Phantoms for radiotherapy equipment

Abstract

To provide a phantom which can be used for quality management for grasping a radiation dose and distribution of a radiation, and can quickly and easily attach a radiation imaging film to a prescribed position.SOLUTION: A phantom 10 comprises: a pair of outer blocks 20 which faces each other in a fastening direction V; and an inner block 30 which is held by the pair of outer blocks 20, and which is formed by joining, a plurality of inner block pieces 30A-D so as to be separated each other freely. Each inner block piece has a mating surface 34 which holds a radiation imaging film 7 on a surface jointed to the inner block piece which is adjacent to the inner block piece in parallel to the fastening direction V and can fix the radiation imaging film, and a slant face 33 to which the outer block 20 contacts in fixing, and which is inclined in a direction where, pressing force in the contact time is dispersed and acts to the mating surface 34 side.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a phantom for a radiotherapy device, and more particularly to a phantom for a radiotherapy device that is used as an index for quality control of the radiotherapy device and can have a radiographic imaging film fixed thereto. [Background technology]

[0002] In recent years, radiotherapy devices have been used in the medical field to irradiate affected areas with radiation for treatment. Examples of radiotherapy devices include "LINAC" (linear accelerator), which irradiates tumor areas with pinpoint radiation such as X-rays or electron beams in cancer treatment, and "CT device" (computed tomography device), which can obtain cross-sectional images of the human body by irradiating X-rays. In this specification, "treatment device" includes not only devices for directly treating affected areas such as LINAC, but also devices for imaging diagnosis such as CT devices.

[0003] At sites where such radiation therapy equipment is used, quality control is carried out daily using phantoms (see, for example, Patent Document 1 and Non-Patent Document 1) that act as targets that can be read by radiation, so that radiation that is invisible to the naked eye can be reliably irradiated to the desired area.

[0004] The phantom described in Patent Document 1 is made of a light-transmitting material and has a main body supporting an X-ray non-transmissive material inside, and the main body has an incident surface having a light-entering part into which a light beam is incident, and a light-receiving surface formed at a position opposite to the incident surface and visibly receiving the light beam incident from the light-entering part. By using a phantom such as that described in Patent Document 1, it is possible to grasp the positional deviation between the light beam of a laser marker or the like visible on the light-receiving surface and the image using radiation of the X-ray non-transmissive material supported inside the main body, and to grasp and calibrate the isocenter of the radiation therapy device. However, the phantom described in Patent Document 1 is not suitable for quality control aimed at grasping the radiation dose and distribution of radiation.

[0005] Therefore, the 3D dose measurement phantom described in Non-Patent Document 1 is configured to include a cube-shaped block that can be divided into a plurality of block pieces, and a radiographic imaging film can be sandwiched and fixed between the block pieces. Each block piece is fixed to each other by a fastener. In addition, an embossment is formed in the block piece, and a hole is formed in the radiographic imaging film, and the positional relationship between the measurement phantom and the radiographic imaging film is determined by fitting the embossment and the hole. According to the 3D dose measurement phantom described in Non-Patent Document 1, the radiation distribution and the irradiation position can be analyzed by determining the position of the measurement phantom so that the center of the measurement phantom is the center of radiation irradiation (using a patient position confirmation device or the like). The 3D dose measurement phantom described in Non-Patent Document 1 is suitable for quality control aimed at grasping the radiation dose and radiation distribution, since the radiographic imaging film is exposed according to the radiation dose. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-042206 A [Non-Patent Document 1] Fujidenolo Co., Ltd. published "Phantom for Radiation QA" document https: / / www.fujidenolo.co.jp / images / business / health / pdf / IMT.pdf Summary of the Invention [Problem to be solved by the invention]

[0007] In a phantom used for quality control to grasp the radiation dose and distribution of radiation as described in Non-Patent Document 1, the radiographic imaging film is frequently attached and detached, and it is therefore desired that the radiographic imaging film can be attached to a predetermined position easily and quickly.

[0008] Therefore, an object of the present invention is to provide a phantom which can be used for quality control for the purpose of grasping the radiation dose and radiation distribution, and to which a radiation imaging film can be easily and quickly attached at a predetermined position. [Means for solving the problem]

[0009] [1] The phantom for a radiation therapy device of the present invention is a phantom that has an index for quality control of a radiation therapy device and is for replaceably fixing a radiation imaging film, and is characterized in that it comprises a pair of outer blocks facing each other in a fastening direction, and an inner block that is sandwiched between the pair of outer blocks and is composed of a plurality of inner block pieces that can be separably joined together, and each of the inner block pieces of the plurality of inner block pieces has a mating surface that is parallel to the fastening direction and meets with an adjacent inner block piece, and is capable of sandwiching and fixing the radiation imaging film, and a slope that is inclined in the direction in which at least one of the outer blocks comes into contact when fixed to the pair of outer blocks, and distributes the force applied at the time of contact toward the mating surface.

[0010] The phantom for a radiotherapy device of the present invention is designed to be a phantom for fixing a radiographic imaging film in a replaceable manner, and can be used for quality control to grasp the radiation dose and radiation distribution.

[0011] The phantom for a radiotherapy device of the present invention includes a pair of outer blocks facing each other in a fastening direction, and an inner block sandwiched between the pair of outer blocks and configured by joining multiple inner block pieces separably together, and has a mating surface where each of the multiple inner block pieces joins with an adjacent inner block piece, which is a surface where a radiographic imaging film can be sandwiched and fixed. As a result, the phantom for a radiotherapy device of the present invention can be easily fixed by sandwiching the radiographic imaging film between the inner block pieces and sandwiching the inner block piece together with the outer block. Moreover, the phantom for a radiotherapy device of the present invention has a slope that is inclined in a direction in which at least one of the outer blocks comes into contact with each other when each inner block piece is fixed to the pair of outer blocks, and the force applied at the time of the contact is distributed and acts on the mating surface side. As a result, in the phantom for a radiotherapy device of the present invention, when the inner block is sandwiched between the outer blocks, a force is applied to each inner block piece to move it toward the mating surface side. That is, in the phantom for a radiotherapy device of the present invention, when the inner block is sandwiched between the outer blocks, the pieces of the inner blocks are tightly attached to each other without the need to be particularly careful to bring them together or press them down, and the radiographic imaging film can be securely sandwiched in. As a result, the phantom for a radiotherapy device of the present invention makes it possible to easily and quickly attach the radiographic imaging film to a predetermined position.

[0012] As a result, the phantom for a radiotherapy device of the present invention can be used for quality control for the purpose of grasping the radiation dose and radiation distribution, and is a phantom to which a radiographic imaging film can be easily and quickly attached at a predetermined position.

[0013] [2] In the phantom for a radiotherapy apparatus of the present invention, it is preferable that the inclined surface include a plurality of inclined surfaces corresponding to each of the pair of outer blocks.

[0014] With this configuration, all of the inner block pieces are brought together toward the center of the inner block, so that a stable inner block shape can be formed without the need for any special effort to bring them together or press them down.

[0015] [3] In the phantom for a radiation therapy device of the present invention, the inner block may be constructed by joining four separable inner block pieces together at a first mating surface and a second mating surface which are perpendicular to each other as the mating surfaces.

[0016] With this configuration, it is possible to grasp the radiation dose and radiation distribution three-dimensionally to some extent.

[0017] [4] In the phantom for a radiotherapy apparatus of the present invention, it is preferable that the outer block has a pressing inclined surface capable of surface-contacting the inclined surface as a part that comes into contact with the inner block.

[0018] With this configuration, the pressing force of the outer block is dispersed and the inner block is clamped and fixed, thereby further reducing the risk of distortion.

[0019] [5] In the phantom for a radiotherapy device of the present invention, it is preferable that the phantom further comprises a thin film guard having a planar shape corresponding to the mating surface of the inner block, and which is placed between the mating surface and the radiographic imaging film when the radiographic imaging film is attached.

[0020] With this configuration, the force with which the mating surfaces directly shift the radiographic imaging film along the fastening direction is reduced, so that the radiographic imaging film can be fixed in a manner that prevents it from shifting.

[0021] [6] In the phantom for a radiotherapy apparatus of the present invention, it is preferable that the film guard has, as the indicator, a pattern made of a material having a different specific gravity from the surrounding area.

[0022] With this configuration, the pattern near the radiation imaging film can be confirmed in a real-time radiation image, etc., so that the radiation irradiating position can be easily grasped.

[0023] [7] In the phantom for a radiotherapy apparatus of the present invention, the pattern may be a curve along a circumference centered on the theoretical isocenter of the phantom.

[0024] With this configuration, the theoretical isocenter position can be determined from the curve, making it easier to determine deviations in the radiation irradiation position and irradiation direction. Effect of the Invention

[0025] According to the present invention, it is possible to provide a phantom which can be used for quality control for the purpose of grasping the radiation dose and radiation distribution, and to which a radiation imaging film can be easily and quickly attached at a predetermined position. [Brief description of the drawings]

[0026] [Figure 1] 1 is a perspective view of a radiation therapy apparatus according to an embodiment. [Diagram 2] FIG. 1 is a perspective view of a phantom for a radiotherapy apparatus according to an embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of the phantom shown in FIG. 2 along line AA. [Figure 4] FIG. 3 is a cross-sectional view of the phantom in FIG. 2 at B-B. [Diagram 5] FIG. 2 is a plan view of the film guard according to the embodiment. [Figure 6] 1 is a flowchart showing an assembly procedure of a phantom for a radiotherapy apparatus according to an embodiment. [Figure 7] 1A to 1C are diagrams for explaining forces applied when assembling the phantom for a radiotherapy apparatus according to an embodiment. [Figure 8] 13A and 13B are diagrams showing modified examples of the contact portion between the outer block and the inner block. [Figure 9] 13A and 13B are diagrams showing modified examples of the film guard. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, a phantom 10 for a radiotherapy device according to one embodiment of the present invention (hereinafter, simply referred to as "phantom 10") will be described with reference to the drawings, but the present invention is not limited to these embodiments. Note that each drawing does not necessarily strictly reflect the actual dimensions. Also, in some drawings, for convenience of explanation, the X direction, Y direction, and Z direction are indicated by arrows with the symbols X, Y, and Z. In this regard, based on the arrangement in the use state in quality control, a plane parallel to the installation surface is indicated as a horizontal plane, a plane perpendicular to the horizontal plane is indicated as a vertical plane, a direction perpendicular to the horizontal plane is indicated as a Z direction, a direction perpendicular to the Z direction and corresponding to the left and right direction of the patient is indicated as an X direction, and a direction perpendicular to the Z direction and the X direction (a direction connecting the top of the patient's head and the toes) is indicated as a Y direction.

[0028] [1-1. About the radiation therapy device 1 subject to quality control using the phantom 10] FIG. 1 is a perspective view of a radiotherapy apparatus 1 according to an embodiment. A phantom 10 according to the embodiment is used for quality control of the radiotherapy apparatus. As an example, the radiotherapy apparatus 1 subject to quality control by the phantom 10 is a medical LINAC system that treats cancer by irradiating an affected area with pinpoint radiation in a medical setting. The radiotherapy apparatus 1 includes a LINAC (linear accelerator) 2, an X-ray imaging device 3, a bed section 4, a line laser sight 5, and a control device (not shown).

[0029] The LINAC2 has a pedestal section 2a, a rotating arm section 2b, a head section 2c, and a detection section 2d. The pedestal section 2a is a pedestal and is grounded in a treatment room. The rotating arm section 2b is an arm supported by the pedestal section 2a so as to be rotatable 360 ​​degrees around a LINAC rotation axis L1 extending in the Y direction. The head section 2c is fixed to the tip of the rotating arm section 2b and is an irradiation head that generates radiation inside and irradiates the radiation from an irradiation port. The detection section 2d is disposed apart from the head section 2c and has a built-in detector that detects radiation irradiated from the irradiation port of the head section 2c. The LINAC2 can irradiate X-rays, X-rays with a high energy level (3MV to 20MV), and electron beams from the head section 2c toward the affected area. The LINAC2 can also irradiate X-rays and electron beams in a desired direction L2 by rotating the rotating arm section 2b and adjusting the energy level.

[0030] The X-ray imaging device 3 is also called an OBI (On Board Imager), and has a support arm 3a extending from a rotating arm section 2b of the LINAC 2, an X-ray irradiation section 3b supported at one end of the support arm 3a, and an X-ray detection section 3c supported at the other end of the support arm 3a. The X-ray imaging device 3 can change the imaging direction L3 by utilizing the rotation of the LINAC 2.

[0031] The bed section 4 is a bed having a platform on which a patient can lie along the LINAC rotation axis L1 direction (Y direction).

[0032] The line laser sight 5 is a device that irradiates a line laser, and is installed in the treatment room around the LINAC 2. The first to fourth line laser sights 5A to 5D are installed in the radiation therapy device 1 as the line laser sights 5. The first to fourth line laser sights 5A to 5D irradiate line lasers as markers that indicate reference lines in the X-, Y-, and Z-directions in the spatial coordinates of the LINAC 2. That is, by grasping the positional relationship between the intersections of the lines in the X-, Y-, and Z-directions indicated by the first to fourth line laser sights 5A to 5D and the isocenters of the LINAC 2 and the X-ray imaging device 3, it is possible to irradiate the affected area with X-rays or electron beams with high accuracy.

[0033] The control device (not shown) has a monitor and an input device, and controls the operation of each device in the radiotherapy device 1. The control device also functions as a display / analysis device for displaying captured images and performing analysis, etc.

[0034] In order to accurately irradiate the affected area with X-rays or electron beams using the thus configured radiotherapy device 1, in the medical field, a human body model 6 (human body model 6 including the affected area) is used, in which a radiation marker is embedded inside or a reference line of a line laser is formed, so that the positioning state can be grasped, and quality control is performed to grasp the radiation dose and radiation distribution three-dimensionally in advance. For this purpose, a phantom 10 is used, in which a radiation imaging film 7 exposed according to the irradiation intensity of radiation can be placed at a predetermined position inside the human body model 6.

[0035] [1-2. Phantom 10 Configuration] Fig. 2 is a perspective view of the phantom 10 of the embodiment. Fig. 3 is a cross-sectional view of the phantom 10 of Fig. 2 taken along line AA. In Fig. 3, some parts are shown separated. Fig. 4 is a cross-sectional view of the phantom 10 of Fig. 2 taken along line BB. In Fig. 4, some parts are shown separated. Fig. 5 is a plan view of the film guard 40 of the embodiment. In the following description, Fig. 1 will also be referred to.

[0036] As shown in FIG. 1, the phantom 10 is disassembled and has a cube shape when assembled, and is installed inside the human body model 6 (specifically, the head human body model 6) for use. The phantom 10 is installed by fitting it perfectly into a cavity formed inside the human body model 6 corresponding to the external shape of the phantom 10. Inside the human body model 6, a cavity is formed so that one or more phantoms 10 can be placed at a part where the radiation dose and radiation distribution are to be grasped. Note that the human body model 6 of this embodiment has a rectangular parallelepiped-shaped cavity formed inside so that two phantoms 10 can be placed side by side with the face side as a lid. The human body model 6 in which the phantom 10 is installed is installed on the bed part 4 while referring to the line laser irradiated from the line laser sight 5 of the radiotherapy device 1, and is used to grasp the radiation distribution and irradiation position of the LINAC 2.

[0037] As shown in Figs. 2 to 4, the phantom 10 has an index for quality control of the radiotherapy device 1 and is capable of fixing a replaceable radiographic imaging film 7. The phantom 10 includes a pair of outer blocks 20 (20A, 20B) facing each other in a fastening direction V, and an inner block 30 that is sandwiched and fixed between the pair of outer blocks 20. The phantom 10 further includes a film guard 40 that is fixed to the inside of the inner block 30. The phantom 10 further includes a fastener 50 that fastens the inner block 30 in a state where it is sandwiched between the pair of outer blocks 20. For ease of explanation, the drawings are indicated by the symbol V, and the direction in which the pair of outer blocks are lined up is viewed as the fastening direction V.

[0038] Here, the radiation imaging film 7 is a sheet-like film that is exposed to the intensity of radiation. The radiation imaging film 7 has a planar shape that corresponds to the outer shape of a mating surface (34), which is the sandwiching surface of the inner block 30 described below, to the extent that it does not protrude from the mating surface (34). The radiation imaging film 7 also has a slit that cuts inward from one side. As a result, by fitting two radiation imaging films 7 together with their slits, a cross-shaped three-dimensional object with planes perpendicular to each other can be formed. Each part that constitutes the phantom 10 will be described below.

[0039] The outer block 20 is composed of a pair of a first outer block 20A and a second outer block 20B, which are plane-symmetrical to each other. The first outer block 20A and the second outer block 20B are generally square rectangular parallelepipeds when viewed from the fastening direction V, and more precisely, are bottomed frames with a quadrangular pyramidal recess 21 formed on one of the faces facing the fastening direction V. The recess 21 of the outer block 20 is formed with a square periphery perpendicular to the fastening direction V. When the phantom 10 is assembled, a protrusion 32 of the inner block 30 described below fits into the recess 21. That is, the recess 21 of the outer block 20 has a pressing slope 23 (slope of the recess) that can come into surface contact with a slope (33) of the inner block 30 as a portion that comes into contact with the inner block 30 described below. The recess 21 of the outer block 20 is formed such that an angle between the bottom surface 22 and the pressing slope 23 is about 120° to 150°. Further, the outer block 20 has through holes 24 formed at its four corners, each extending along the fastening direction V as holes through which a fastener 50 described below passes.

[0040] The inner block 30 is configured by combining a plurality of inner block pieces (four inner block pieces 30A to 30D in the embodiment) in a separable manner. The inner block 30 in a state where the inner block pieces 30A to 30D are combined has a central portion 31 having a square rectangular parallelepiped shape as viewed in the fastening direction V, and a protruding portion 32 protruding in a quadrangular pyramid shape from each of both faces of the central portion 31 facing the fastening direction V, which are integrated together. The central portion 31 of the inner block 30 is formed to have the same size as the outer block 20 as viewed in the fastening direction V, and the protruding portion 32 is formed to have a shape that fits into the recessed portion 21 of the outer block 20. That is, the protruding portion 32 of the inner block 30 has a slope 33 that is a contact portion with the pressing slope 23 of the recessed portion 21 of the outer block 20. In addition, the inner block 30 has through holes 36 at its four corners as holes through which the fasteners 50 described below pass, and which are aligned with the through holes 24 of the outer block 20 when assembled. In addition, a spherical index 37 made of a material having a different specific gravity from the surroundings is disposed in the central portion (center of gravity) of the inner block 30.

[0041] The inner block 30 is configured to be separable by a first mating surface 34A and a second mating surface 34B which are perpendicular to each other as mating surfaces 34. The first mating surface 34A and the second mating surface 34B of the inner block 30 are surfaces which are perpendicular to each other, pass through a line connecting the midpoints of the opposing sides of the central portion 31 as viewed in the fastening direction V, and extend along the fastening direction V. The first mating surface 34A and the second mating surface 34B of the inner block 30 pass through the center of gravity of the inner block 30 without twisting with respect to the inclined surface 33 of the inner block 30.

[0042] That is, each of the inner block pieces 30A to 30D in the inner block 30 has a first mating surface 34A and a second mating surface 34B which are parallel to the fastening direction V and can be mated with the adjacent inner block piece to sandwich and fix the radiographic imaging film 7. Each of the inner block pieces 30A to 30D in the inner block 30 has an inclined surface 33 which is inclined in a direction in which the first outer block 20A or the second outer block 20B comes into contact with the inner block 30 when the inner block 30 is fixed to the pair of outer blocks 20, and which is pressed upon contact and acts toward the first mating surface 34A or the second mating surface 34B. The inclined surfaces 33 have a plurality of inclined surfaces corresponding to each of the pair of outer blocks.

[0043] The film guard 40 is thin and has a planar shape corresponding to the mating surface 34 of the inner block 30, and is placed between the mating surface 34 and the radiographic imaging film 7 when the radiographic imaging film 7 is attached. As shown in FIG. 5, the film guard 40 has a pattern 41 made of a material having a different specific gravity from the surroundings as an index. This pattern 41 has a circular shape centered on the theoretical isocenter of the phantom 10. The film guard 40 may be composed of a plurality of pieces depending on the usage situation. In this embodiment, two radiographic imaging films 7 combined to be perpendicular to each other are placed inside the phantom 10, so two film guards 40 are used for one side of one radiographic imaging film 7. That is, when one side of one radiographic imaging film 7 is pressed, the film guard 40 is partitioned by the other radiographic imaging film 7, so the planar shape of one film guard 40 corresponds to the planar shape of the mating surface 34 of the inner block pieces 30A-D of the inner block 30. In the film guard 40, a semicircular pattern (41) is formed on one film guard (40), and when two film guards are arranged side by side, the pattern 41 is configured to have a circular shape. Note that, in order to fill the cavity, it is preferable that the width of the film guard 40 differs depending on the pressing direction. Specifically, as shown in Fig. 4, it is preferable that the width of the film guard 40a on the pressing side from one side is longer by the plate thickness than the width of the film guard 40b on the pressing side from the other side.

[0044] The fasteners 50 are so-called bolts and nuts that pass through the through holes 24 of the outer block 20 and the through holes 36 of the inner block 30 to fasten the outer block 20 and the inner block 30 together.

[0045] The phantom 10 thus configured, in an assembled state, is a cube with the outer surface of the outer block 20 and the side surface of the central portion of the inner block 30 exposed on the surface. The phantom 10 has a configuration in which the radiation imaging film 7 is sandwiched between the first mating surfaces 34A or the second mating surfaces 34B parallel to the fastening direction V of the inner block pieces 30A to 30D via the film guard 40, and the inner block pieces 30A to 30D are sandwiched between the pair of outer blocks 20 along the fastening direction V and fastened with fasteners 50 to be integrated.

[0046] [1-3. Assembly of Phantom 10] Fig. 6 is a flow chart showing the procedure for assembling the phantom 10 for a radiotherapy apparatus according to the embodiment. Fig. 7 is a diagram for explaining the forces applied when assembling the phantom for a radiotherapy apparatus according to the embodiment. In the following description, Figs. 1 to 5 will also be referred to as appropriate.

[0047] The phantom 10 is assembled by executing a radiographic film setting step ST1, a film guard setting step ST2, an inner block setting step ST3, an outer block setting step ST4, and a fastening step ST5, as shown in Fig. 6. When disassembling the phantom 10, the reverse steps are carried out.

[0048] In the radiographic imaging film setting step ST1, first, the first outer block 20A is placed on a horizontal plane with the recesses 21 facing upward. Next, in the radiographic imaging film setting step ST1, two radiographic imaging films 7 are fitted together at their slits to form a cross-shaped radiographic imaging film ASSY(7) whose planes are perpendicular to each other, and then the cross-shaped radiographic imaging film ASSY(7) is dropped into the recesses 21 of the first outer block 20A.

[0049] In the film guard setting step ST2, a plurality of film guards 40 are arranged following each surface of the radiographic imaging film 7. In this embodiment, two radiographic imaging films 7 are arranged in a cross shape, partitioning each other to form a radiographic imaging film ASSY(7) having eight surfaces, and therefore eight film guards 40 are used. In the film guard setting step ST2, the film guards 40 are arranged so as to drop into the recesses 21 of the first outer block 20A.

[0050] In the inner block setting process ST3, the four inner block pieces 30A-30D are each placed into the four spaces of the recess 21 of the first outer block 20A separated by the radiographic imaging film 7, with the pressing inclined surface 23 of the first outer block 20A facing the inclined surface 33 of the inner block piece.

[0051] In the outer block setting step ST4, the second outer block 20B is placed over the inner block 30 such that the pressing slope 23 of the second outer block 20B faces the slope 33 of the inner block piece exposed after the inner block setting step ST3.

[0052] In the fastening step ST5, the bolt of the fastener 50 is passed through the communicating through hole 24 of the outer block 20 and the through hole 36 of the inner block 30, and the outer block 20 and the inner block 30 are fastened together using a nut. Then, as shown in Fig. 7, a fastening force F1 of the outer block 20 facing the fastening direction V is transmitted from the pressing slope 23 to the slopes 33 of the inner block pieces 30A to 30D. Because the slopes of the inner block pieces 30A to 30D are inclined, the transmitted force is dispersed and also acts as a force F2 in a direction in which the inner block pieces approach each other, and the inner block 30 more firmly holds the radiographic imaging film 7 arranged between the inner block pieces.

[0053] In this manner, the phantom 10 can be assembled by dropping in and tightening together without requiring particularly precise alignment.

[0054] [1-4. Use of Phantom 10] A method of using the phantom 10 will be described. First, the phantom 10 assembled as described above is set inside the human body model 6 as shown in FIG. 1, and the human body model 6 is placed on the bed 4 of the radiotherapy device 1. Next, the X-ray imaging device 3 checks in real time whether the human body model 6 placed on the radiotherapy device 1 is placed in the correct position. Next, while the human body model 6 is placed in the correct position, radiation is irradiated from the LINAC 2 so that the radiation is concentrated on the pattern 41 made of a material with a different specific gravity from the surroundings in the film guard 40. Thereafter, the phantom 10 is disassembled, the exposure state of the radiation imaging film 7 is confirmed, and the radiation dose and radiation distribution are grasped. In addition, the spherical index 37 made of a material with a different specific gravity from the surroundings in the inner block 30 of the phantom 10 and the shadow of the pattern 41 made of a material with a different specific gravity from the surroundings in the film guard 40 are also recorded on the radiation imaging film 7. As a result, the position of the radiation can be grasped from the exposure state of the radiation imaging film 7. Specifically, for example, it can be grasped by evaluating the amount of deviation of the position where radiation is concentrated from the center of the pattern 41 from the distance between the center of the gravity of the portion darkened by radiation in the radiation imaging film 7 and the center of the pattern 41 of the film guard 40. The radiation therapy device 1 is calibrated after the radiation irradiation position, radiation dose, and radiation distribution are confirmed using the phantom 10.

[0055] [1-5. Actions and Effects of the Embodiments]

[0056] The phantom 10 is intended to be a phantom for fixing the radiographic imaging film 7 in a replaceable manner, and can be used for quality control to grasp the radiation dose and radiation distribution.

[0057] The phantom 10 includes a pair of outer blocks 20 facing each other in the fastening direction V, and an inner block 30 sandwiched between the pair of outer blocks 20 and configured by separably joining a plurality of inner block pieces 30A-30D, and has a mating surface 34 where each of the inner block pieces (30A-30D) joins with an adjacent inner block piece, which is a surface where the radiation imaging film 7 can be sandwiched and fixed. This allows the phantom 10 to be easily fixed by sandwiching the radiation imaging film 7 between the inner block pieces 30A-30D and sandwiching the inner block pieces 30A-30D together with the outer block 20. Moreover, the phantom 10 has an inclined surface 33 that is inclined in a direction in which at least one of the outer blocks 20 comes into contact with each of the inner block pieces when the inner block pieces are fixed to the pair of outer blocks 20, and which is inclined in a direction in which the force applied at the time of the contact acts in a dispersed manner toward the mating surface 34 side. As a result, in the phantom 10, when the inner block 30 is sandwiched between the outer blocks 20, a force is applied to each of the inner block pieces 30A-30D to move them toward the mating surface 34. In other words, in the phantom 10, when the inner block 30 is sandwiched between the outer blocks 20, the inner block 30 is formed with the inner block pieces firmly in contact with each other, and the radiation imaging film 7 can be firmly sandwiched, without any special effort to move them closer or press them down. As a result, with the phantom 10, it is possible to easily and quickly attach the radiation imaging film 7 to a predetermined position with good reproducibility.

[0058] As a result, the phantom 10 can be used for quality control purposes to ascertain the radiation dose and radiation distribution, and is a phantom to which the radiographic imaging film 7 can be easily and quickly attached in a predetermined position.

[0059] Phantom 10 has a plurality of inclined surfaces 33 corresponding to each of the pair of outer blocks. Therefore, according to Phantom 10, all of the inner block pieces 30A-30D are brought toward the center of the inner block 30, so that a stable inner block shape can be formed without any special effort to bring them together or press them down.

[0060] In the phantom 10, the inner block 30 is configured by joining four inner block pieces 30A to 30D that can be separated by a first mating surface 34A and a second mating surface 34B that are perpendicular to each other as mating surfaces. This makes it possible to grasp the radiation dose and radiation distribution three-dimensionally to some extent with the phantom 10.

[0061] In the phantom 10, the outer block 20 has a pressing inclined surface 23 capable of surface contact with the inclined surface 33 as a portion that comes into contact with the inner block 30. Therefore, according to the phantom 10, the pressing force of the outer block 20 is dispersed to sandwich and fix the inner block 30, thereby further reducing the risk of distortion.

[0062] The phantom 10 further includes a film guard 40 which is thin and has a planar shape corresponding to the mating surface 34 of the inner block 30, and which is disposed between the mating surface 34 and the radiographic imaging film 7 when the radiographic imaging film 7 is attached. Therefore, with the phantom 10, the force that the mating surface 34 directly displaces the radiographic imaging film 7 along the fastening direction V is reduced, so that the radiographic imaging film 7 can be fixed in a manner that prevents it from being displaced.

[0063] In the phantom 10, the film guard 40 has, as an index, a pattern 41 made of a material having a different specific gravity from the surroundings. As a result, with the phantom 10, the pattern 41 near the radiographic film 7 can be confirmed even in a real-time radiation image, making it easy to grasp the radiation irradiation position.

[0064] In the phantom 10, the pattern 41 has a circular shape centered on the theoretical isocenter of the phantom 10, so that the theoretical isocenter position can be grasped, and it is easy to grasp the deviation of the radiation irradiation position and irradiation direction.

[0065] If the phantom 10 of the embodiment is constructed, it can be used for quality control to grasp the radiation dose and radiation distribution, and a phantom can be provided to which the radiation imaging film 7 can be easily and quickly attached in a specified position.

[0066] [Other embodiments] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment. The present invention can be embodied in various forms without departing from the spirit of the present invention, and for example, the following modifications are also possible.

[0067] (1) The number, shape, position, orientation, arrangement, size, and material of the components described in the above embodiment are examples and can be changed without impairing the effects of the present invention.

[0068] (2) In the above embodiment, the phantom 10 is described as being a cube, but the present invention is not limited to this. For example, the phantom may be a rectangular parallelepiped phantom or a cylindrical phantom.

[0069] (3) In the above embodiment, the phantom 10 is described as having a film guard 40, but the present invention is not limited to this. For example, the phantom may be configured so that the radiographic film is directly sandwiched between the inner blocks without using a film guard.

[0070] Figure 8 shows modified examples of the contact portion between the inner block and the outer block. Figure 8(a) shows a modified example in which the inner block and the outer block contact each other with a spherical surface. Figure 8(b) shows a modified example in which the inner block and the outer block contact each other with a point contact or line contact.

[0071] (4) In the above embodiment, the pressing slope 23 of the outer block 20 and the slope 33 of the inner block 30 are described as planar slopes that make surface contact, but the present invention is not limited to this. The contact portion between the outer block and the inner block may be, for example, as shown in FIG. 8(a), such that the recess 121 of the outer block 120 is formed as a spherical surface and the protrusion 132 of the inner block 130 is formed as a spherical surface having a shape corresponding to the recess 121, so that they make spherical contact. Also, for example, as shown in FIG. 8(b), such that the recess 221 of the outer block 220 is formed as a slope having a protrusion T along a plane perpendicular to the fastening direction and the protrusion 232 of the inner block 230 is formed as a slope, so that they make point contact or line contact.

[0072] FIG. 9 shows a modified example of the film guard.

[0073] (5) In the above embodiment, the film guard 40 is described as having a circular pattern 41 formed as an indicator, the pattern being made of a material with a different specific gravity from the surrounding area, but the present invention is not limited to this. The pattern formed on the film guard and having a different specific gravity from the surrounding area may be, for example, a curved pattern 141 along a circumference centered on the theoretical isocenter of the phantom, as in the film guard 140 shown in FIG. [Explanation of symbols]

[0074] 1. Radiation therapy device, 2. LINAC, 3. X-ray imaging device, 4. Head, 5. Line laser sight, 6. Human body model, 7. Radiation imaging film, 10. Phantom for radiation therapy device, 20, 120, 220. Outer block, 20A. First outer block, 20B. Second outer block, 21, 121, 221. Recess, 22. Bottom surface, 23. Pressing slope, 24. Through hole, 30, 130, 230. Inner block, 30A to 30D ‥Inner block piece, 31‥Central portion, 32, 132, 232‥Convex portion, 33‥Slope, 34‥Mating surface, 34A‥First mating surface, 34B‥Second mating surface, 36‥Through hole, 37‥Spherical index, 40, 140‥Film guard, 41, 141‥Pattern, 50‥Fastener, ST1‥Radiation imaging film setting step, ST2‥Film guard setting step, ST3‥Inner block setting step, ST4‥Outer block setting step, ST5‥Fastening step, V‥Fastening direction

Claims

1. A phantom having an index for quality control of a radiotherapy device and for replacingably fixing a radiographic imaging film, A pair of outer blocks facing each other in a fastening direction; an inner block sandwiched between the pair of outer blocks and configured by combining a plurality of inner block pieces in a separable manner; A phantom for a radiation therapy device, characterized in that each of the multiple inner block pieces has a mating surface that is parallel to the fastening direction and meets with an adjacent inner block piece, allowing the radiographic imaging film to be sandwiched and fixed, and a slope that inclines in a direction that disperses the force applied by at least one of the outer blocks to the mating surface when the inner block pieces are fixed to the pair of outer blocks and that contacts the mating surface.

2. 2. The phantom for a radiotherapy apparatus according to claim 1, wherein the inclined surface comprises a plurality of inclined surfaces corresponding to each of the pair of outer blocks.

3. The phantom for a radiation therapy device according to claim 1 or 2, characterized in that the inner block is constructed by joining four inner block pieces which are separable by a first mating surface and a second mating surface which are perpendicular to each other as the mating surfaces.

4. The phantom for a radiotherapy apparatus according to any one of claims 1 to 3, characterized in that the outer block has a pressing inclined surface capable of surface-contacting the inclined surface as a part that comes into contact with the inner block.

5. 5. The phantom for a radiotherapy device according to claim 1, further comprising a film guard which is thin and has a planar shape corresponding to the mating surface of the inner block, and which is disposed between the mating surface and the radiographic imaging film when the radiographic imaging film is attached.

6. 6. The phantom for a radiotherapy apparatus according to claim 5, wherein the film guard has, as the indicator, a pattern made of a material having a different specific gravity from that of the surrounding area.

7. 7. The phantom for a radiotherapy apparatus according to claim 6, wherein the pattern is a curve along a circumference of a circle centered on a theoretical isocenter of the phantom.

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