(19) Japan Patent Office (JP)
`
`(12) Unexamined Patent Application Publication (A)
`(11) Patent Application Publication No.
`P2002-210026A
`
`(51) Int. Cl.7
`A61N 5/10
`A61B 6/06
`G21K 1/04
`
`Identification Code
`
`300
`
`FI
`A61N 5/10
`A61B 6/06
`G21K 1/04
`
`K
`300
`D
`
`(43) Publication Date: 2002.7.30
`Theme Code (Reference)
`4C082
`4C093
`
`(10 Pages Total)
`
`(21) Filing No. P2001-11297
`
`(22) Filing Date 2001.1.19
`
`(72) Inventor
`
`Examination Request: Not Made No. of Claims: 4 OL
`(71) Applicant
`000003078
`Toshiba Corp.
`1-1-1 Shibaura, Minato-ku, Tokyo
`Tadashi Noguchi
`c/o Toshiba Corp. Nasu
`Operations
`1385-1 Higashiyama,
`Shimoishigami, Ōtawara-shi,
`Tochigi-ken
`100083161
`Hideaki Togawa, Patent Attorney
`4C082 AC09 AE01 AG22 AG23
`AG24 AG27
`4C093 AA21 AA25 CA32 EA12
`
`(74) Agent
`
`F Terms (Ref.)
`
`(54) [Title] Radiotherapy Apparatus and Diaphragm Apparatus for Setting Radiation Field
`
`[Abstract]
`[Problem] To provide a radiotherapy apparatus
`whose diaphragm apparatus is reduced in size.
`[Solution] In a radiotherapy apparatus that, in
`order to set a radiation range of radiation
`radiated from a radiation source, disposes a
`plurality of diaphragms so these are overlapped
`in a radiation direction of the radiation, each
`diaphragm being configured by a pair of blocks
`that move toward and away from each other, a
`first diaphragm is configured by supports 60A
`and 60B that are driven in a direction
`perpendicular to a radiation axis I of the
`radiation, which is radiated from a radiation
`source S, and substantially semicylindrical
`semicylinders 62A and 62B that are supported
`on opposing-face sides of these supports so as to
`rotate around horizontal axes 63A and 63B
`orthogonal to the movement direction of the
`supports and so cut faces 62a and 62b thereof
`are exposed. This enables a length of the
`diaphragm apparatus to be shortened.
`
`ViewRay Exhibit 1014
`Page 1 of 25
`
`

`

`[Claims]
`[Claim 1] A radiotherapy apparatus, comprising: a first diaphragm having a pair of
`supports that are driven so as to move toward and away from each other in a direction
`perpendicular to a radiation axis of radiation radiated from a radiation source and
`substantially semicylindrical semicylinders that are supported on opposing-face sides of
`these supports so as to rotate around horizontal axes orthogonal to the movement
`direction of the supports and so flat faces thereof are exposed; and
`a second diaphragm that is disposed overlapping this first diaphragm in the radiation
`direction of the radiation, is configured by a pair of blocks disposed in a direction
`orthogonal to the movement direction of the supports of the first diaphragm, and closely
`arranges a plurality of leaves that move toward and away from each other concentrically to
`a circle whose center is the radiation source.
`[Claim 2] The radiotherapy apparatus of claim 1, wherein as the supports move toward and
`away from each other, the flat faces of the semicylinders had by the first diaphragm rotate
`so as to be parallel to a radiation flux radiated from the radiation source.
`[Claim 3] The radiotherapy apparatus of any one among claim 1 and claim 2, wherein the
`second diaphragm is disposed in two stages with a gap therebetween in the radiation
`direction of the radiation, contact faces of adjacent leaves of the diaphragm positioned in
`the upper stage and contact faces of adjacent leaves of the diaphragm positioned in the
`lower stage are disposed in shifted positions so these do not overlap in a direction wherein
`a radiation flux spreads, each leaf of the diaphragm positioned in the upper stage is formed
`with teeth for driving on a curved inner end portion thereof, each leaf of the diaphragm
`positioned in the lower stage is formed with teeth for driving on a curved outer end portion
`thereof, and these leaves are moved toward and away from each other by drive forces of
`gears meshing with the teeth.
`[Claim 4] A diaphragm apparatus for setting a radiation range of radiation radiated from a
`radiation source, comprising:
`a pair of supports that are driven so as to move toward and away from each other in a
`direction perpendicular to a radiation axis of the radiation radiated from the radiation
`source;
`substantially semicylindrical semicylinders that are supported on opposing-face sides of
`these supports so as to rotate around horizontal axes orthogonal to the movement
`direction of the supports and so flat faces thereof are exposed; and
`a means of rotating these semicylinders so, as the supports move toward and away from
`each other, the flat faces thereof are parallel to a radiation flux.
`[Description]
`[0001]
`[Field] The present invention relates to a radiotherapy apparatus used to treat a disease
`such as a malignant tumor and particularly relates to a diaphragm apparatus that is
`provided in this radiotherapy apparatus and sets a radiation field.
`[0002]
`[Background] FIG. 9 is an external view illustrating a conventionally used radiotherapy
`apparatus. First, a schematic configuration of a radiotherapy apparatus is described with
`reference to this diagram. A radiotherapy apparatus is largely configured from a radiation
`apparatus 10 that radiates radiation from a radiation source to a subject and a treatment
`table 20, whereon the subject rests, that positions a radiation site. The radiation device 10
`
`ViewRay Exhibit 1014
`Page 2 of 25
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`

`

`has a fixed frame 11 installed to the floor, a rotating frame 12 rotatably supported by the
`fixed frame 11, a radiation head 13 provided on a tip portion extending from one end of the
`rotating frame 12, and a diaphragm apparatus 14 incorporated into the radiation head 13.
`Moreover, the rotating frame 12 can rotate substantially 360 degrees around a horizontal
`rotation center axis H of the fixed frame 11, and the diaphragm apparatus 14 can also
`rotate around a radiation axis I. Note that an intersection between the rotation center axis
`H of the rotating frame 12 and the radiation axis I is referred to as an isocenter IC.
`Moreover, the rotating frame 12 is configured to be able perform not only fixed radiation
`but also rotation corresponding to other various radiation aspects such as rotational
`radiation, pendular radiation, and intermittent radiation. Meanwhile, the treatment table
`20 is disposed on the floor so as to be able to rotate over a predetermined angular range
`along an arc centered around the isocenter IC. Moreover, a top plate 21 whereon the
`subject rests is provided in an upper portion of the treatment table 20. This top plate 21
`can be moved in a front-rear direction and a left-right direction and raised and lowered in
`an up-down direction by a moving mechanism that is not illustrated.
`[0003] Now, when conducting radiotherapy, it is necessary to focus radiation to only a
`treatment site, such as a malignant tumor, so as to not damage normal tissue. As such, to
`prevent radiation to normal tissue as much as possible, the diaphragm apparatus 14, which
`is for regulating a radiation field, is incorporated into the radiation head 13 so as to be able
`to rotate around the radiation axis I. One example of this diaphragm apparatus 14 is
`illustrated in FIG. 10 to FIG. 12. Next, these diagrams are referred to give an overview of the
`diaphragm apparatus 14. Note that FIG. 10 and FIG. 11 are explanatory views of the
`diaphragm apparatus 14 as seen from mutually orthogonal directions and FIG. 12 is an
`explanatory view of a second diaphragm. The diaphragm apparatus 14 is normally
`provided with two types of diaphragms 30, 40, made of a heavy metal such as tungsten, so
`these overlap in a direction of radiation from a radiation source S. Moreover, each
`diaphragm 30, 40 is divided into a pair of diaphragms as respectively indicated by the
`reference signs 30A and 30B, and 40A and 40B in FIG. 10 and FIG. 11. First diaphragms 30A
`and 30B, which are provided on a side closer to the radiation source S, are configured as
`single bodies. Moreover, they are driven by drive apparatuses 31A and 31B so as to move
`in an arrow X direction—concentrically to a circle whose center is the radiation source S—
`toward and away from each other relative to the radiation axis I.
`[0004] Meanwhile, as illustrated in FIG. 11, second diaphragms 40A and 40B, which are
`provided on a side farther from the radiation source S, are provided so as to move,
`concentrically to a circle whose center is the radiation source S, in a direction orthogonal to
`the First diaphragms 30A and 30B—that is, in an arrow Y direction—toward and away
`from each other relative to the radiation axis I. Moreover, as schematically illustrated in
`FIG. 10 and illustrated in detail as a plan view in FIG. 12, the second diaphragms 40A and
`40B are configured as assemblies of a plurality of closely adjacent leaves 41A1 to 41An and
`41B1 to 41Bn and are multi-segmented apparatuses suited to forming a radiation field of
`an irregular shape. As such, the leaves 41A1 to 41An and 41B1 to 41Bn of the second
`diaphragms 40A and 40B are respectively driven by drive apparatuses 42A1 to 42An, 42B1
`to 42Bn so as to be able to move independently. The leaves 41A1 to 41An and 41B1 to
`41Bn are of course formed of a heavy metal. A combination of moving these first
`diaphragms 30A and 30B toward and away from each other in the X direction and moving
`the leaves 41A1 to 41An and 41B1 to 41Bn of the second diaphragms 40A and 40B so as to
`
`ViewRay Exhibit 1014
`Page 3 of 25
`
`

`

`individually move toward and away from each other in the Y direction forms a radiation
`field U of an irregular shape that approximates a shape T of the treatment site as illustrated
`in FIG. 13.
`[0005] Now, as above, multi-segmented apparatuses that form a radiation field of an
`irregular shape such as the second diaphragms 40A and 40B are configured as assemblies
`of a plurality of closely adjacent leaves 41A1 to 41An and 41B1 to 41Bn. However, when
`numbers of leaves 41A1 to 41An and 41B1 to 41Bn segmenting the diaphragms 40A and
`40B are small (that is, when a leaf width is large), it is difficult to cause the shape of the
`radiation field U to approximate the shape T of the treatment site, leading to radiation of
`even normal tissue. As such, it is desirable for the multi-segmented apparatuses to divide
`the second diaphragms 40A and 40B into as many leaves 41A1 to 41An and 41B1 to 41Bn
`as possible. However, for the leaves 41A1 to 41An and 41B1 to 41Bn to form an irregular
`radiation field, each must be able to move independently, and individual drive means for
`such must also be provided. Moreover, to prevent radiation leakage from between the
`adjacent leaves 41A1 to 41An and 41B1 to 41Bn, a gap between each leaf 41A1 to 41An and
`41B1 to 41Bn must be made as small as possible—for example, about 0.05 to 0.1 mm.
`[0006] However, the more the second diaphragms 40A and 40B are divided, the narrower
`the width of the leaves 41A1 to 41An and 41B1 to 41Bn becomes; because these are
`normally formed to a thickness of about 2 to 3 mm, this creates manufacturing problems
`such as warping arising and making it difficult to obtain desired precision. Moreover,
`difficulties also accompany disposing a support mechanism, a drive mechanism, a detection
`mechanism for detecting a movement amount, and the like for individually moving a large
`number of closely adjacent leaves 41A1 to 41An and 41B1 to 41Bn. JP H7-67491 B2
`discloses a multi-leaf collimator as one idea for solving such problems. FIG. 14 illustrates
`the multi-leaf collimator disclosed in JP H7-67491 B2; (a) is a sectional side view, and (b) is
`a plan view. As illustrated in this diagram, the multi-leaf collimator disposes a first
`collimator 51—disposed so a pair of leaf groups 51A, 51B made of a plurality of leaves 510
`of a quadrangular prism shape oppose each other across a radiation direction of a beam
`52—and a second collimator 53—likewise disposed so a pair of leaf groups 53A and 53B
`made of a plurality of leaves 530 of a quadrangular prism shape oppose each other across
`the radiation direction of the beam 52—in two stages in the radiation direction of the beam
`52. Moreover, width directions of the respective leaves 510 and 530 of the collimators 51
`and 53 are made to partially overlap in the radiation direction of the beam 52.
`[0007]
`[Technical Problem] However, because the leaves 510, 530 of the multi-leaf collimator
`disclosed in JP H7-67491 B2 illustrated in FIG. 14 are formed in a quadrangular prism
`shape, end faces and side faces thereof do not match the radiation direction of the beam 52,
`which exhibits a conical shape. As such, there is a disadvantage of a large penumbra at the
`radiation site. Moreover, because the conventional first diaphragms 30A and 30B
`illustrated in FIG. 10, FIG. 11 move in the arrow X direction concentrically to a circle whose
`center is the radiation source S, a length dimension of the diaphragm apparatus 14
`increases in correspondence with this movement range. However, when the length of the
`diaphragm apparatus 14 increases, a tip of the diaphragm apparatus 14 accordingly moves
`closer to a top-plate 21 side. This is not preferable because it creates a sense of oppressive
`proximity for the subject resting on the top plate 21. A difficulty also arises of various
`
`ViewRay Exhibit 1014
`Page 4 of 25
`
`

`

`auxiliary tools installed to the tip of the diaphragm apparatus 14 according to treatment
`content becoming limited. The present invention is made to solve these problems.
`[0008]
`[Solution to Problem] To solve the above problems, the invention of claim 1 is a
`radiotherapy apparatus equipped with a first diaphragm having a pair of supports that are
`driven so as to move toward and away from each other in a direction perpendicular to a
`radiation axis of radiation radiated from a radiation source and substantially
`semicylindrical semicylinders that are supported on opposing-face sides of these supports
`so as to rotate around horizontal axes orthogonal to the movement direction of the
`supports and so flat faces thereof are exposed and a second diaphragm that is disposed
`overlapping this first diaphragm in the radiation direction of the radiation, is configured by
`a pair of blocks disposed in a direction orthogonal to the movement direction of the
`supports of the first diaphragm, and closely arranges a plurality of leaves that move toward
`and away from each other concentrically to a circle whose center is the radiation source.
`This can shorten a length dimension of a diaphragm apparatus, mitigate a sense of
`oppressive proximity for a subject during treatment, and increase freedom in various
`auxiliary tools installed to a tip of the diaphragm apparatus.
`[0009] Furthermore, the invention of claim 2 is the radiotherapy apparatus of claim 1,
`wherein as the supports move toward and away from each other, the flat faces of the
`semicylinders had by the first diaphragm rotate so as to be parallel to a radiation flux
`radiated from the radiation source. This enables end faces of the diaphragm to be
`continually parallel to the radiation flux according to an operation of setting a radiation
`field and enables conducting radiotherapy without generating a penumbra. Moreover, the
`invention of claim 3 is the radiotherapy apparatus of any one among claim 1 and claim 2,
`wherein the second diaphragm is disposed in two stages with a gap therebetween in the
`radiation direction of the radiation, contact faces of adjacent leaves of the diaphragm
`positioned in the upper stage and contact faces of adjacent leaves of the diaphragm
`positioned in the lower stage are disposed in shifted positions so these do not overlap in a
`direction wherein a radiation flux spreads, each leaf of the diaphragm positioned in the
`upper stage is formed with teeth for driving on a curved inner end portion thereof, each
`leaf of the diaphragm positioned in the lower stage is formed with teeth for driving on a
`curved outer end portion thereof, and these leaves are moved toward and away from each
`other by drive forces of gears meshing with the teeth. This enables each leaf to be driven
`while keeping the gap between the diaphragms overlappingly disposed in two stages small,
`facilitates leaf manufacturing, and enables a radiation field approximating a shape of a
`treatment site to be formed with precision without generating a penumbra.
`[0010] Furthermore, the invention of claim 4 is a diaphragm apparatus for setting a
`radiation range of radiation radiated from a radiation source, equipped with a pair of
`supports that are driven so as to move toward and away from each other in a direction
`perpendicular to a radiation axis of the radiation radiated from the radiation source,
`substantially semicylindrical semicylinders that are supported on opposing-face sides of
`these supports so as to rotate around horizontal axes orthogonal to the movement
`direction of the supports and so flat faces thereof are exposed, and a means of rotating
`these semicylinders so, as the supports move toward and away from each other, the flat
`faces thereof are parallel to a radiation flux. This enables end faces of the diaphragm to be
`continuously parallel to the radiation flux according to an operation of setting a radiation
`
`ViewRay Exhibit 1014
`Page 5 of 25
`
`

`

`field. As such, a diaphragm apparatus that does not generate a penumbra, is easily
`operated, and has a small length dimension is provided.
`[0011]
`[Description of Embodiments] One embodiment of a diaphragm apparatus of a
`radiotherapy apparatus of the present invention is described in detail below with reference
`to FIG. 1 to FIG. 8. Note that in these diagrams, portions identical to FIG. 9 to FIG. 14 are
`illustrated labeled with the same reference signs. FIG. 1 and FIG. 2 illustrate an overall
`image of a diaphragm apparatus 14′ of the radiotherapy apparatus of the present invention
`and respectively correspond to FIG. 10 and FIG. 11 illustrating the conventional diaphragm
`apparatus. Moreover, like the diaphragm apparatus 14 described using FIG. 9, this
`diaphragm apparatus 14′ is incorporated into a radiation head 13 of a rotating frame 12 so
`as to be able to rotate around a radiation axis I. The diaphragm apparatus 14′ is configured
`from three layers of diaphragms 60, 70, and 80, each formed of a heavy metal such as
`tungsten, provided so as to overlap in a radiation-axis I direction from a radiation source S.
`As respectively indicated by reference signs A and B, these diaphragms 60, 70, and 80 are
`divided into pairs that move toward and away from each other relative to the radiation axis
`I.
`[0012] First, first diaphragms 60A and 60B provided on a side closest to the radiation
`source S are described. The first diaphragms 60A and 60B are driven by drive apparatuses
`61A and 61B so as to move toward and away from each other in an arrow X direction that
`is perpendicular to the radiation axis I. Moreover, substantially semicylindrical diaphragms
`62A and 62B are respectively rotatably fitted on opposing-face sides of the first
`diaphragms 60A and 60B with flat cut faces 62a and 62b thereof facing outward. Moreover,
`the substantially semicylindrical diaphragms 62A and 62B have axes 63A and 63B
`orthogonal to the movement direction of the diaphragms 60A and 60B that is orthogonal to
`the radiation axis I. These axes 63A and 63B are positioned in what would be cylinder
`centers if the diaphragms 62A and 62B were cylindrical. As such, these substantially
`semicylindrical diaphragms 62A and 62B are made to be able to rotate with these cylinder
`center axes 63A and 63B as the axes. Moreover, the substantially semicylindrical
`diaphragms 62A and 62B are combined to a linking mechanism illustrated in FIG. 3 so the
`cut faces 62a and 62b thereof continuously match a direction of a radiation flux Ia from the
`radiation source S as the diaphragms 60A and 60B move toward and way from each other.
`[0013] Next, the mechanism for rotating the substantially semicylindrical diaphragms 62A
`and 62B fitted to the first diaphragms 60A and 60B is described with reference to FIG. 3.
`Note that FIG. 3 illustrates details of the first diaphragms 60A and 60B, (a) being a plan
`view and (b) being a side view. That is, the diaphragms 60A and 60B are supported on an
`inner side of a frame 60a so both sides of the diaphragms can slide. Moreover, the
`diaphragms 60A and 60B are fitted with the substantially semicylindrical diaphragms 62A
`and 62B that can rotate around the axes 63A and 63B. On an outer side of the frame 60a,
`linking guides 60b for the substantially semicylindrical diaphragms 62A and 62B are
`respectively provided at a predetermined incline, these guides 60b having one end of a
`linking arm 60c slidably engaged therewith. Moreover, another end of this arm 60c is
`rotatably joined to another end of a second arm 60d whose one end is rotatably fixed to
`side faces of the substantially semicylindrical diaphragms 62A and 62B near an outer
`periphery along the cut faces 62a and 62b. This is detailed below, but a ball screw 61b of
`the drive apparatuses 61A and 61B is connected to the diaphragms 60A and 60B, and the
`
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`Page 6 of 25
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`

`

`diaphragms 60A and 60B move toward and away from each other by this ball screw 61b
`rotating. For example, FIG. 3 illustrates a state wherein the diaphragm 60B is in a closed
`position and the cut face 62b of the substantially semicylindrical diaphragm 62B is in an
`orientation aligned with the radiation axis I from the radiation source S. When the
`diaphragm 60B is pulled to the right from this state in FIG. 3, the arm 60c engaged with the
`guides 60b moves while being pulled upward along the guides 60b. This causes a force in a
`pushing direction to act on a second-arm 60d joining-end side, rotating the substantially
`semicylindrical diaphragm 62B in a counterclockwise direction around the axis 63B. Note
`that when the diaphragm 60B is pushed to the left, the substantially semicylindrical
`diaphragm 62B rotates clockwise.
`[0014] Meanwhile, the diaphragm 60A illustrated in FIG. 3 is illustrated in a state of being
`in an open position. When the diaphragm 60A is pushed to the right from this state, the arm
`60c engaged with the guides 60b moves while being pulled downward along the guides
`60b. This causes a force in a pulling direction to act on a second-arm 60d joining-end side,
`rotating the substantially semicylindrical diaphragm 62A in a counterclockwise direction
`around the axis 63A. Note that when the diaphragm 60A is pulled to the left, the
`substantially semicylindrical diaphragm 62A rotates clockwise. In this manner, when the
`diaphragms 60A and 60B move, the cut faces 62a and 62b of the substantially
`semicylindrical diaphragms 62A and 62B incline according to the direction of this
`movement; the linking mechanism is set so these inclination angles continuously match the
`radiation flux Ia from the radiation source S. Of course, when the cut faces 62a and 62b of
`the substantially semicylindrical diaphragms 62A and 62B contact each other, these faces
`match the radiation axis I.
`[0015] Next, the drive apparatuses that drive the first diaphragm 60 above are described.
`FIG. 4 is a perspective view illustrating an overview of one of the divided diaphragms of the
`first diaphragm 60—the diaphragm 60B—and the drive apparatus 61B thereof. Note that
`the other divided diaphragm 60A and the drive apparatus 61A thereof are configured
`similarly. That is, the first diaphragm 60B is connected to a tip of the ball screw 61b, and
`the ball screw 61b is joined to a motor 61c that is a drive source via a drive-force
`transmission mechanism 61d such as a worm gear. Moreover, a potentiometer 61e, an
`encoder 61f, and the like for detecting a rotation amount are connected to this drive-force
`transmission mechanism 61d. Therefore, when the motor 61c is driven, the ball screw 61b
`rotates via the drive-force transmission mechanism 61d and the first diaphragm 60B
`moves in a horizontal direction. That is, it moves toward and away from the radiation axis I.
`At this time, the motor 61c is controlled by a control means that is not illustrated based on
`information from the potentiometer 61e, the encoder 61f, and the like, and the first
`diaphragm 60B is moved to a desired position according to the rotation amount thereof.
`Note that the substantially semicylindrical diaphragm 62B that rotates according to the
`movement of the diaphragm 60B is as described using FIG. 3.
`[0016] The first diaphragms 60A and 60B configured in this manner move in a direction
`perpendicular to the radiation axis I from the radiation source S. As such, a length
`dimension of the diaphragm apparatus 14′ can be shortened. This enables the mitigation of
`a sense of oppressive proximity for a subject and increased freedom in various auxiliary
`tools installed to a tip of the diaphragm apparatus 14′. Moreover, because the cut faces 62a
`and 62b of the substantially semicylindrical diaphragms 62A and 62B provided on the
`opposing end faces of the diaphragms 60A and 60B move so as to be continuously parallel
`
`ViewRay Exhibit 1014
`Page 7 of 25
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`

`to the radiation flux Ia as the diaphragms 60A and 60B move, no radiation penumbra arises
`at a treatment site, and a desired dose of radiation can be radiated to the treatment site.
`[0017] Next, second and third diaphragms 70A, 70B, 80A, and 80B provided on a side
`farther from the radiation source S are described. The second and third diaphragms 70A,
`70B, 80A, and 80B are multi-segmented diaphragm apparatuses. As illustrated in FIG. 1 and
`FIG. 2, these are provided in two stages with a small gap therebetween and are respectively
`provided so as to move toward and away from each other in a direction orthogonal to the
`first diaphragms 60A and 60B—that is, in an arrow Y direction, concentrically to a circle
`whose center is the radiation source S. Respective end faces of the diaphragms 70A and
`70B, and 80A and 80B that oppose each other across the radiation axis I are supported so
`as to continuously match the direction of the radiation flux Ia from the radiation source S.
`Like the diaphragm illustrated in FIG. 10 to FIG. 12, these second diaphragms 70A and 70B
`and third diaphragms 80A and 80B are respectively configured as assemblies of a plurality
`of closely adjacent leaves 71A1 to 71An, 71B1 to 71Bn, 81A1 to 81An, and 81B1 to 81Bn.
`Moreover, each leaf 71A1 to 71An, 71B1 to 71Bn, 81A1 to 81An, and 81B1 to 81Bn can be
`moved individually by respectively provided drive apparatuses 72A1 to 72An, 72B1 to
`72Bn, 82A1 to 82An, and 82B1 to 82Bn.
`[0018] Furthermore, each leaf 71A1 to 71An and 71B1 to 71Bn of the second diaphragms
`70A and 70B and each leaf 81A1 to 81An and 81B1 to 81Bn of the third diaphragms 80A
`and 80B has a flat face formed in a fan shape that converges toward the radiation source S
`and has a side face formed to be flat or wedge shaped. Note that end faces of the leaves
`71A1 to 71An and 71B1 to 71Bn of the second diaphragms 70A and 70B and the leaves
`81A1 to 81An and 81B1 to 81Bn of the third diaphragms 80A and 80B that oppose each
`other make close contact when closest to each other and match the direction of the
`radiation flux Ia when separated from each other. Moreover, as illustrated in FIG. 6, width
`directions of the leaves 71A1 to 71An and 71B1 to 71Bn of the second diaphragms 70A and
`70B and the leaves 81A1 to 81An and 81B1 to 81Bn of the third diaphragms 80A and 80B
`are provided so as to partially overlap in the direction of the radiation flux Ia. That is, leaf
`positions are mutually shifted so contact faces of the adjacent leaves 71A1 to 71An and
`71B1 to 71Bn of the second diaphragms 70A and 70B positioned in the upper stage and
`contact faces of the adjacent leaves 81A1 to 81An and 81B1 to 81Bn of the third
`diaphragms 80A and 80B positioned in the lower stage do not match in a direction wherein
`the radiation flux Ia spreads.
`[0019] Next, these leaves 71A1 to 71An and 71B1 to 71Bn and 81A1 to 81An and 81B1 to
`81Bn of the second and third diaphragms 70 and 80 and the drive apparatuses 72 and 82
`driving these are described with reference to FIG. 5. Note that as above, the second and
`third divided diaphragms 70A and 70B, and 80A and 80B each share a configuration of
`having a plurality of leaves and each leaf being provided with a drive apparatus to be made
`individually movable. As such, FIG. 5 illustrates in a perspective view an overview of one
`leaf 81 of the third diaphragm 80 and the drive apparatus 82 thereof as an example. The
`leaf 81 has the flat face formed in the fan shape that converges toward the radiation source
`S and the side face formed to be flat or wedge shaped, and teeth are cut in a curved outer
`end portion 81a. Moreover, a drive gear 82a meshes with the teeth of this leaf 81. The drive
`gear 82a is fixed to a tip of a shaft 82b, and the shaft 82b is joined to a motor 82c that is a
`drive source via a drive-force transmission mechanism 82d such as a worm gear. Note that
`a potentiometer 82e, an encoder 82f, and the like are also disposed to detect a rotation
`
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`Page 8 of 25
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`

`amount, and based on information therefrom, the motor 82c is controlled by a control
`means that is not illustrated. This sets the leaf 81 in a desired position to form a radiation
`field of an irregular shape. Therefore, when the motor 81c is driven, the shaft 81b rotates
`via the drive-force transmission mechanism 81d and the leaves 81 move toward or away
`from each other in the Y direction concentrically to a circle whose center is the radiation
`source S. At this time, the motor 81c is controlled by the control means that is not
`illustrated based on the information from the potentiometer 81e, the encoder 81f, and the
`like, and the first leaves 81 are moved to desired positions according to the rotation
`amount thereof.
`[0020] Note that it is described that the leaf 81 of the third diaphragm 80 has teeth cut into
`the curved outer end portion 81a and that these teeth mesh with the drive gear 82a.
`However, when teeth are cut into a curved outer end portion 71a of a leaf 71 of the second
`diaphragm 70 disposed above and overlapping the third diaphragm 80 (that is, on a first-
`diaphragm 60 side) with a small gap therebetween and these teeth are meshed with a drive
`gear 72a, the gap between the second diaphragm 70 and the third diaphragm 80 increases,
`creating problems of radiation leakage and a longer length dimension of the diaphragm
`apparatus 14′. As such, teeth are cut into a curved inner end portion 71b of the leaf 71 of
`the second diaphragm 70 (in terms of the leaf 81, a side labeled as 81b), and these teeth are
`meshed with the drive gear 72a (see FIG. 2). This can decrease the gap between the second
`diaphragm 70 and the third diaphragm 80, eliminate a risk of radiation leakage from the
`gap, and reduce a size of the diaphragm apparatus 14′. A combination of moving the first
`diaphragms 60A and 60B configured as above toward and away from each other in the X
`direction perpendicular to the radiation axis I and moving the leaves 71A1 to 71An and
`71B1 to 71Bn of the second diaphragms 70A and 70B and the leaves 81A1 to 81An and
`81B1 to 81Bn of the third diaphragms 80A and 80B so as to individually move toward and
`away from each other in the Y direction concentrically to a circle whose center is the
`radiation source S forms with precision a radiation field U of an irregular shape that
`approximates a shape T of the treatment site illustrated in FIG. 6.
`[0021] Now, as a means of movably supporting each adjacent leaf in the diaphragms 70A
`and 70B, and 80A and 80B, the means previously filed by the present applicant as JP H11-
`239997 can be adopted. As such, this means is described next. FIG. 7 is a plan view
`illustrating two adjacent leaves 81, 81′ in the diaphragm 80 and represents the two leaves
`81, 81′ moving relative to each other in an arc in the arrow Y direction. Note that portions
`in FIG. 7 identical to FIG. 5 are labeled with the same reference signs and description of
`these portions is omitted. This is also the case for the diaphragm 70. A plurality of V-shaped
`or U-shaped grooves 81c, 81c′ are bored into both faces of these leaves 81, 81′. Moreover, a
`plurality of ball bearings 83 and a plurality of retainers 84 are alternately stored in each
`groove 81c formed in one face of the leaf 81. Note that the retainers 84 are for preventing
`the ball bearings 83 from contacting each other and locking up. Moreover, stoppers 85, 85′
`are respectively provided at both end