JP2007037828A - Multileaf collimator and radiation therapy equipment having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an art capable of precisely focusing the irradiation field of radiation to the shape of an affected part in the art practicing a therapy by applying radiation to the subject. <P>SOLUTION: This multileaf collimator disposed in the radiation direction from a radiation source S is provided with a bendable lead wire 622 engraved with a feed screw along its shaft, a driving unit 624 axially rotating the lead wire, a nut 621 threadedly engaged with the lead wire and being movable along the shaft, and a leaf block 61B fixed to the nut. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for narrowing an irradiation field of radiation to be exposed to a subject.

  Conventionally, radiation treatment aimed at the treatment has been widely performed by exposing radiation to an affected area such as cancer or tumor, thereby destroying tissue cells of the affected area or preventing division. In this radiotherapy, it is important to accurately irradiate the affected part with radiation in order to minimize damage to normal tissues around the affected part and to effectively irradiate the affected part.

  Therefore, the generated radiation is narrowed by a diaphragm block or a multi-leaf collimator so that the irradiation field becomes the same as the shape of the affected part. An example of a multi-leaf collimator is shown in FIGS.

  As shown in FIG. 7, the multi-leaf collimator includes a plurality of leaf blocks and a moving mechanism paired with the leaf blocks. The leaf block is made of a material that absorbs radiation, such as tungsten. By moving the leaf block between the radiation source S and a location where radiation is not necessary, the radiation field F is narrowed to a predetermined shape.

  The multi-leaf collimator C includes leaf blocks B facing each other with an exposure region in between, and a plurality of leaf blocks B arranged in parallel perpendicular to the radiation direction of radiation. By separating, the irradiation field F is narrowed down to a predetermined shape (see, for example, “Patent Document 1”).

  The moving mechanism T is arranged with a nut N fixed to the bottom surface of the leaf block B. Further, a shaft A inserted into the nut N is disposed in the approach or separation direction of the leaf block B, and a drive unit U that rotates the shaft A is provided. The nut N and the shaft A are each provided with a thread groove, and the nut and the shaft are screwed together by the thread groove.

  This moving mechanism operates the drive unit U to rotate the shaft A. When the shaft A rotates, the nut N screwed with the shaft A moves in the axial direction of the shaft A, and the leaf block B having a fixed relationship with the nut N also moves.

  The multi-leaf collimator C is narrowed down to a desired irradiation field F shape by appropriately controlling the movement amount. The amount of movement is detected by providing a detection unit such as a potentiometer or an encoder (not shown).

  Here, the shaft A is generally made of a material having a certain degree of rigidity, such as aluminum or plastic, and is arranged using a universal joint or the like in consideration of shaft rotation. In the radiotherapy apparatus, since the installation space of the multi-leaf collimator C is limited, the universal joint cannot be used without limitation. Therefore, the installation location of the drive unit U is substantially limited to the axis of the shaft A.

  FIG. 8 is a side view of the multi-leaf collimator C viewed from a direction orthogonal to the direction in which the leaf blocks B are arranged in parallel. The drive units U are arranged in a line in parallel with the leaf blocks B arranged side by side. Due to the installation space of the multi-leaf collimator C, the number of drive units U arranged in parallel is limited by the influence of the outer diameter. Since the leaf block B and the drive unit U are a pair, when the number of the drive units U is limited, the number of the leaf blocks B arranged in parallel is also limited.

  When the number of leaf blocks B is limited, each leaf block B becomes thick, the outer edge shape of the irradiation field F becomes rough, and it becomes difficult to approximate the shape of the affected part. If it does so, the radiation will also be exposed to the normal tissue of the vicinity of an affected part tissue, and the range which a radiation will not be exposed will arise even if it is an affected part tissue.

  If the bending of the shaft A by the universal joint is limited, the portion of the shaft A where the nut N does not move is also disposed in the vicinity of the leaf block B.

  When the space in the vicinity of the leaf block B is consumed due to the arrangement of the shaft A, the detection unit for detecting the movement amount is installed at a location away from the leaf block B. In order to transmit the movement amount of the leaf block B to the detection unit, a large number of gears (not shown) are provided between the leave block B and the detection unit. Since the detection unit passes through these many gears, the detection accuracy of the detected movement amount is lowered due to the influence of backlash or the like. This may cause the drive unit U to stop despite the leaf block B not reaching the originally desired position, and the shape of the irradiation field F may be different from the shape of the affected part. is there.

JP-A-11-216197

  The present invention has been made in view of the above-described problems, and an object thereof is related to a technique for treating a subject by irradiating radiation, and the radiation field of radiation can be accurately narrowed down to the shape of the affected part. To provide technology.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a multi-leaf collimator arranged in the direction of radiation irradiation from the radiation source and narrowing the radiation field to a predetermined shape, and a feed screw along its axis A bendable lead wire inscribed with, a drive unit for axially rotating the lead wire, a nut that can be screwed into the lead wire and moved along the shaft, and a leaf block fixed to the nut It is characterized by providing these.

  The lead wire may be bent from the drive unit to the nut, and the drive unit may be installed off the extension line of the movement locus of the nut.

  A plurality of the leaf blocks are provided in parallel, and a plurality of the lead wires, the drive units, and the nuts are paired with the leaf blocks, and the lead wires are bent from the drive units to the nuts. The drive units may be arranged side by side in a parallel direction of the leaf blocks and in a direction crossing the parallel direction.

  In addition, a detection unit for detecting the movement amount of the leaf block may be further provided in the vicinity of the leaf block.

  The leaf block may be provided with a rack portion, and the detection portion may have a gear meshing with the rack portion, and the movement amount may be detected from the rotation amount of the gear.

  The lead wire may be disposed along an arc centered on the radiation source.

  In the present invention, in a multi-leaf collimator, a bendable lead wire in which a feed screw is engraved along its axis, a drive unit for rotating the lead wire, and a lead wire screwed together along the axis. A movable nut and a leaf block fixed to the nut are provided. According to this invention, since the lead wire can be freely bent, the layout of the drive unit becomes free, it becomes possible to increase the drive unit, install a detection unit near the leaf block, etc. The radiation field can be narrowed down by approximating the shape of the affected area with high accuracy.

  FIG. 1 is a schematic diagram illustrating a configuration example of a radiation therapy apparatus 1 according to the present embodiment. The radiotherapy apparatus 1 includes a treatment table 2 on which a subject is placed, a rotating table 3, and a rotation support table 4 that rotatably supports the table 3.

  The treatment table 2 is provided with a top plate 21 that can be moved in the body axis direction of the subject (in the direction of arrow A in FIG. 1), and can move up and down (in the direction of arrow B in FIG. 1). is there. The treatment table 2 can be rotated (arrow C in FIG. 1) in which the surface of the top plate 21 maintains a parallel relationship with the installation surface of the radiotherapy device 1.

  The rotation support 4 supports the rotation mount 3 via a rotation shaft 41. The rotation support table 4 rotates the rotation shaft 41 so that the rotation frame 3 can rotate around the axis (in the direction of arrow D in FIG. 1).

  The rotary mount 3 has a substantially L-shaped solid shape. An L-shaped one arm portion 3 a is supported on the rotation support 4. The irradiation head 5 is provided in the other one-arm portion 3b. The irradiation head 5 is provided with a radiation source (not shown). The radiation source includes an electron accelerator, a counter-electron beam target, and the like, and generates radiation by accelerating electrons with the electron accelerator and colliding with the counter-electron beam target. The generated radiation is a photon beam (X-ray, γ-ray, etc.), electron beam, heavy particle beam (proton, helium, carbon, neon, π-meson beam, neutron beam, etc.).

  In this radiotherapy apparatus 1, the subject is placed on the top plate 21, and an isocenter where the axis of the rotating shaft 41 (the dashed line in the figure) intersects with the axis of the irradiation head 5 (also the dashed line in the figure). Then, adjust to match the position of the affected area to which the radiation is exposed. The position adjustment of the isocenter is performed by moving the treatment table 2, moving up and down, rotating, and rotating the rotating mount 3 around the axis. When the affected area and the isosensor match, the radiation field of the generated radiation is narrowed to a predetermined shape, and the radiation is exposed from the radiation source to the affected area.

  The irradiation field is a region where radiation is irradiated, and is narrowed down according to the shape of the affected area. The diaphragm adapted to the shape of the affected area of the irradiation field is performed by a diaphragm block (not shown) and a multi-leaf collimator 6 provided in the irradiation head 5. FIG. 2 is a perspective view showing the multi-leaf collimator 6 that narrows down the irradiation field according to the shape of the affected part. The multi-leaf collimator 6 is installed in the radiation direction of the radiation exposed from the radiation source. The diaphragm block is disposed between the radiation source and the multi-leaf collimator 6.

  The multi-leaf collimator 6 includes leaf blocks 61 </ b> A and 61 </ b> B that face each other with the radiation exposed from the radiation source interposed therebetween. The leaf blocks 61 </ b> A and 61 </ b> B have a taper in cross section and an arch shape in which a side surface is short. The arch of the outer circumferential arc surface 61c has the same curve radius as the arc centered on the radiation source. The material is a material that absorbs radiation, such as tungsten.

  A plurality of leaf blocks 61 </ b> A and 61 </ b> B are arranged side by side in a direction orthogonal to the side surfaces thereof. The multi-leaf collimator 6 includes a moving mechanism 62 that moves the pair of leaf blocks 61A and 61B toward or away from each other along the same circular arc trajectory centered on the radiation source. By moving the arbitrary leaf block 61A or 61B closer to or away from the predetermined movement amount by the moving mechanism 62, the irradiation field F is narrowed to an appropriate shape. The radiation radiated to places other than the irradiation field F is absorbed by the leaf blocks 61A and 61B, and only the radiation passing through the irradiation field F passes through the multi-leaf collimator 6.

  FIG. 3 is a side view of the multi-leaf collimator 6. Here, only the portion of the leaf block 61B will be described, but the same applies to the leaf block 61A. The moving mechanism 62 is arranged in a one-to-one correspondence with the plurality of leaf blocks 61A and 61B. The moving mechanism 62 includes a nut 621 fixed to the outer peripheral arc surface 61c of the leaf block 61B. The opening of the nut 621 faces the irradiation field F diaphragm direction of the leaf block 61B.

  A lead wire 622 is inserted into the opening of the nut 621. The lead wire 622 is disposed along an arc centered on the radiation source S while being supported loosely by the wire support portion 623. That is, the leaf block 61B is disposed along the outer circumferential arc surface 61c. A drive unit 624 is connected to one end of the lead wire 622. The drive unit 624 includes a motor and a speed reducer (not shown). One end of the lead wire 622 is connected to the rotor of the motor.

  FIG. 4 is a cross-sectional view of the nut 621 and the lead wire 622. As shown in FIG. 4, the lead wire 622 has a spiral thread groove engraved as a feed screw 622 b along its axis 622 a. The nut 621 has a thread groove 621a formed on the inner peripheral wall. The feed screw 622b of the lead wire 622 and the screw groove 621a of the nut 621 are screwed together.

  When such a moving mechanism 62 drives the drive unit 624 and rotates the rotor of the motor, the lead wire 622 rotates about the shaft 622a. If the lead wire 622 is curved, the shaft 622a is also curved. Since a plurality of leaf blocks 61B are arranged in parallel, rotation of the lead wire 622 in the direction around the axis is impossible. Therefore, when the lead wire 622 rotates, the nut 621 having the thread groove 621a screwed with the feed screw 622b moves in the direction of the shaft 622a of the lead wire 622.

  Since the leaf block 61B is fixed to the nut 621, the leaf block 61B moves in the direction of the shaft 622a of the lead wire 622 together with the nut 621. Since the lead wire 622 is disposed along an arc centered on the radiation source S, the leaf block 61B moves along an arc centered on the radiation source S.

  By controlling the motor rotation amount of each drive unit 624, each leaf block 61A and 61B moves independently by a predetermined amount, and the irradiation field F is narrowed down to a shape matching the shape of the affected part as each leaf block 61A and 61B as a whole. .

  By the way, the lead wire 622 can be disposed between the nut 621 and the drive unit 624 by its bending ability, and the shaft can be rotated without displacing the disposed position even if it is bent. Is possible. The lead wire 622 is supported by the wire support portion 623 and curved in an arc shape, and then can be further freely curved and connected to the drive unit 624. That is, the drive unit 624 can be laid out at any position by the lead wire 622.

  For example, FIG. 5 is a side view of the multi-leaf collimator 6 viewed from a direction orthogonal to the parallel direction of the leaf blocks 61B. As shown in FIG. 5, in the multi-leaf collimator 6 of this embodiment, each drive unit 624 is arrange | positioned two-dimensionally. It arrange | positions in the parallel arrangement direction of the leaf block 61B, and also arrange | positions in multistage in the direction orthogonal to the parallel arrangement direction of the leaf block 61B. Each lead wire 622 is arranged to be bent from the connection end of each drive unit 624 to the wire support portion 623.

  By arranging the drive units 624 two-dimensionally in multiple stages, a large number of drive units 624 can be arranged in a limited space, and the drive force can be transmitted to each leaf block 61B by the lead wire 622. it can. Thereby, with the increase in the number of drive units 624, more leaf blocks 61B having a narrow cross-sectional width can be arranged in the same space.

  When the number of leaf blocks 61A and 61B increases and the cross-sectional width is narrow, the shape of the irradiation field F narrowed by each leaf block 61A and 61B becomes smoother. The irradiation field F thus obtained can be easily approximated to a shape that matches the shape of the affected area. Therefore, unnecessary exposure to other than the affected part can be prevented with higher accuracy, and exposure to the affected part can be performed without omission.

  As another example of the layout of the drive unit 624, as shown in FIG. 6, the drive unit 624 is disposed off the extended line of the movement locus of the nut 621. As a result, from the connection end of the lead wire 622 to the drive unit 624 to the portion where the nut 621 does not move, the lead wire 622 is separated from the movement locus without being along the outer circumferential arc surface 61c of the leaf block 61B. A detection unit 625 is installed in a space near the outer circumferential arc surface 61c created by detaching this portion.

  The leaf block 61B is provided with a rack portion 61d having a gear cut on the outer circumferential arc surface 61c. The detection unit 625 includes a gear (not shown) and a potentiometer (not shown), and detects the rotation amount of the gear with the potentiometer. The gear meshes with the rack portion 61d of the leaf block 61B. By this meshing, the leaf block 61B moves to rotate the gear. The amount of rotation of the gear becomes the amount of movement of the leaf block 61B, and the detection unit 625 directly detects the amount of movement of the leaf block 61B. The detecting unit 625 may include an encoder instead of the potentiometer.

  Thus, by providing the lead wire 622, the drive unit 624 can be laid out at any position, and for example, a space can be created in the vicinity of the outer peripheral arc surface 61c of the leaf block 61B. By providing the detection unit 625 in this space, it becomes possible to directly detect the amount of movement of the leaf block 61B by eliminating many other gears that only connect the leaf block 61B and the detection unit 625. For this reason, it is possible to detect the amount of movement with high accuracy without being affected by backlash caused by passing through another gear, and thus it is possible to narrow down the irradiation field with high accuracy.

It is a schematic diagram which shows the structural example of the radiotherapy apparatus which concerns on this embodiment. It is a perspective view which shows the multileaf collimator which concerns on this embodiment. It is a side view of the multileaf collimator concerning this embodiment. It is sectional drawing of a nut and a lead wire part among the moving mechanisms which concern on this embodiment. It is the side view which looked at the multileaf collimator of this embodiment from the direction orthogonal to the parallel direction of a leaf block. It is a side view which shows a multileaf collimator provided with the detection part which concerns on this embodiment. It is a figure which shows the conventional multileaf collimator. It is the side view which looked at the conventional multi-leaf collimator from the direction orthogonal to the parallel direction of a leaf block.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation therapy apparatus 2 Treatment table 21 Top plate 3 Rotation stand 4 Rotation support stand 5 Irradiation head 6 Multi leaf collimator 61A Leaf block 61B Leaf block 62 Movement mechanism 621 Nut 622 Lead wire 623 Wire support part 624 Drive unit 625 Detection part S Radiation Source F Irradiation field

Claims (12)

A multi-leaf collimator that is arranged in the direction of radiation irradiation from the radiation source and narrows the radiation field to a predetermined shape,
A bendable lead wire with a lead screw engraved along its axis;
A drive unit for axially rotating the lead wire;
A nut threadably engaged with the lead wire and movable along the axis;
A leaf block fixed to the nut;
Providing
Multi-leaf collimator characterized by The lead wire is arranged curved from the drive unit to the nut,
The drive unit is installed off the movement locus extension line of the nut;
The multi-leaf collimator according to claim 1. A plurality of the leaf blocks are provided in parallel, and a plurality of the lead wires, the drive unit, and the nuts are provided in pairs with the leaf blocks,
Each lead wire is curvedly arranged from the drive unit to the nut,
The drive units are arranged side by side in a direction parallel to the leaf blocks and in a direction crossing the parallel direction.
The multi-leaf collimator according to claim 1. Further comprising a detector for detecting the amount of movement of the leaf block in the vicinity of the leaf block;
The multi-leaf collimator according to claim 2 or 3, wherein The leaf block is engraved with a rack portion,
The detection unit has a gear that meshes with the rack unit, and detects the movement amount from the rotation amount of the gear;
The multi-leaf collimator according to claim 4. The lead wire is disposed along an arc centered on the radiation source;
The multi-leaf collimator according to claim 1. A radiation therapy apparatus comprising a radiation source that irradiates radiation and a multi-leaf collimator that is arranged in a radiation irradiation direction from the radiation source and narrows the radiation field to a predetermined shape,
The multi-leaf collimator is
A bendable lead wire with a lead screw engraved along its axis;
A drive unit for rotating the lead wire;
A nut threadably engaged with the lead wire and movable along the axis;
A leaf block fixed to the nut;
Providing
A radiotherapy apparatus characterized by the above. The lead wire is arranged curved from the drive unit to the nut,
The drive unit is installed off the movement locus extension line of the nut;
The radiotherapy apparatus according to claim 7. A plurality of the leaf blocks are provided in parallel, and a plurality of the lead wires, the drive unit, and the nuts are provided in pairs with the leaf blocks,
Each lead wire is curvedly arranged from the drive unit to the nut,
The drive units are arranged side by side in a direction parallel to the leaf blocks and in a direction crossing the parallel direction.
The radiotherapy apparatus according to claim 7. The multi-leaf collimator further includes a detection unit that detects a movement amount of the leaf block in the vicinity of the leaf block;
10. A radiotherapy apparatus according to claim 8 or 9, wherein: The leaf block is engraved with a rack portion,
The detection unit has a gear that meshes with the rack unit, and detects the movement amount from the rotation amount of the gear;
The radiotherapy apparatus according to claim 10. The lead wire is disposed along an arc centered on the radiation source;
The radiotherapy apparatus according to claim 7.

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