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 to 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. Since it is difficult to create a treatment plan with a mountain-like shape, a flattening filter (FF) is used to make the dose distribution flat. 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 needs to be highly repeatable.

[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 which irradiation is performed at a higher dose rate in a flattening filter-free (FFF) state, which does not use a flattening filter.

[0005] Some existing radiotherapy devices are equipped with a function to automatically switch between the presence and absence of a flattening filter within the same device (see, for example, Patent Document 1). The irradiation head has a limited space because it is equipped with a multi-leaf collimator, a dosimeter, etc. in addition to the flattening filter. On the other hand, the irradiation head should not be made too large because it may easily cause interference between 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 conventional technology, there is a concern that they may be damaged by 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-mentioned object, one representative dose adjustment mechanism of the present invention is characterized in that it 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 be switched 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 the operating axis of the actuator does not intersect with the radiation axis. Furthermore, a representative radiation therapy apparatus of the present invention includes a radiation irradiation device, a gantry which rotates the radiation irradiation device around an isocenter, a patient support which supports a patient so that a part to be treated is positioned at the isocenter, and a dose adjustment mechanism which adjusts the dose of radiation irradiated by the radiation irradiation device, wherein the dose adjustment mechanism includes an actuator arranged away from a radiation axis along which the radiation therapy device irradiates radiation, and an interference element which 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 motion axis of the actuator does not intersect with the radiation axis. Effect 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 failures. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010] [Figure 1] Diagram of a radiation therapy device [Diagram 2] Illustration of radiation exposure (FF) [Diagram 3] Illustration of radiation exposure (FFF) [Figure 4] Explanatory diagram of dose adjustment mechanism [Diagram 5] Diagram of the dose adjustment mechanism seen from the electron gun direction [Figure 6] Modification of the dose adjustment mechanism [Figure 7] Illustration of the control of the dose adjustment mechanism DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described with reference to the drawings. EXAMPLES

[0012] FIG. 1 is an explanatory diagram of a radiotherapy device. As shown in Fig. 1, a radiation therapy device 10 includes a couch 11 which is a patient support, a gantry 20 equipped with a rotation mechanism, and a radiation irradiation device 30. The gantry 20 supports the radiation irradiation device 30 and rotates the radiation irradiation device 30 around an isocenter. The couch 11 positions a part of the patient to be treated at the isocenter. The radiation irradiation device 30 includes a swing mechanism and 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 disposed so that its central axis faces a substantially horizontal direction. The rotating ring has an 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 oscillating mechanism has a gimbal structure on which the radiation irradiation device 30 is mounted, and can tilt the radiation irradiation device 30 about 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, and irradiates the electron beam 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 uniforms 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 where the flattening filter 33 is applied is called the FF state.

[0016] As shown in Fig. 3, in a flattening filter free (FFF) state in which the flattening filter 33 is not used, the dose rate is highest on the beam axis and decreases depending on the distance from the beam axis. Irradiation in this type of FFF 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 with respect to the radiation axis (beam axis). The actuator 42 is disposed on the outside of the frame member 41 . The movable member 43 is a flattening filter installation section on which the flattening filter 33 is mounted. The movable member 43 also has a hole 34 that transmits the radiation as it is.

[0018] The moving member 43 slides along the linear motion guide 44. That is, the linear motion guide 44 corresponds to the movement axis of the moving member 43. The linear motion guide 44 realizes highly accurate linear movement of the moving member 43.

[0019] In addition, 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. By this movement, the dose adjustment mechanism 40 switches 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. Also, the motion axis of the actuator 42 is disposed so as not to intersect with the radiation axis. Specifically, the motion axis of the actuator 42 and the movement direction of the moving member 43 (movement direction of the flattening filter 33) are parallel, and the support member extends from the motion axis of the actuator 42 to hold the moving member 43.

[0021] If a moving member is provided on the motion 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 farther the center of gravity moves from the radiation axis, the lower the accuracy of position control of radiation irradiation may be. In addition, if the distance from the radiation axis to the actuator 42 is large, the possibility of interference with the gimbal mechanism increases. 4, the actuator 42 can be positioned closer to the radiation axis by arranging the motion axis of the actuator 42 and the movement axis of the flattening filter 33 in parallel, which contributes to improving the accuracy of radiation irradiation and also suppresses interference with the gimbal mechanism.

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

[0023] The abutment stop surface 46 (46a and 46b) has a spherical surface and contacts the moving member 43 at the spherical surface. As an example, the abutment stop surface 46 may have a spherical notch shape cut out from a sphere. By making the abutment stop surface 46 spherical, the probability of a foreign object being caught can be reduced.

[0024] 5, the dose adjustment mechanism 40 has opposing abutment surfaces 46, and the actuator 42 presses the moving member 43 against one of the abutment surfaces 46 to switch between two states. This eliminates the need to adjust the position of the moving member 43, and the state 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] Further, the dose adjustment mechanism 40 has a sensor 45 in the vicinity of the stop surface 46. Specifically, the sensor 45a is located in the vicinity of the stop surface 46a, and the sensor 45b is located in the vicinity of the stop surface 46b. The sensor 45 outputs 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 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 abutment stop surface 46 in order to remove foreign matter adhering to the abutment stop surface 46. The nozzle 47 may be provided on both the abutment stop surface 46a and the abutment stop surface 46b, but in the configuration of Fig. 5, the nozzle 47 is selectively provided on the abutment stop surface 46a. This is because the state in which the moving member 43 abuts against the abutment stop surface 46a is an FF state, which requires highly accurate positioning, whereas the state in which the moving member 43 abuts against the abutment stop surface 46b is an 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 performs direction conversion between the operating direction of the actuator 42 and the moving direction of the moving member 43 (moving direction of the flattening filter 33). The actuator 42a positions the flattening filter 33 by continuously pressing the moving member 43, so that accuracy can be ensured even if there is wobble in a configuration using multiple parts. In this way, the configuration using a link member improves the degree of freedom in arranging the actuator 42.

[0029] 7 is an explanatory diagram of the control of the dose adjustment mechanism 40. The two sensors 45a are disposed near the stop surface 46a and are touch switches that detect the FF mode. The two sensors 45b are disposed 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, the two sensors 45a detect contact with each other, and the controller 51 detects that the FF mode is active. The current position of the movable member 43 is roughly 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, a target position is transmitted from the controller 51 to the actuator 42, and the movable member 43 moves. (2) When the value of the encoder 52 enters a certain range, a pressing operation starts. The pressing operation is an operation in which the actuator continues to try to move toward the target position with a set force. (3) When the movable member 43 comes into contact with the abutment 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" in its processing. (5) Radiation irradiation is permitted based on both mode detection and the "pressing completion flag."

[0032] As described above, the disclosed dose adjustment mechanism 40 includes an actuator 42 arranged 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 be switched between a state in which it is positioned on the axis of the radiation axis and a state in which 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 placed 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 replacement easier and improving maintainability. In addition, 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 the size of the device exterior, preventing a reduction in the device's movable range and preventing an expansion of the area required for installing the device.

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

[0034] As an example, a direction change between the operating direction of the actuator 42 and the moving direction of the interference element is performed via a link member 42b that connects between the operating axis of the actuator 42a and the moving axis of the interference element.

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

[0036] The dose adjustment mechanism 40 further includes a movable member 43 carrying the interference element and moving by the operation of the actuator, and a frame member 41 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, in the dose adjusting mechanism 40, with the movable member 43 in contact with the surface facing the predetermined surface, the interference element is not positioned on the radiation axis (FFF). In this manner, the dose adjusting mechanism 40 can easily switch between FF and FFF.

[0037] Moreover, the dose adjustment mechanism 40 includes a sensor 45 in the vicinity of the predetermined surface, and determines the consistency between the output of the sensor 45 and the control state of the actuator 42 . Moreover, when the controlled state of the actuator 42 of the dose adjustment mechanism 40 is the reference position, the interference element is placed on the radiation axis. This can improve safety when an abnormality occurs.

[0038] Moreover, the dose adjustment 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-mentioned embodiment, and various modifications are included. For example, the above-mentioned embodiment is described in detail to easily explain the present invention, and is not necessarily limited to the embodiment having all the described configurations. Moreover, the present invention is not limited to the deletion of the configurations, and it is also possible to replace or add the configurations. 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: abutment 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 axis of the radiation axis and a state in which it is not disposed on the axis of the radiation axis by an operation of the actuator; a moving member having the interference element mounted thereon and moving by the operation of the actuator; a frame member fixed to the radial axis, the interference element is disposed on the axis of the radiation axis with the movable member in contact with a predetermined surface of the frame member, A dose adjusting mechanism, characterized in that the motion 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 an operating axis of the actuator and a 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.

4. 2. The dose adjustment mechanism according to claim 1, A dose adjustment mechanism characterized by converting the direction between the operating direction of the actuator and the moving direction of the interference element via a link member connecting between 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 is in contact with a surface opposing the specified 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 is provided in the vicinity of the predetermined surface, A dose adjusting mechanism that determines the 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, The dose adjustment mechanism further comprises a nozzle for injecting air onto the specified 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 a 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 axis of the radiation axis and a state in which it is not disposed on the axis of the radiation axis by an operation of the actuator; a moving member having the interference element mounted thereon and moving by the operation of the actuator; a frame member fixed to the radial axis, the interference element is disposed on the axis of the radiation axis with the movable member in contact with a predetermined surface of the frame member, A radiation therapy device, characterized in that the motion axis of the actuator does not intersect with the radiation axis.

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