JPH01206300A - Collimator for radiation irradiation device - Google Patents

Abstract

PURPOSE:To lessen leakage dose from gaps between leaf bodies of a collimator to the utmost by making many-leaf body structure of each collimator block for opening and closing in each direction of X and Y. CONSTITUTION:A first collimator block 12 for opening and closing in the X direction and a second collimator block 13 for opening and closing in the Y direction are divided into a plurality of leaf block pieces along radiation from a radiation source T to make many-leaf body structure. An irradiation hole of a fixed collimator block is like a quadrangular pyramid and maximum fixed irradiation field 20 can be obtained. In this case a part 21 for irradiating a sound part becomes small. Since the irradiation field 22 obtained by both the blocks 12, 13 is formed in the inside of the irradiation field 20 and both the blocks 12, 13 other than the irradiation field 22 are overlapped in the inside of the irradiation field 20, a shielding effect is large and the same shielding effect can be obtained in half thickness as compared with the conventional.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention mainly relates to a radiation irradiation device for treatment such as X-rays and electron beams, and is applicable to irregular irradiation fields (irradiation fields of arbitrary planar shapes). The present invention relates to a collimator suitable for irradiating a sufficient dose within the irradiation field and as small a dose as possible outside the irradiation area.

[Prior art]

The conventional radiation irradiation apparatus has a radiation irradiation head 4 as shown in FIG. 6 (front view) and FIG. 7 (side view of FIG. 6).
1. In the radiation irradiation head 41, the electron beam travels downward in the direction of the arrow in a vacuum chamber 42, exits into the atmosphere through a vacuum window (usually a thin plate made of aluminum) 43, and is exposed to a thin plate or X-ray that scatters the electron beam. A target plate 44 made of a thin heavy metal plate to be converted into is irradiated with radiation downward using the radiation source T. In reality, a filter is further used to uniformly distribute the radiation within the irradiation field, but it is omitted here.

In radiotherapy, it is desirable to irradiate only healthy areas with radiation, and not to anything else. Therefore,
The portion corresponding to the non-healthy portion is a fixed collimator block 45. Upper movable collimator block 46A, 46B
, are shielded by lower movable collimator blocks 47A and 47B. This shielding reduces the radiation dose to 1/1000th.
Since the law stipulates that the collimator block is made of heavy metal, it is necessary to make it sufficiently thick.For example, 75m5 of tungsten
The thickness shall be .

In FIGS. 6 and 7, the distance d from the radiation source T to the patient 48 is typically approximately 1000 millimeters (1 mm). Upper movable collimator block 48A, 4
When the thickness a of the lower movable collimator 6B and the thickness b of the lower movable collimators 47A and 47B increase, the radiation irradiation head 41 increases by that amount.
The distance C between the front surface of the patient 48 and the patient 48 becomes smaller,
Since it is necessary to attach accessories such as a two-booth for electron beams between this period, it is inconvenient to make the size small.Normally, the size is 450 millimeters (am) or more. For this purpose, the thickness a of the upper movable collimators 46A, 46B and the thickness b of the lower movable collimators 47A, 47B are required.
, which contradicts the purpose of improving the shielding effect mentioned above. A structure that satisfies both of these constraints is required. In addition, in FIG. 6 and FIG. 7, 49 is the affected area to which radiation is irradiated.

The fixed collimator block 45 is usually made of tungsten,
It is made of a heavy metal such as lead with a conical hole.

Determine the fixed maximum field. The irradiation field in practical use is upper and lower movable collimator blocks 46A, 46B, and 47A.

47B. These upper and lower movable collimator blocks 46A, 46B and 47A, 47B are supported by a mechanism that opens and closes so that their inner walls are in contact with the radiation from the radiation source T.

The fixed collimator block 45. The irradiation field obtained by the upper and lower movable collimator blocks 46A, 46B and 47A, 47B is as shown in FIG.
5, there is an undesirable healthy portion 56 that is not shielded from radiation. Furthermore, since there are portions 57a and 57b that are shielded by only one collimator of the upper and lower movable collimator blocks 46A, 46B and 47A, 47B, sufficient shielding effect can be obtained with only one collimator. , it needs to be of sufficient thickness. In this case, the portion 58 where both blocks overlap and are shielded becomes thicker than necessary.

Therefore, in order to prevent the unshielded portion 56 from occurring, as shown in FIG. 9, the lower movable collimator block 47A shown in FIGS. 6 and 7 is used.

4713 is divided into a plurality of leaf block pieces along the radiation from the radiation source T to form multi-leaf structures 53A and 53B. In this case, the upper and lower movable collimators 46A,
46B, 47A, 47B z-Z formed by
The irradiation field on a plane has a shape as shown in FIG.

[Problem to be solved by the invention]

However, as shown in FIG. 9, the lower movable collimator blocks 47A, 47B have a multi-lobed structure 53A.

53B, the portion 56 of the healthy part that is not shielded from radiation as shown in FIG. However, there was still a problem that the technology had not been improved.

Furthermore, this structure has the problem that radiation leaks from the gaps between the leaves of the multi-lobed collimator.

The present invention has been made to solve the above problems.

An object of the present invention is to provide a technology that can reduce the thickness of a collimator block to the necessary minimum in a collimator for a radiation irradiation device, increase the shielding thickness of healthy parts as much as possible, and reduce the size and weight. .

Another object of the present invention is to provide a technique that can minimize the amount of radiation leaked from gaps between the leaves of a multi-lobed collimator.

The above and other objects and novel features of the present invention will become clear from the description of the present specification and the accompanying drawings.

(Means for solving m!!I!) A brief overview of one typical invention disclosed in this application is as follows.

That is, in a collimator for a radiation irradiation device including a first collimator block that opens and closes in the X direction and a second collimator block that opens and closes in the Y direction, both the first collimator block and the second collimator block have a multilobal structure. It is characterized by the fact that

[Effect]

According to the above-mentioned means, since the first collimator block that opens and closes in the X direction and the second collimator block that opens and closes in the Y direction have a multi-lobed structure, the gaps between the respective lobes of the multi-lobed collimator are reduced. It is possible to reduce the amount of turbulent radiation from the body as much as possible, to minimize the thickness of the collimator block, to increase the shielding thickness of the healthy part as much as possible, and to achieve a reduction in size and weight.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In addition, in all the figures for explaining the embodiment, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

FIG. 5 is an explanatory diagram for explaining the schematic configuration of the radiation irradiation head of the radiation irradiation apparatus according to the present invention.

As shown in FIG. 5, the radiation irradiation head of the radiation irradiation apparatus according to the present invention includes a ``''-shaped housing 1. A bending magnet 3 for bending an electron beam running inside a vacuum pipe (usually a stainless steel pipe 2) is provided in this housing 1, and a vacuum window 4 of the vacuum chamber 2 is provided at the next stage. A target holder 6 housing an X-ray target plate (or a scattering plate for scattering electron beams) 5 is provided in front of the vacuum window 4. The target plate 5 is a thin heavy metal plate that converts the electron beam into X-rays. When irradiating a patient with an electron beam, a scattering plate is used to scatter the electron beam.

The electron beam, which is bent by the bending magnet 3 and exits into the atmosphere from the vacuum window 4, hits a target plate 5. Radiation is then irradiated downward using this target plate 5 as a radiation source.

A fixed collimator block 7 is provided below the target holder 6. The irradiation hole of this fixed collimator block 7 has a square heel shape, and its irradiation field has a quadrilateral shape. A flattening filter 8 is provided below this for flattening the X-rays. A transmission dosimeter 9 is provided below this flattening filter 8, and a wedge filter 10 is provided below it. An optical mirror 11 is provided below this, and the irradiation field is positioned using the light beam from the positioning light source 11A.

Upper movable collimator block 12 under optical mirror 11
(first movable collimator block) and a lower movable collimator block (second movable collimator block) 13 are provided. A shadow tray 15 that accommodates an X-ray shadow mask 14 is provided below the lower movable collimator block 13.

Next, an embodiment of the collimator for a radiation irradiation apparatus according to the present invention will be described.

FIG. 1 is a plan view showing an irradiation field on a Z-Z plane for explaining the schematic configuration of an embodiment of a collimator for a radiation irradiation apparatus according to the present invention.

As shown in FIG. 1, the collimator for a radiation irradiation apparatus of this embodiment has an upper movable collimator block 12 and a lower movable collimator block 13 shown in FIG. The body is divided into block pieces to create a multi-lobed structure.

As described above, the irradiation hole of the fixed collimator block 7 is not conical but square-heel shaped so that a fixed maximum irradiation field 20 can be obtained.

In this case, the portion 21 that irradiates the healthy area is small. Moreover, the irradiation field 22 obtained by the upper movable collimator block 12 and the lower movable collimator block 13 is formed inside the irradiation field 20.

Inside this irradiation field 20, the upper movable collimator block 12 and the lower movable collimator block 13 overlap in the area other than the irradiation field 22, so the shielding effect is large, and the shielding effect is great, compared to the conventional one shown in FIGS. 9 and 10. Similar shielding effects can be obtained with approximately half the thickness.

Next, drive control of the upper movable collimator block 12 and the lower movable collimator block 13 will be explained.

2 and 3 are front and side views, respectively, showing the schematic configuration of the multi-lobed drive unit of the collimator for the radiation irradiation device shown in FIG. 1, and FIG. 4 is a view seen from the direction of the arrow and the Y arrow shown in FIG. 3. FIG.

In FIGS. 2 to 4, the upper movable collimator block 12 is composed of a left multi-lobed body 12L and a right multi-lobed body 12R, each of which is composed of nine leaf block pieces. Similarly, the lower movable collimator block 13 is
It consists of a left multilobed body 13L and a right multilobed body 13R, each of which is composed of nine leaf block pieces. Each multilobed body 12L.

The inside (upper side in FIGS. 2 and 3) and outside (lower side in FIGS. 2 and 3) of 12R, 13L, and 13R are cylindrical surfaces with the radiation source point T as the central axis. Each of the multilobes 12L.

12R, 13L, and 13R are rotatably supported by a shaft 31 (FIG. 4) via a pair of guide rollers 30 that are in contact with the inner and outer sides of each roller. The shaft 31 is a support block 32
(33) is fixed. Each multilobed body 12L, 12R.

13L and 13R are supported by four guide rollers 30 and are rotatable about an axis passing through the radiation source T. In FIGS. 2 and 3, the left multilobed body 12L and the right multilobed body 13L show the collimator fully open position, and the right multilobed body 12R and the right multilobed body 13R show the collimator closed position to the center (axis of symmetry). ing.

34 is a small gear, and the upper movable collimator block 1
2 and each multi-lobed body 12 of the lower movable collimator block 13
It meshes with the teeth provided on the outside of L, 12R, 13L, and 13R. Here, each multilobed body 12L, 12R, 13
Approximately half of the outer sides of L and 13R are cylindrical, and the remaining half is a small gear 34. Details of the teeth of the pinion are omitted in the figure.

That is, in FIG. 4, a motor 36 is fixed to a support block 32 (33) and connected to a small gear 34 via a shaft 35. Although omitted in the figure, axis 3
If 5 is long, a bearing should be provided in the middle. This motor 36. The set of small gears 34 consists of each multiplane body 12L, 12
R, 13L, and 13R, and nine sets are provided in FIG. 4. As the motor 36 rotates, each multiplane body 12
L, 12R, 13L, and 13R rotate on a cylindrical surface with the radiation source T as the central axis.

The support blocks 32 (33) are an upper movable collimator block 12 and a lower movable collimator block 1, respectively.
It also acts as a block to restrict the lateral movement of 3.

Each of the multilobes 12L and 12R of the upper movable collimator block 12 and the lower movable collimator block 13.

Control for each month of 13L and 13R is performed by an automatic conformal irradiation device using a conventional computer. That is,
The motor 36 rotates each of the multilobes 12L, 12R, 13L, and 13R according to the rotation of the housing 1 of the radiation irradiation head.
An irregularly shaped irradiation field is formed under the control of , and rotational irradiation is performed.

As can be seen from the above explanation, according to this embodiment, compared to a conventional collimator, the same shielding effect can be achieved with approximately half the thickness (38 mm), so the collimator can be made smaller and lighter. Therefore, the entire radiation irradiation head 1 becomes lighter, and furthermore, when mounted on a rotating gantry, less balance weight is required, and the entire apparatus becomes smaller and lighter.

Also, the gaps between each leaf block piece of the upper movable collimator block 12 and the gaps between the leaf block pieces of the lower movable collimator block 13 are the gaps between each leaf block piece of the upper movable collimator block 12 and the gaps between the leaf block pieces of the lower movable collimator block 13, respectively. Since it is shielded by each leaf block piece,
The X-ray dose irradiated to the healthy part of the irradiated body can be reduced as much as possible.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

〔Effect of the invention〕

As described above, according to the present invention, the first collimator block opens and closes in the X direction, and the second collimator block opens and closes in the Y direction.
Since the collimator block and the collimator block have a multi-lobed structure, it is possible to reduce the amount of rippled X-rays from the gap between the multi-lobed collimators as much as possible, and to minimize the thickness of the collimator block to shield healthy parts. By making the thickness as thick as possible, it is possible to reduce the size and weight.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an irradiation field on a 2-2 plane for explaining the schematic configuration of an embodiment of a collimator for a radiation irradiation apparatus according to the present invention. 2 and 3 are front and side views respectively showing the schematic structure of the drive section of the multi-lobed body of the collimator for radiation irradiation equipment shown in FIG. 1, and FIG. 4 shows the X arrow and FIG. 5 is an explanatory diagram for explaining the schematic configuration of the radiation irradiation head of the radiation irradiation apparatus according to the present invention, and FIGS. 6 to 10 are views of the conventional FIG. 3 is a diagram for explaining the problem of the collimator for a radiation irradiation device according to the present invention. In the figure, 1... the housing of the radiation irradiation head, 2...
・Vacuum chamber, 3...Bending magnet, 4...
Vacuum window, 5... Target plate, F... Fixed collimator block, T... Radiation source, 12... Upper movable collimator block, 12L, 13L... Left side multiplane body,
12R, 13R...Right side multi-lobed body, 30...Guide roller, 31.35...Shaft. 32 (33)... Support block, 34... Small gear,
36...Motor.

Claims (1)

[Claims] (1) A first collimator block that opens and closes in the X direction, and a
A collimator for a radiation irradiation device comprising a second collimator block that opens and closes in the direction of the radiation irradiation device, wherein the first collimator block and the second collimator block both have a multi-lobed structure.