JPH0452598A - Medical radiation shielding chamber - Google Patents

Abstract

PURPOSE:To reduce the primary scattering rays incident on the door of an entrance and exit by shielding radiation by providing a plurality of partition walls having radiation shielding capacity to the wall surface opposed to the entrance and exit. CONSTITUTION:Partition walls 6A - 6C are provided on the wall surface of an entrance and exit. The walls A, B has the radiation shielding capacity to leak X-rays going toward a front wall from a high energy X-ray generator 21 and the wall 6C has the radiation shielding capacity to the primary scattering rays going toward the entrance and exit. Further, two small chamber structures having opening parts in the direction of the entrance and exit are constituted of the walls 6A, 6B. With respect to the primary scattering surface seen through from the point P of the door 1 of the entrance and exit, the planar expanse among the leak rays radially generated from the generator 21 becomes the range determined by a side wall 4 and the wall 6c when looked from the point P within the range determined by the side wall 4 and the walls 6A, 6B. The height direction thereof becomes the range of the opening height falling from a floor surface and determined by a wall 5. Therefore, the primary scattering surface becomes the range determined by the opening dimension of the wall 5 among the front wall of the wall 6B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a medical radiation shielding chamber, and more particularly to a medical radiation shielding chamber having a structure that minimizes primary scattered rays incident on an entrance/exit door.

[Conventional technology]

Conventionally, in this type of medical radiation shielding room, the maze and the primary line or leakage line of the radiation source pass through this opening and are irradiated to the ceiling @ wall and floor that can be seen from the entrance door, and the -order randomization here is While the rays (reflections) were directed toward the entrance/exit door, primary scattered rays were prevented from occurring from the ceiling and the upper part of the wall, which were shielded by the falling walls.

FIG. 3 is a diagram illustrating the principle of a medical radiation shielding room according to the prior art.

According to FIG. 3, the structure of the medical radiation shielding room according to the prior art is composed of an outer periphery formed by an entrance/exit door 1 and a partition wall 2, a sleeve wall 104 provided inside, and a labyrinth 111 and an irradiation chamber 12. .

A high-energy X-ray generator 21 serving as a radiation source irradiates primary X-rays toward a patient set up on a treatment table 22.

The iron plate 3 is arranged in a U-shape including the ceiling or in a square-shape including the area under the floor to prevent leakage of radiation from the high-energy X-ray generator 21. The leakage dose that reaches the outside from the radiation source, particularly the point P of the entrance/exit door 1, first reaches through the route 36, and is reduced by the wing wall 104. Next, the dose that is irradiated from the radiation source on the surface of the partition wall 102 facing the point P and is scattered and reaches the point P is transmitted to the route 35A.
and those reaching through the route 35B in the maze 111 are reduced by the structure of the wing walls 104 and the descending walls 5.

[Problem to be solved by the invention]

The above-mentioned shielding structure using a descending wall at the opening has a shielding effect of about 40% of the total scattering surface facing the normal entrance/exit door, but it cannot be said to be sufficient. In particular, in the case of high-energy X-ray generators, most of the energy bands used to be 10 MV or less, which did not pose much of a problem in shielding neutron beams, but in recent years, high-energy devices of 15 MV and 18 MV have become popular. With the rapid increase in neutron beams in this energy band, the above-mentioned shielding structure poses a problem of shielding load on the entrance/exit door, which poses many operational problems.

As an example, the order is often 30 mm of lead and 120 mm of polyethylene. For this reason, the external dimensions including the exterior iron plate are 2000 x 2000 x 18.
0mm, the weight reaches 5 tons, and the opening/closing time is on the order of minutes. Also, there is a sense of anxiety towards the patient.

[Means to solve the problem]

The medical radiation shielding room of the present invention is a medical radiation shielding room having a labyrinth structure, in which a partition wall having a radiation shielding ability is provided on a wall surface facing an entrance/exit, and an opening is formed in the wall surface of the partition wall in the direction of the entrance/exit. It is configured with a plurality of chamber structures.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a plan view showing the configuration of an embodiment of the present invention.

The basic structure of a medical radiation shielding room is an entrance/exit door 1 and a partition wall 2.
The outer periphery is formed by a labyrinth 11 and an irradiation chamber 12 with sleeve walls 4 provided inside.

The high-energy X-ray generator 21 aims at the patient who is set up on the treatment table 22 and uses a beam cone (-X
ray) (i.e., from the 360@ direction centered on the treatment table 22 in plane A, the primary
rays).

The iron plate 3 is arranged in a U-shape including the ceiling, and provides additional shielding against 360° irradiation of the beam used. In addition, this is an example where the floor surface is underground, and if there is a lower floor, 360
°It goes without saying that iron plates are required throughout. Instead of this iron plate, a convex wall made of concrete may be used on the inside or outside of the shielded room.

Unnecessary leakage lines are irradiated radially in other directions with respect to the above-mentioned use line cone within the legally defined range, and are shielded by the concrete thickness shown by the partition wall 2. In addition, the leakage rays that go down toward the entrance/exit door and pass through the opening formed at the lower part of the wall 5 are irradiated onto the wall surface etc. that can be seen from the entrance/exit door 1, and are reflected back to the entrance/exit via the primary scattered ray route, which will be described later. occurs.

Partition walls 6A to 6C provided on the wall facing the entrance/exit
is the shielding structure of the present invention, which significantly reduces leakage of primary scattered radiation incident on the entrance/exit door based on the principle described later.

FIGS. 2(a) and 2(b) are principle explanatory diagrams specifically showing the shielding effect of the shielding structure of the present invention.

FIG. 2(a) is a drawing of the primary scattering surface that can be seen from point P of the entrance/exit door 1. The primary scattering surface that can be seen here is within the irradiation range determined by the wing wall 4 and the partition walls 6A and 6B of the present invention in terms of planar spread among the leakage rays generated radially from the high-energy X-ray generator. The range defined by the wing wall 4 and the partition wall 6C of the present invention when viewed from a point,
That is, the range is indicated by diagonal lines.

Further, in the height direction, the opening height falls from the floor surface and is determined by the wall 5. Therefore, the -th scattering surface is the partition wall 6
Among the front walls of B, the floor surface indicated by diagonal lines, which is determined by the height of the opening of the descending wall 5, is targeted.

On the other hand, Fig. 2(b) shows an example when jumping from point Q of the entrance/exit door 1, in which there are no primary scattered rays from the front wall, but instead primary scattered rays from the side walls indicated by diagonal lines. line is expected.

The primary scattered rays incident on the entrance/exit door are proportional to the target primary scattering area and the scattering ratio there, based on the amount of leaked X-rays from the equipment side, and are the inverse of the respective distances represented by the -order scattering routes 31A and 31B. Proportional to the square. Among these, the scattering ratio depends on the incident angle from the source with respect to a line perpendicular to the target primary scattering surface and the reflection angle toward the entrance/exit door, and both values become larger as the angle becomes more acute.

In the example of this X-ray generator, the normal radiation source position is downward irradiation (directional utilization factor 1), and the height is approximately 1.3 m.
The angle of incidence of X-rays on the wall near the partition wall when viewed from the entrance/exit door 1 is an acute angle on the front wall or side wall (on the right side as seen from the entrance/exit door 1), and an obtuse angle on the floor. In the case of a neutron beam with an X-ray energy of 15 MV or more, the difference in scattering ratio between the front wall or side wall and the floor surface is usually around 4:1 depending on the above-mentioned angle.

Therefore, the primary scattering area of the target front wall should be made as small as possible. That is, the key points are how to avoid irradiation to the front wall and how to avoid primary scattering from the side walls. The partition walls 6A to 6C of the present invention are provided for this purpose, and are effectively about one-fifth of the primary scattering area shown in the conventional embodiment described later.

In this embodiment, there are three partition walls, but it is clear that no matter how many partition walls are provided, a corresponding effect can be obtained compared to the conventional structure in which the entire surface is a scattering surface. Furthermore, the protrusion size and width of the partition wall have a shielding effect corresponding to the reduction in the primary scattering area determined by drawing.

That is, the partition walls 6A and 6B of the present invention have high energy
The partition wall 6C has a radiation shielding ability against leaked X-rays toward the front wall from the ray generator 21, and the partition wall 6C has a radiation shielding ability against primary scattered rays toward the entrance/exit. The partition walls E3A and 6B constitute two small chambers each having an opening in the direction of the entrance and exit. In the shielding calculation at point P, in addition to the above primary scattered rays, the wing wall 4 from the leakage route 32
A leakage line is added according to the thickness.

Next, with regard to the conventional technique and the embodiment of the present invention, FIG. 3 shows a diagram of the primary scattering surface, which is the object of interest here, drawn by the conventional technique. As shown in FIG. 3, the primary scattering area of the front wall in question is about five times larger than that of this embodiment. However, in the case of the conventional technology, the distance between the primary scattered ray routes 35A and 35B is approximately 1.25 times longer than the distance between the primary scattered ray routes 31A and 31B according to the present embodiment, so the amount of attenuation is reduced. The ratio is 5X (1/1.25) 2X (1/1.25
) 2 gorges 2, and when comparing the present embodiments, the shielding effect of the present embodiment is about 1/2.

This example is an example in which the total length in the vertical direction of the figure is long as in the conventional technology, and therefore, in general, it is 1.25 times shorter than this example, and it can be expected to be around 1/3 in terms of transmittance. . By the way, this value of transmittance 1/3 is equivalent to 30-
The thickness corresponds to around 100m, which cannot be ignored since around 100m is normally used. In addition, a secondary effect of the present invention is that the flow line toward the irradiation chamber is shortened.

〔Effect of the invention〕

As explained above, the present invention provides a plurality of partition walls having radiation shielding ability on the wall facing the entrance/exit to prevent the generation of primary scattered radiation by the wall facing the entrance/exit,
Alternatively, even if the primary scattered rays are partially generated, by blocking the primary scattered rays toward the entrance/exit door, the primary scattered rays incident on the entrance/exit door are significantly reduced as a result.

For this reason, the entrance/exit door becomes light and thin, opening and closing speed is increased, and the patient's psychological anxiety is alleviated. It also has the effect of shortening the flow line within the shielded room.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the configuration of an embodiment of the present invention, FIGS. 2(a) and (b) are principle explanatory diagrams showing the shielding effect of the radiation shielding chamber of this embodiment, and FIG. FIG. 2 is a diagram illustrating the principle of a medical radiation shielding room according to technology. 1... Entrance/exit door, 2... Partition wall, 3... Iron plate, 4...
...Sleeve wall, 5...Downward wall, 6A-6C...Partition wall, 11...Maze, 12...Irradiation room, 21...High energy X-ray generator, 22...Treatment Stand, 31A・3
1B... -th order scattered ray route, 32... leakage ray route, 33A/33B... -th order scattered ray route, 34...
leakage line route.

Claims (1)

[Claims] In a medical radiation shielding room having a labyrinth structure, a plurality of partition walls having a radiation shielding ability are provided on a wall surface facing an entrance/exit, and a plurality of small chamber structures having openings on the wall surface of the partition wall in the direction of the entrance/exit are provided. A medical radiation shielding room characterized by comprising: