Dose adjustment mechanism and radiation therapy device

Abstract

To reduce an influence of radiation in a dose adjustment mechanism of a radiation therapy device and suppress occurrence of a failure.SOLUTION: A dose adjustment mechanism 40 comprises: an actuator 42 separated from a radiation axis on which a radiation therapy device 10 emits radiation; and a flattening filter 33, which is an interference element that moves in a direction perpendicular to the radiation axis through an operation of the actuator 42 and is capable of switching between a state of being located on the radiation axis and a state of not being located on the radiation axis; where an operation axis of the actuator 42 does not intersect the radiation axis.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a dose adjustment mechanism and a radiotherapy apparatus. [Background technology]

[0002] In a radiation therapy device, directional radiation emitted from a target is irradiated onto the affected area. The radiation dose distribution in a plane perpendicular to the beam axis decreases as the distance from the beam axis increases, forming a mountain-like shape. Because a mountain-like shape makes it difficult to create a treatment plan, a flattening filter (FF) is used to create a flat dose distribution. Since the dose distribution differs depending on the beam energy, it is common to use different flattening filters depending on the beam energy.

[0003] The flattening filter is attached inside the irradiation head. The flattening filter is generally conical, and if the center of the cone is shifted from the beam axis, the flatness of the dose at the isocenter changes significantly. Therefore, the position of the flattening filter must be highly reproducible.

[0004] In recent years, with the spread of high-precision radiation therapy, such as intensity-modulated radiation therapy and stereotactic radiation therapy, which do not require flattening of the dose distribution, treatments are being performed in a flattening filter-free (FFF) state, which does not use a flattening filter, and in which higher dose rates are irradiated.

[0005] Some existing radiotherapy devices are equipped with a function that automatically switches between the presence and absence of a flattening filter within the same device (see, for example, Patent Document 1). The irradiation head has limited space because it is equipped with a multi-leaf collimator, a dosimeter, and other components in addition to the flattening filter. On the other hand, the irradiation head should not be made too large because it may easily interfere with the patient and the device, so it is desirable to implement a mechanism for switching between the presence and absence of a flattening filter within a limited space. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Publication No. 8890100 Summary of the Invention [Problem to be solved by the invention]

[0007] If structures such as actuators are placed near the beam axis as in the prior art, there is a risk of failure due to the effects of radiation. Therefore, an object of the present invention is to provide a dose adjustment mechanism and a radiotherapy apparatus that reduce the effects of radiation and suppress the occurrence of malfunctions. [Means for solving the problem]

[0008] In order to achieve the above object, one representative dose adjustment mechanism of the present invention comprises an actuator arranged away from the radiation axis along which the radiation therapy device irradiates radiation, and an interference element that moves perpendicular to the radiation axis by the operation of the actuator and can switch between a state where it is positioned on the axis of the radiation axis and a state where it is not positioned on the axis of the radiation axis, and is characterized in that the operating axis of the actuator does not intersect with the radiation axis. Furthermore, one representative radiation therapy apparatus of the present invention comprises a radiation irradiation device, a gantry that rotates the radiation irradiation device around an isocenter, a patient support that supports a patient so that a treatment target area is positioned at the isocenter, and a dose adjustment mechanism that adjusts the dose of radiation irradiated by the radiation irradiation device, wherein the dose adjustment mechanism comprises an actuator arranged apart from a radiation axis along which the radiation therapy device irradiates radiation, and an interference element that moves perpendicular to the radiation axis by operation of the actuator and is switchable between a state where it is positioned on the axis of the radiation axis and a state where it is not positioned on the axis of the radiation axis, and wherein the operating axis of the actuator does not intersect with the radiation axis. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the influence of radiation on the dose adjustment mechanism of a radiotherapy device and suppress the occurrence of malfunctions. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiment. [Brief explanation of the drawings]

[0010] [Figure 1] Radiation therapy equipment diagram [Figure 2] Illustration of radiation exposure (FF) [Figure 3] Illustration of radiation exposure (FFF) [Figure 4] Explanatory diagram of dose adjustment mechanism [Figure 5] Explains the dose adjustment mechanism as seen from the electron gun direction [Figure 6] Modified example of dose adjustment mechanism [Figure 7] Illustration of the control of the dose adjustment mechanism DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment will be described with reference to the drawings. [Example]

[0012] FIG. 1 is an explanatory diagram of a radiotherapy device. As shown in Figure 1, the radiation therapy device 10 includes a couch 11, which is a patient support, a gantry 20 equipped with a rotation mechanism, and a radiation irradiator 30. The gantry 20 supports the radiation irradiator 30 and rotates the radiation irradiator 30 around the isocenter. The couch 11 positions the area of ​​the patient to be treated at the isocenter. The radiation irradiator 30 includes a swing mechanism, which can swing the irradiation axis of the irradiated radiation.

[0013] The gantry 20 includes a ring frame and a rotating ring. The ring frame is positioned so that its central axis faces a substantially horizontal direction. The rotating ring has its outer peripheral surface supported by the inner peripheral surface of the ring frame and is rotatable along the inner peripheral surface of the ring frame. The rotating ring is driven by a rotation drive mechanism and rotates around the central rotation axis.

[0014] The swing mechanism has a gimbal structure on which the radiation irradiation device 30 is mounted, and can tilt the radiation irradiation device 30 around two axes, a pan axis and a tilt axis.

[0015] 2 and 3 are explanatory diagrams of radiation irradiation. A radiation irradiation device 30 accelerates electrons emitted by an electron gun to generate an electron beam, which is then irradiated onto a target 32. The target 32 ​​emits radiation (e.g., X-rays) when irradiated with the electron beam. The flattening filter 33 has conical protrusions made of aluminum or the like, and uniformizes the dose distribution in a plane perpendicular to the radiation emission direction. Figure 2 shows the relationship between the distance from the beam axis of the electron beam and the dose rate. As shown in Figure 2, by applying the flattening filter 33, the dose rate value becomes uniform within a certain range from the beam axis. For convenience, the state in which the flattening filter 33 is applied is referred to as the FF state.

[0016] As shown in Figure 3, in the flattening filter-free (FFF) state where the flattening filter 33 is not used, the dose rate is highest on the beam axis and decreases with the distance from the beam axis. Irradiation in this FFF state is suitable for treatments that do not require flattening the dose distribution and require a higher dose rate, such as intensity-modulated radiation therapy and stereotactic therapy.

[0017] The dose adjusting mechanism 40 disclosed in this embodiment is a mechanism for switching between FF and FFF. Fig. 4 is an explanatory diagram of the dose adjusting mechanism. The dose adjusting mechanism 40 includes a frame member 41 , an actuator 42 , a moving member 43 , and a linear guide 44 . The frame member 41 is fixed relative to the radiation axis (beam axis). The actuator 42 is installed on the outside of the frame member 41 . The moving member 43 is a flattening filter installation portion that mounts the flattening filter 33. The moving member 43 also has a hole portion 34 that transmits radiation as it is.

[0018] The moving member 43 slides along the linear guide 44. That is, the linear guide 44 corresponds to the movement axis of the moving member 43. The linear guide 44 enables the moving member 43 to move linearly with high accuracy.

[0019] The moving member 43 is connected to the actuator 42 via a support member, and moves in a direction perpendicular to the radiation axis by the operation of the actuator 42. This movement causes the dose adjusting mechanism 40 to switch between a state in which the flattening filter 33 is arranged on the radiation axis (FF) and a state in which the hole 34 is located on the radiation axis (FFF).

[0020] The actuator 42 is disposed away from the radiation axis to reduce the influence of radiation. The movement axis of the actuator 42 is disposed so as not to intersect with the radiation axis. Specifically, the movement axis of the actuator 42 and the movement direction of the moving member 43 (the movement direction of the flattening filter 33) are parallel, and the support member extends from the movement axis of the actuator 42 and holds the moving member 43.

[0021] If a moving member is provided on the movement axis of the actuator 42, the distance from the radiation axis to the actuator 42 increases, and the center of gravity moves away from the radiation axis. The further the center of gravity moves away from the radiation axis, the lower the accuracy of position control of radiation irradiation may become. Furthermore, if the distance from the radiation axis to the actuator 42 is large, the possibility of interference with the gimbal mechanism increases. 4, the position of the actuator 42 can be brought closer to the radiation axis by arranging the operation axis of the actuator 42 and the movement axis of the flattening filter 33 parallel to each other. As a result, this contributes to improving the accuracy of radiation irradiation and also reduces interference with the gimbal mechanism.

[0022] 5 is an explanatory diagram of the dose adjustment mechanism 40 as viewed from the direction of the electron gun. The moving member 43 is in the FF state when it abuts against a stop surface 46a provided on the inside of the frame member 41. Also, it is in the FFF state when it abuts against a stop surface 46b opposite to the stop surface 46a.

[0023] The stop surfaces 46 (46a and 46b) have spherical surfaces that come into contact with the moving member 43. As an example, the stop surfaces 46 may have a spherical indentation cut out from a sphere. Making the stop surfaces 46 spherical reduces the possibility of foreign matter getting caught.

[0024] As shown in Fig. 5, the dose adjustment mechanism 40 has opposing stop surfaces 46, and switches between two states by having an actuator 42 press a movable member 43 against one of the stop surfaces 46. This eliminates the need to adjust the position of the movable member 43, and the states can be switched with a simple mechanism and control. As a result, the dose adjustment mechanism 40 can be made compact, low-cost, and highly accurate.

[0025] The dose adjustment mechanism 40 also has a sensor 45 near the stop surface 46. Specifically, it has a sensor 45a near the stop surface 46a and a sensor 45b near the stop surface 46b. The sensor 45 outputs an output indicating the presence or absence of the movable member 43. The dose adjustment mechanism 40 can determine the consistency between the output of the sensor 45 and the control state of the actuator 42.

[0026] The dose adjustment mechanism 40 is in the FF state when the control state of the actuator 42 is in the reference position. If an abnormality occurs in the operation of the actuator 42, it is highly likely to stop in the reference state. If the flattening filter 33 is applied in the reference state, safety can be improved in the event of an abnormality.

[0027] The dose adjustment mechanism 40 also has a nozzle 47 that sprays air onto the stop surface 46 to remove foreign matter adhering to the stop surface 46. The nozzle 47 may be provided on both the stop surface 46a and the stop surface 46b, but in the configuration of Fig. 5, it is selectively provided on the stop surface 46a. This is because the state in which the movable member 43 abuts on the stop surface 46a is the FF state, which requires highly accurate positioning, whereas the state in which the movable member 43 abuts on the stop surface 46b is the FFF state, which does not require highly accurate positioning.

[0028] FIG. 6 shows a modified example of the dose adjustment mechanism 40. The actuator 42a shown in FIG. 6 has its operating axis connected to the moving axis of the moving member 43 by a link member 42b, and converts direction between the operating direction of the actuator 42 and the moving direction of the moving member 43 (the moving direction of the flattening filter 33). The actuator 42a positions the flattening filter 33 by continuously pressing the moving member 43, so accuracy can be ensured even if there is rattle in a configuration using multiple parts. In this way, using a link member increases the degree of freedom in arranging the actuator 42.

[0029] 7 is an explanatory diagram of the control of the dose adjustment mechanism 40. Two sensors 45a are arranged near the stop surface 46a and are touch switches that detect the FF mode. Two sensors 45b are arranged near the stop surface 46b and are touch switches that detect the FFF mode.

[0030] The touch switches are connected in series and behave like an AND circuit. In Fig. 7, both sensors 45a detect contact, and the controller 51 detects that the FF mode is active. The approximate current position of the moving member 43 is monitored by the encoder 52.

[0031] Specifically, the dose adjusting mechanism 40 sequentially performs the following operations (1) to (5). (1) Depending on the selected mode, the controller 51 transmits a target position to the actuator 42, and the moving member 43 moves. (2) When the value of the encoder 52 falls within a certain range, a pressing operation begins. The pressing operation is an operation in which the actuator continues to move toward the target position with a set force. (3) When the moving member 43 comes into contact with the stop surface 46, the sensor 45, which is a touch switch, detects this, and the controller 51 detects the mode. (4) The pressing operation continues, but since there is no change in position, the controller 51 sets the "pressing completion flag." (5) Radiation irradiation is permitted based on both the mode detection and the "pressing completion flag."

[0032] As described above, the disclosed dose adjustment mechanism 40 includes an actuator 42 positioned away from the radiation axis along which the radiation therapy device 10 irradiates radiation, and a flattening filter 33 which is an interference element that moves perpendicular to the radiation axis by the operation of the actuator 42 and can switch between a state where it is positioned on the axis of the radiation axis and a state where it is not positioned on the axis of the radiation axis, and is characterized in that the operating axis of the actuator 42 does not intersect with the radiation axis. As an example, the device may further include a frame member 41 fixed relative to the radiation axis, the actuator 42 may be mounted in a position where it is stationary relative to the frame member 41, and the operating axis may be configured to pass outside the irradiation range of the radiation. Therefore, the influence of radiation on the dose adjusting mechanism 40 of the radiotherapy apparatus 10 can be reduced, and the occurrence of failures can be suppressed. Specifically, the actuator can be installed away from the beam axis, reducing the probability of failure due to radiation. Furthermore, the actuator can be installed outside the frame of the irradiation head, making it easier to replace and improve maintainability. Furthermore, because the size of the mechanism in the filter movement direction can be reduced, the device can be mounted in a limited space without increasing its external size, preventing a reduction in the device's range of motion and preventing an expansion of the area required for device installation.

[0033] As an example, the operating axis of the actuator 42 and the moving direction of the interference element are parallel to each other, and the interference element is held via a support member extending from the operating axis.

[0034] As an example, the direction of movement of the actuator 42 and the direction of movement of the interference element are converted via a link member 42b that connects the operation axis of the actuator 42a and the movement axis of the interference element.

[0035] The interference element is a filter that smooths the intensity distribution of the radiation. The interference element may also be an optical element, for example a mirror that aligns the light to the radiation axis to illuminate the radiation field.

[0036] The dose adjustment mechanism 40 further includes a movable member 43 that carries the interference element and moves by the operation of the actuator, and a frame member 41 that is fixed to the radiation axis, and when the movable member 43 abuts a predetermined surface of the frame member 41, the interference element is positioned on the axis of the radiation axis (FF). Furthermore, the dose adjusting mechanism 40 is in a state (FFF) in which the interference element is not positioned on the radiation axis with the moving member 43 in contact with the surface opposite to the predetermined surface. In this way, the dose adjusting mechanism 40 can easily switch between FF and FFF.

[0037] The dose adjusting mechanism 40 also includes a sensor 45 in the vicinity of the predetermined plane, and determines the consistency between the output of the sensor 45 and the control state of the actuator 42 . Furthermore, when the control state of the actuator 42 of the dose adjusting mechanism 40 is the reference position, the interference element is placed on the radiation axis. This improves safety in the event of an abnormality.

[0038] Moreover, the dose adjusting mechanism 40 further includes a nozzle 47 that injects air onto the predetermined surface. Therefore, foreign matter adhering to the predetermined surface can be removed, and a decrease in the accuracy of positioning of the interference element can be avoided.

[0039] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, not only can the configurations be deleted, but also replacements and additions of configurations are possible. For example, an element other than the flattening filter 33 may be used, and another element may be placed in the hole . [Explanation of symbols]

[0040] 10: Radiation therapy device, 11: Couch, 20: Gantry, 30: Radiation irradiation device, 32: Target, 33: Flattening filter, 34: Hole, 40: Dose adjustment mechanism, 41: Frame member, 42: Actuator, 43: Moving member, 44: Linear guide, 45: Sensor, 46: Stop surface, 51: Controller, 52: Encoder

Claims

1. an actuator disposed apart from a radiation axis along which the radiation therapy device irradiates radiation; an interference element that can be switched between a state in which it is disposed on the radiation axis and a state in which it is not disposed on the radiation axis by operation of the actuator; a moving member that carries the interference element and moves by the operation of the actuator; a frame member fixed to the radial axis, the interference element is disposed on the radial axis with the moving member in contact with a predetermined surface of the frame member, A dose adjusting mechanism, wherein the operating axis of the actuator does not intersect with the radiation axis.

2. 2. The dose adjustment mechanism according to claim 1, the actuator is mounted at a location that is stationary relative to the frame member; A dose adjustment mechanism characterized in that the operating axis passes outside the irradiation range of the radiation.

3. 2. The dose adjustment mechanism according to claim 1, A dose adjusting mechanism, characterized in that the operating axis of the actuator and the moving direction of the interference element are parallel, and the interference element is held via a support member extending from the operating axis.

4. 2. The dose adjustment mechanism according to claim 1, A dose adjustment mechanism characterized by converting the direction of movement of the actuator and the direction of movement of the interference element via a link member connecting the operating axis of the actuator and the moving axis of the interference element.

5. 2. The dose adjustment mechanism according to claim 1, The dose adjusting mechanism is characterized in that the interference element is a filter that smoothes the intensity distribution of the radiation.

6. 2. The dose adjustment mechanism according to claim 1, The dose adjusting mechanism is characterized in that the interference element is an optical element.

7. 2. The dose adjustment mechanism according to claim 1, A dose adjusting mechanism characterized in that, when the movable member abuts against a surface opposite to the predetermined surface, the interference element is not positioned on the axis of the radiation axis.

8. 2. The dose adjustment mechanism according to claim 1, a sensor provided in the vicinity of the predetermined surface; A dose adjusting mechanism that determines consistency between the output of the sensor and the control state of the actuator.

9. 2. The dose adjustment mechanism according to claim 1, A dose adjusting mechanism characterized in that, when the control state of the actuator is a reference position, the interference element is positioned on the radiation axis.

10. 2. The dose adjustment mechanism according to claim 1, A dose adjusting mechanism further comprising a nozzle for injecting air onto the predetermined surface.

11. a radiation irradiator; a gantry that rotates the radiation irradiator around an isocenter; a patient support that supports a patient so that a treatment target site is positioned at the isocenter; and a dose adjustment mechanism that adjusts the dose of radiation irradiated by the radiation irradiator; The dose adjustment mechanism includes: an actuator disposed apart from a radiation axis along which the radiation therapy device irradiates radiation; an interference element that can be switched between a state in which it is disposed on the radiation axis and a state in which it is not disposed on the radiation axis by operation of the actuator; a moving member that carries the interference element and moves by the operation of the actuator; a frame member fixed to the radial axis, the interference element is disposed on the radial axis with the moving member in contact with a predetermined surface of the frame member, A radiation therapy device, characterized in that the operating axis of the actuator does not intersect with the radiation axis.

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