JPS59230199A - Collimating plate for neutron ray - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a collimating plate for neutron beams that is lightweight and has improved shielding performance for radioactivity generated by neutron beams and neutron beams.

As is well known, when using neutron beams for cancer treatment, it is important that the neutron beams are irradiated only to the lesion and do not damage healthy tissue. Since neutrons are emitted radially from a radiation source, the ideal collimator has a three-dimensional shape in which the space is a cone connecting the outlines of the radiation source and the irradiation target, and the rest is filled with a shield.

However, since the outline of the irradiation target differs depending on the treatment target, it has been impossible to manufacture an ideal collimator for each treatment.

Therefore, it was considered to make the outline of the irradiation target almost step-like and to create a conical space by combining collimating plates of a plurality of divided conical cylinders (conical plates).

FIG. 1 is an explanatory diagram showing a combination of the collimating plates as described above.

In this figure, 1 indicates the entire collimating plate.

IR indicates a stack of collimating plates on the right f1 portion, and IR,, IR2,..., IRゎ indicates individual collimation plates 7-1.
・Show the board. Note that FIG. 4 shows an example in which 10 sheets are stacked. In addition, IL is a stack of collimating plates on the left side, which is shown by two-dot chain lines, and although not shown, the individual collimating plates IL, IL2, . . .
,IL,. and is arranged at a symmetrical position to the collimating plate IR.

The collimating plate l performs a rotational movement centering on X111]. Therefore, adjacent collimating plates 1 are composed of conical plates having different cone angles.

Figure 2 (schematic plan view of an irradiation head formed by a collimator using ai'd laminated collimating plates, Figure 2 (1)) shows the collimator in Figure 2 (a) viewed from the front A direction. A perspective view of FIG. 2(c) is a perspective view of FIG. 2(tb) viewed from the direction B on the back side. In these figures 1
Reference numeral 1 denotes a neutron collimator 11, which is a radiation head, and 12, a cooget, which is a radiation source that emits neutrons. 13 is a collimator, and 14 is a housing of the above-mentioned remeter 13, in which collimating plates IR and IL are arranged symmetrically, each collimating plate IR,, IR2゜...+lR1゜r
1LI+IL2+.-1IL1qk are connected to respective adjustment devices 16 via respective link devices 15, so that they can be rotated separately. 17 is the radiation source 1
an entrance window (fixed frimeter) that receives neutrons from 2;
Reference numeral 18 denotes a passageway forming the entire cone-shaped space formed by the collimating plates IR and IL, and 19 the radiation source 12.
These are an entrance window 17, a radiation window through which neutrons are emitted through a passage 18, and an opening formed to connect the frimate plates IL and IR to the link device 15.

Next, the operation will be explained.

Each collimating plate LL, ~IL,. , IR, ~IR,.

By moving each adjustment device 16 in the direction of arrow C, link device 15+1? Rotate it in the direction of the arrow.

As a result, each collimating plate IL, ~IL, o, I
R, ~IR,. For example, an irradiation field is formed in a shape as shown in FIG.

By the way, in order to manufacture the above-mentioned collimating plates IR and IL'z, it is necessary to form conical plates having different cone angles and cut them out from the conical plates.

In order to approximate the contour of the irradiation target, it is necessary to make the stepped increments small and to combine a large number of collimating plates.

Thin conical plates were still manufactured mainly from iron because they required precision, but manufacturing was difficult due to the occurrence of processing distortion.Also, it required a heavy drive source with a large output, which led to an increase in costs. . In addition, those made of iron have a large amount of residual radioactivity, which makes them radioactive over time, making them dangerous and inconvenient to handle.

As described above, although the principle of the conical surface type collimator 13 is known, it is not put into practical use due to the difficulty of manufacturing it.Especially in cancer treatment using neutron beam G, the conventional parallel plate laminated collimator, which is easy to manufacture, has not been put into practical use. Although it has been used, it has drawbacks such as a large penumbra and the impossibility of soybean irradiation.

This invention was made to eliminate the above-mentioned drawbacks, and it uses a lightweight plastic that has high plasticity, and a filler that absorbs neutron beams and the radioactivity generated by the neutron beams. The present invention also provides a collimating plate for neutron beams. This invention will be explained below.

FIGS. 4 and 5 show a plastic mold and a multilayer mold used for manufacturing the neutron beam collimating plate of the present invention.

First, in Fig. 4, 21 is a plastic molding die (
21A and 21B indicate an upper mold and a lower mold. Regarding epoxy resin as a plastic, first, epoxy resin mixed with a hardening agent is molded in a mold 21. In this case, for example, while the curing temperature is 100°C, the mold is held at 70°C and taken out in a semi-cured state. After producing a predetermined number of collimated plates IR2IL in a semi-cured (semi-cured) state formed in this way, the collimated plates IR and IL in a flexible state are heated again to around 70°C, as shown in Figure 5. It is placed in the multilayer mold 22 shown. In addition, 22A, 22BB: 2-type Yoshishita mold of the above-mentioned multi-molding mold 22 is shown.

22 multilayer molds are preheated (e.g. 70℃)
). A mold release agent (solicon grease, etc.) is applied to the surfaces of the collimating plates IR, IR, to prevent mutual adhesion.

Next, the clamped multilayer mold 22 is heated and molded in a furnace until hardening conditions are reached, and held (for example, at 100°C for 8
time), then the collimating plate IR, ~IR.

are taken out from the multilayer molds 22'A and 22B, collimating plates IR, ~I with their respective cone angles are
R, is obtained.

In this way, each of the two types of molds 21Δ, 21B, 22A,
By preparing 22B, adjacent collimating plates I
Since R, to IR6 can be molded with each other having the role of a mold, it is possible to manufacture many types of conical surface type collimating plates IR and IL.

FIG. 6 is a perspective view of a neutron beam collimating plate showing an embodiment of the present invention. In this figure, 31 is a collimating plate mainly made of epoxy resin, and 31A is an arbitrary one of the ones on the right side shown in Figure 1. 31B is a layer containing boron and is a thermal neutron absorption layer that absorbs and removes thermal neutrons; 31C is a γ-ray attenuation layer containing lead; fast neutron moderation layer 31A; It attenuates the gamma rays generated in the magnetic absorption layer.

Each of the layers 31A, 31B, and 31C is made by mixing an epoxy resin with additives, and Table 1 shows an example of the components.

Table 1 The weight of the collimating plate 31 manufactured from the above components is 40% of that of iron.

As explained above, the present invention consists of a plastic molding mold and a multilayer molding mold, each of which is mainly made of epoxy resin, has a fast neutron moderating layer containing iron powder, and a thermal neutron absorbing layer containing boron. and r containing lead to attenuate the γ-rays generated in the fast neutron moderation layer and heat absorption removal layer.
Since a collimating plate is formed with the attenuation layer, there is less residual radioactivity compared to a collimating plate made of iron plate, and the residual radioactivity is shielded by the lead layer, so there is no harm caused by radioactivity and it is convenient to handle. Since the weight is reduced, a drive source with a small output is required, which has advantages such as cost reduction.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the combination of collimating plates, Figure 2
Figure (a) shows the approximate flat surface of the irradiation nozzle formed by freemake using laminated collimating plates [Figure 7ij, 2nd
Figures (bl is a perspective view of the collimator in Figure 2 (a) seen from the front A direction, Figure 2 (c) is a perspective view of the collimator in Figure 2 (a) from the back side B
Fig. 3 is a front view showing the irradiation field formed by the collimating plate, Fig. 4 is an exploded perspective view of the plastic molding die used for carrying out this invention, and Fig. 5 is also a multilayer FIG. 6 is a side sectional view showing a molding die, and a perspective view of a neutron beam collimating plate showing an embodiment of the present invention. In the figure, 1, IR, IL, IR,, IR2,=-・, I
R, o. l L+ + I L2 + “”” + L L 1
0 is a collimating plate, 21 is a plastic mold, 21
A is an upper mold, 21B is a lower mold, 22 is a multilayer mold, 22A
is the upper mold, 22B is the lower mold, 311d collimating plate, 31A
is a fast neutron moderation layer, 31B is a thermal neutron absorption layer, 31C
is the gamma-ray attenuation layer. Figure 1 Figure 2 (U) Figure 2

Claims (1)

[Claims] In a neutron beam collimator in which a radiation cone space is approximately formed by stacking collimating plates of a divided conical cylinder, and neutrons from a radiation source are integrated and radiated from the radiation cone space, each of the collimating plates is moved from the radiation source side. Toward evening, a fast neutron moderating layer made of epoxy resin containing iron powder, a thermal neutron absorption layer also containing no boron, and a neutron damping layer also containing lead were formed. A collimating plate for neutron beams, characterized in that it is configured by providing.