JP2018143591A - Charged particle beam treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam treatment device which can prevent increase in size of a multi-leaf collimator.SOLUTION: A side face of a leaf is inclined toward an irradiation axis direction. Accordingly, a gap formed between the leaves are configured to incline toward the irradiation axis direction. For example, when a charged particle beam is irradiated in the gap extending straight in the irradiation axis direction, the beam may pass through the gap without being into contact with a member of the leaf. On the other hand, when the gap is inclined, although the charged particle beam may pass through at some regions of the gap in the irradiation axis direction, the beam passes through a member of the leaf at other regions. Thus, there is no need for providing a receiving part for receiving the charged particle beam leaked from a gap between the leaves.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a charged particle beam therapy apparatus.

  Conventionally, for example, an apparatus described in Patent Document 1 is known as a charged particle beam therapy apparatus that performs treatment by irradiating a patient's affected part with a charged particle beam. In the charged particle beam therapy system described in Patent Document 1, the charged particle beam accelerated by the accelerator is enlarged, and some unnecessary charged particle beams are blocked using a multi-leaf collimator, and then the shape of the irradiated object Irradiation of charged particle beams is performed in an irradiation field matched to The multi-leaf collimator has a side surface extending straight along the direction in which the irradiation axis of the charged particle beam extends.

JP 2009-034443 A

  Here, in order to sufficiently shield the charged particle beam by each leaf, the thickness in the direction along the irradiation axis of the leaf must be large to some extent. For example, since there is a gap between the leaves, in order to reduce the charged particle beam leaking from the gap, a receiving part for receiving the charged particle beam leaking from the gap has been formed. And in order to fully shield a charged particle beam, the thickness of the said receiving part also needed to be enlarged (for example, refer FIG. 9). As a result, there is a problem that the multi-leaf collimator is enlarged and the entire irradiation unit is also enlarged.

  On the other hand, by using a high-density material for the leaf, it is conceivable to reduce the thickness of the leaf while ensuring the shielding ability of the charged particle beam. However, if a charged particle beam is shielded with a high-density material, many neutron beams are generated at that time, and this neutron beam processing becomes a problem. That is, a member for performing neutron beam processing must be provided, and only that portion is enlarged. Therefore, it has been difficult to reduce the size of the multi-leaf collimator using a high-density material.

  Then, an object of this invention is to provide the charged particle beam therapy apparatus which can suppress the enlargement of a multileaf collimator.

  In order to solve the above problems, a charged particle beam treatment apparatus according to the present invention includes an accelerator that accelerates charged particles and emits the charged particle beam, an irradiation unit that irradiates the irradiated object with the charged particle beam, and irradiation. A multi-leaf collimator that is provided in the unit and defines an irradiation range of the charged particle beam in accordance with the shape of the irradiated object, and the multi-leaf collimator is in a first orthogonal direction orthogonal to the irradiation axis of the charged particle beam. The plurality of leaves arranged side by side, and each leaf has a first end portion on the upstream side and a second end portion on the downstream side facing each other in the irradiation axis direction in which the irradiation axis extends, and a first end portion And a side surface connecting the second end portions, and the side surface is inclined with respect to the irradiation axis direction.

  In this charged particle beam therapy system, the multi-leaf collimator has a plurality of leaves arranged in a first orthogonal direction orthogonal to the irradiation axis of the charged particle beam. Each leaf connects the first end portion and the second end portion on the upstream side and the second end portion on the downstream side facing each other in the irradiation axis direction in which the irradiation axis extends. And a side. A gap is formed between the leaves so that the side faces face each other. Here, the side surface of the leaf is inclined with respect to the irradiation axis direction. Accordingly, the gap formed between the leaves is also configured to be inclined with respect to the irradiation axis direction. For example, when a charged particle beam is irradiated to a gap that extends straight in the irradiation axis direction, the gap may pass through the gap without contacting the leaf member. On the other hand, when the gap is inclined, even if the charged particle beam may pass through the gap at any position in the irradiation direction, it passes through the leaf member at other positions. Therefore, it is not necessary to provide a receiving part for receiving charged particle beams leaking from the gap between the leaves. As a result, an increase in size of the multi-leaf collimator can be suppressed.

  The charged particle beam treatment apparatus according to the present invention is provided with an accelerator that accelerates charged particles and emits a charged particle beam, an irradiation unit that irradiates the irradiated object with the charged particle beam, and an irradiation unit. A multi-leaf collimator that defines an irradiation range of the charged particle beam according to the shape of the body, and the multi-leaf collimator includes a plurality of leaves arranged in a first orthogonal direction orthogonal to the irradiation axis of the charged particle beam. And each leaf has a first shielding part made of a material that shields the charged particle beam, and a second shielding part made of a material that shields the charged particle beam and has a higher density than the first shielding part. And the second shielding part has at least a portion arranged at a position different from the first shielding part in the first orthogonal direction.

  In this charged particle beam therapy system, the leaf has a first shielding part and a second shielding part. Further, the second shielding part has at least a portion arranged at a position different from the first shielding part in the first orthogonal direction. Therefore, the 2nd shielding part can function as a receiving part which receives the charged particle beam which leaked from the crevice formed between the 1st shielding parts of each leaf. Here, the second shielding part is made of a material having a higher density than the first shielding part. That is, generation of neutron beams can be suppressed by adopting a member having a low density as the material of the first shielding part that functions as a main part for shielding charged particle beams. On the other hand, the thickness of the receiving part can be reduced by adopting a high-density member as the material of the second shielding part that functions as a receiving part that receives the charged particle beam leaking from the gap. As a result, an increase in size of the multi-leaf collimator can be suppressed.

  In the charged particle beam therapy system, the second shielding unit may be disposed on the downstream side in the irradiation axis direction in which the irradiation axis extends. Thereby, the effect of self-shielding can be acquired.

  ADVANTAGE OF THE INVENTION According to this invention, the charged particle beam therapy apparatus which can suppress the enlargement of a multileaf collimator can be provided.

1 is a schematic configuration diagram of a charged particle beam therapy system according to an embodiment of the present invention. It is a schematic block diagram of the irradiation part vicinity of the charged particle beam therapy apparatus of FIG. It is the figure which looked at the multileaf collimator from the irradiation direction. It is sectional drawing of the multileaf collimator along the IV-IV line shown in FIG. It is sectional drawing of the multileaf collimator which concerns on a modification. It is sectional drawing of the multileaf collimator which concerns on a modification. It is sectional drawing of the multileaf collimator which concerns on a modification. It is sectional drawing of the multileaf collimator which concerns on a modification. It is sectional drawing of the multileaf collimator which concerns on a comparative example.

  Hereinafter, a charged particle beam therapy system according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 1, a charged particle beam therapy apparatus 1 according to an embodiment of the present invention is an apparatus used for cancer treatment or the like by radiation therapy, and charged particles generated by an ion source (not shown). Accelerating the beam 2 and emitting it as a charged particle beam, an irradiation unit 8 for irradiating the irradiated body with the charged particle beam, and a beam transport line 45 for transporting the charged particle beam emitted from the accelerator 2 to the irradiation unit 8 It is equipped with. The irradiation unit 8 is attached to a rotating gantry 17 provided so as to surround the treatment table 16. The irradiation unit 8 can be rotated around the treatment table 16 by a rotating gantry 17.

  In the following description, the terms “X direction”, “Y direction”, and “Z direction” will be used. The “Z direction” is a direction in which the base axis AX of the charged particle beam R extends. The “base axis AX” is an irradiation axis of the charged particle beam R when it is not deflected by scanning electromagnets 3a and 3b described later. FIG. 2 shows a state where the charged particle beam R is irradiated along the base axis AX. In the following description, it is assumed that the direction in which the charged particle beam R is irradiated along the base axis AX is the “irradiation direction of the charged particle beam R”. The “X direction” is one direction in a plane orthogonal to the Z direction. The “Y direction” is a direction orthogonal to the X direction in a plane orthogonal to the Z direction.

  With reference to FIG. 2, the structure of the charged particle beam therapy apparatus which concerns on a wobbler method is demonstrated. As shown in FIG. 2, the charged particle beam therapy system 1 includes an accelerator 2, scanning electromagnets 3a and 3b, monitors 4a and 4b, a scatterer 5, a ridge filter 22, a multi-leaf collimator 24, a bolus 26, a patient collimator 27, and a degrader. 30 and a control device 7. The scanning electromagnets 3a and 3b, the monitors 4a and 4b, the scatterer 5, the ridge filter 22, the multi-leaf collimator 24, the bolus 26, the patient collimator 27, the degrader 30 and the control device 7 are provided outside the irradiation unit 8. However, the control device 7 may be provided outside the irradiation unit 8.

  The accelerator 2 is a generation source that accelerates charged particles and continuously generates charged particle beams R. Examples of the accelerator 2 include a cyclotron, a synchrotron, a cyclosynchrotron, and a linac. The charged particle beam R generated by the accelerator 2 is transported to the irradiation unit 8 by a beam transport system. The accelerator 2 is connected to the control device 7, and the supplied current is controlled.

  The scanning electromagnets 3a and 3b are each composed of a pair of electromagnets, change the magnetic field between the pair of electromagnets according to the current supplied from the control device 7, and scan the charged particle beam R passing between the electromagnets. The X-direction scanning electromagnet 3a scans the charged particle beam R in the X direction (first scanning direction), and the Y-direction scanning electromagnet 3b in the Y direction (second scanning direction orthogonal to the first scanning direction). The charged particle beam R is scanned. These scanning electromagnets 3 a and 3 b are arranged in this order on the base axis AX and downstream of the accelerator 2.

  The monitor 4a monitors the beam position of the charged particle beam R, and the monitor 4b monitors the absolute value of the dose of the charged particle beam R and the dose distribution of the charged particle beam R. Each of the monitors 4a and 4b outputs the monitored monitoring information to the control device 7. The monitor 4a is disposed on the base axis AX of the charged particle beam R and downstream of the accelerator 2 and upstream of the X-direction scanning electromagnet 3a. The monitor 4b is disposed on the base axis AX and downstream of the Y-direction scanning electromagnet 3b.

  The scatterer 5 diffuses the passing charged particle beam R into a wide beam having a spread in a direction orthogonal to the irradiation axis. The scatterer 5 has a plate shape and is formed of, for example, tungsten having a thickness of several millimeters. The scatterer 5 is arranged on the upstream side of the monitor 4b on the downstream side of the scanning electromagnet 3b on the base axis AX.

  The ridge filter 22 adjusts the dose distribution of the charged particle beam R. Specifically, the ridge filter 22 gives an enlarged Bragg peak (SOBP) to the charged particle beam R so as to correspond to the thickness (length in the irradiation direction) of the tumor 14 in the body of the patient 13. The ridge filter 22 is arranged on the downstream side of the scatterer 5 and upstream of the monitor 4b on the base axis AX.

  The degrader 30 adjusts the range of the charged particle beam R by reducing the energy of the charged particle beam R passing therethrough. The range is adjusted roughly by a degrader (not shown) provided immediately after the accelerator 2, and finely adjusted by the degrader 30 in the irradiation unit 8. The degrader 30 is provided on the base axis AX and on the downstream side of the charged particle beam R with respect to the scanning electromagnets 3a and 3b, and adjusts the maximum reachable depth of the charged particle beam R in the body of the patient 13. The degrader 30 is a plate-like member that extends in the X direction and the Y direction. In the present embodiment, the “range” is a distance traveled until the charged particle beam R loses kinetic energy and stops. More specifically, the range is a depth that is deeper than the irradiation distance (depth) at which the maximum dose is obtained and the dose is 90% when the maximum dose is 100%.

  A multi-leaf collimator 24 shapes the shape (planar shape) of the charged particle beam R in a plane direction perpendicular to the irradiation direction, and includes shielding portions 24a and 24b including a plurality of comb teeth. doing. The shielding portions 24a and 24b are disposed so as to face each other, and an opening 24c is formed between the shielding portions 24a and 24b. The multi-leaf collimator 24 cuts the charged particle beam R into a contour corresponding to the shape of the opening 24c by passing the charged particle beam R through the opening 24c.

  Further, the multi-leaf collimator 24 can change the position and shape of the opening 24c by moving the shielding portions 24a and 24b back and forth in a direction orthogonal to the Z direction. Further, the multi-leaf collimator 24 is guided along the irradiation direction by the linear guide 28 and is movable along the Z direction. The multi-leaf collimator 24 is disposed on the downstream side of the monitor 4b.

  The bolus 26 shapes the three-dimensional shape of the portion where the charged particle beam R reaches the maximum depth to match the shape of the maximum depth portion of the tumor 14. The shape of the bolus 26 is calculated based on, for example, the outline of the tumor 14 and the electron density of the surrounding tissue obtained from the X-ray CT data. The bolus 26 is disposed on the downstream side of the multi-leaf collimator 24 on the base axis AX. The patient collimator 27 finally shapes the planar shape of the charged particle beam R in accordance with the planar shape of the tumor 14. The patient collimator 27 is disposed on the downstream side of the bolus 26 on the base axis AX. The bolus 26 and the patient collimator 27 are provided at the distal end 8 a of the irradiation unit 8.

  When the charged particle beam therapy apparatus 1 shown in FIG. 2 irradiates the charged particle beam R by the wobbler method, the degrader 30 that can be adjusted to a predetermined range is set, and the shielding portions 24a, 24a of the multi-leaf collimator 24 are set. 24b is advanced and retracted so that the opening 24c has a predetermined shape.

  Subsequently, a charged particle beam R is emitted from the accelerator 2. The emitted charged particle beam R is scanned in a circle by the scanning electromagnets 3a and 3b and diffused by the scatterer 5, and then the ridge filter 22, the degrader 23, the multi-leaf collimator 24, the bolus 26, and the patient collimator 27. Is shaped and adjusted by Thereby, the charged particle beam R is irradiated to the tumor 14 in the uniform irradiation range along the shape of the tumor 14.

  As shown in FIG. 3, the multi-leaf collimator 24 includes a pair of leaf groups 31 and 32 facing each other in the X direction, and a pair of shielding blocks that are provided at both ends of the pair of leaf groups 31 and 32 and face each other in the Y direction. 35, 36.

  The pair of leaf groups 31 and 32 face each other in the Y direction across the reference axis A on the XY plane orthogonal to the reference axis A. The pair of leaf groups 31 and 32 includes a leaf member 40 including a large number of leaves 41 that can be advanced and retracted independently in the X direction.

  The leaf member 40 includes a leaf 41, a support portion 42 that supports the leaf 41, and a leaf drive portion 43 that moves the leaf 41. The leaf member 40 is disposed along the XY plane so that the leaf 41 of the leaf member 40 included in the leaf group 31 and the leaf 41 of the leaf member 40 included in the leaf group 32 face each other.

  The leaf 41 is a rectangular plate-like member extending along the X direction. Since the leaf 41 is a member used for shielding charged particle beams, the leaf 41 is manufactured from a material capable of shielding charged particle beams. Examples of the material capable of shielding charged particle beams include brass, copper, tantalum, and molybdenum, but it is preferable to use brass having a high shielding ability.

  The width (length in the Z direction) of the leaf 41 is set so that the charged particle beam can be shielded by the leaf 41. Therefore, when the leaf 41 is made of brass having a high shielding ability, the width of the leaf 41 can be reduced, and the multi-leaf collimator 24 can be downsized.

  The support portion 42 that supports the leaf 41 is a member that is attached to one end portion in the longitudinal direction of the leaf 41 and extends in the X direction. The material of the support part 42 is not particularly limited. The support portion 42 only needs to be able to support the leaf 41 in a state where the leaf 41 can advance and retreat in the X direction. Such a configuration includes, for example, a configuration in which the support portion 42 itself can be expanded and contracted, but the support portion 42 itself may be a rod-shaped member that does not expand and contract.

The leaf drive unit 43 is drive means for moving the leaf 41 forward and backward in the X direction. When the support portion 42 of the leaf member 40 is configured to be able to expand and contract, it is possible to control the advance and retreat of the leaf 41 in the X direction by changing the expansion and contraction of the support portion 42 by driving the leaf drive portion 43. it can. Further, when the support portion 42 of the leaf member 40 does not expand or contract, the support portion 42 is moved by driving the leaf drive portion 43 to control the advance and retreat of the leaf 41 integrated with the support portion 42 in the X direction. can do. The leaf drive unit 43 may directly move the leaf 41. In that case, the support part 42 is not provided and the leaf drive part 43 and the leaf 41 are directly connected.
Next, the configuration of the multi-leaf collimator 24 will be described in more detail with reference to FIG. As described above, the multi-leaf collimator 24 has a plurality of leaves 41 arranged in the Y direction. Further, the leaves 41 are separated from each other in the Y direction. Therefore, a gap GP is formed between the leaves 41.

  Each leaf is 41, an upstream first surface (first end) 41a and a downstream second surface (second end) facing each other in the irradiation axis direction (that is, the Z direction) in which the base axis AX extends. Part) 41b and side surfaces 41c and 41d for connecting the first surface 41a and the second surface 41b to each other. The side surface 41c is a side surface on the Y direction positive side. The side surface 41d forms a negative side surface in the Y direction. The side surfaces 41c and 41d are inclined with respect to the irradiation axis direction (Z direction). The side surfaces 41c and 41d are inclined with respect to the irradiation axis direction (Z direction) in a cross-sectional view cut along a plane parallel to the YZ plane. Further, the leaf 41 extends in the Y direction in the same shape with the cross-sectional shape.

  A gap GP is formed between the side surface 41c of one leaf 41 adjacent to the Y direction and the side surface 41d of the other leaf 41. Since the side surface 41c of one leaf 41 and the side surface 41d of the other leaf 41 face each other substantially in parallel, the gap GP extends in the irradiation axis direction (Z direction) with a substantially constant width dimension g. And inclined with respect to the irradiation axis direction.

  Specifically, the multi-leaf collimator 24 shown in FIG. 4 has three types of shapes, leaves 41A, 41B, and 41C. One leaf 41A is arranged near the center position in the Y direction of the multi-leaf collimator 24, a plurality of leaves 41B are arranged on the positive side in the Y direction with respect to the leaf 41A, and a leaf 41C is arranged on the negative side in the Y direction with respect to the leaf 41A. Several are arranged.

  In the leaf 41A, the side surface 41Ac and the side surface 41Ad are inclined from the upstream first surface 41Aa to the downstream second surface 41Ab so that the mutual separation distance in the Y direction increases. . Therefore, the second surface 41Ab on the downstream side of the leaf 41A is wider in the Y direction than the first surface 41Aa on the upstream side. The side surface 41Ac of the leaf 41A extends from the end on the Y direction positive side of the first surface 41Aa toward the end on the Y direction positive side of the second surface 41Ab, and is inclined toward the Y direction positive side. Yes. The side surface 41Ad of the leaf 41A extends from the end portion on the Y direction negative side of the first surface 41Aa toward the end portion on the Y direction negative side of the second surface 41Ab, and is inclined toward the Y direction negative side. Yes.

  In the leaf 41B, the side surface 41Bc and the side surface 41Bd are inclined from the first upstream surface 41Ba to the downstream second surface 41Bb so that the distance in the Y direction between them is constant. . The second surface 41Bb on the downstream side of the leaf 41B has the same width in the Y direction as the first surface 41Ba on the upstream side, and is disposed on the Y direction positive side with respect to the first surface 41Ba. The side surface 41Bc of the leaf 41B extends from the end on the Y direction positive side of the first surface 41Ba toward the end on the Y direction positive side of the second surface 41Bb, and is inclined toward the Y direction positive side. Yes. The side surface 41Bd of the leaf 41B extends from the end portion on the Y direction negative side of the first surface 41Ba toward the end portion on the Y direction negative side of the second surface 41Bb, and is inclined toward the Y direction positive side. Yes. The side surface 41Bd of the leaf 41B is substantially parallel to the side surface 41Bc of the leaf 41A. The side surface 41Bc of the leaf 41B is substantially parallel to the side surface 41Bd of the adjacent leaf 41B.

  In the leaf 41 </ b> C, the side surface 41 </ b> Cc and the side surface 41 </ b> Cd are inclined from the first upstream surface 41 </ b> Ca to the downstream second surface 41 </ b> Cb so that the distance in the Y direction between them is constant. . The second surface 41Cb on the downstream side of the leaf 41C has the same width in the Y direction as the first surface 41Ca on the upstream side, and is disposed on the Y direction negative side with respect to the first surface 41Ca. The side surface 41Cc of the leaf 41C extends from the end on the Y direction positive side of the first surface 41Ca toward the end on the Y direction positive side of the second surface 41Cb, and is inclined toward the Y direction negative side. Yes. The side surface 41Cd of the leaf 41C extends from the end portion on the Y direction negative side of the first surface 41Ca toward the end portion on the Y direction negative side of the second surface 41Cb, and is inclined toward the Y direction negative side. Yes. The side surface 41Cc of the leaf 41C is substantially parallel to the side surface 41Cd of the leaf 41A. The side surface 41Cd of the leaf 41C is substantially parallel to the side surface 41Cc of the adjacent leaf 41C.

  In the multi-leaf collimator 24 configured as shown in FIG. 4, a gap GP that is inclined toward the Y-direction positive side is formed between the adjacent leaves 41 </ b> B and 41 </ b> B. A gap GP is formed between the leaf 41B and the leaf 41A so as to incline toward the Y direction positive side. A gap GP is formed between the leaf 41A and the leaf 41C so as to incline toward the Y direction negative side. A gap GP that inclines toward the Y direction negative side is formed between adjacent leaves 41C. Note that the inclination direction of the gap GP is described based on the direction from the upstream side to the downstream side in the irradiation axis direction (Z direction). In the following description, the direction is used as a reference unless otherwise specified.

  Here, when the multi-leaf collimator 24 is viewed from the irradiation axis direction (Z direction), the gap GP is formed so that there is no portion penetrating the multi-leaf collimator 24. That is, the charged particle beam R irradiated along the irradiation axis direction passes through any part of the leaf 41 regardless of the position of the multi-leaf collimator 24 (without passing through the leaf 41 at all). It does not pass only through the gap GP).

  For example, in the case of the gap GP inclined to the Y direction negative side, the inlet portion GP1 of the gap GP is disposed at a position shifted to the Y direction positive side from the outlet portion GP2, and the inlet portion GP1 and the outlet portion GP2 are disposed. Does not have an overlapping portion in the irradiation axis direction (Z direction). In the case of the gap GP inclined to the Y direction positive side, the entrance portion GP1 of the gap GP is disposed at a position shifted to the Y direction negative side from the exit portion GP2, and the entrance portion GP1 and the exit portion GP2 are irradiated. There are no overlapping parts in the axial direction (Z direction).

  When a charged particle beam R traveling in the irradiation axis direction (Z direction) is irradiated to any position in the Y direction of the multi-leaf collimator 24, the distance passing through the inside of the leaf 41 is equal to or greater than a predetermined value. The shape of each leaf 41 and the size of the gap GP are set so that the relationship is established.

  Next, operations and effects of the charged particle beam therapy system 1 according to this embodiment will be described.

  First, the configuration of the multi-leaf collimator of the charged particle beam therapy system according to the comparative example will be described. In order to sufficiently shield the charged particle beam by each leaf, the thickness in the direction along the irradiation axis of the leaf must be large to some extent. For example, in the multi-leaf collimator 90 shown in FIG. 9, a gap is formed between the upstream portions 91 </ b> A of the leaves 91. In order to reduce the charged particle beam leaking from the gap, a receiving portion 91B that receives the charged particle beam leaking from the gap is formed. In order to sufficiently shield the charged particle beam, it is necessary to increase the thickness (size in the irradiation axis direction) of the receiving portion 91B. For example, when the thickness of the upstream portion 91A is set to the thickness T1, the receiving portion 91B needs to have the thickness T1 in order to sufficiently shield the charged particle beam. As a result, the total length L of the multi-leaf collimator 90 was approximately twice the thickness T1. Thereby, there existed a problem that the multileaf collimator 90 will be enlarged and the whole irradiation part will also be enlarged.

  On the other hand, by applying a high-density material to the entire leaf 91, it is conceivable to reduce the thickness of the leaf 91 while ensuring the shielding ability of charged particle beams. However, if a charged particle beam is shielded with a high-density material, many neutron beams are generated at that time, and this neutron beam processing becomes a problem. Therefore, it is difficult to reduce the size of the multi-leaf collimator 90 using a high-density material.

  On the other hand, in the charged particle beam therapy system 1 according to this embodiment, the multi-leaf collimator 24 includes a plurality of leaves 41 arranged in the Y direction orthogonal to the irradiation axis of the charged particle beam. Each leaf 41 connects the first surface 41a on the upstream side and the second surface 41b on the downstream side, and the first surface 41a and the second surface 41b that face each other in the irradiation axis direction in which the irradiation axis extends. Side surface 41c and side surface 41d. A gap GP is formed between the plurality of leaves 41 such that the side surface 41c and the side surface 41d face each other. Here, the side surfaces 41c and 41d of the leaf 41 are inclined with respect to the irradiation axis direction. Accordingly, the gap GP formed between the leaves 41 is also inclined with respect to the irradiation axis direction. For example, since the gap formed between the portions 91A in FIG. 9 extends straight in the irradiation axis direction, when the charged particle beam is irradiated, the gap passes through the gap without contacting the portion 91A. On the other hand, when the gap GP is inclined, even if the charged particle beam may pass through the gap GP at any position in the irradiation direction, it passes through the member of the leaf 41 at other positions. To do. Therefore, it is not necessary to separately provide a receiving part for receiving the charged particle beam leaking from the gap between the leaves 41. As a result, an increase in size of the multi-leaf collimator 24 can be suppressed.

  For example, as shown in FIG. 4, when the charged particle beam is irradiated onto the first surface 41Ca of the leaf 41C, the charged particle beam passes through the leaf 41C by the thickness T1 and passes through the gap GP by the thickness T2. To do. Since the thickness T2 is smaller than the thickness T1, the total length L of the leaf 41C is at least smaller than the total length L of the leaf 91 shown in FIG.

  The present invention is not limited to the above-described embodiment.

  For example, as another example, a multi-leaf collimator 50 as shown in FIG. 5 may be adopted. The multi-leaf collimator 50 shown in FIG. 5 has two types of shapes, leaves 51A and 51B. Leaves 51A and leaves 51B are alternately arranged in the Y direction. The leaf 51A has the same configuration as the leaf 41A shown in FIG. That is, the first surface 51Aa, the second surface 51Ab, the side surface 51Ac, and the side surface 51Ad of the leaf 51A are the first surface 41a, the second surface 41b, the side surface 41c, and the side surface of the leaf 41A. It has the same configuration as 41d.

  The leaf 51B has a cross-sectional shape of an isosceles triangle having a bottom surface on the upstream side. The leaf 51B includes an upstream end surface (first end portion) 51Ba and a downstream end portion (second end portion) 51Bb that face each other in the irradiation axis direction (Z direction), and the end surface 51Ba and the end portions 51Bb. The side surfaces 51Bc and 51Bd are connected to each other. The side surface 51Bc on the Y direction positive side is inclined to the Y direction negative side with respect to the irradiation axis direction (Z direction). The Y direction negative side surface 51Bd is inclined to the Y direction positive side with respect to the irradiation axis direction (Z direction).

  In the multi-leaf collimator 50 configured as shown in FIG. 5, a gap GP that is inclined to the Y direction positive side is formed between the side surface 51Ac of the leaf 51A and the side surface 51Bd of the leaf 51B that are adjacent to each other. A gap GP is formed between the side surface 51Ad of the leaf 51A and the side surface 51Bc of the leaf 51B.

  Also in this case, when the charged particle beam is applied to the end surface 51Ba of the leaf 51B, the charged particle beam passes through the leaf 51B by the thickness T1 and passes through the gap GP by the thickness T2. Since the thickness T2 is smaller than the thickness T1, the total length L of the leaf 51B is at least smaller than the total length L of the leaf 91 shown in FIG.

  In addition, as shown in FIGS. 4 and 5, the multi-leaf collimator as shown in FIGS. 6 and 7 may be employed instead of the multi-leaf collimator whose side surface is inclined. In the multi-leaf collimator according to FIGS. 6 and 7, each leaf has a plurality of types of shielding portions.

  Specifically, the plurality of leaves 61 of the multi-leaf collimator 60 shown in FIG. 6 each have a first shielding part 62 and a second shielding part 63. Further, the second shielding part 63 has at least a part arranged at a position different from the first shielding part 62 in the Y direction.

  The first shielding part 62 is made of a material that shields the charged particle beam R. The second shielding part 63 is made of a material that shields the charged particle beam R and has a higher density than the first shielding part 62. For example, the material of the first shielding part 62 may be boron-containing metal (such as boron steel), and the material of the second shielding part 63 may be high-density metal (such as tungsten, platinum, iridium).

  As shown in FIG. 6, in a cross-sectional view when viewed from the X direction, the first shielding portion 62 has a rectangular shape that extends straight along the irradiation axis direction (Z direction). In addition, a gap GP that extends straight in the irradiation axis direction (Z direction) is formed between the first shielding part 62 of one leaf 61 and the first shielding part 62 of another adjacent leaf 61. The

  The second shielding part 63 is disposed at the downstream end of the first shielding part 62. The second shielding part 63 has at least a portion arranged at a position different from the first shielding part 62 in the Y direction. Specifically, the second shielding portion 63 includes a first portion 63a connected to the downstream end portion of the first shielding portion 62, and a Y-direction negative side (even on the positive side) from the first portion 63a. And a second portion 63b projecting to (good). The second portion 63b is disposed at a position different from the first shielding portion 62 when viewed from the irradiation axis direction (Z direction), and is provided so as to close the gap GP.

  According to the multi-leaf collimator 60 as shown in FIG. 6, the leaf 61 has the first shielding part 62 and the second shielding part 63. Further, the second shielding part 63 has at least a second portion 63b that is arranged at a position different from the first shielding part 62 in the Y direction. Therefore, the second shielding part 63 can function as a receiving part that receives a charged particle beam leaking from a gap formed between the first shielding parts 62 of each leaf 61. Here, the second shielding part 63 is made of a material having a higher density than the first shielding part 62. That is, as a material of the first shielding part 62 that functions as a main part that shields charged particle beams, a member having a low density can be used to suppress generation of neutron beams. On the other hand, the thickness of the receiving part can be reduced by adopting a high-density member as the material of the second shielding part 63 that functions as a receiving part that receives the charged particle beam leaking from the gap. As a result, an increase in size of the multi-leaf collimator 60 can be suppressed. For example, while the thickness of the first shielding portion 62 is the thickness T1, the thickness of the second portion 63b of the second shielding portion 63 can be a thickness T2 smaller than the thickness T1. Therefore, the total length L of the leaf 61 can be made shorter than the total length L of the leaf 91 shown in FIG.

  The second shielding part 63 may be arranged on the downstream side in the irradiation axis direction. Thereby, the effect of self-shielding can be acquired.

  Moreover, you may employ | adopt the multileaf collimator 70 as shown in FIG. Each leaf 71 of the multi-leaf collimator 70 shown in FIG. 7 has an upper step portion 71A disposed on the upstream side and a lower step portion 71B disposed on the downstream side. A gap GP extending straight in the irradiation axis direction (Z direction) is formed between the upper step portion 71A of one leaf 71 and the upper step portion 71A of another adjacent leaf 71. The lower step portion 71B of one leaf 71 is disposed at a position shifted in the Y direction with respect to the upper step portion 71A. That is, the lower step portion 71B is arranged at a position different from the upper step portion 71A when viewed from the irradiation axis direction (Z direction), and is provided so as to close the gap GP. The upper stage portion 71A includes a first shielding portion 71Aa and a second shielding portion 71Ab made of a material having a higher density than the first shielding portion 71Aa. The second shielding part 71Ab is disposed downstream of the first shielding part 71Aa. The lower stage portion 71B includes a first shielding portion 71Ba and a second shielding portion 71Bb made of a material having a higher density than the first shielding portion 71Ba. 2nd shielding part 71Bb is arrange | positioned downstream from 1st shielding part 71Ba.

  In the configuration of FIG. 7, the upper shielding portion 71 </ b> Aa and the lower shielding portion 71 </ b> Bb are the “first shielding portion” and the “second shielding portion” in the claims. The first shielding part 71Ba on the lower stage side and the second shielding part 71Ab on the upper stage side are in a relation between the “first shielding part” and the “second shielding part” in the claims.

  Further, as shown in FIG. 8, a multi-leaf collimator 80 having side surfaces of the roofs inclined with respect to the irradiation axis direction and having different types of shielding portions may be employed. The multi-leaf collimator 80 has leaves 81A, 81B, and 81C. In a cross-sectional view as viewed from the X direction, the leaf 81A is an isosceles triangle having a bottom surface on the downstream side. The leaf 81B has a parallelogram shape that is inclined along the side surface 81Ac on the Y direction positive side of the leaf 81A. The leaf 81C has a parallelogram shape that is inclined along the side surface 81Ad on the Y direction negative side of the leaf 81A. The leaves 81 </ b> A, 81 </ b> B, and 81 </ b> C are configured such that the upstream portion is configured as the first shielding portion 82 and the downstream portion is configured as the second shielding portion 83. Thus, in each leaf 81A, 81B, 81C, the 2nd shielding part 83 has at least the part arrange | positioned in the position different from the 1st shielding part 82 in a Y direction.

  The second shielding part 63 may be arranged on the upstream side of the first shielding part 62.

  In the above-described embodiment, the leaves arranged in the Y direction are arranged so that the positions in the Z direction are constant. Instead of this, the leaf may be gradually arranged on the upstream side from the leaf arranged at the center position in the Y direction to the leaf arranged on both ends. Thereby, when it sees from a X direction, you may arrange | position so that a circular arc may be drawn by each leaf.

  Moreover, the structure of the irradiation part 8 is not limited to what is shown in FIG. 2, It can change suitably.

  Further, the irradiation method applied in the present invention is not limited to the wobbler method, and other irradiation methods (for example, a scanning method, a layered body method, etc.) may be adopted. Moreover, you may abbreviate | omit suitably each apparatus in the irradiation part 8 with an irradiation method.

  DESCRIPTION OF SYMBOLS 1 ... Charged particle beam therapy apparatus, 2 ... Accelerator, 8 ... Irradiation part, 24, 50, 60, 70, 80 ... Multi-leaf collimator, 41, 51, 61, 71, 81 ... Leaf, 62 ... 1st shielding part 63 ... second shielding part.

With reference to FIG. 2, the structure of the charged particle beam therapy apparatus which concerns on a wobbler method is demonstrated. As shown in FIG. 2, the charged particle beam therapy system 1 includes an accelerator 2, scanning electromagnets 3a and 3b, monitors 4a and 4b, a scatterer 5, a ridge filter 22, a multi-leaf collimator 24, a bolus 26, a patient collimator 27, and a degrader. 30 and a control device 7. The scanning electromagnets 3 a and 3 b, the monitors 4 a and 4 b, the scatterer 5, the ridge filter 22, the multileaf collimator 24, the bolus 26, the patient collimator 27, and the degrader 30 are provided inside the irradiation unit 8. The control device 7 is provided outside the irradiation unit 8.

Claims (3)

An accelerator that accelerates charged particles and emits charged particle beams;
An irradiation unit for irradiating the irradiated body with the charged particle beam;
A multi-leaf collimator provided in the irradiation unit and defining an irradiation range of the charged particle beam in accordance with the shape of the irradiated object,
The multi-leaf collimator has a plurality of leaves arranged in a first orthogonal direction orthogonal to the irradiation axis of the charged particle beam,
Each of the leaves includes an upstream first end and a downstream second end facing each other in the irradiation axis direction in which the irradiation axis extends, the first end, and the second end. And a side surface connecting each other,
The charged particle beam therapy apparatus, wherein the side surface is inclined with respect to the irradiation axis direction. An accelerator that accelerates charged particles and emits charged particle beams;
An irradiation unit for irradiating the irradiated body with the charged particle beam;
A multi-leaf collimator provided in the irradiation unit and defining an irradiation range of the charged particle beam in accordance with the shape of the irradiated object,
The multi-leaf collimator has a plurality of leaves arranged in a first orthogonal direction orthogonal to the irradiation axis of the charged particle beam,
Each said leaf
A first shielding portion made of a material that shields the charged particle beam;
A second shielding part that shields the charged particle beam and is made of a material having a density higher than that of the first shielding part, and
The said 2nd shielding part is a charged particle beam therapy apparatus which has at least the part arrange | positioned in a position different from a 1st shielding part in the said 1st orthogonal direction.   The charged particle beam therapy system according to claim 2, wherein the second shielding unit is disposed on a downstream side in an irradiation axis direction in which the irradiation axis extends.

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