JP7417263B2 - Radiation detection device - Google Patents

Description

The present invention relates to a radiation detection device.

Patent Document 1 discloses an invention aimed at measuring the dose distribution of a radiation beam with high precision. The present invention includes a holder that holds a plurality of parallel plate ionization chambers in a stacked manner. The holder is characterized in that it has a spacer that forms a space between each of the parallel plate ionization chambers. By doing so, Patent Document 1 claims that the three-dimensional distribution of X-ray irradiation intensity can be accurately grasped based on the ionization chambers arranged in a stacked manner (paragraph 0008).

Japanese Patent Application Publication No. 2012-042415

In dose distribution measurement, it is desirable to measure a three-dimensional dose distribution in a homogeneous phantom (homogeneous medium). However, when parallel plate ionization chambers are stacked underwater, the radiation is greatly disturbed by the detector, making it difficult to measure accurate dose distribution. Also, where the detector is placed can limit the size of the detector, limiting spatial resolution.
As a dose distribution measuring device that can solve the above problems, a small ionization chamber dosimeter and a plurality of smaller semiconductor detectors are arranged on a two-dimensional plane (two-dimensional dose distribution measuring device) for dose distribution measurement. The vessel is known. The three-dimensional dose distribution can be measured using this dose distribution measuring device by operating the two-dimensional dose distribution measuring device underwater during radiation beam irradiation. However, such measurements take time, so it is difficult to measure the three-dimensional dose distribution of high-precision radiotherapy such as intensity modulated radiation therapy (IMRT), which changes the radiation beam intensity and irradiation field over time. is difficult.
An object of the present invention is to provide a radiation detection device that solves the above-mentioned problems.

The radiation detection device according to the present invention includes a main body made of a light emitting body that exhibits a light emission distribution according to the intensity distribution of irradiated X-rays; a shielding part that shields external light that is exposed to the outside light, and a plurality of X-ray detection parts arranged inside the shielding part at different positions in the central axis direction of the main body part and in different positions in the circumferential direction. .
Furthermore, the X-ray detection section of the radiation detection device is a light emitter that emits light in response to irradiation with X-rays.
The radiation detection device further includes a guide fiber that guides the light emitted from the X-ray detection section to an end face in the central axis A direction.
Further, in the X-ray detection section of the radiation detection device, an arrangement pattern defined in a predetermined range in the circumferential direction is repeatedly applied along the circumferential direction.

According to at least one of the above aspects, the radiation dose distribution can be understood three-dimensionally, including in the depth direction, with high accuracy.

1 is a diagram showing the overall configuration of a dose distribution measurement system according to an embodiment. FIG. 2 is a diagram showing the configuration of a phantom according to an embodiment. FIG. 2 is a diagram showing the configuration of a phantom according to an embodiment. It is a flow chart showing operation of a dose distribution measurement system concerning one embodiment.

《Overall configuration of dose distribution measurement system》
Hereinafter, the overall configuration of the dose distribution measurement system 1 will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing the overall configuration of a dose distribution measurement system 1. As shown in FIG.
The dose distribution measurement system 1 measures the dose distribution of radiation irradiated by the radiation therapy apparatus X. Examples of radiation emitted by a radiation therapy device include X-rays and gamma rays. Moreover, the radiation therapy apparatus X is used for high-precision radiation therapy. Examples of high precision radiotherapy include intensity modulated radiotherapy and volumetric modulated arc therapy (VMAT).

As shown in FIG. 1, the dose distribution measurement system 1 is installed on a couch X1 of a radiation therapy apparatus X.
The dose distribution measurement system 1 includes a CCD (Charge Coupled Device) camera 2, a phantom 3, and a control device (not shown). The phantom 3 is an example of a radiation detection device.

The CCD camera 2 includes a CCD image sensor (not shown) as an imaging device. CCD image sensors convert light into electrical signals. The CCD camera 2 is arranged so that the optical axis of the camera coincides with the central axis A of the phantom 3.
The phantom 3 is placed in the radiation therapy apparatus X at a position surrounded by the gantry X2.

The gantry X2 of the radiation therapy apparatus X is a mechanism that irradiates X-rays toward the inside thereof. By rotating the gantry X2, the direction of X-ray irradiation is changed. Here, the central axis A of the phantom 3 is arranged to coincide with the axis of rotation of the X-rays by the gantry X2. Furthermore, the X gantry X2 is movable in translation relative to the couch X1. Thereby, the radiation therapy apparatus X can further perform translational movement in the depth direction (direction of the central axis A) while rotating the X-ray irradiation direction around the central axis A. Such operations for X-ray irradiation (rotation and translation of the irradiation direction) are defined in advance based on a treatment plan (X-ray irradiation range) determined for each patient. The treatment plan is recorded in advance in a storage unit (not shown) of the control device.

《Phantom configuration》
2 and 3 are diagrams showing the configuration of the phantom 3.
The phantom 3 detects the X-rays irradiated by the radiotherapy device X and emits light.
As shown in FIGS. 2 and 3, the phantom 3 includes a main body portion 30, a shielding portion 31, an X-ray detection portion 32, and a guide fiber 33.

The main body portion 30 is formed in a cylindrical shape and is composed of a scintillator. Note that the main body portion 30 is not limited to a cylindrical shape. A scintillator is an example of a light emitter. The luminescent material constituting the scintillator absorbs energy upon collision with incident particles related to X-rays and emits light. Therefore, the scintillator can exhibit a luminescence distribution depending on the intensity distribution of the X-rays irradiated by the gantry X2. Examples of scintillators include plastic scintillators. Plastic scintillators are composed of low atomic number elements such as carbon, hydrogen, and oxygen. Therefore, plastic scintillators have higher accuracy in detecting radiation than materials containing high atomic number elements.

The shielding part 31 is formed to surround the main body part 30 with a constant thickness throughout the circumferential direction, and blocks external light entering the main body part 30. Note that the shielding part 31 is not limited to a certain thickness. An example of the shielding part 31 is a ring-shaped structure made of black acrylic. By making the shielding part 31 black, the external light shielding performance of the shielding part 31 can be improved. Since the shielding part 31 shields external light entering the main body part 30, the light emitted inside the shielding part 31 is light emitted by the scintillator after absorbing the irradiated X-rays.

As shown in FIGS. 2 and 3, the X-ray detection sections 32 are arranged inside the shielding section 31 at different positions in the direction of the central axis A of the main body section 30 and in different positions in the circumferential direction. Further, the X-ray detection section 32 is a scintillator that emits light in response to X-ray irradiation. Examples of scintillators include small plastic scintillators. Further, as shown in FIGS. 2 and 3, in the X-ray detection section 32, an arrangement pattern defined in a predetermined range in the circumferential direction is repeatedly applied along the circumferential direction. The arrangement patterns shown in FIGS. 2 and 3 are examples, and the arrangement patterns are not limited thereto. Note that the dimensions and angles of the phantom 3 shown in FIG. 3 are merely examples, and the dimensions and angles of the phantom 3 are not limited thereto.

The guide fiber 33 is connected to the X-ray detection section 32 and guides the light emitted from the X-ray detection section 32 to an end surface (light-emitting surface 33a) in the central axis A direction. An example of the guide fiber 33 is a cylindrical rod made of acrylic. Since the positions of the X-ray detection sections 32 in the direction of the central axis A differ, the length D of the guide fiber 33 differs for each X-ray detection section 32 to be connected. The guide fiber 33 guides the light emitted by the X-ray detection section 32 inside the shielding section 31 to the end surface of the shielding section 31 . Thereby, the dose distribution measurement system 1 can detect the light emitted by the X-ray detection section 32 inside the shielding section 31 outside the shielding section 31. Note that the light guided by the guide fiber 33 is light emitted by the X-ray detection sections 32 located at different positions in the central axis A direction. Therefore, the dose distribution measurement system 1 can detect not only the light related to the two-dimensional end face where the CCD camera 2 and the phantom 3 face each other, but also the light emitted from the back side of the end face. That is, the dose distribution measurement system 1 determines which X-ray detection section 32 is emitting light among the X-ray detection sections 32 having different positions in the direction of the central axis A, thereby determining the three dimensions including the depth direction. Dimensional light distribution can be detected. Moreover, by imaging the three-dimensional light distribution with the CCD camera 2, the dose distribution measurement system 1 can measure the three-dimensional dose distribution.

《Configuration of control device》
The control device sends a signal to the CCD camera 2 and controls the CCD camera 2 to image the end surface of the phantom 3 (the end surface of the phantom 3 facing the CCD camera). Thereby, the CCD camera 2 captures an image showing the three-dimensional dose distribution.

The control device controls the position of the gantry X2 on the central axis A (hereinafter referred to as the front-back position) based on the treatment plan stored in the storage unit. The control device also controls a position (hereinafter referred to as an irradiation position) at which the gantry X2 irradiates X-rays in the circumferential direction of the phantom 3 based on the treatment plan stored in the storage unit.

The control device captures an image showing the three-dimensional dose distribution captured by the CCD camera 2, the time at which the image was captured (hereinafter referred to as "imaging time"), the position before and after the imaging time, and the irradiation position at the imaging time. and are recorded in a storage unit (not shown) as measurement information. In this way, since the control device records the three-dimensional dose distribution and the imaging time in association with each other, it is possible to measure the four-dimensional dose distribution including the time dimension. Due to the recording by the control device, the storage unit stores measurement information related to a plurality of four-dimensional dose distributions.

The control device outputs the treatment plan and corresponding measurement information to a display device (not shown). The display on the display device allows the user of the dose distribution measurement system 1 to grasp the four-dimensional dose distribution measured in real time. Note that the user of the dose distribution measurement system 1 can understand the accuracy of the X-ray emission of the radiation therapy apparatus X based on the treatment plan by comparing the displayed image related to the treatment plan and the image related to the measurement information. I can do it. In addition, when the accuracy of radiation is low, the user of the dose distribution measurement system 1 can identify the irradiation position and the front and rear positions associated with the measurement information related to low accuracy by comparing the treatment plan and the measurement information. . Thereby, the user of the dose distribution measurement system 1 can specify the operation of the gantry X2 related to low radiation accuracy.

《Operation of dose distribution measurement system》
The operation of the dose distribution measurement system 1 will be explained below.
FIG. 4 is a flowchart showing the operation of the dose distribution measurement system 1.

The control device operates the radiation therapy device X based on a treatment plan recorded in advance (step S1). Specifically, the control device operates the gantry X2 to change the irradiation position and front-rear position of the gantry X2 based on the treatment plan.

The control device causes the phantom 3 to be irradiated with X-rays from the gantry X2 (step S2).
The main body section 30 and the X-ray detection section 32 absorb the X-rays irradiated in step S2 and emit light (step S3).
The guide fiber 33 guides the light emitted in step S3 to the end face where the phantom 3 and the CCD camera 2 face each other (step S4).

The CCD camera 2 images the end face where the phantom 3 and the CCD camera 2 face each other (step S5). Thereby, the CCD camera 2 can capture an image related to the three-dimensional dose distribution by converting light into an electrical signal. The above-mentioned light is the light emitted by the main body section 30 in step S3.
The control device associates the image showing the three-dimensional dose distribution taken in step S5, the imaging time, the position before and after the imaging time, and the irradiation position at the imaging time and records it in the storage unit as measurement information (step S6 ). Thereby, the control device can measure the four-dimensional dose distribution including the imaging time.

The control device outputs the measurement information measured in step S6 to the display device together with the corresponding treatment plan (step S7). Thereby, the user of the dose distribution measurement system 1 can understand the four-dimensional dose distribution in real time.

Note that the operations from step S1 to step S7 described above are repeatedly performed based on the treatment plan.

《Action/Effect》
The radiation detection device according to the present invention includes a main body 30 made of a light emitter that exhibits a luminescence distribution according to the intensity distribution of irradiated X-rays, and a main body 30 that is formed to surround the entire circumference of the main body 30. A shielding part 31 that shields external light incident on the main body part 30, and a plurality of A line detection section 32 is provided.

The X-ray detection sections 32, which are arranged at different positions in the direction of the central axis A and in the circumferential direction of the main body section 30, detect the intensity distribution of X-rays. Thereby, the radiation detection device can grasp the radiation dose distribution three-dimensionally, including in the depth direction, with high precision.

Further, the X-ray detection unit 32 of the radiation detection device is a light emitting body that emits light in response to irradiation with X-rays.
The luminous body emits light due to the emitted X-rays. The radiation detection device can accurately grasp the radiation dose distribution three-dimensionally, including in the depth direction, based on the emitted light.

The radiation detection device further includes a guide fiber 33 that guides the light emitted from the X-ray detection section 32 to an end face in the central axis A direction.
The guide fiber 33 guides the light emitted from the X-ray detection section 32 to an end face. Thereby, the radiation detection device can grasp the radiation dose distribution three-dimensionally, including in the depth direction, with high precision based on the light guided to the end face.

Further, in the X-ray detection section 32 of the radiation detection device, an arrangement pattern defined in a predetermined range in the circumferential direction is repeatedly applied along the circumferential direction.
The radiation detection device can grasp the radiation dose distribution three-dimensionally, including in the depth direction, with high precision based on the light emitted by the X-ray detection unit 32 according to the repeatedly applied arrangement. can.

<Other embodiments>
Although one embodiment has been described above in detail with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Also, some of the processes may be executed in parallel.
The control device according to the above-described embodiment may be configured by a single computer, or the configuration of the control device may be divided into multiple computers and controlled by the multiple computers cooperating with each other. It may also function as a device. At this time, some computers constituting the control device may be installed inside the working machine, and other computers may be provided outside the working machine.

The X-ray detection unit 32 according to the embodiment described above is not limited to this. For example, the X-ray detection section 32 according to another embodiment may emit light of a different color for each length D of the guide fiber 33 connected to the X-ray detection section 32. In this case, the dose distribution measurement system 1 can measure the X-ray dose distribution in the depth direction based on the color of the light emitted by the X-ray detection unit 32.

The X-ray detection unit 32 and guide fiber 33 according to the embodiment described above are not limited to this. For example, the X-ray detection unit 32 and the guide fiber 33 according to other embodiments may be arranged in a plurality of rows in the direction toward the center of the phantom 3. For example, the dose distribution measurement system 1 may configure the X-ray detection section 32 and the guide fiber 33 in two rows toward the center of the phantom 3. The dose distribution measurement system 1 has two rows of X-ray detection units 32 lined up in the direction of the center of the phantom 3 at different positions in the direction of the central axis A, thereby detecting X-rays emitted from the gantry X2 with higher accuracy. can be detected.

1 Dose distribution measurement system 2 CCD camera 3 Phantom 30 Main body 31 Shielding section 32 X-ray detection section 33 Guide fiber 33a Light emitting surface X Radiation detection device X1 Couch X2 Gantry A Central axis

Claims (4)

a main body formed in a cylindrical shape and made of a light emitting body that exhibits a light emission distribution according to the intensity distribution of X-rays incident through the side surface from a predetermined irradiation direction in the circumferential direction;
a shielding portion that is a ring-shaped member that is in contact with the entire side surface of the cylindrical main body portion and has a predetermined thickness in the radial direction;
A plurality of X-ray detection units arranged inside the shielding unit at different positions in the central axis direction and in the circumferential direction of the main body formed in a cylindrical shape;
Equipped with
The X-ray detection section is entirely embedded and disposed inside the thick wall of the shielding section, which is a ring-shaped structure.
Radiation detection device. The X-ray detection unit is a light emitter that emits light in response to irradiation with the X-rays.
The radiation detection device according to claim 1. further comprising a guide fiber that guides the light emitted from the X-ray detection unit to the end face in the central axis direction;
The radiation detection device according to claim 2. In the X-ray detection unit, an arrangement pattern defined in a predetermined range in the circumferential direction is repeatedly applied along the circumferential direction.
The radiation detection device according to any one of claims 1 to 3.

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