Moving body tracking device and radiation irradiation system

Abstract

A moving body tracking device obtains the position of a tracking object 55, and generates a signal for permitting irradiation of a target 50 with radiation when it is determined that the tracking object 55 exists inside a gate range. In the moving body tracking device, the gate range varies between timing when the tracking object 55 enters the inside from the outside of the gate range and timing when the tracking object exits from the inside to the outside. Accordingly, provided are a moving body tracking device and a radiation irradiation system with which it is possible to suppress a change in the dose distribution and a decrease in irradiation efficiency due to the influence of latency.

Description

Moving Object Tracking Device and Radiation Irradiation System

[0001] The present invention relates to a radiation irradiation system for treating a diseased part such as a tumor by irradiating radiation such as a particle beam, and a moving object tracking device suitable for such a radiation irradiation system.

[0002] Patent Document 1 discloses an accelerator that generates and emits a charged particle beam, an irradiation device that has a scanning electromagnet that scans the charged particle beam and irradiates the charged particle beam onto an irradiation target, a target monitoring device that measures the position of the irradiation target, a tracking irradiation that corrects the excitation current value of the scanning electromagnet based on a signal from the target monitoring device and irradiates the charged particle beam onto the irradiation target, and a gate irradiation that irradiates the charged particle beam when the irradiation target is within a predetermined emission permission range based on a signal from the target monitoring device. The control device performs tracking irradiation when the position of the irradiation target measured by the target monitoring device is within the emission permission range of the gate irradiation.

[0003] Non-Patent Document 1 describes, as part of guidelines regarding the method of commissioning and quality assurance of RGPT when tracking implanted fiducial markers using the pulse fluoroscopy method in real-time gated proton therapy, the workflow of the commissioning at the target center and the daily and monthly QA procedures.

[0004] Japanese Patent No. 5976353

[0005] HQ Tan et al., “Real-time gated proton therapy with a reduced source to imager distance: Commissioning and quality assurance”, Physica Medica,(2024) 122, 103380.

[0006] Methods of irradiating patients with radiation such as particle beams and X-rays for diseases such as cancer are known. Particle beams include proton beams, carbon beams, and the like. The radiation irradiation system used for irradiation forms a dose distribution suitable for the shape of a target such as a tumor in the body of a patient fixed on a patient bed called a couch.

[0007] As a method for forming dose distributions in radiation irradiation systems, scanning irradiation, which involves scanning a narrow particle beam with an electromagnet to form the dose distribution, is beginning to become widespread.

[0008] When targets such as tumors move due to respiration or other factors, accurate irradiation with particle beams becomes difficult. Therefore, gated irradiation, which irradiates the target only when it is within a predetermined range (gate range), has been realized in recent years. Patent document 1, mentioned above, describes a method called motion tracking irradiation, which performs gated irradiation based on the position of a marker embedded near the affected area.

[0009] On the other hand, Non-Patent Document 1 reports that a time called latency occurs between the measurement of the marker position and the determination of the gate.

[0010] Specifically, when a marker moves outside the gate range, the irradiation permission state may continue due to latency, even though the marker is actually outside the gate range. In this case, particle beams may be irradiated while the marker is outside the gate range, leaving room for improvement in the dose distribution.

[0011] Conversely, when a marker moves from outside the gate range into the gate range, the marker may actually be within the gate range, but the irradiation prohibition state may continue due to latency. In this case, since the particle beam is not irradiated despite the marker being within the gate range, there is room to shorten the irradiation time.

[0012] The object of the present invention is to provide a motion tracking device and a radiation irradiation system that can suppress changes in dose distribution and decreases in irradiation efficiency due to latency compared to conventional systems.

[0013] The present invention includes multiple means for solving the above problems, but one example is a motion tracking device that determines the position of a target to be tracked and generates a signal to permit radiation irradiation to a target when it is determined that the target to be tracked is inside the irradiation permission range, wherein the irradiation permission range differs at the timing when the target to be tracked enters the irradiation permission range from outside to inside and at the timing when it exits the irradiation permission range from inside to outside.

[0014] According to the present invention, changes in dose distribution and decreases in irradiation efficiency due to latency can be suppressed compared to conventional methods. Other problems, configurations, and effects will be clarified by the following description of the examples.

[0015] This is an overall configuration diagram of the proton beam irradiation system of Example 1. This is a conceptual diagram of the motion tracking irradiation device acquiring captured images. This is a flowchart of the motion tracking irradiation device in the proton beam irradiation system of Example 1 determining whether irradiation is possible from the captured images. This is a diagram showing the display portion of the console when setting the parameters used to determine whether irradiation is possible in the motion tracking irradiation device of Example 1. This is a diagram showing an example of a screen that shows the current status displayed on the console during irradiation in the proton beam irradiation system of Example 1. This is a conceptual diagram explaining the irradiation position shift due to latency in the conventional method. This is a conceptual diagram explaining the effect of the motion tracking irradiation device of Example 1 on suppressing irradiation position shift. This is a conceptual diagram explaining the effect of the motion tracking irradiation device of Example 2 on suppressing irradiation position shift.

[0016] Embodiments of the motion tracking device and radiation irradiation system of the present invention will be described below with reference to the drawings.

[0017] In the drawings used in this specification, identical or corresponding components are denoted by the same or similar reference numerals, and repeated explanations of these components may be omitted.

[0018] <Example 1> Example 1 of the motion tracking device and radiation irradiation system of the present invention will be described with reference to Figures 1 to 7.

[0019] The present invention can be applied to radiation irradiation systems such as X-ray irradiation systems and proton beam irradiation systems. In this embodiment, a proton beam irradiation system will be used as an example and explained with reference to Figure 1.

[0020] First, the overall configuration of the proton beam irradiation system 1 and the configuration for acquiring fluoroscopic images will be explained using Figures 1 and 2. Figure 1 is an overall configuration diagram of the proton beam irradiation system of Example 1, and Figure 2 is a conceptual diagram of the motion tracking irradiation device acquiring the captured image.

[0021] One embodiment of the present invention, the proton beam irradiation system 1, as shown in Figure 1, comprises a proton beam generator 10, a beam transport system 20, an irradiation nozzle 22, a motion tracking control device 41, a couch 27, and an irradiation control device 40. The proton beam irradiation device (radiation irradiation device) for irradiating a target 50 with a proton beam comprises a proton beam generator 10, a beam transport system 20, and an irradiation nozzle 22.

[0022] The proton beam generator 10 comprises an ion source 12, a linac 13, and a synchrotron 11. The synchrotron 11 comprises a deflection electromagnet 14, a quadrupole electromagnet (omitted for illustrative purposes), a high-frequency accelerator 18, a high-frequency emission device 19, and an emission deflector 17.

[0023] The ion source 12 is connected to the linac 13, which is connected to the synchrotron 11. In the proton beam generator 10, protons generated from the ion source 12 are pre-accelerated by the linac 13 and then injected into the synchrotron 11. The proton beam, further accelerated in the synchrotron 11, is emitted into the beam transport system 20.

[0024] The beam transport system 20 is equipped with multiple deflection magnets 21 and a quadrupole magnet (not shown) and is connected to the synchrotron 11 and the irradiation nozzle 22. In addition, a part of the beam transport system 20 and the irradiation nozzle 22 are installed in a cylindrical gantry 25 and can rotate together with the gantry 25. The proton beam emitted from the synchrotron 11 passes through the beam transport system 20, is focused by the quadrupole magnet, and has its direction changed by the deflection magnets 21 before being incident on the irradiation nozzle 22.

[0025] The irradiation nozzle 22 is equipped with two scanning electromagnets, a dose monitor, and a position monitor. The scanning electromagnets are positioned perpendicular to each other and generate a magnetic field by excitation current, which can deflect the proton beam so that it reaches a desired position in a plane perpendicular to the beam axis at the location of the target 50. The dose monitor measures the amount of irradiated proton beam. The position monitor can detect the position through which the proton beam has passed. The proton beam that has passed through the irradiation nozzle 22 reaches the target 50 within the irradiation target 26. When treating patients with cancer or the like, the irradiation target 26 represents the patient, and the target 50 represents a tumor or the like.

[0026] The bed on which the irradiation target 26 is placed is called the couch 27. Based on instructions from the irradiation control device 40, the couch 27 can move in the direction of three orthogonal axes and can also rotate around each axis. Through these movements and rotations, the position of the irradiation target 26, including the target 50, can be moved to a desired position.

[0027] The irradiation control device 40 is a device for controlling the irradiation and stopping of the proton beam based on information transmitted from the motion tracking device (details will be described later), and is electrically connected to the proton beam generator 10, beam transport system 20, irradiation nozzle 22, motion tracking control device 41, couch 27, console 42, etc., in order to control the equipment such as the proton beam generator 10, beam transport system 20, and irradiation nozzle 22.

[0028] The motion tracking device comprises a first X-ray imaging device, a second X-ray imaging device, and a motion tracking control device 41.

[0029] Of the motion tracking devices, the first X-ray imaging device includes an imaging X-ray generator 23A and an X-ray measuring instrument 24A that capture a fluoroscopic image including a tracking target 55 (see Figure 2) for tracking the position of the target 50 within the irradiation target 26. The second X-ray imaging device includes an imaging X-ray generator 23B and an X-ray measuring instrument 24B that capture a fluoroscopic image including the tracking target 55.

[0030] As shown in Figure 2, the first X-ray imaging device and the second X-ray imaging device are installed so that their respective X-ray paths intersect. It is preferable that the two pairs of imaging X-ray generators 23A, 23B and X-ray measuring instruments 24A, 24B are installed in directions perpendicular to each other, but this is not required. Furthermore, the imaging X-ray generators 23A, 23B and X-ray measuring instruments 24A, 24B do not necessarily have to be located inside the gantry 25; they may be placed in fixed locations such as the ceiling or floor.

[0031] The tracking target 55 is one or more of the following: an artificial object such as a gold marker, living tissue within the irradiation target 26 such as bone or diaphragm, or the target 50 itself.

[0032] The motion tracking control device 41 determines the position of the target 55 from the images captured by the imaging X-ray generators 23A and 23B and the X-ray measuring instruments 24A and 24B. When it is determined that the target 55 is inside the gate range (permitted irradiation range), it generates a signal (permitted irradiation signal) that permits the irradiation of the proton beam to the target 50. When it is determined that the target 55 is outside the gate range (permitted irradiation range), it generates a signal (not permitted irradiation signal) that does not permit the irradiation of the proton beam to the target 50. The generated signals are then transmitted to the irradiation control device 40. Based on the input signals, the irradiation control device 40 performs the irradiation of the proton beam to the target 50.

[0033] Alternatively, the system may output only a signal that permits proton beam irradiation and irradiate only when that signal is input, or it may output only a signal that does not permit proton beam irradiation and not irradiate when that signal is not input.

[0034] More specifically, as shown in Figure 2, the motion tracking control device 41 irradiates the area including the tracking target 55 with X-rays generated from the imaging X-ray generator 23A, and images the tracking target 55 by measuring the two-dimensional dose distribution of the X-rays that have passed through the irradiated object 26, which includes the tracking target 55, using the X-ray measuring instrument 24A. Alternatively, the tracking target 55 is also imaged by irradiating the tracking target 55 with X-rays generated from the imaging X-ray generator 23B, and measuring the two-dimensional dose distribution of the X-rays that have passed through the irradiated object 26 using the X-ray measuring instrument 24B.

[0035] The motion tracking control device 41 calculates the three-dimensional position of the tracking target 55 embedded in the irradiation target 26 from the image acquired by the X-ray measuring instruments 24A and 24B, and determines the position of the tracking target 55 (i.e., the target 50) based on the result.

[0036] The motion tracking control device 41 also determines whether the position of the tracked target 55 is within the gate range. If it determines that the position of the tracked target 55 is within the gate range, it transmits a gate-on signal to the irradiation control device 40 to permit emission. Conversely, if it determines that the position of the tracked target 55 is not within the gate range, it transmits a gate-off signal to deny emission. The irradiation control device 40 controls the emission of the proton beam based on the gate-on and gate-off signals generated by the motion tracking control device 41. This gate range is set by the user considering the irradiation time and irradiation accuracy.

[0037] The acquisition of images by the first and second X-ray imaging devices is performed, for example, at regular intervals of 30 Hz, but may be at higher or lower frequencies and is not particularly limited.

[0038] The irradiation control device 40 and the motion tracking control device 41 described above may each have a central processing unit (CPU) and memory connected to this CPU, or they may be configured as a single computer, and are not particularly limited in any way.

[0039] Furthermore, the control processes for the actions to be performed may be combined into a single program, divided into multiple programs, or a combination of these.

[0040] Some or all of the programs contained within each device may be implemented using dedicated hardware, or they may be modularized. Furthermore, various programs may be installed on each device via a program distribution server or external storage media, or existing devices may be updated.

[0041] Furthermore, each device may be an independent device connected by a wired or wireless network, or two or more devices may be integrated into a single unit.

[0042] Next, a method for determining irradiation permission will be described more specifically with reference to FIGS. 3 and 4. FIG. 3 is a flowchart for the moving body tracking irradiation device in the proton beam irradiation system of Example 1 to determine whether irradiation is possible from a captured image, and FIG. 4 is a diagram showing a display portion of a console when setting parameters used for determining whether irradiation is possible in the moving body tracking irradiation device of Example 1.

[0043] In the moving body tracking control device 41 of this embodiment, prior to the start of irradiation, a planned position and two types of gate widths are set. Specifically, the gate range is different at the timing when the tracking target 55 enters from the outside to the inside of the gate range and at the timing when it exits from the inside to the outside. In this embodiment, specifically, the gate range is set to be different when it is determined that the tracking target 55 is approaching the irradiation planned position and when it is determined that the tracking target 55 is departing from the irradiation planned position. More specifically, the gate range in the case where it is determined that the target is approaching is set to be wider than the gate range in the case where it is determined that the target is departing.

[0044] The gate range is set as a spherical region centered on the planned position and having the gate width as the radius. The gate width is set for each of the approaching phase and the departing phase. Here, the approaching phase means the phase in which the tracking target 55 approaches the planned position, and includes the timing when the tracking target 55 enters from the outside to the inside of the gate range. On the other hand, the departing phase means the phase in which the tracking target 55 moves away from the planned position, and includes the timing when the tracking target 55 exits from the inside to the outside of the gate range.

[0045] Fig. 3 exemplifies a parameter setting screen 60 displayed on the console 42. As shown in Fig. 3, on the setting screen 60, an approaching phase gate width input field 62 for inputting the approaching phase gate width and a departing phase gate width input field 64 for inputting the departing phase gate width are displayed. These are set by the user inputting predetermined values into the approaching phase gate width input field 62 and the departing phase gate width input field 64 for inputting the departing phase gate width. However, if the values entered in the approaching phase gate width input field 62 and the departing phase gate width input field 64 are the same, the setting is rejected, and it is desirable to reject the setting if the value entered in the approaching phase gate width input field 62 is smaller than the value entered in the departing phase gate width input field 64.

[0046] Note that it is not necessary for the gate range to be spherical. For example, it is also possible to set a cubic region as the gate range where the distances from the planned position in three perpendicular directions are within the gate width.

[0047] Fig. 4 is a flowchart for determining whether irradiation is possible. When the determination of whether irradiation is possible starts in step S101, a fluoroscopic image is captured in step S102 and the position of the tracking target 55 is measured.

[0048] In step S103, the phase is determined based on the measured position of the tracking target 55. Specifically, compared with the position of the tracking target 55 on the fluoroscopic image measured one time before, if the tracking target 55 is approaching the planned position, it is determined as the approaching phase, and if the tracking target 55 is moving away from the planned position, it is determined as the departing phase.

[0049] In step S104, the gate range is set based on the determined phase. In step S105, it is determined whether the tracking target 55 is inside or outside the gate range. If it is within the gate range, irradiation is permitted, if it is outside the gate range, irradiation is prohibited, and the determination of irradiation permission ends in step S106.

[0050] Here, the determination of the position of the tracking target 55 can be made including the position of the tracking target 55 at one or more previous determination timings including the immediate previous one. Specifically, the position of the tracking target 55 evaluated in step S105 may be the average of a plurality of measured values measured immediately before.

[0051] Since measurement errors are inevitably included in the measured values, if the movement of the tracked object 55 fluctuates little, the phase may change frequently due to fluctuations in the measured values ​​caused by measurement errors. Therefore, by determining the average of multiple measured values ​​taken immediately beforehand as the measured value, this fluctuation can be suppressed.

[0052] Furthermore, the motion tracking control device 41 can output signals to the console 42 that display a graph of time on one axis and a graph of the gate range and the position of the tracked object 55 on the other axis.

[0053] Figure 5 illustrates a gate determination screen 70 that shows the current status displayed on the console 42 during irradiation. As shown in Figure 5, the gate determination screen 70 on the console 42 displays the current status, an image display field 72 that displays a translucent image 1 showing the current measured position of the tracking target 55 and the planned position, an image display field 74 that displays a translucent image 2, a result display field 76 that displays the gate determination result, and irradiation determination result display fields 77 and 78 that show the current irradiation feasibility status, all of which are updated in real time.

[0054] Next, the effects obtained by this embodiment will be explained using Figures 6 and 7. Figure 6 is a conceptual diagram illustrating the shift in irradiation position due to latency in the conventional method, and Figure 7 is a conceptual diagram illustrating the effect of suppressing the shift in irradiation position by the motion tracking device of Embodiment 1.

[0055] First, Figure 6 will be used to explain the conventional method of tracking and irradiating a moving object. The horizontal axis in Figure 6 represents time, and Figure 6(A) represents the distance between the planned position and the tracking target 55, or the position of the tracking target 55 relative to the planned position in the direction of a certain axis. In Figure 6(A), the solid line represents the real-time position of the tracking target 55, the dots represent the position of the tracking target 55 recognized by the motion tracking control device 41, and the dashed line represents the gate range. As can be seen in Figure 6(A), the dots are delayed by the latency time. This latency value is determined by the calculation time from image acquisition to gate determination, and is therefore a value specific to the equipment. Figure 6(B) shows the state of the gate signal, where a low value means irradiation is prohibited, and a high value means irradiation is permitted.

[0056] In conventional methods, the gate width is constant regardless of the approach phase and departure phase. In the area indicated by the black arrow in Figure 6(A), the target object 55 is actually outside the gate range, but the gate signal may be in an illumination permission state.

[0057] Next, the motion tracking irradiation in this embodiment will be explained using Figure 7. The horizontal axis in Figure 7 represents time. The vertical axis in Figure 7(A) is R, which represents the distance between the planned position and the tracking target 55, or the position of the tracking target 55 relative to the planned position in the direction of a certain axis. The solid line represents the real-time position of the tracking target 55, the dots represent the position of the tracking target 55 recognized by the motion tracking control device 41, and the dashed line represents the gate range. Figure 7(B) shows the state of the gate signal, where a low value means irradiation is prohibited and a high value means irradiation is permitted. Figure 7(C) shows the change in R ΔR from the previous perspective image. Figure 7(D) shows the state of the phase, where a high value means approaching phase and a low value means departing phase.

[0058] As shown in Figure 7, a negative change in the amount of change ΔR indicates an approach phase, while a positive change indicates an exit phase. In Figure 7, the gate width in the approach phase is the same as the value in Figure 6, but the gate width in the exit phase is set smaller than the value in Figure 6. By setting a smaller gate width in the exit phase, the time at which the gate signal prohibits irradiation is brought forward. This shortens the time during which the target 55 is outside the gate range in Figure 6 and is in an irradiation-permitted state. Similarly, by setting the gate width in the approach phase to be larger than the value in Figure 6, the time at which the gate signal permits irradiation is brought forward, making it possible to improve irradiation efficiency. In other words, according to the present invention, changes in dose distribution and decreases in irradiation efficiency due to latency can be suppressed compared to conventional methods.

[0059] Furthermore, the gate range differs depending on whether the target 55 is judged to be approaching the irradiation plan position or moving away from the irradiation plan position. In particular, the gate range when it is judged to be approaching is wider than the gate range when it is judged to be moving away. Therefore, it becomes possible to set a more appropriate gate range according to the movement of the target 50, and the effects of shortening the irradiation time and improving accuracy can be obtained more significantly.

[0060] Furthermore, by determining the position of the tracking target 55 by including the position of the tracking target 55 at one or more previous determination timings, including the one immediately preceding it, the influence of fluctuations in measured values ​​due to measurement errors can be further reduced, enabling a more accurate determination of whether or not to fire.

[0061] Furthermore, by outputting a signal where one axis represents time and the other axis displays a graph of the gate range and the position of the tracked object 55, the user can easily grasp the current situation visually.

[0062] Furthermore, by providing imaging X-ray generators 23A, 23B and X-ray measuring instruments 24A, 24B for imaging the tracking target 55, and a motion tracking control device 41 that determines the position of the tracking target 55 from the images captured by the imaging X-ray generators 23A, 23B and X-ray measuring instruments 24A, 24B, it is possible to handle cases where the tracking target 55 or target 50 is located within the irradiation target 26.

[0063] <Example 2> An example of the motion tracking device and radiation irradiation system of the present invention will be described with reference to Figure 8. Figure 8 is a conceptual diagram illustrating the effect of suppressing irradiation position deviation by the motion tracking irradiation device of Example 2.

[0064] The difference between the motion tracking irradiation device and radiation irradiation system of this embodiment and that of Embodiment 1 lies in the method of determining the phase.

[0065] In this embodiment, the gate range differs depending on whether the tracking target 55 was inside the gate range and irradiation was permitted at a determination timing one or more prior to the immediately preceding tracking determination timing, or whether the tracking target 55 was outside the gate range and irradiation was not permitted. Specifically, the gate range when irradiation was permitted is narrower than the gate range when the tracking target 55 was outside the gate range and irradiation was not permitted.

[0066] In terms of the difference in processing flow, in step S103 shown in Figure 4, the phase is determined based on the position of the tracking target 55, i.e., the position of the target 50, at a determination timing one or more prior to the immediately preceding tracking determination timing, including the previous tracking determination timing.

[0067] Specifically, if the gate signal at the time of determination is in a state of irradiation prohibition, it is determined to be in an approach phase; if the gate signal at the time of determination is in a state of irradiation permission, it is determined to be in a close phase.

[0068] Furthermore, in this embodiment, if the difference in gate width between the approach phase and the departure phase is large, the determination of whether irradiation is permissible may change again immediately after the determination of whether irradiation is permissible has changed.

[0069] To avoid this, after the determination of whether irradiation is permissible or not changes, the irradiation permission / denial can be kept fixed for a predetermined time or for a predetermined number of tracking timing periods for the target 55 being tracked.

[0070] Specifically, it is possible to set a grace period after a change in the irradiation feasibility determination, and to control the system so that the phase does not change during this grace period. The grace period can be set by time or by the number of measurements of the position of the tracked object 55.

[0071] The motion tracking irradiation in this embodiment will be explained using Figure 8. The horizontal axis in Figure 8 represents time. The vertical axis in Figure 8(A) is R, which represents the distance between the planned position and the tracking target 55, or the position of the tracking target 55 relative to the planned position in the direction of a certain axis. The solid line represents the real-time position of the tracking target 55, and the dots represent the position of the tracking target 55 recognized by the motion tracking control device 41. The dashed line represents the gate range. Figure 8(B) shows the state of the gate signal, where a low value means irradiation is prohibited, and a high value means irradiation is permitted.

[0072] In this embodiment, if the gate signal at the time of determination is in the irradiation prohibition state, it is set to the approach phase, and if the gate signal at the time of determination is in the irradiation permission state, it is set to the departure phase. Therefore, in the example of Figure 8, the gate signal becomes in the irradiation permission state for the first time at the left phase x1, and thereafter it becomes the departure phase and determination is made using a narrow gate width.

[0073] Next, at the point in phase x2 on the right, it is determined that the target 55 is outside the gate range, and thereafter it enters the proximity phase and is determined using a wider gate width. As a result, the time during which the target 55 is outside the gate range in Figure 8 and is in an irradiation-permitted state is shortened.

[0074] The other configurations and operations are substantially the same as those of the motion tracking device and radiation irradiation system in Example 1 described above, and details are omitted.

[0075] As in the motion tracking device and radiation irradiation system of Embodiment 2 of the present invention, even if the gate range differs depending on whether the tracking target 55 is inside the gate range and irradiation is permitted at a determination timing one or more prior to the immediately preceding tracking determination timing, including the gate range when the tracking target 55 is outside the gate range and irradiation is not permitted, it is possible to suppress changes in dose distribution and a decrease in irradiation efficiency due to latency, similar to the motion tracking device and radiation irradiation system of Embodiment 1 described above.

[0076] Furthermore, because the gate range when irradiation is permitted is narrower than the gate range when the target 55 is outside the gate range and irradiation is not permitted, it becomes possible to set a more appropriate gate range according to the movement of the target 50, thereby achieving greater effects in shortening irradiation time and improving accuracy.

[0077] Furthermore, by calculating the difference between the gate range when irradiation is permitted and the gate range when irradiation is not permitted, and if the difference is greater than or equal to a predetermined value, the irradiation permission / denial status is kept fixed for a predetermined time or a predetermined number of tracking timing times for the target 55, it is possible to prevent the judgment result from fluctuating between the approach phase and the departure phase, and to prevent the switching between irradiation permission and denial from being abrupt and unstable.

[0078] <Other> The present invention is not limited to the embodiments described above, and includes various modifications. The embodiments described above are explained in detail for clarity and are not necessarily limited to those having all the configurations described.

[0079] Furthermore, it is possible to replace parts of the configuration of one embodiment with parts of the configuration of another embodiment, and it is also possible to add parts of the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with parts of other configurations.

[0080] For example, in the above embodiment, we described a case where two X-ray imaging devices are used to image the target, but it is not necessarily required to use two X-ray imaging devices. For example, by moving one X-ray imaging device, images of the tracking target 55 may be acquired from two different directions. Furthermore, it is also possible to use ultrasound or MRI instead of an X-ray imaging device for imaging.

[0081] Furthermore, although the above embodiments described a proton beam irradiation system as an example, the radiation irradiation system of the present invention can be similarly applied to systems that irradiate with particle beams other than proton beams, such as carbon beams, as well as X-rays, electron beams, etc. For example, when using X-rays, the radiation irradiation apparatus consists of an X-ray generator, a beam transport system, and an irradiation nozzle.

[0082] Furthermore, in the case of a particle beam irradiation system, the particle beam generator may be a cyclotron, a synchrocyclotron, or even another type of accelerator, in addition to the synchrotron 11 described in the above embodiment.

[0083] 1…Proton beam irradiation system (radiation irradiation system) 10…Proton beam generator 11…Synchrotron 12…Ion source 13…Linac 14…Bending electromagnet 17…Exit deflector 18…Radio frequency accelerator 19…Radio frequency exit device 20…Beam transport system 21…Bending electromagnet 22…Irradiation nozzle 23A, 23B…X-ray generator for imaging (imaging device) 24A, 24B…X-ray detector (imaging device) 25…Gantry 26…Irradiation target 27…Couch 40…Irradiation control device 41…Motion tracking control device 42…Console 50…Target 55…Tracked object 60…Setting screen 62…Approach phase gate width input field 64…Departure phase gate width input field 70…Gate determination screen 72, 74…Image display field 76…Result display field 77, 78…Irradiation determination result display field

Claims

1. A motion tracking device that determines the position of a target and generates a signal to permit radiation irradiation to a target when it is determined that the target is inside the permitted irradiation range, wherein the permitted irradiation range differs depending on when the target enters the permitted irradiation range from outside to inside and when it exits the permitted irradiation range from inside to outside.

2. A motion tracking device according to claim 1, wherein the permitted irradiation range differs depending on whether the tracking target is determined to be approaching the irradiation plan position or whether the tracking target is determined to be moving away from the irradiation plan position.

3. A motion tracking device according to claim 2, wherein the irradiation permission range when it is determined that the object is approaching is wider than the irradiation permission range when it is determined that the object is moving away.

4. A motion tracking device according to claim 2, wherein the determination of the position of the object to be tracked includes the position of the object to be tracked at one or more previous determination timings, including the one immediately preceding it.

5. A motion tracking device according to claim 1, wherein, at a determination timing one or more prior to the immediately preceding tracking determination timing, the permitted irradiation range differs between the permitted irradiation range when the target being tracked is inside the permitted irradiation range and irradiation is permitted, and the permitted irradiation range when the target being tracked is outside the permitted irradiation range and irradiation is not permitted.

6. A motion tracking device according to claim 5, wherein the permitted irradiation range when irradiation is permitted is narrower than the permitted irradiation range when irradiation is not permitted.

7. A motion tracking device according to claim 5, wherein, after the determination of whether to permit or deny irradiation changes, the permit / denial of irradiation is kept fixed for a predetermined time or for a predetermined number of tracking timing times of the target being tracked.

8. A motion tracking device according to claim 5, wherein the determination of the position of the object to be tracked includes the position of the object to be tracked at one or more previous determination timings, including the one immediately preceding it.

9. A motion tracking device according to claim 1, wherein one axis outputs a signal that displays a graph of the irradiation permission range and the position of the tracking target, and the other axis outputs a signal that displays a graph of time.

10. A motion tracking device according to claim 1, comprising: an imaging device for imaging the target to be tracked; and a control device for determining the position of the target to be tracked from the image captured by the imaging device.

11. A radiation irradiation system comprising: a radiation irradiation device for irradiating a target with radiation; an irradiation control device for controlling the radiation irradiation device; and a motion tracking device according to any one of claims 1 to 10, wherein the motion tracking device transmits the signal to the irradiation control device, and the irradiation control device controls the irradiation and stopping of the radiation based on the transmitted information.

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