Biological information monitoring device and magnetic resonance imaging apparatus

Abstract

This invention provides a biological information monitoring device and a magnetic resonance imaging device. One embodiment of the biological information monitoring device includes: an antenna device comprising at least one antenna disposed close to a subject; a signal generator that generates a high-frequency signal; and a displacement detection circuit that uses the high-frequency signal to detect the physical displacement of the subject; the antenna is configured to include: a dipole antenna having a power supply section at its center to which the high-frequency signal is supplied; a coaxial line supplying the high-frequency signal to the power supply section; and a quarter-wavelength conductor element, one end of which is short-circuited to the outer conductor of the coaxial line.

Description

[0001] This application is based on Japanese Patent Application 2021-042231 (filed on March 16, 2021), from which it enjoys priority. This application incorporates the entire contents of that application by reference. Technical Field

[0002] The embodiments disclosed in this specification and accompanying drawings relate to biological information monitoring devices and magnetic resonance imaging devices. Background Technology

[0003] During magnetic resonance imaging (MRI) scans, the collected data can vary due to bodily activities such as heartbeat and respiration. Therefore, for example, regarding heartbeats, methods are used such as attaching electrocardiogram (ECG) electrodes to the body and adjusting the timing of the scan using signals from the ECG output, or correcting the collected data based on the ECG signal.

[0004] However, attaching electrodes to the human body is a burden for patients, and it is also a major reason for reduced work efficiency for photography technicians.

[0005] Furthermore, the following technique is known: separately collecting data (referred to as navigation data) for monitoring body movements caused by respiration, in addition to collecting data used to generate diagnostic images, and using the navigation data to correct for the effects of body movements caused by respiration. However, in this method, collecting navigation data takes additional time, resulting in a longer imaging time. From this perspective, there is an urgent need for a non-contact body movement monitoring device that does not burden the patient.

[0006] Non-contact body movement monitoring devices are urgently needed not only in the context of using magnetic resonance imaging (MRI) devices for imaging but also in the field of health management. For example, there is an urgent need for a body movement monitoring device that can monitor heart rate and respiration during sleep and while driving without causing any burden to the human body and without contact.

[0007] On the other hand, a device has been proposed in the past that uses radio waves to detect the activity of a subject, such as heart rate and respiratory rate. This involves sending radio waves from an antenna to the subject and detecting changes in the reflected waves from the subject to detect its activity.

[0008] However, in conventional detection devices that use radio waves, not only are reflected waves from the subject received, but also reflected waves from various structures around the subject. As a result, attenuation occurs, making it difficult to reliably and stably detect the subject's heartbeat and respiration. Summary of the Invention

[0009] One technical problem to be solved by the embodiments disclosed in this specification and accompanying drawings is to be able to reliably and stably detect biological information such as heartbeat and respiration of the subject without burdening the subject.

[0010] However, the technical problems to be solved by the embodiments disclosed in this specification and the accompanying drawings are not limited to the technical problems described above. It is also possible to identify other technical problems as those corresponding to the effects of the structures shown in the embodiments described below.

[0011] The biological information monitoring device of the embodiment includes:

[0012] An antenna device comprising at least one antenna disposed close to the subject;

[0013] A signal generator that generates a high-frequency signal; and

[0014] A displacement detection circuit that uses the high-frequency signal to detect the physical displacement of the object under test;

[0015] The antenna is configured to have:

[0016] A dipole antenna, wherein a power supply section for supplying the high-frequency signal is provided at the center;

[0017] A coaxial line supplies the high-frequency signal to the power supply unit; and

[0018] A quarter-wavelength conductor element, one end of which is short-circuited to the outer conductor of the coaxial line.

[0019] Alternatively, the conductor element can be formed in an L-shape.

[0020] Alternatively, the conductor element may be formed from a conductor of a linear shape.

[0021] Alternatively, the conductor element may be formed from a strip-shaped conductor.

[0022] Alternatively, the end of the conductor element closer to the power supply section of the dipole antenna can be open, while the end farther from the power supply section can be short-circuited with the outer conductor.

[0023] Alternatively, the distance between the open end of the conductor element and the power supply section of the dipole antenna can be set to be shorter than 1 / 4 wavelength.

[0024] Alternatively, the conductor element may be arranged in a manner substantially parallel to the coaxial line, and the spacing between the conductor element and the coaxial line may be set to be shorter than 1 / 10 of the wavelength.

[0025] Alternatively, the dipole antenna and the conductor element can be formed on the same substrate.

[0026] Alternatively, the front end of the coaxial line can be connected to the power supply section of the dipole antenna formed on the substrate, and the outer conductor of the coaxial line can be short-circuited to a predetermined part of the conductor element formed on the substrate.

[0027] Alternatively, the specified location of the conductor element may be the end that is farther from the power supply section of the dipole antenna.

[0028] Alternatively, the dipole antenna can be configured as a planar dipole antenna, wherein the region in the conductor of the planar dipole antenna from the power supply section to which the high-frequency signal is supplied to a predetermined position leading to both ends of the planar dipole antenna is formed into a meandering shape, and the region from the predetermined position to the two ends is formed into a continuous surface.

[0029] Alternatively, the conductor element can be formed in the shape of a bow tie.

[0030] Alternatively, the conductor element may be formed in a spiral shape.

[0031] Alternatively, the end of the conductor element closer to the power supply section of the dipole antenna can be open, while the end farther from the power supply section can be short-circuited with the outer conductor.

[0032] Alternatively, the distance between the open end of the conductor element and the power supply section of the dipole antenna can be set to be shorter than 1 / 4 wavelength.

[0033] Alternatively, the conductor element may be configured as a plurality of conductor elements having different lengths of the long axis portion in an L-shape.

[0034] Alternatively, the conductor element may be configured as a plurality of conductor elements having bowtie shapes of different sizes.

[0035] A magnetic resonance imaging device, which includes the aforementioned biological information monitoring devices. Attached Figure Description

[0036] Figure 1 This is a block diagram showing the overall configuration of the biological information monitoring device according to the first embodiment.

[0037] Figure 2 This is a diagram illustrating the operational concept of the biological information monitoring device according to the first embodiment.

[0038] Figure 3In the diagram, (a) is a line graph representing an example of the measured value of the reflected signal from the antenna, (b) is a line graph representing the waveform of breathing extracted from the reflected signal, and (c) is a line graph representing the waveform of heartbeat extracted from the reflected signal.

[0039] Figure 4 This diagram compares loop antennas and dipole antennas as antennas used in biological information monitoring devices.

[0040] Figure 5 This is a diagram illustrating an example of the antenna configuration used in the first embodiment.

[0041] Figure 6 This is a block diagram showing the overall configuration of the biological information monitoring device according to the second embodiment.

[0042] Figure 7 This is a diagram illustrating the operational concept of the biological information monitoring device according to the second embodiment.

[0043] Figure 8 In the diagram, (a) is a line graph representing an example of the measured value of the transmitted signal from the transmitting antenna to the receiving antenna, (b) is a line graph representing the waveform of breathing extracted from the transmitted signal, and (c) is a line graph representing the waveform of heartbeat extracted from the transmitted signal.

[0044] Figure 9 This is a diagram illustrating an example of the configuration of the transmitting and receiving antennas used in the second embodiment.

[0045] Figure 10 This is a block diagram showing the overall configuration of the biological information monitoring device according to the third embodiment.

[0046] Figure 11 This is a diagram showing an example of the configuration of four antennas used for diversity processing.

[0047] Figure 12 This is a diagram illustrating an example of the configuration of a magnetic resonance imaging device equipped with a biological information monitoring device.

[0048] Figure 13 In the figure, (a) is a diagram illustrating an example of the configuration of a biological information monitoring device used in a magnetic resonance imaging apparatus, and (b) is a diagram illustrating an example of the transmission and reception of high-frequency signals for biological monitoring.

[0049] Figure 14 This is an example of a diagram showing the location of an antenna, representing a local coil or bed plate.

[0050] Figure 15 This diagram illustrates the technical problems with traditional antennas.

[0051] Figure 16 This is a diagram showing an example of the appearance and structure of the antenna according to the first embodiment.

[0052] Figure 17 This is a diagram illustrating the effect of the antenna in the first embodiment.

[0053] Figure 18 This is a diagram illustrating the limitations of the antenna construction in the first embodiment.

[0054] Figure 19 This is a line diagram illustrating the technical effects of the antenna according to the first embodiment.

[0055] Figure 20 This is the first diagram showing a construction example of the antenna according to the second embodiment.

[0056] Figure 21 This is the second diagram showing a construction example of the antenna according to the second embodiment.

[0057] Figure 22 A diagram illustrating an example of antenna construction in another embodiment.

[0058] Figure 23 This is a diagram illustrating an example of the construction of an antenna consisting of multiple conductor elements (L-shaped elements) of different lengths.

[0059] Figure 24 This is a diagram illustrating an example of the construction of an antenna consisting of multiple conductor elements (boob tie shape) of different sizes. Detailed Implementation

[0060] (First Implementation)

[0061] Hereinafter, the first embodiment of the present invention will be described with reference to the accompanying drawings.

[0062] Figure 1 This is a block diagram showing the overall configuration of the biological information monitoring device 1 according to the first embodiment. The biological information monitoring device 1 includes an antenna 10 and a biological information monitoring device body 20 (hereinafter simply referred to as body 20). The antenna 10 is an antenna device (not shown). In the first embodiment, the biological information monitoring device body 20 is basically a structure with one antenna, so the antenna device is composed of one antenna. On the other hand, in other embodiments described later, there are cases where the biological information monitoring device body 20 has multiple antennas, in which case the antenna device is composed of multiple antennas.

[0063] The antenna 10 is attached to the subject when close to the human body. Unlike the electrodes of an electrocardiograph, the antenna 10 does not need to be directly attached to the skin of the subject; for example, it can be attached to the subject's clothing. Furthermore, in Figure 1The illustration shows an example of an antenna 10 being attached to the chest of a subject lying on a bed board 510 of a hospital bed. However, the subject's posture and the location of the antenna 10 are not limited to these specific conditions. Figure 1 Examples include antenna 10, which can be placed on the chest or back of a standing subject, or on the chest or back of a subject seated while driving a vehicle.

[0064] The main body 20 includes an RF signal generator 30, a transmitting circuit 40, a coupling detection circuit 50, and a displacement detection circuit 60.

[0065] The RF signal generator 30 generates a high-frequency signal in the continuous wave mode. The frequency of the high-frequency signal is not particularly limited and can be selected according to factors such as the size of the antenna, for example, in the VHF or UHF bands.

[0066] After passing the high-frequency signal through the bandpass filter (BPF) 41, the transmitting circuit 40 amplifies it to a specified power using the power amplifier (PA) 42 and outputs it to the antenna 10 via the directional coupler (DC) 43.

[0067] The coupling detection circuit 50 has the function of detecting the coupling amount of near-field coupling caused by the electric field between the test object and the antenna 10. For example, it is configured to have a bandpass filter (BPF) 51, a low noise amplifier (LNA / AGC) 52 with automatic gain adjustment function and a detection circuit 53.

[0068] The RF signal generator 30, the transmitting circuit 40, and the coupling detection circuit 50 can be mounted, for example, on a printed circuit board housed in a housing.

[0069] The high-frequency signal output from the directional coupler 43 of the transmitting circuit 40 is input to the antenna 10. A portion of this high-frequency signal does not face the object being tested, but bounces (reflects) at the input end of the antenna 10 and returns to the directional coupler 43, and is input to the branch of the coupling detection circuit 50.

[0070] The coupling detection circuit 50 measures the magnitude of the reflected signal from the antenna 10 by detecting the signal output from the branch end of the directional coupler 43 using the detection circuit 53. Then, the coupling amount of the near-field coupling is detected based on the magnitude of the reflected signal.

[0071] If the power output from the transmitting circuit 40 to the antenna 10 is considered to be a constant value, then the coupling detection circuit 50 equivalently detects the S11 parameter representing the reflection loss (i.e., return loss) of the antenna 10.

[0072] Figure 2 This is a diagram illustrating the operational concept of the biological information monitoring device 1 according to the first embodiment. Figure 2(a) is a schematic diagram illustrating the operation when the distance D between the subject and antenna 10 is small. Figure 2 (b) is a diagram schematically illustrating the operation when the distance D between the subject and the antenna 10 is relatively large. Since the subject (human body) is a conductive object, it easily absorbs energy from the antenna 10 when the antenna 10 is close to the subject.

[0073] Therefore, such as Figure 2 As shown in (a), when the distance D between the test subject and the antenna 10 is small, the energy absorbed by the test subject is large. This means that the near-field coupling between the test subject and the antenna 10 is large. The power Sin input to the antenna 10 is mainly divided into the power Sb absorbed by the test subject and the power Sr reflected from the antenna end 10a of the antenna 10. When the distance D is small, the power Sb absorbed by the test subject is large, and correspondingly, the power Sr reflected from the antenna end 10a is small. For example, when the power Sin input to the antenna 10 is set to 100, the power Sb absorbed by the test subject is 70, and the power Sr reflected from the antenna end 10a is 30.

[0074] This means that when the distance D between the object being tested and the antenna 10 is small, the reflected signal from the antenna end 10a decreases, and the reflection loss (return loss) of the antenna 10 also decreases. In other words, the S11 parameter, which is an indicator of the degree of mismatch of the antenna 10, exhibits a small value. The S11 parameter is an indicator expressed as the square root of the ratio of the reflected power from the antenna 10 to the input power to the antenna 10.

[0075] In contrast, such as Figure 2 As shown in (b), when the distance D between the test subject and the antenna 10 is large, the energy absorbed by the test subject is small. This means that the near-field coupling between the test subject and the antenna 10 is small. As a result, when the distance D is large, the power Sb absorbed by the test subject is small, and correspondingly, the power Sr reflected from the antenna end 10a is large. For example, when the power Sin input to the antenna 10 is set to 100, the power Sb absorbed by the test subject is 30, and the power Sr reflected from the antenna end 10a is 70.

[0076] This means that when the distance D between the object being tested and the antenna 10 is large, the reflected signal from the antenna end 10a increases, and the reflection loss (return loss) of the antenna 10 becomes greater. In other words, the S11 parameter, which is an indicator of the degree of mismatch of the antenna 10, exhibits a large value.

[0077] Thus, when the input power to antenna 10 is set to a constant, the reflected signal from antenna end 10a varies depending on the distance D between the subject and antenna 10. In other words, the degree of mismatch of antenna 10 or the value of parameter S11 also varies depending on the distance D between the subject and antenna 10. Furthermore, since the distance D between the subject and antenna 10 varies due to body movements such as heartbeat and respiration, the magnitude of the reflected signal from antenna end 10a or the value of parameter S11 varies according to changes in body movements such as heartbeat and respiration.

[0078] The biological information monitoring device 1 of the first embodiment utilizes this characteristic to detect bodily movements such as heartbeat and respiration by detecting the magnitude of the reflected signal from the antenna 10 disposed near the subject.

[0079] Figure 3 (a) is a line graph representing an example of the measured value of the reflected signal from antenna 10. The horizontal axis of the line graph is time, and the vertical axis is the amplitude of the reflected signal. Figure 3 As shown in (a), the reflected signal from antenna 10 is a waveform formed by superimposing a short-period vibration waveform (corresponding to a heartbeat) onto a longer-period vibration waveform (corresponding to respiratory activity). The reflected signal from antenna 10 is detected by the detection circuit 53 of coupling detection circuit 50 and output to displacement detection circuit 60.

[0080] The displacement detection circuit 60 can be configured as a dedicated printed circuit board with a processor, or as an information processing device such as a personal computer or tablet terminal with a display.

[0081] The displacement detection circuit 60 performs filtering on the reflected signal detected by the detector circuit 53, extracting the frequency components corresponding to respiratory activity and the frequency components corresponding to heartbeat, respectively, to generate... Figure 3 The waveform of respiration shown in (b) and Figure 3 The waveform of the heartbeat is shown in (c). Alternatively, the displacement detection circuit 60 can also extract the frequency components corresponding to respiratory activity and the frequency components corresponding to the heartbeat after performing a Fourier transform on the reflected signal from the antenna 10, and perform an inverse Fourier transform on each extracted frequency component to generate... Figure 3 The waveform of respiration shown in (b) and Figure 3 The waveform of the heartbeat is shown in (c).

[0082] The displacement detection circuit 60 can display the generated respiratory waveform and heartbeat waveform on an appropriate display, and it can also analyze the generated respiratory waveform and heartbeat waveform. For example, the displacement detection circuit 60 can analyze the respiratory waveform and heartbeat waveform to determine the respiratory rate and respiratory cycle, or the heartbeat rate and heartbeat cycle, etc., and it can also detect whether there are any abnormalities in breathing or heartbeat from the respiratory rate and heartbeat rate.

[0083] Figure 4 This diagram compares a loop antenna and a dipole antenna as antennas 10 used in a biological information monitoring device 1.

[0084] Figure 4 (a) shows a loop antenna with a loop length equal to the resonant length, i.e., a 1-wavelength loop antenna. Because the current distributions on opposite sides of a 1-wavelength loop antenna are out of phase, the electric fields do not cancel each other out. Therefore, the electric field component is larger than the magnetic field component in the near field. As for the antenna shape, although it also depends on the frequency used, it is a relatively large shape.

[0085] Figure 4 (b) shows a loop antenna with a loop length shorter than the resonant length. In this type of loop antenna, the electric fields cancel each other out because the current distributions on the corresponding sides are not in opposite phase. Therefore, in the near field, the magnetic field component is larger than the electric field component. Consequently, the coupling with the human body in the near field is magnetic field coupling. Magnetic field coupling indicates a tendency to easily pass through the interior of the body.

[0086] Figure 4 (c) shows a half-wavelength dipole antenna. Because there is no electric field cancellation in a half-wavelength dipole antenna, the electric field component is larger in the near field.

[0087] Figure 4 Figure (d) shows a dipole antenna with an element length shorter than the resonant length. Even though the element length is shorter than the resonant length (i.e., half-wavelength), the current distribution shape does not change. Therefore, similar to a half-wavelength dipole antenna, the electric field component is larger in the near field. Furthermore, it can be miniaturized compared to a half-wavelength dipole antenna. Because the electric field component is larger in the near field, the coupling with the human body in the near field is electric field coupling. Electric field coupling indicates a tendency to propagate easily across the surface of the body.

[0088] From a miniaturization perspective, a loop antenna with a shorter loop length than the resonant length is preferred. Figure 4 (b) and dipole antennas shorter than half a wavelength Figure 4 (d) The bio-information monitoring device 1 can use any type of antenna. However, in comparison with a loop antenna, it is generally believed that a dipole antenna can extract more subtle electrocardiogram waveforms.

[0089] Ordinary antennas used in communications require minimizing reflected signals from the antenna to maximize power output into space. Therefore, the voltage standing wave ratio (VSWR) of the antenna is preferably as close to 1.0 as possible. In contrast, in the biological information monitoring device 1 of the first embodiment, heartbeat and respiratory activity are detected by detecting reflected signals from the antenna 10. Therefore, it is preferable that there is a certain degree of reflected signal from the antenna 10. Thus, the voltage standing wave ratio (VSWR) of the antenna 10 used in the biological information monitoring device 1 of the first embodiment is preferably set to, for example, 2.0 to 5.0.

[0090] Figure 5 This diagram illustrates an example configuration of the antenna 10 used in the biological information monitoring device 1 according to the first embodiment. In principle, only one antenna 10 is used in the first embodiment, but various variations can be considered in terms of its configuration and orientation. As a basic idea, it is preferable to place the antenna 10 at a location where body movement is most clearly visible; in the case of detecting heartbeats, it is preferable to place it as close to the heart as possible.

[0091] Figure 5 In the examples of antennas 10, dipole antennas are shown. Generally speaking, the heart's range of motion is greater in the head-to-foot direction than in the left-right direction of the subject. Therefore, in Figure 5 In (a), the antenna 10 is positioned near the heart, with the length direction of the dipole antenna aligned with the head-to-foot direction of the subject, and on the ventral side of the subject in the dorsal-ventral direction. On the other hand, in Figure 5 In (b), an antenna 10 is placed near the heart on the dorsal side of the subject (the length direction of the dipole antenna is in the head-to-foot direction of the subject).

[0092] Regarding the configuration of antenna 10, some physical limitations are considered. For example, when imaging a subject with a magnetic resonance imaging device, and when measuring heart rate using a bio-information monitoring device 1, the local coil 200 of the magnetic resonance imaging device 100 is placed on the subject. In the case where the local coil 200 is a chest coil, for example, as... Figure 5 As shown in (c), the antenna 10 is positioned to avoid the chest coil and as close to the heart as possible. Alternatively, for example, if the antenna 10 is positioned on the dorsal side and the local coil 200 is a spinal coil, for example, as... Figure 5 As shown in (d), the antenna 10 is positioned to avoid the spinal coil and as close to the heart as possible.

[0093] As described above, in the biological information monitoring device 1 of the first embodiment, changes in the coupling amount of the near-field coupling between the antenna 10 and the human body are detected by body movements such as heartbeat and respiration. Furthermore, the changes in this near-field coupling amount are measured as changes in the reflected signal reflected from the input end of the antenna 10 or changes in the reflection loss of the antenna 10, i.e., the value of parameter S11. Therefore, the biological information monitoring device 1 of the first embodiment uses a non-contact detection method with radio waves, and is less susceptible to attenuation caused by reflected waves from structures surrounding the subject, such as the pedestal structure of a magnetic resonance imaging device, or various devices within the examination room, enabling high-reliability detection of heartbeat and respiratory activity.

[0094] (Second Implementation)

[0095] Figure 6 This is a block diagram showing the overall configuration of the biological information monitoring device 1 according to the second embodiment. The biological information monitoring device 1 of the first embodiment is in principle equipped with one antenna 10, while the biological information monitoring device 1 of the second embodiment has at least two antennas, such as a transmitting antenna 10 (first antenna) and a receiving antenna 11 (second antenna).

[0096] Regarding the main body 20 of the biological information monitoring device, it has a structure that is substantially the same as that of the first embodiment, and includes an RF signal generator 30, a transmitting circuit 40, a coupling detection circuit 50, and a displacement detection circuit 60.

[0097] The difference between the main body 20 and the first embodiment is that the transmitting circuit 40 in the second embodiment does not have a directional coupler (DC) 43. The power amplifier (PA) 42 and the transmitting antenna 10 of the transmitting circuit 40 are directly connected without passing through the directional coupler (DC) 43, and the bandpass filter (BPF) 51 and the receiving antenna 11 of the coupling detection circuit 50 are also directly connected without passing through the directional coupler (DC) 43.

[0098] The coupling detection circuit 50 of the second embodiment detects the coupling amount of near-field coupling based on the magnitude of the transmitted signal by detecting the transmitted signal transmitted from the high-frequency signal output from the RF signal generator 30 from the transmitting antenna 10 to the receiving antenna 11 using the detection circuit 53.

[0099] If the power output from the transmitting circuit 40 to the transmitting antenna 10 is considered to be a constant value, then the coupling detection circuit 50 equivalently detects the S21 parameter, which represents the insertion loss (i.e., insertion loss) from the transmitting antenna 10 to the receiving antenna 11.

[0100] Figure 7 This is a diagram illustrating the operational concept of the biological information monitoring device 1 according to the second embodiment. Figure 7(a) is a schematic diagram illustrating the operation when the distance D between the subject and antenna 10 is small. Figure 7 (b) is a diagram schematically illustrating the operation when the distance D between the subject and antenna 10 is relatively large. As mentioned earlier, since the subject (human body) is a conductive object, it easily absorbs energy from the transmitting antenna 10 when the distance between the transmitting antenna 10 and the subject is small. Therefore, the energy absorbed from the transmitting antenna 10 to the subject is relatively large. This means that the near-field coupling between the subject and the transmitting antenna 10 is relatively large.

[0101] Similarly, if the receiving antenna 11 is close to the test subject, the energy input from the test subject to the receiving antenna 11 also increases, which means that the near-field coupling between the test subject and the receiving antenna 11 is larger. The power Sin input to the antenna 10 is absorbed by the test subject as power Sb1, propagates inside and on the surface of the test subject, and is transmitted to the receiving antenna 11 as power Sb2. When the distance D is small, the power Sb1 absorbed from the transmitting antenna 10 to the test subject is larger, and correspondingly, the power Sb2 transmitted from the test subject to the receiving antenna 11 is also larger. For example, when the power Sin input to the transmitting antenna 10 is set to 100, the power Sb absorbed from the transmitting antenna 10 to the test subject is 70, the power Sb2 released from the test subject to the receiving antenna 11 is 60, and therefore, the power St exiting from the receiving antenna 11 is also 60.

[0102] This means that when the distance D between the object being examined and the transmitting antenna 10 and the receiving antenna 11 is small, the transmitted signal from the transmitting antenna 10 to the receiving antenna 11 increases, and the insertion loss from the transmitting antenna 10 to the receiving antenna 11 decreases. In other words, the S21 parameter (true value), which is an indicator of the insertion loss from the transmitting antenna 10 to the receiving antenna 11, exhibits a large value.

[0103] In contrast, such as Figure 7 As shown in (b), if the distance D between the transmitting antenna 10 and the subject is large, the subject is less likely to absorb energy from the transmitting antenna 10. Therefore, the energy absorbed from the transmitting antenna 10 to the subject is small. This means that the near-field coupling between the subject and the receiving antenna 11 is small. Similarly, if the distance D between the receiving antenna 11 and the subject is large, the energy input from the subject to the receiving antenna 11 is also small. This means that the near-field coupling between the subject and the receiving antenna 11 is also small. For example, when the power Sin input to the transmitting antenna 10 is set to 100, the power Sb absorbed from the transmitting antenna 10 to the subject is 30, the power Sb2 released from the subject to the receiving antenna 11 is 20, and therefore, the power St exiting from the receiving antenna 11 is also 20.

[0104] This means that when the distance D between the subject and the transmitting antenna 10 or the distance D between the subject and the receiving antenna 11 is large, the transmitted signal from the transmitting antenna 10 to the receiving antenna 11 decreases, and the insertion loss from the transmitting antenna 10 to the receiving antenna 11 increases. In other words, the S21 parameter (true value), which is an indicator of the insertion loss from the transmitting antenna 10 to the receiving antenna 11, exhibits a small value.

[0105] Figure 8 (a) is a line graph showing an example of the measured value of the transmitted signal from the transmitting antenna 10 to the receiving antenna 11. The horizontal axis of the line graph is time, and the vertical axis is the amplitude of the transmitted signal. The transmitted signal in the second embodiment is similar to the reflected signal in the first embodiment. Figure 3 (a) is a waveform formed by superimposing a shorter-period vibration waveform (a waveform corresponding to respiratory activity) onto a longer-period vibration waveform (a waveform corresponding to heartbeat). This transmitted signal is also detected by the detection circuit 53 of the coupling detection circuit 50 and output to the displacement detection circuit 60.

[0106] Similar to the first embodiment, the displacement detection circuit 60 generates a signal by performing filtering and Fourier transform processing on the reflected signal detected by the detection circuit 53, extracting the frequency components corresponding to respiratory activity and the frequency components corresponding to heartbeat, respectively. Figure 8 The waveform of respiration shown in (b) and Figure 8 The waveform of the heartbeat is shown in (c).

[0107] Figure 9 This diagram illustrates an example configuration of the transmitting antenna 10 and receiving antenna 11 used in the biological information monitoring device 1 according to the second embodiment. Various modifications can be considered regarding the configuration and orientation of the transmitting antenna 10 and receiving antenna 11 used in the second embodiment. As a basic idea, it is preferable to arrange the transmitting antenna 10 and receiving antenna 11 such that they are positioned to clamp the body parts where bodily movement is most clearly visible. For example, in the case of detecting heartbeats, it is preferable to arrange the antennas such that the heart is clamped in any of the following directions: dorsal-ventral, lateral, or head-to-foot.

[0108] Figure 9 of (a), Figure 9 (b) Figure 9 In (c), a dipole antenna is shown as an example of a type of antenna. Figure 9 (d) illustrates a monopole antenna. Figure 9 (a) shows an example of a configuration in which the heart is held from the dorsal and ventral direction of the subject using a transmitting antenna 10 and a receiving antenna 11.

[0109] Figure 9(b) shows an example of a configuration in which the heart is held from the left and right sides of the subject using the transmitting antenna 10 and the receiving antenna 11. Figure 9 (c) shows an example of a configuration in which the heart is held from the head-to-foot direction of the subject using a transmitting antenna 10 and a receiving antenna 11. Figure 9 (d) shows an example of a configuration in which the heart is held from the head-to-foot direction of the subject using a transmitting antenna 10 and a receiving antenna 11 as monopole antennas.

[0110] Note that there is no need to specifically distinguish between transmitting antenna 10 and receiving antenna 11. Figure 9 (a)~ Figure 9 In any example of (d), the configuration can be set to swap the transmitting antenna 10 with the receiving antenna 11.

[0111] Similar to the antenna 10 in the first embodiment, the voltage standing wave ratio (VSWR) of the transmitting antenna 10 used in the biological information monitoring device 1 of the second embodiment is also preferably set to 2.0 to 5.0, for example. However, for the receiving antenna 11, a VSWR of 2.0 or less is preferred, for example.

[0112] (Third Implementation)

[0113] Figure 10 This is a block diagram showing the overall configuration of the biological information monitoring device 1 according to the third embodiment. The biological information monitoring device 1 of the third embodiment is an embodiment that combines the first embodiment and the second embodiment. Specifically, it is an embodiment configured to be able to select a first mode corresponding to the first embodiment and a second mode corresponding to the second embodiment.

[0114] In the first mode, a high-frequency signal is input to antenna 11, and the heartbeat, respiratory activity, etc. of the subject are measured based on the reflected signal from antenna 11 (or the S11 parameter of antenna 11). On the other hand, in the second mode, a high-frequency signal is input to antenna 10, and the heartbeat, respiratory activity, etc. of the subject are measured based on the transmitted signal from antenna 10 to antenna 11 (or the S21 parameter from antenna 10 to antenna 11).

[0115] The RF signal generator 30 and the first transmitting circuit 40 are structures corresponding to the high-frequency signal generation function in the first mode. The RF signal generator 30a and the second transmitting circuit 40a are structures corresponding to the high-frequency signal generation function in the second mode. The coupling detection circuit 50 is a structure used in both the first and second modes.

[0116] Diversity determination circuit 70 monitors the reflected signal detected in the first mode and the transmitted signal detected in the second mode, and selects either the first mode or the second mode. When monitoring the reflected signal in the first mode, diversity determination circuit 70 switches to... Figure 10 The indicated state is that both switch 44 of the first transmitting circuit 40 and switch 54 of the coupling detection circuit 50 are switched to the directional coupler 43 side. In the second mode, when monitoring the transmitted signal, switches 44 and 54 are switched to... Figure 10 The opposite side of the state shown.

[0117] The diversity determination circuit 70 compares the variation amplitude of the reflected signal with the variation amplitude of the transmitted signal and selects the mode with the larger variation amplitude. For example, if it is determined that the variation amplitude of the reflected signal is larger than that of the transmitted signal, the diversity determination circuit 70 selects the first mode. Alternatively, the diversity determination circuit 70 can also perform Fourier transforms on the reflected signal and the transmitted signal separately, selecting the mode with the larger frequency component corresponding to the heartbeat, or the mode with the larger frequency component corresponding to respiration.

[0118] After selecting either the first mode or the second mode, the diversity determination circuit 70 sets the switches 44 and 54 to the state corresponding to the selected mode, and uses the selected mode to measure the reflected signal or the transmitted signal, and detect body movement signals such as heartbeat and breathing.

[0119] (A variation of the third embodiment)

[0120] The biological information monitoring device 1 of the third embodiment uses two or more antennas 10 and 11 for diversity processing. In this diversity processing, one antenna that can best detect body movement signals is selected, or a combination of two or more antennas that can best detect body movement signals is selected.

[0121] Figure 11 This is a diagram illustrating an example configuration of four antennas used for diversity processing. In this case, for example, as... Figure 11 As shown in (a), the four dipole antennas 10 and 11 can be arranged to surround the heart. Additionally, as... Figure 11 As shown in (b), the heart can also be configured by using antennas 10, 11 of the type that bend the dipole antenna at a roughly right angle in the center to surround it.

[0122] When performing diversity processing using the biological information monitoring device 1 of the first embodiment, and when performing diversity processing using the first mode of the third embodiment, one of the four antennas is selected that can best detect body movement signals.

[0123] In addition, when performing diversity processing using the biological information monitoring device 1 of the second embodiment and when performing diversity processing using the second mode of the third embodiment, for example, one transmitting antenna 10 is selected and one of the three receiving antennas 11 that can best detect body movement signals is selected, or the remaining three receiving antennas 11 are combined in any combination.

[0124] In a variation of the third embodiment, for example, it can be set with... Figure 10 The diversity determination circuit 70 shown has a similar function. Furthermore, this circuit performs the aforementioned antenna selection processing or antenna combining processing.

[0125] (Magnetic resonance imaging device)

[0126] Figure 12 This is a diagram illustrating a configuration example of a magnetic resonance imaging apparatus 100 equipped with the biological information monitoring device 1 of the above embodiments.

[0127] The magnetic resonance imaging device 100 includes a static magnetic field magnet 118, an inclined magnetic field coil 119, a WB (Whole Body) coil 120, etc., which are housed in a cylindrical shell. In addition, the magnetic resonance imaging device 100 includes a bed 500 and a local coil 200. The bed 500 has a bed body 520 and a bed board 510, and the local coil 200 is disposed close to the subject.

[0128] Furthermore, the magnetic resonance imaging device 100 includes a tilting magnetic field power supply 310, an RF receiver 320, an RF transmitter 330, and a sequence controller 340. In addition, the magnetic resonance imaging device 100 includes a computer, i.e., a console, which includes a processing circuit 400, a storage circuit 410, a display 420, and an input device 430.

[0129] In addition to the biological information monitoring device 1 Figure 1 , Figure 6 , Figure 10 In addition to the main body 20 shown, it also includes antennas 10 and 11. Antennas 10 and 11 are positioned close to the subject, but do not necessarily need to be directly attached to the skin. Antennas 10 and 11 can be individually positioned near the subject, but still function as... Figure 12 As shown, it can be built into the local coil 200, or it can be built into the bed board 510.

[0130] Figure 13 Figure (a) illustrates an example configuration of the biological information monitoring device 1 used in the magnetic resonance imaging apparatus 100. The magnetic resonance imaging apparatus 100 can be used in any of the embodiments described above. Figure 13The second embodiment of the bio-information monitoring device 1 is shown as an example. In the magnetic resonance imaging device 100, a very high-power MR RF pulse is output from the RF transmitter 330, and the RF pulse is emitted from the WB coil 120 toward the subject. Therefore, a very high RF power is input to the main body 20 of the bio-information monitoring device 1 via the antennas 10 and 11.

[0131] Therefore, the biological information monitoring device 1 used in the magnetic resonance imaging apparatus 100 is provided with a protective switch 45 and a switch 55 at the output terminal of the transmitting circuit 40 and the input terminal of the coupling detection circuit 50, respectively. The protective switches 45 and 55 are switched on and off using control signals sent from the main body of the magnetic resonance imaging apparatus 100.

[0132] Figure 13 (b) is a diagram illustrating an example of the transmission and reception of high-frequency signals used for biological monitoring. Figure 13 As shown in (b), in order to avoid interference between the magnetic resonance imaging device 100 and the biological information monitoring device 1, a high-frequency signal for object monitoring is received during the period of avoiding the transmission of RF pulses for MR and the reception of MR signals.

[0133] The repetition period T of the high-frequency signal used for biological monitoring can be defined based on the heartbeat and respiratory cycles. The heartbeat frequency can be assumed to be approximately 2 Hz or less, and the respiratory frequency can be assumed to be approximately 0.5 Hz or less. According to the sampling theorem, the waveforms of the heartbeat and respiration can be measured by sampling at twice the higher frequency, i.e., 4 Hz or more. Therefore, the repetition period T can be set to 250 ms (=1 / 4 Hz) or less.

[0134] The frequency of the high-frequency signal used for biological monitoring is preferably higher than the Larmor frequency used in the magnetic resonance imaging device 100. By setting the frequency of the high-frequency signal used for biological monitoring to be higher than the Larmor frequency, it is possible to prevent not only the high-frequency signal itself used for biological monitoring, but also its higher harmonics from entering the receiving frequency band of the MR signal of the magnetic resonance imaging device 100.

[0135] Figure 14This is an example of a marking indicating the position of antennas 10, 11 in the local coil 200 or bed board 510. As previously described, antennas 10, 11 of the bio-information monitoring device 1 can be embedded in the local coil 200 or the bed board 510 of the bed 500. In the case of measuring heartbeat, antennas 10, 11 are preferably positioned near the heart of the subject. Therefore, markings can be made so that the user can easily visually confirm the antennas 10, 11 embedded in the local coil 200 or bed board 510, and adjust the position of the subject or the local coil 200 so that the markings are located near the heart of the subject.

[0136] (First embodiment of an antenna with conductor elements)

[0137] Here, as Figure 5 , Figure 9 , Figure 11 As shown, a typical example of the antenna elements of antennas 10 and 11 used in the biological information monitoring device 1 is illustrated, and the structure using a dipole antenna is explained.

[0138] Traditional antennas that use dipole antennas as antenna elements are typically constructed by supplying high-frequency signals to the dipole antenna via a coaxial line (e.g., a coaxial cable).

[0139] Figure 15 Figures (a) to (c) illustrate the technical problems of conventional antennas with this structure. Figure 15 (a) is a diagram showing the measurement of the subject's pulsation and respiratory movements by placing the antenna (a conventional antenna) of the biological information monitoring device 1 on the chest of the subject.

[0140] Figure 15 (b) is a diagram showing a conventional antenna configuration example, in which a high-frequency signal is supplied to the dipole antenna via a coaxial line. As is well known, a dipole antenna is a balanced circuit, while a coaxial line is an unbalanced circuit. Therefore, leakage current generated at the boundary between the balanced and unbalanced circuits, i.e., the boundary between the dipole antenna and the coaxial line, i.e., the power supply section, flows into the outer conductor of the coaxial line.

[0141] When measuring the pulsation and respiratory movements of the subject, as previously described, the antenna is positioned on the subject. At this time, the coaxial line near the power supply is positioned on the subject along with the dipole antenna (e.g., on the chest or abdomen of the subject).

[0142] Therefore, the leakage current flowing into the outer conductor of the coaxial line is coupled to the test object together with the current on the dipole antenna, and the return loss of the antenna (S11 parameter) varies according to the activity of the test object surface.

[0143] For example, such as Figure 15As illustrated in (a), when the outer conductor of the coaxial line is close to the abdomen of the subject, the abdominal changes caused by breathing are greater than the chest changes caused by heartbeat. Therefore, the abdomen has a greater influence on the S11 parameter caused by the aforementioned leakage current.

[0144] Therefore, as Figure 15 As shown in the line graph (c), the variations in S11 parameters caused by heartbeat (shorter-period variations) are overshadowed by the variations in S11 parameters caused by respiration (longer-period variations), making it difficult to capture heartbeat activity.

[0145] In contrast, by configuring the antenna used in the biological information monitoring device 1 as an antenna 10 with a conductor element 104 of 1 / 4 wavelength, the leakage current flowing through the outer conductor can be reduced, thus solving the above-mentioned problem.

[0146] The following is for reference Figures 16 to 22 Various embodiments of the antenna 10 with a quarter-wavelength conductor element 104 will be described. Note that in Figure 15 In (a), the antenna is illustrated as a transmit and receive antenna for parameter detection in S11, but it can also be used even if it is set as a transmit antenna 10 and a receive antenna 11 for parameter detection in S21.

[0147] Figure 16 This is a diagram showing an example of the appearance and structure of an antenna 10 according to a first embodiment of an antenna 10 with a quarter-wavelength conductor element 104. The antenna 10 is configured to include a dipole antenna 101, a coaxial line 103, and a conductor element 104.

[0148] A power supply unit 102 is located at the center of the dipole antenna 101. High-frequency signals supplied from the main body 20 of the bio-information monitoring device are transmitted to the power supply unit 102 via a coaxial line 103.

[0149] Coaxial line 103 is, for example, a coaxial cable that uses a component made of fine wires braided together to form the outer conductor, and uses an insulating protective film such as ethylene plastic called a sheath to cover its outer periphery. Alternatively, coaxial line 103 may also be a coaxial cable that uses a seamless metal sheath as the outer conductor and exposes the outer conductor to the outside, i.e., a so-called semi-rigid cable.

[0150] The conductor element 104 is a linear or strip conductor whose length is approximately 1 / 4 wavelength. One end of the conductor element 104 is configured as a short-circuit portion 105 that is short-circuited to the outer conductor of the coaxial line 103, and the other end of the conductor element 104 is configured as an open end (open end 106).

[0151] The conductor element 104 can be configured as an L-shaped element 104, for example. The L-shaped element 104 has a short shaft portion formed by bending one end of a linear conductor or strip conductor relatively short, and a long shaft portion for the rest. The front end of the short shaft portion of the L-shaped element 104 is short-circuited with the outer conductor of the coaxial line 103, and the long shaft portion is arranged substantially parallel to the coaxial line 103 at a predetermined interval.

[0152] Regarding conductor element 104, it is not necessary to make a limitation, but as Figure 16 As illustrated, the end closer to the power supply section 102 of the dipole antenna 101 is open, and the end farther from the power supply section 102 of the dipole antenna 101 is short-circuited with the outer conductor of the coaxial line 103.

[0153] Figure 17 This is a diagram illustrating the effect of the antenna 10 in the first embodiment. Figure 17 Use dashed lines Figure 16 The diagram of antenna 10 shown includes an additional current distribution. Figure 17 The current distribution shown is the current distribution generated in the rectangular portion formed by the outer conductor and the L-shaped element 104.

[0154] In the rectangular portion formed by the L-shaped element 104, whose length is 1 / 4 wavelength of the resonant frequency of the dipole antenna 101, and the outer conductor, a current is generated that is maximum at the short-circuit portion 105 of the L-shaped element 104 and minimum at the open end 106.

[0155] Therefore, the impedance of the rectangular portion formed by the outer conductor and the L-shaped element 104, as viewed from the power supply section 102, is greatest at the open end 106 of the L-shaped element 104.

[0156] As a result, the leakage current in the direction of the outer conductor is cut off at the open end 106, which can suppress the leakage current flowing into the outer conductor.

[0157] Conventionally, devices known as notch filters are used to suppress leakage current from a dipole antenna to its outer conductor. A notch filter consists of a cylindrical conductor that covers the outer periphery of a coaxial line near the power supply point of the dipole antenna. Conventional notch filters are three-dimensional, while the L-shaped element 104 of this embodiment is a planar structure such as a linear conductor or a strip conductor. Therefore, the manufacturing process of the antenna 10 of this embodiment is simpler than that of conventional antennas using notch filters.

[0158] Figure 18 This diagram illustrates the limitations of the construction of the antenna 10 in the first embodiment. Wherein, Figure 18 (a) is a diagram showing the limitation on the height H of the L-shaped element 104 (i.e., the spacing between the L-shaped element 104 and the outer conductor of the coaxial line 103).

[0159] like Figure 18 As shown in (a), the height H of the L-shaped element 104 is preferably less than 1 / 10 of the wavelength. This is because by setting the height H of the L-shaped element 104 to less than 1 / 10 of the wavelength, it is possible to prevent the L-shaped element 104 from radiating radio waves as a monopole antenna.

[0160] Figure 18 (b) is a diagram showing the limitation on the distance D between the open end 106 of the L-shaped element 104 and the power supply section 102.

[0161] like Figure 18 As shown in (b), the distance D between the open end 106 of the L-shaped element 104 and the power supply section 102 is preferably less than 1 / 4 wavelength. This is because by setting the distance D to less than 1 / 4 wavelength, standing waves are prevented from being generated in the coaxial line 103, and as a result, near-field coupling between the coaxial line 103 and the test object can be prevented.

[0162] Figure 19 This is a line diagram showing the technical effects of the antenna 10 according to the first embodiment. Figure 19 The line graphs shown in (a) and (b) are examples of measured data representing the changes in the S11 parameter over time as measured by the biological information monitoring device 1. For comparison with the antenna 10 of the embodiment, Figure 19 (a) shows the variation of the S11 parameter over time using a conventional antenna without the L-shaped element 104. On the other hand, Figure 19 (b) shows the variation of the S11 parameter over time using an embodiment of the antenna 10 with an L-shaped element 104.

[0163] Figure 19 In the variations of S11 parameters shown in (a) and (b) over time, the longer variations with a period of about 5 to 10 seconds are due to respiratory movements such as abdominal breathing. In contrast, the shorter variations with a period of less than 1 second are due to activities (pulsations) caused by the heartbeat.

[0164] like Figure 19 As shown in (a), in the S11 parameters measured using a conventional antenna without the L-shaped element 104, the signal variation caused by heartbeat is buried by the signal variation caused by breathing, making it difficult to detect.

[0165] In contrast, by Figure 19 As can be seen from (b), in the S11 parameters measured using the antenna 10 of the embodiment with L-shaped element 104, the influence of respiratory action is reduced, and signal changes caused by heartbeat can be easily detected.

[0166] As described above, the antenna 10 according to the embodiment having a conductor element 104 (e.g., an L-shaped element 104) can suppress leakage current generated at the power supply section 102, the boundary between the dipole antenna 101 and the coaxial line 103. As a result, the influence of breathing is reduced, and signal fluctuations caused by heartbeats can be easily detected.

[0167] (Second embodiment of the antenna with conductor element)

[0168] Figure 20 as well as Figure 21 This is a diagram illustrating a construction example of a second embodiment of an antenna with a conductor element. (As shown...) Figure 20 As shown in (a), the antenna 10 of the second embodiment is configured to have a portion other than the coaxial line 103 formed on the substrate 107, namely the dipole antenna 101 and the conductor element 104 (e.g., L-shaped element 104).

[0169] on the other hand, Figure 20 (b) shows a coaxial line 103 that should be fixed to the substrate 107. The coaxial line 103 has an inner conductor 109 at the center and an outer conductor 110 at the outer periphery. The outer conductor 110 can be like... Figure 20 As shown in (b), the coaxial cable (e.g., a semi-rigid cable) can be exposed to the outside, or an insulating protective film made of ethylene plastic or the like can be provided on the outer periphery of the outer conductor.

[0170] The substrate 107 is formed into a T-shape, with a lateral component corresponding to the position of the dipole antenna 101 and a longitudinal component corresponding to the position of the conductor element 104.

[0171] The dipole antenna 101 and the conductor element 104 are formed, for example, by etching a copper foil disposed on one side of the substrate 107.

[0172] The dipole antenna 101 can also make the entire surface a continuous surface, but as... Figure 20 As shown in (a), the conductor (e.g., copper foil) of the dipole antenna 101 is formed into a meandering shape in the region from the power supply section 102 to a predetermined position leading to both ends of the dipole antenna 101, and the conductor (e.g., copper foil) of the dipole antenna 101 is formed into a continuous surface in the region from the predetermined position to both ends.

[0173] Here, the region where the conductor is formed in a meandering shape is a region in which multiple thin conductors with a width sufficiently smaller than the width of the conductor in the short side direction of the dipole antenna 101 are bent into a crank-like pattern; that is, a region in which the conductor is formed into a pattern of so-called meandering lines. Furthermore, the term "continuous surface" refers to a surface where the conductor layer is seamlessly covered over the entire surface of the substrate 107, or a surface where the conductor layer is continuously covered over a large area of ​​the surface of the substrate 107.

[0174] On the other hand, the conductor element 104 is a conductor pattern formed on the longitudinal part of the substrate 107. The conductor element 104 is formed such that its length (the length of the conductor element 104 in the direction orthogonal to the dipole antenna 101) is 1 / 4 wavelength of the resonant frequency of the dipole antenna 101.

[0175] The end of the conductor element 104 closer to the power supply section 102 is an open end that is insulated from the dipole antenna 101. The end of the conductor element 104 farther from the power supply section 102 is bent at a shorter right angle. Furthermore, by electrically connecting this bent area to the outer conductor of the coaxial line 103, for example, using solder, the outer conductor 110 of the coaxial line 103 can be short-circuited with the conductor element 104.

[0176] Note that the pad 108 located near the center of the conductor element 104 is provided for fixing the coaxial line 103 to the substrate 107. By bonding the pad 108 to the outer conductor 110 of the coaxial line 103 with solder, for example, the coaxial line 103 can be fixed to the substrate 107.

[0177] Figure 21 This figure shows an example of the appearance of an antenna 10 formed by bonding a dipole antenna 101 and a conductor element 104 formed on a substrate 107 with a coaxial line 103. The inner and outer conductors of the coaxial line 103 are connected to the antenna elements on the left and right sides of the dipole antenna 101, respectively, at the power supply section 102, supplying high-frequency signals to the dipole antenna 101.

[0178] Additionally, the outer conductor 110 of the coaxial line 103 is short-circuited with the conductor element 104 at the end of the conductor element 104 that is farther from the power supply section 102, forming a short-circuit section 105. Alternatively, it can be achieved by using solder or the like to... Figure 20 The pad 108 shown is soldered to the outer conductor 110 of the coaxial line 103 to strengthen the connection between the coaxial line 103 and the substrate 107.

[0179] Note that if the coaxial line 103 is of the type that has an insulating protective film on the outer periphery of the outer conductor 110, the coaxial line 103 can be bonded to the substrate 107 after removing the insulating protective film at the short-circuit portion 105 and the insulating protective film at the bonding portion with the pad 108.

[0180] According to the antenna 10 of the second embodiment described above, since the dipole antenna 101 and the conductor element 104 are formed on the same substrate 107, the ease of installation can be improved and the manufacturing time can be shortened. In addition, as a result, the manufacturing cost can be reduced.

[0181] (Other embodiments of antennas with conductor elements)

[0182] Figure 22 This is a diagram illustrating another embodiment of an antenna with a conductor element. Figure 22 Figure (a) illustrates an embodiment using a bowtie-shaped element as conductor element 104. The bowtie-shaped conductor element 104 is formed as a longitudinally elongated triangular shape with a short-circuit portion 105 as its base and an open end 106 as its vertex. The length of the bowtie-shaped conductor element 104 is approximately 1 / 4 wavelength, and by forming the conductor element 104 into a planar shape, it can function as a conductor element 104 throughout the entire bandwidth.

[0183] For example, when the shape of the conductor element 104 is set as a right triangle, by setting the length of the hypotenuse to L2 and the sum of the lengths of the opposite side and the base to L1 (L1 > L2), the conductor element 104 can achieve a wideband characteristic determined by the lower limit frequency specified by the length L1 and the upper limit frequency specified by the length L2.

[0184] Figure 22 Figure (b) shows an embodiment in which the conductor element 104 is arranged in a spiral shape. In this embodiment, the conductor element 104 is arranged as a wire element and is spirally wound around the outer periphery of the coaxial line 103. In this embodiment, at least one of the outer periphery of the conductor element 104 and the outer periphery of the wire element is covered by an insulating film, and they are mutually insulated except for the short-circuit portion 105.

[0185] In this embodiment, the length L3 from the short-circuit portion 105 of the conductor element 104 to the open end 106 can be shorter than 1 / 4 wavelength, enabling miniaturization of the antenna 10.

[0186] Figure 23 It means Figure 21 The diagram shows a modified example of the conductor element 104 of the antenna 10. In this modified example, the conductor element 104 is constructed using multiple conductor elements of different lengths, for example, three conductor elements 104a, 104b, and 104c.

[0187] Figure 23 Example (a) illustrates a conductor element 104, which is configured to have three conductor elements (L-shaped elements) 104a, 104b, and 104c integrally formed at the base, and to be constructed such that they are short-circuited at one point with the outer conductor 110 of the coaxial line 103. On the other hand, Figure 23 (b) illustrates a conductor element 104, which is constructed such that three conductor elements (L-shaped elements) 104a, 104b, and 104c are independently short-circuited at three points with the outer conductor 110 of the coaxial line 103.

[0188] Even when the conductor element 104 has a fixed length, it's possible that the optimal length may not be achieved depending on the body shape of the subject. In contrast, in... Figure 23 In the illustrated embodiment, by making the lengths of the three conductor elements (L-shaped elements) different, such as short, medium, and long, conductor element (short) 104a can be used for subjects with a slender build, conductor element (medium) 104b can be used for subjects with a standard build, and conductor element (long) 104c can be used for subjects with an obese build.

[0189] Figure 23 The antenna 10 of the embodiments shown in (a) and (b) can be easily implemented because the conductor element 104 is planar, whereas conventional three-dimensional notch filters are generally considered difficult to implement.

[0190] Figure 24 It means Figure 22 Figure (a) shows a modified example of the antenna 10 with a bowtie-shaped conductor element 104. In this modified example, the conductor element 104 is composed of multiple conductor elements 104a, 104b, and 104c that have approximately similar shapes but different sizes.

[0191] Although the bowtie-shaped conductor element 104 has wide bandwidth characteristics, its uniform size means that its optimal length may not be achieved depending on the body shape of the subject. In contrast, in Figure 24 In the illustrated embodiment, by making the three bow-tie shaped conductor elements different in size, such as small, medium, and large, conductor element (small) 104a can be used for subjects with a slender build, conductor element (medium) 104b can be used for subjects with a standard build, and conductor element (large) 104c can be used for subjects with an obese build.

[0192] Figure 24 The antenna 10 of the embodiment shown can be easily implemented because the conductor element 104 is planar, whereas conventional three-dimensional notch filters are generally considered difficult to implement.

[0193] The biological information monitoring device 1 according to the various embodiments described above can reliably and stably detect biological information such as heartbeat and respiration of the subject without burdening the subject.

[0194] Note that while some embodiments of the invention have been described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the invention as described in the claims and its equivalents.

Claims

1. A biological information monitoring apparatus characterized by comprising: Possessing: an antenna device composed of at least one antenna disposed close to a subject; a signal generator that generates a high-frequency signal; and a displacement detection circuit that detects a physical displacement of the subject using the high-frequency signal; the antenna is configured to have: a dipole antenna in which a power feeding portion to which the high-frequency signal is fed is provided in the center; a coaxial line that feeds the high-frequency signal to the power feeding portion; and a 1 / 4 wavelength conductor element configured as a linear conductor or a strip conductor, one end of the 1 / 4 wavelength conductor element being short-circuited to an outer conductor of the coaxial line; the 1 / 4 wavelength conductor element is disposed in substantially parallel to the coaxial line, and a distance between the 1 / 4 wavelength conductor element and the coaxial line is set to be shorter than 1 / 10 wavelength.

2. The living body information monitoring device according to claim 1, wherein the 1 / 4 wavelength conductor element is formed in an L shape.

3. The living body information monitoring device according to claim 1, wherein an end portion of the 1 / 4 wavelength conductor element closer to the power feeding portion of the dipole antenna is open, and an end portion farther from the power feeding portion is short-circuited to the outer conductor.

4. The living body information monitoring device according to claim 3, wherein a distance between the open end portion of the 1 / 4 wavelength conductor element and the power feeding portion of the dipole antenna is set to be shorter than 1 / 4 wavelength.

5. The living body information monitoring device according to claim 1, wherein the dipole antenna and the 1 / 4 wavelength conductor element are formed on the same substrate.

6. The living body information monitoring device according to claim 5, wherein a front end portion of the coaxial line is connected to the power feeding portion of the dipole antenna formed on the substrate, and the outer conductor of the coaxial line is short-circuited to a prescribed portion of the 1 / 4 wavelength conductor element formed on the substrate.

7. The living body information monitoring device according to claim 6, wherein the prescribed portion of the 1 / 4 wavelength conductor element is an end portion farther from the power feeding portion of the dipole antenna.

8. The living body information monitoring device according to claim 5, wherein the dipole antenna is configured as a planar dipole antenna, and a region of a conductor of the planar dipole antenna from a power feeding portion to which the high-frequency signal is fed to a prescribed position toward both ends of the planar dipole antenna is formed in a meandering shape, and a region from the prescribed position to the both ends is formed in a continuous plane.

9. The living body information monitoring device according to claim 1, wherein the 1 / 4 wavelength conductor element is formed in a bow tie shape.

10. The living body information monitoring device according to claim 9, wherein an end portion of the 1 / 4 wavelength conductor element closer to the power feeding portion of the dipole antenna is open, and an end portion farther from the power feeding portion is short-circuited to the outer conductor.

11. The living body information monitoring device according to claim 10, wherein a distance between the open end portion of the 1 / 4 wavelength conductor element and the power feeding portion of the dipole antenna is set to be shorter than 1 / 4 wavelength. Possessing:

12. A biological information monitoring apparatus characterized by comprising: an antenna device composed of at least one antenna disposed close to a subject; a signal generator that generates a high-frequency signal; and a displacement detection circuit that detects a physical displacement of the subject using the high-frequency signal; a displacement detection circuit that detects a physical displacement of the object using the high-frequency signal; the antenna is configured to have: a dipole antenna that has a power feeding portion supplied with the high-frequency signal at a center thereof; a coaxial line that supplies the high-frequency signal to the power feeding portion; and a 1 / 4 wavelength conductor element that has one end portion short-circuited to an outer conductor of the coaxial line; the conductor element is configured to have a plurality of conductor elements having lengths of long axis portions in an L shape different from each other, or the conductor element is configured to have a plurality of conductor elements having sizes different from each other in a bow-tie shape. The biological information monitoring device according to any one of claims 1 to 12.

13. A magnetic resonance imaging apparatus, characterized by ​

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