fiber 210 installed inside the spine coil unit 300. The connector 302 uses a push-pull method for connecting and disconnecting a receptacle 302A and a plug 302B.

[0163] 26 may be connected to the electrical wiring inside the table 132 using a push-pull type connector installed near the center of the table 132. An optical fiber connector 302 may be added to the electrical wiring connector.

[0164] This allows the sensor unit 200E to be attached to and detached from the table 132 when the spine coil unit 300 is attached to and detached from the table 132.

[0165] Sensor unit 200E includes a first mat 310, a neck rest 312, and a second mat 314. The first mat 310 and the second mat 314 may be made of the same material as the mat 212 shown in Fig. 10. The neck rest 312 may be made of the same material and have the same shape as the neck rest 216 shown in the same figure.

[0166] The first mat 310 shown in Fig. 26 is placed on the upper surface 132A of the table 132, in a non-installation area where the spine coil unit 300 is not installed. Fig. 26 illustrates the first mat 310 placed on the side of the head of the subject Exa, in the non-installation area of ​​the spine coil unit 300.

[0167] The thickness of the first mat 310 may be the same as the sum of the thickness of the spine coil unit 300 and the thickness of the weight-addition prevention cover 206. This can reduce the stiff feeling on the back of the subject Exa, and can provide the effect of allowing the subject Exa to relax during measurement.

[0168] The thickness of the first mat 310 may be thinner or thicker than the sum of the thickness of the spine coil unit 300 and the thickness of the weight prevention cover 206, as long as the above-mentioned effects are obtained.

[0169] The neck rest 312 is placed at the neck of the subject Exa to support the neck of the subject Exa, which has the effect of allowing the subject Exa to relax during measurement.

[0170] The second mat 314 is placed on the upper surface 300A of the spine coil unit 300 in a non-installation area where the FBG optical fiber 202 and the weight prevention cover 206 are not installed. The thickness of the second mat 314 may be the same as the thickness of the weight prevention cover 206, or may be thinner than the thickness of the weight prevention cover 206, or may be thicker than the thickness of the weight prevention cover 206. This can reduce the stiff feeling on the back of the subject Exa, and has the effect of allowing the subject Exa to relax during measurement.

[0171] [Sensor unit according to the seventh embodiment] 27 is a schematic diagram showing a state in which a sensor unit according to the seventh embodiment is used. In the sensor unit 200F shown in the figure, an FBG optical fiber 202 is installed inside a housing 301 of a spine coil unit 300. Specifically, the FBG optical fiber 202 is embedded in an upper surface plate 301A of the spine coil unit 300, and a part of the upper surface plate 301A of the spine coil unit 300 functions as a fixing member for fixing the FBG optical fiber 202.

[0172] An opening is formed in the upper surface plate 301A of the housing 301 of the spine coil unit 300 at the position of the diffraction grating 204, exposing the diffraction grating 204. A heartbeat transmitting device 208 is installed at the position of the opening corresponding to the diffraction grating 204.

[0173] The sensor unit 200F includes a second optical fiber 2104. The second optical fiber 2104 is installed outside the housing 301 of the spine coil unit 300 and is connected to the FBG optical fiber 202. The housing 301 of the spine coil unit 300 may be provided with a connector that connects the FBG optical fiber 202 and the second optical fiber 2104.

[0174] The second optical fiber 2104 is connected to the first optical fiber 2103 via a connector 302. The first optical fiber 2103 is connected to an interrogator 220. The interrogator 220 makes incident light incident on the FBG optical fiber 202 via the first optical fiber 2103 and the second optical fiber 2104, and acquires reflected light from the diffraction grating 204.

[0175] 26, the position of the connector 302 relative to the table 132 is fixed, and the position of the spine coil unit 300 relative to the table 132 is fixed. This means that the position of the diffraction grating 204 relative to the table 132 is fixed in the z direction, making it difficult to adjust the position of the diffraction grating 204 in the z direction according to the position of the heart Ha of the subject Exa.

[0176] On the other hand, the sensor unit 200F shown in FIG. 27 is capable of adjusting the position of the diffraction grating 204 in the z direction within the length of the second fiber 2104 in accordance with the position of the heart Ha of the subject Exa.

[0177] The upper surface plate 301A of the housing 301 of the spine coil unit 300 is an example of a plate-like member on the side opposite to the table in the housing that houses the coil provided in the coil unit of the present disclosure.

[0178] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the technical idea of ​​the present disclosure. [Explanation of symbols]

[0179] 100...MRI device 110...Gantry 130...Bed 130A...top plate 132...Table 200...Sensor unit 202...FBG optical fiber 204...Diffraction grating 206...Weight prevention cover 206A...Cover hole 208...Heartbeat transmitter

Claims

1. A sensor unit attached to a surface of a bed on which a subject is placed, the sensor unit detecting a heartbeat of the subject, a fiber Bragg grating sensor including one or more sensor elements for detecting the subject's heart rate; a fixing member that fixes a side of the fiber Bragg grating sensor opposite to a side facing the subject, the fixing member having a surface on which the fiber Bragg grating sensor is fixed having a specified rigidity; a cover that covers a side of the fiber Bragg grating sensor facing the subject, the cover having a structure in which a cover hole is formed at a position corresponding to the sensor element on the surface facing the subject; A sensor unit comprising:

2. a contact assistant member disposed at a position corresponding to the sensor element in the fiber Bragg grating sensor and at a position on the side of the cover hole, the contact assistant member having a shape protruding from the cover hole; The sensor unit according to claim 1 .

3. a first surface of the contact assistant member that is brought into contact with the subject has a length longer than a second surface of the contact assistant member that is brought into contact with the sensor element in a longitudinal direction of the bed on which the sensor unit is installed; The sensor unit according to claim 2 .

4. a first elastic member having a predetermined elasticity, the first elastic member being disposed at a position corresponding to the sensor element in the fiber Bragg grating sensor and at a position on the side of the fixing member; The sensor unit according to claim 1 .

5. a second elastic member that is attached to the fixing member, has a predetermined elasticity, and has a thickness that contacts the subject; The sensor unit according to claim 1 .

6. The fixing member is installed on the bed and also serves as a table on which the subject is placed. The sensor unit according to claim 1 .

7. the fixing member has a shape that follows the shape of a surface of a table that is placed on the bed, on which the sensor unit is placed. The sensor unit according to claim 1 .

8. the cover has a shape that covers the entire length of the fiber Bragg grating sensor in the direction in which the fiber Bragg grating sensor extends. The sensor unit according to claim 1 .

9. the cover has a shape whose longitudinal direction is the direction in which the fiber Bragg grating sensor extends; The sensor unit according to claim 8 .

10. the cover has a polygonal or circular planar shape on a surface on which the fiber Bragg grating sensor extends; The sensor unit according to claim 8 .

11. the fiber Bragg grating sensor comprises a first sensor element and a second sensor element different from the first sensor element; The cover has a first cover hole formed at a position corresponding to the first sensor element, and a second cover hole formed at a position corresponding to the second sensor element. The sensor unit according to any one of claims 1 to 10.

12. a first contact assistant member disposed at a position corresponding to the first sensor element in the fiber Bragg grating sensor and having a shape protruding from the first cover hole; a second contact assistant member disposed at a position corresponding to the second sensor element in the fiber Bragg grating sensor and having a shape protruding from the second cover hole; Equipped with The sensor unit according to claim 11.

13. a first fiber Bragg grating sensor including the first sensor element; a second fiber Bragg grating sensor including the second sensor element; Equipped with The sensor unit according to claim 12.

14. a bed on which the subject can be placed; a measurement device that measures the subject; a measurement data processing device that generates a medical image of the subject based on the measurement results of the subject; a sensor unit attached to a surface of the bed on which the subject rests, and detecting a heartbeat of the subject; Equipped with The sensor unit includes: a fiber Bragg grating sensor including one or more sensor elements for detecting the subject's heart rate; a fixing member that fixes a side of the fiber Bragg grating sensor opposite to a side facing the subject, the fixing member having a surface on which the fiber Bragg grating sensor is fixed having a specified rigidity; a cover that covers a side of the fiber Bragg grating sensor facing the subject, the cover having a structure in which a cover hole is formed at a position corresponding to the sensor element on the surface facing the subject; A medical imaging apparatus comprising:

15. one or more processors; the one or more processors select one of the plurality of sensor elements based on an image of the subject; 15. The medical imaging device of claim 14.

16. the fixing member is installed on the bed and also serves as a coil unit installed on a table on which the subject sits; 16. A medical imaging apparatus according to claim 14 or 15.

17. the fiber Bragg grating sensor is embedded in a plate-like member on the opposite side of the table in a housing that houses a coil provided in the coil unit; 17. The medical imaging device of claim 16.

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