Motion detection device and radiation therapy device

Abstract

This invention provides a motion detection device that detects patient movement during radiation therapy. [Solution] A motion detection device 1 comprising an oscillation unit 14 that generates a millimeter-wave signal, an irradiation antenna 8 that irradiates a target with the millimeter-wave signal as a millimeter wave, a receiving unit 18 that receives the reflected wave from the target with a receiving antenna 9 and outputs it as a reflected wave signal at each sampling period, a data buffer signal processing unit 12 that stores the reflected wave signal output from the receiving unit in a data buffer 12b and outputs it as a first reflected wave signal after one sampling period, a wavelength analysis unit 16 that uses the reflected wave signal output from the receiving unit after one sampling period as a second reflected wave signal and determines the amount of motion from the first reflected wave signal and the second reflected wave signal, a motion threshold storage unit 20 that records the motion threshold, and a motion comparison unit that compares the amount of motion with the motion threshold and outputs a motion detection signal when the amount of motion is greater than the motion threshold.

Description

Technical Field

[0001] The present invention relates to a body movement detection device that detects the movement of a patient during radiation therapy.

Background Art

[0002] Management of patient movement in radiation therapy is an important issue for ensuring the safety and positioning accuracy of the patient during treatment. This is because unexpected body movement during treatment can cause a positional shift from the planned irradiation area, potentially leading to a decrease in the dose to the tumor and over-irradiation of surrounding normal tissues. This problem is particularly prominent in high-precision techniques such as intensity-modulated radiation therapy (IMRT) and stereotactic radiation therapy (SRT), where positional accuracy in millimeters is essential.

[0003] Current body movement monitoring methods mainly rely on visual observation by radiation oncologists and medical radiation technologists through cameras in the treatment room, and do not have an objective evaluation function. The judgment of irradiation interruption and readjustment by image guidance often depends on empirical judgment. Therefore, in order to realize a more quantitative evaluation function, advanced commercial systems have been developed. For example, image-guided radiation therapy (IGRT) systems and surface-guided radiation therapy (SGRT) systems have evolved to enable monitoring of the displacement of the body surface and treatment site before and during radiation irradiation, and tracking of internal and external body movements.

[0004] Notable examples include the ExacTrac Dynamic system, which combines SGRT and IGRT with infrared or CCD camera tracking technology, and Varian's IDENTIFY TM SGRT systems. The latter realizes sub-millimeter-level movement monitoring accuracy in a closed-beam line accumulator (CLB). AlignRT has been successfully applied to PTV margin analysis in lung SBRT.

[0005] Motion monitoring is particularly important in thoracic and abdominal treatments where respiratory motion affects target location. Advanced systems like CyberKnife Synchrony create correlation models between external markers and internal tumor locations and even enable automatic beam interruption if significant movement is detected. However, these advanced commercial systems are typically expensive and often difficult to integrate with existing facilities.

[0006] Current radiation therapy allows for radiation delivery with an accuracy of a few millimeters, provided the patient remains still. Therefore, there was a need for a motion detection device that, while not as high-performance as IGRT or SGRT, was affordable and compatible with existing equipment.

[0007] On the other hand, millimeter waves are known to be able to detect the movement of objects with high precision. In the medical field, there is an invention that transmits ultra-broadband millimeter waves to a patient and obtains vital information such as respiratory intervals and heart rate intervals from the reflected waves (Patent Document 1). In addition, 24 GHz band millimeter wave sensors are also being used in the medical field (Non-Patent Document 1). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2023-533883 [Non-patent literature]

[0009] [Non-Patent Document 1] Kosaka H, ​​Kubo K, Matsumoto K, Nakamura Y, Monzen H.Exploring the feasibility of millimeter-wave sensors for non-invasive respiratory motion visualization in diagnostic imaging and therapy. Med Phys.2025;52(5):3088-3096 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Millimeter-wave radar can detect patient movements with high precision, but it also detects vital information such as respiratory and heart rate intervals. In other words, it detects movements that are too subtle from the perspective of body movement, leading to frequent false positives. On the other hand, it is thought that limb and body movements can produce larger signals than respiration and heartbeats, so one approach is to only use larger signals. However, if only large movements are detected, small body movements cannot be detected, resulting in a decrease in detection rate.

[0011] Furthermore, when attempting to detect the body movements of a single patient using a single millimeter-wave radar, it was difficult to detect the movement of parts of the body that were in shadow, posing a challenge in confirming that the patient was maintaining a resting posture during radiation therapy. [Means for solving the problem]

[0012] This invention was conceived in view of the above problems, and provides a highly accurate body motion detection device with a simple configuration.

[0013] More specifically, the motion detection device according to the present invention is: An oscillator (14) that generates a millimeter-wave signal, An illumination antenna (8) that irradiates the target with the aforementioned millimeter-wave signal as millimeter waves, A receiving unit (18) receives the reflected wave from the aforementioned target with a receiving antenna (9) and outputs it as a reflected wave signal at each sampling period. A data buffer signal processing unit (12) stores the reflected wave signal output from the receiving unit (18) in a data buffer (12b) and outputs it as a first reflected wave signal (Wave(n)) after one sampling period, The reflected wave signal output from the receiving unit (18) after the first sampling period is second Let the reflected wave signal be (Wave(n+1)), and the aforementioned first reflected wave signal (Wave(n)) and the above Second reflected wave signal (Wave(n+1)) The magnitude of the change in the reflected waveform is shown from the Doppler wave obtained by analyzing it. A wavelength analysis unit (16) for obtaining the amount of movement (Move(n+1)), A body movement threshold value storage unit (20) for recording the body movement threshold value (Moth), A body motion threshold determination unit (24) records 25 times the maximum value of the amount of movement during a predetermined period of resting as the body motion threshold in the body motion threshold storage unit, It is characterized by having a movement comparison unit (22) that compares the amount of movement (Move(n+1)) with the body movement threshold value (Moth) and outputs a body movement detection signal (EV) when the amount of movement is greater than the body movement threshold value.

Effect of the Invention

[0014] The body movement detection device according to the present invention determines the movement related to the patient's biological activity and the movement of the hands, feet and body based on the body movement threshold value, and thus shows high performance with a detection rate exceeding about 90% at a movement distance of 5 mm.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram showing the configuration of the body movement detection device according to the present invention. [Figure 2] It is a diagram showing the arrangement of the body movement detection device. [Figure 3] It is a flowchart showing the operation flow of the body movement detection device. [Figure 4] It is a specific example of the reflected wave. [Figure 5] It is a specific example of obtaining the amount of movement. [Figure 6] It is a graph showing individual differences in the body movement threshold value.

Mode for Carrying Out the Invention

[0016] Hereinafter, the body movement detection device according to the present invention will be described with reference to the drawings and examples. The following description illustrates one embodiment and one example of the present invention, and the present invention is not limited to the following description. The following description can be modified without departing from the gist of the present invention.

[0017] In this specification, any movement that causes a patient to deviate from a resting position and interfere with radiation therapy is referred to as "body movement." In other words, "body movement" is body movement excluding at least biological activities such as breathing and heartbeat, as well as movement caused by noise from equipment and vibrations from the environment.

[0018] Figure 1 shows the configuration of the motion detection device 1 according to the present invention. The motion detection device 1 includes an oscillation unit 14, an irradiation antenna 8, a receiving antenna 9, a receiving unit 18, a data buffer signal processing unit 12, a wavelength analysis unit 16, a data buffer 12b, a motion comparison unit 22, a motion threshold storage unit 20, and a control unit 10 that controls the whole system. It is even more preferable to have a motion threshold determination unit 24.

[0019] The oscillator 14 sends a signal SmmW that generates millimeter waves to the irradiation antenna 8. The irradiation antenna 8 irradiates the millimeter waves mmW toward the target (patient). The receiving antenna 9 receives the reflected wave RmmW from the target. The receiving unit 18 converts the reflected wave RmmW into a reflected wave signal Wave(n). Here, n represents time. Therefore, the reflected wave signal Wave(n) represents the reflected wave signal at time n, and the reflected wave signal Wave(n+1) represents the reflected wave signal at time n+1.

[0020] The receiver 18 outputs a reflected wave signal at a constant sampling frequency. The sampling frequency is not particularly limited, but it can be suitably operated at a frequency f of about 40 to 100 Hz. The sampling period T is a time expressed as 1 / f. Therefore, the difference between time n and time n+1 is only the sampling period T (time).

[0021] The reflected wave signal Wave(n), which is the output from the receiving unit 18, is sent to the data buffer signal processing unit 12. The data buffer signal processing unit 12 performs the process of saving the reflected wave signal Wave(n) to the data buffer. The data buffer 12b is a so-called RAM (Random Access Memory) that temporarily stores the reflected wave signal Wave(n) in a readable format.

[0022] After the reflected wave signal Wave(n) received at time n is stored in the data buffer 12b, and then the reflected wave signal Wave(n) is output from the receiving unit 12, the reflected wave signal Wave(n+1) is output from the receiving unit 18 at time n+1, after one sampling period has elapsed. At this time, the data buffer signal processing unit 12 reads out the reflected wave signal Wave(n) from the data buffer 12b that was stored in the data buffer 12b at time n+1. In other words, at time n+1, the reflected wave signal WAVE(n) in the data buffer 12b is read out by the data buffer signal processing unit 12.

[0023] The wavelength analysis unit 16 analyzes the reflected wave signal Wave(n+1) and the reflected wave signal Wave(n) read from the data buffer 12b by the data buffer signal processing unit 12, and determines and outputs the patient's movement amount Move(n+1) from the Doppler wave obtained as a result of the analysis. In other words, the movement amount Move(n+1) at time n+1 is determined by the reflected wave signal Wave(n+1) at time n+1 and the reflected wave signal Wave(n) at time n.

[0024] The value stored in the body movement threshold memory unit 20 determines the upper limit of movement that becomes therapeutically problematic. In other words, it is the threshold beyond which any movement is considered body movement. A value is selected that eliminates movement from daily activities at rest, as well as vibrations from equipment and the environment, while still allowing for the acquisition of body movement with a high probability.

[0025] For this purpose, a body movement threshold Moth is set. The method for measuring the amount of movement Move(n+1) itself will be described later. Since the body movement threshold Moth differs from person to person, movement based on biological activity in a resting state is always measured before treatment. The actual body movement threshold Moth is obtained by multiplying the amount of movement Move(n+1) (called the basic movement amount MBve) based on biological activity in a resting state by K. The body movement threshold memory unit 20 is a memory that stores the body movement threshold Moth.

[0026] The motion comparison unit 22 compares the amount of motion Move(n+1) from the wavelength analysis unit 16 with the body motion threshold Moth from the body motion threshold storage unit 20. If the amount of motion Move(n+1) is greater than the body motion threshold Moth, it generates and outputs a body motion detection signal EV indicating that body motion has occurred.

[0027] The receiver of the body motion detection signal EV can preferably be a monitor or speaker (not shown). More specifically, the monitor that receives the body motion detection signal EV will display an indication that the patient has moved. In the case of a speaker, it will output sound to notify the operator of the medical device that the patient has moved.

[0028] The control unit 10 controls the movement of these components. For example, an input / output terminal that receives instructions from an external source may be connected to the control unit 10. The control unit 10 may also be connected to the oscillation unit 14, the data buffer signal processing unit 12, the receiving unit 18, the wavelength analysis unit 16, the motion threshold storage unit 20 and motion comparison unit 22, and the motion threshold determination unit 24, and may be configured to control their operation and return the signals generated by each element to the control unit. In Figure 1, thick double-headed arrows are placed around the control unit 10 and each element to indicate that control commands and generated signals can be exchanged between the control unit 10 and each element.

[0029] Furthermore, a laser pointer 28 aligned with the irradiation direction and irradiation axis may be provided so that the irradiation direction of the irradiation antenna 8 can be visually confirmed. The laser pointer 28 may also be called an indicator. Since millimeter waves are invisible to the naked eye, it is not possible to know exactly where on the patient they are being irradiated. However, if the irradiation position of the millimeter waves can be determined using the laser pointer 28, it becomes easier to adjust the position of the body motion detection device 1.

[0030] The laser pointer 28 may be connected to the control unit 10. In other words, the control unit 10 may be configured to control the operation of the laser pointer 28. Furthermore, the oscillator 14, irradiation antenna 8, receiving antenna 9 and receiving unit 18, data buffer 12b, and data buffer signal processing unit 12 may use commercially available millimeter-wave sensors or parts thereof.

[0031] <Movement amount Move(n+1)> The amount of patient movement is determined for each sampling period. The amount of movement at time n+1, Move(n+1), is calculated as shown in equation (1).

[0032]

number

[0033] Here, Wave(n) is the signal obtained from the reflected wave at time n (reflected wave signal). In other words, the amount of motion at time n+1, Move(n+1), is the magnitude of the change in the reflected waveform from time n to time n+1. Also, since the difference between time n+1 and time n is the sampling period, the amount of motion Move is a value obtained for each sampling period.

[0034] Furthermore, the motion amount Move(n+1) represents the amount of movement after the sampling period of the motion amount Move(n). For example, if the sampling frequency is 50 Hz, the sampling period is 1 / 50 second. This sampling frequency is sufficient to detect small positional movements and general body movements, including clinically important movements such as coughing and limb movements. Note that equation (1) is performed in the wavelength analysis unit 16 in Figure 1.

[0035] Figure 2 shows the arrangement of the body motion detection device 1 according to the present invention during operation. Patient A is at rest or fixed on the treatment table 54 of the radiotherapy device 50. The radiotherapy device 50 has at least a radiation irradiation unit 52, a treatment table 54, and a treatment device control unit 56 that controls the radiation irradiation unit 52, and it is sufficient for the treatment device control unit 56 to control the radiation irradiation unit 52. Figure 2 also shows that the treatment device control unit 56 can also control the movement of the treatment table 54.

[0036] Figure 2(a) is a side view, and Figure 2(b) is a top view. Radiation irradiation units 52 are arranged around the treatment table 54, and radiation is irradiated onto patient A. If patient A does not maintain the prescribed posture, the radiation dose to the torso will decrease, and radiation will be irradiated onto healthy tissue. The treatment table 54 has the direction of gravity as the Y-axis (Figure 2(a)), the left and right sides when viewed from above as the X-axis, and the direction from the legs to the head as the Z-axis. Positive (+) and negative (-) directions are distinguished in each direction.

[0037] Traditionally, during treatment, the radiologist visually monitored patient A's body movements. Therefore, if patient A moved slightly while the radiologist was operating the equipment, the change might go unnoticed, and treatment could continue. The body movement detection device 1 detects patient A's body movements and notifies the operator.

[0038] The motion detection device 1 is positioned relative to patient A as follows: First, the millimeter wave irradiation position is set to the body center of patient A (approximately the position of the navel). By irradiating with millimeter waves at this position, even a single motion detection device 1 can detect the movement of various parts of patient A's body.

[0039] Next, the following three parameters are defined for determining the position of the body motion detection device 1. First, it is the direction inclined toward patient A from a line Acp parallel to the centerline Ac of patient A's body (see Figure 2(b)). This is called the azimuth angle θ. The centerline Ac of the body is the line that divides the body vertically in half, as shown in Figure 2(b), within the line connecting the head and feet of patient A lying supine on the treatment table 54. If patient A is lying on their side, it may be the direction from the head of patient A toward the tailbone when viewed from above. In addition, the millimeter wave irradiation position may be near the radiation irradiation site.

[0040] Secondly, referring to the side view of patient A (Figure 2(a)), the direction of the downward angle φ toward patient A. The downward angle φ is the angle from which patient A is viewed from a plane PP parallel to the surface 54a of the treatment table 54. Furthermore, thirdly, the distance L from the millimeter wave irradiation position of patient A.

[0041] In other words, with the millimeter-wave irradiation position being the navel of patient A, the motion detection device 1 is positioned at an azimuth angle θ, depression angle φ, and distance L. For example, if the azimuth angle θ is 0°, the depression angle φ is 90°, and the distance L is 100cm, then millimeter waves will be irradiated vertically onto patient A from a position 1m directly above patient A's navel. The millimeter-wave irradiation position can also be set in a part close to the radiation irradiation position. The azimuth angle θ can be between 10° and 90°, the depression angle φ can be between 10° and 90°, and the distance L can be between 50cm and 150cm. Thus, the motion detection device 1 is positioned above the surface 54a of the treatment table 54.

[0042] Furthermore, as shown in the embodiments described later, the motion detection device 1 according to the present invention was able to obtain suitable detection performance by being positioned within a range where the azimuth angle θ is 45°±2°, the depression angle φ is 35°±2°, and the distance L is 140cm±10cm. Note that these positional locations exist in four directions from the perspective of patient A. In Figure 2, in addition to the motion detection device 1, three other locations are indicated by reference numerals 1a, 1b, and 1c. The position of the motion detection device 1 can be any of these positions.

[0043] However, to mitigate the effects of the radiation source, it is preferable to position the device at a certain distance from the source. The azimuth angle θ, depression angle φ, and distance L mentioned above can be changed according to the irradiation output and directivity of the irradiation antenna 8 and the receiving sensitivity and directivity of the receiving antenna 9 in the motion detection device 1, and predetermined angles or distances may be set according to the characteristics of the motion detection device used. However, in order to detect motion in the vertical (Y direction), horizontal (X direction), and longitudinal (Z direction) directions described later, it is desirable that the azimuth angle θ and depression angle φ be 10° or more, taking into account the directivity characteristics of a typical irradiation antenna 8 and receiving antenna 9.

[0044] For example, when irradiating the upper body, the radiation is applied from the feet (reference numeral 1 or 1a), and when irradiating the lower body, the radiation is applied from the head (reference numeral 1b or 1c).

[0045] Figure 3 illustrates the operation of the motion detection device 1 according to the present invention. This processing flow may also be represented as processing by the control unit 10. First, assume that patient A is lying on the treatment table 54 in a position to receive radiation. The motion detection device 1 is started up prior to radiation therapy. Assume that the basic motion amount MBve of the motion detection device 1 is preset to zero. Furthermore, all subsequent flow descriptions assume time n. Therefore, in Figure 3, the time "(n)" is omitted from the motion amount Move. When the motion detection device 1 is activated (step S100), it detects the motion amount Move of patient A (step S102).

[0046] Patient A's movement amount, Move, is compared to the baseline movement amount, MBve (step S104). If Move is greater than the baseline movement amount, MBve (Y branch in step S104), then Move is set as the baseline movement amount, MBve (step S106). If Move is not greater than the baseline movement amount, MBve (N branch in step S104), step S106 is skipped.

[0047] Next, it is determined whether t0 seconds have elapsed since activation (step S108). In other words, the purpose is to obtain the baseline motion volume MBve for each patient A during the first t0 seconds. This baseline motion volume MBve includes the movements caused by patient A's breathing and heartbeat.

[0048] If t0 seconds have not elapsed (N branch in step S108), the process returns to step S102 and the process of acquiring the movement amount Move is repeated. If t0 seconds have elapsed (Y branch in step S108), the basic movement amount MBve has been obtained from the movement amount Move during t0 seconds, so the basic movement amount MBve is multiplied by K to obtain the body movement threshold Moth (step S110). In other words, the body movement threshold Moth used during measurement is a value with a margin of K times the basic movement amount MBve, which is recorded as movement related to biological activities such as breathing and heartbeat. The body movement threshold Moth is stored in the body movement threshold storage unit 20.

[0049] The steps S102 to S110 described above can be considered the initial setup process for the motion detection device 1. The actual measurement will begin in the next step. Therefore, radiation therapy will be performed from the next step onward. It should also be assumed that the motion threshold determination unit 24 is executed based on instructions from the control unit 10 (see Figure 1) in steps S102 to S110.

[0050] Referring again to step S112 of the flow in Figure 3, first, the amount of motion Move is detected (step S112). Next, the amount of motion Move is compared with the body motion threshold Moth (step S114). If the amount of motion Move is greater than the body motion threshold Moth (Y branch in step S114), a body motion detection signal EV indicating that body motion has occurred is output (step S116). If the amount of motion Move is not greater than the body motion threshold Moth (N branch in step S114), step S116 is skipped.

[0051] Then a termination determination is made (step S118). The termination determination may be, in addition to switching off the motion detection device 1, stopping the radiation therapy device or other emergency stop reasons. If termination is determined (Y branch in step S118), the device stops as is (step S120). If termination is not determined (N branch in step S118), the process returns to step S112 and the following processes continue.

[0052] In the above explanation, the motion detection device 1 itself measures the individual motion threshold Moth each time a new patient is encountered and stores it in the motion threshold storage unit 20. However, the motion threshold Moth may also be saved to the motion threshold storage unit 20 manually. In that case, steps S102 to S110 may be skipped in the flow chart of Figure 3. [Examples]

[0053] The following describes an embodiment of the motion detection device 1 according to the present invention. A Milweb Application Kit manufactured by SMK Corporation was used as the millimeter-wave sensor. This is a Doppler-type millimeter-wave sensor that emits 24 GHz radio waves and can measure the velocity of an object by detecting the frequency change of the reflected wave from the object.

[0054] In this embodiment, the millimeter-wave sensor is customized to fit the motion detection device 1 according to the present invention, and the oscillation unit 14, irradiation antenna 8, receiving unit 18, receiving antenna 9, data buffer 12b, data buffer signal processing unit 12, wavelength analysis unit 16, motion threshold storage unit 20, motion comparison unit 22, motion threshold determination unit 24, and control unit 10 are integrated into a single unit.

[0055] The motion detection device 1 is configured by adding a laser pointer 28 to the millimeter-wave sensor. Furthermore, t0 (the time to acquire the motion threshold Moth) in Figure 3 was set to 5 seconds. Therefore, the patient needed to remain at rest for 5 seconds. A resting state refers to a state of quiet lying down without performing any movements other than breathing.

[0056] Furthermore, based on systematic preliminary tests using multiple coefficients, it was found that a constant K value of 25 is preferable in Figure 3. This is because K=25 showed the optimal balance between detection sensitivity (correct detection rate of approximately 80%) and specificity (false positive rate of approximately 10%). In subsequent experiments, the value of K was always set to 25.

[0057] The radiation therapy equipment used was the Vero4DRT manufactured by MITSUBISHI HEAVY INDUSTRIES, Ltd. (Tokyo, Japan). The detection rate and false posivitive rate were defined as shown in equations (2) and (3).

[0058]

number

[0059] Equation (2) shows the detection rate. Here N perf This is the total number of times the movement was performed, N det This represents the number of times a movement was detected. All performed movements have a sufficient amount of movement (Move) to be classified as a body movement. This index represents the system's ability to accurately identify actual body movements. It is calculated as the ratio of the number of times a movement was detected to the total number of body movements performed.

[0060]

number

[0061] (3) Equation (3) shows the false positive rate. Here, N total This is the total number of motion detections, N false This represents the number of false positives. This metric indicates the tendency for the system to incorrectly detect movements that are not actually occurring. It was calculated as the percentage of waveform peaks that did not correspond to the actual movement of the treatment table or the instructed body movements that were detected as body movements.

[0062] The experiment consisted of two parts: (Experiment 1) evaluation of the detection rate of the body motion detection device 1 (based on the distance traveled along each axis), and (Experiment 2) evaluation of the detectability of patient A's body movements under clinical conditions.

[0063] The participants in Experiment 1 were 26 healthy volunteers (median age: 31 years, range: 23-55 years, 17 males, 9 females).

[0064] Experiment 2 involved 10 healthy volunteers (median age: 29.5 years, range: 23-55 years, 5 males, 5 females) to assess the detectability of body movements (e.g., coughing, vocalization, nodding, arm movements, leg movements) during radiation therapy.

[0065] Ethical Approval: This study was conducted with the approval of the Okayama Central Hospital Ethics Review Committee (20241001). Informed consent was obtained from all subjects who participated in this study.

[0066] <Result> The reflected wave signal Wave, obtained from the reflected wave from the patient, can be plotted as waveform data. After plotting the waveform data, frequency analysis was performed to remove unwanted frequency components. Figure 4 shows the raw waveform of the reflected wave signal Wave obtained from the reflected wave. The horizontal axis is time (seconds), and the vertical axis is amplitude (arbitrary unit). Figure 4 can be considered as the reflected wave signal Wave(n+1) at time n+1.

[0067] Figure 5 shows the reflected wave signal Wave(n+1) from Figure 4 and the processed waveform after applying equation (1) to the reflected wave signal Wave(n) at time n one sample period earlier. This is the motion amount Move(n+1). The horizontal axis is time (seconds), and the vertical axis is the motion amount Move. The left end of the graph is the time (5 seconds) for acquiring the body movement threshold. The line parallel to the horizontal axis is the body movement threshold Moth, which is obtained by multiplying the base motion amount by K=25. It can be seen that the patient made some kind of body movement during the elapsed time when there is a peak above the body movement threshold. In Figure 5, heart marks are placed where body movement occurred.

[0068] For example, in the subject Move(n+1) shown in Figure 4, the baseline motion amount MBve during a 5-second resting period was measured to be 148.7. When the value of K is set to 25, the motion threshold obtained by multiplying the baseline motion amount MBve by K becomes 3718, which is shown by the dashed line in Figure 5. In other words, any movement that exceeds this motion threshold Moth is judged to be "motion".

[0069] Figure 6 shows the distribution of motion threshold Moth calculated from 26 subjects (total of 104 datasets) with K set to 25. The motion threshold Moth showed a mean of 1793, a median of 534, a standard deviation of 1107, a maximum of 7285, and a minimum of 359. These values ​​indicate large variability in baseline motion between subjects and between measurements taken at rest.

[0070] While some subjects showed baseline movement levels nearly four times the average, most data fell within ±50% of the average, indicating that individual body movement thresholds (Moth) are crucial for accurate motion detection.

[0071] <Experiment 1: Evaluation of the detection rate of millimeter-wave sensors based on the distance traveled in each axial direction> Twenty-six healthy volunteers (median age: 31 years, range: 23-55 years, 17 males, 9 females) lay supine on treatment table 54 one by one and remained at rest.

[0072] The treatment table 54 was moved according to the specified direction and amount of movement, and the detection accuracy was evaluated. The treatment table 54 was moved by 5 mm, 3 mm, 2 mm, and 1 mm in the positive and negative directions for each axis (X: left / right, Y: up / down, Z: front / back). The time required to move the treatment table 54 was approximately 20 seconds, allowing sufficient time for the treatment table 54 to stabilize after the move. This was to ensure accurate operation of the treatment table 54.

[0073] More specifically, the test was performed on patient A, who was lying on treatment table 54, in the following manner. (1) The motion threshold Moth was acquired over a 5-second period. (2) The amount of movement, Move, was acquired while moving the treatment table 54 5 mm in the X-axis (+) direction. (3) Keep it still for 5 seconds. (4) The treatment table 54 was returned to its original position (moved in the negative direction by the same distance it was moved). (5) The amount of movement, Move, was acquired while moving the treatment table 54 3 mm in the X-axis (+) direction.

[0074] The following steps (3) through (5) were repeated while varying the distance of movement. Once the movement in the X-axis (+) direction was completed, the same movement was repeated in the X-axis (-) direction. After the movement in the X-axis was completed, the amount of movement (Move) was repeatedly obtained by moving along the Y-axis and Z-axis.

[0075] The results are shown in Table 1. The detection rate decreased in the order of vertical (Y direction), horizontal (X direction), and longitudinal (Z direction). For vertical (Y direction) movement, the detection rate exceeded 80% in the range of movement distance from 5 mm to 2 mm. However, in the longitudinal (Z direction), it fell below 60%. The detection rate decreased as the amount of movement decreased; it was approximately 90% at 5 mm, but dropped to 60% at 1 mm.

[0076] [Table 1]

[0077] Next, to evaluate the reliability of the body motion detection device 1, the false positive rate for each travel distance was analyzed (see Table 2). The false positive rate represents the proportion of detected waveform peaks that do not match the actual movement of the treatment table 54.

[0078] [Table 2]

[0079] As the detection rate decreased, the false positive rate tended to increase. This is because the amount of movement of the treatment table 54 that was correctly detected (the denominator in the calculation) decreased. As a result, even if the number of false positives remained the same, the false positive rate increased proportionally.

[0080] <Experiment 2: Evaluation of Patient A's motion detection ability under clinical conditions> The patients were 10 healthy volunteers. The subjects were asked to perform specified movements according to instructions while at rest. Specifically, for arm movements, the subjects were asked to rotate their elbows inward. For leg movements, the subjects were asked to bring their legs together from a position with their legs extended and feet shoulder-width apart. Each movement was repeated three times, with a break of approximately 15 seconds between each repetition.

[0081] Table 3 shows the detection rates of physical movements (coughing, vocalization, nodding, arm movements, leg movements) under simulated clinical conditions.

[0082] [Table 3]

[0083] Referring to Table 3, all actions except vocalization were detected with 100% accuracy. Although the vocalization consisted of a short phrase, "yes," the microphone inside the examination room could detect patient A's vocalization, so even with a body movement detection rate of 80%, it is not expected to have a significant impact on clinical implementation.

[0084] Furthermore, Experiment 1 showed that the detection rate in the longitudinal direction (Z direction) was relatively lower compared to the vertical direction (Y direction) and the horizontal direction (X direction). However, most of the important movements of patient A during radiation therapy (coughing, nodding, limb movements, etc.) involve three-axis motion amounts that generate signals detected across multiple axes. Therefore, the fact that the detection rate in the longitudinal direction (Z direction) is lower compared to the other axes does not have a clinical impact.

[0085] As described above, the motion detection device according to the present invention can achieve high monitoring accuracy using a relatively inexpensive millimeter-wave sensor. It can also be easily adapted to existing treatment equipment. Furthermore, because it is a non-contact measurement, it reduces the burden on patients and also reduces the workload of radiotherapists who previously relied on visual monitoring. [Industrial applicability]

[0086] The motion detection device according to the present invention can be suitably used in the field of radiation therapy. [Explanation of Symbols]

[0087] 1. Motion detection device 8 Irradiation antennas 9 Receiving antenna 10 Control Unit 12. Data buffer signal processing unit 12b Data buffer 14. Oscillator 16 Wavelength analysis section 18 Receiving Unit 20 Motion threshold memory unit 22. Motion Comparison Section 24 Body movement threshold determination unit 28 Laser Pointer 50 Radiation therapy equipment 52 Radiation irradiation area 54 Treatment table 56 Treatment device control unit A patient SmmW signal that generates millimeter waves mmW Millimeter wave RmmW Reflected wave Wave(n+1) Reflected wave signal Wave(n) Reflected wave signal Move(n+1) Amount of movement Move amount Moth body movement threshold MBve base motion EV motion detection signal AC center line Acp parallel lines θ Azimuth angle φ depression angle L distance

Claims

1. An oscillator that generates millimeter-wave signals, An illumination antenna that irradiates the target with the aforementioned millimeter-wave signal as millimeter waves, The reflected wave from the aforementioned object is received by the receiving antenna, and the reflected wave signal is obtained at each sampling period. The receiving unit that outputs to and The reflected wave signal output from the receiving unit is stored in the data buffer, and one sample is taken. A data buffer signal processing unit that outputs the first reflected wave signal after a period, The reflected wave signal output from the receiving unit after one sampling period is used as the second reflected wave signal, and the wavelength analysis unit determines the amount of motion, which indicates the magnitude of the change in the reflected waveform, from the Doppler wave obtained by analyzing the first reflected wave signal and the second reflected wave signal. A body motion threshold storage unit that records the body motion threshold, A body movement threshold determination unit records 25 times the maximum value of the amount of movement during a predetermined period of resting as the body movement threshold in the body movement threshold storage unit, The amount of motion is compared with the body motion threshold, and if the amount of motion is greater than the body motion threshold, body motion A motion detection device having a motion comparison unit that outputs a detection signal.

2. At a predetermined distance from the millimeter-wave irradiation position on the patient, along the centerline of the patient's body A predetermined azimuth angle from a parallel direction toward the patient, and the treatment in which the patient is lying down. A motion detection device according to claim 1, fixed at a predetermined downward angle from a surface parallel to the surface of the table. Place.

3. The aforementioned distance is 140 cm ± 10 cm. The azimuth angle is 45° ± 2°, The motion detection device according to claim 2, wherein the depression angle is 35° ± 2°.

4. The motion detection device according to claim 1 further comprises an indicator that shows the location to which the millimeter waves are irradiated. Output device.

5. The motion detection device according to claim 1, wherein the wavelength analysis unit calculates the amount of motion (Move(n+1)) from the second reflected wave signal (Wave(n+1)) and the first reflected wave signal (Wave(n)) based on equation (1). [Number 100]

6. A motion detection device as described in claim 1, A radiation irradiation unit that irradiates with radiation, A radiotherapy device with a treatment table on which the patient is immobilized.

7. The treatment device further comprises at least a treatment device control unit that controls the radiation irradiation unit, The radiotherapy apparatus according to claim 6, wherein the treatment apparatus control unit controls the body motion detection device.

8. The aforementioned motion detection device is Above the surface of the treatment table, The azimuth angle θ is 10° to 90°, and the angle from a line parallel to the centerline of the patient fixed on the treatment table toward the treatment table is 10° to 90°. The angle from the plane parallel to the treatment table toward the treatment table is a downward angle φ of 10° or more and 90° or less. A radiotherapy apparatus according to claim 7, which is fixed on the treatment table and positioned at a distance of 50 cm to 150 cm from the patient.

9. The azimuth angle θ is 45° ± 2°, The aforementioned depression angle φ is 35° ± 2°, A radiotherapy apparatus according to claim 8, wherein the aforementioned distance is 140 cm ± 10 cm.

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