JPH11221294A - Manufacture of silicone bolus for radiotherapy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a bolus keep durability against repeated use and various kinds of sterilization treatment by making transparent silicone gel as an inner packing material, using silicone rubber for an outer skin part, and mixing both materials to constitute the middle layer between both. SOLUTION: Silicone gel used for an inner packing material is made by mixing 398.4 pt. of polysiloxane, 1.6 pt. of methylhydrogen polysiloxane, and 0.06 pt. of 1% chloroplatinic acid alcohol solution, and agitation and completely defoaming at room temperature. Silicone rubber used for an outer skin part is made by mixing 99.66 pt. of a main agent, polysiloxane added with 4% of aerosol silica, 0.4 pt. of methyl hydrogen polysiloxane, and 0.02 pt. of 1% chloroplatinic acid alcohol solution, agitating, and completely defoaming at room temperature. The product is at 40 deg.C kept for 15 hours so as to be a 0.6 mm thick outer skin to be cured. Next, a material made by mixing the material for silicone rubber used for the outer layer part and the material for silicone gel used for the inner packing material in a ratio of 1:2, agitating, and defoaming is coated thereon and kept at 40 deg.C for 15 hours for curing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bolus used in close contact with a human body to modify the distribution of absorbed dose in radiotherapy, and more particularly to a method for manufacturing a reusable silicone bolus.

[0002]

2. Description of the Related Art Radiation such as X-rays, γ-rays, proton beams, and electron beams is widely applied to human bodies for treatment. During this treatment, normal tissue other than the affected area may be exposed to unnecessary radiation, which may have serious consequences, including harmful effects. Therefore, in radiation therapy, it is necessary to adjust the dose distribution by interposing a bolus between the irradiation device and the human body in order to efficiently supply a necessary amount of treatment dose to the affected part. As such a bolus, one in which a water-soluble synthetic resin, paraffin, agar, a gum base, or the like is covered with a soft plastic film such as polyethylene or urethane resin is known.

Generally, a bolus worthy of practical use must satisfy at least the following characteristics and conditions. Be a human tissue equivalent. Be homogeneous. Excellent plasticity, appropriate elasticity, and good shape conformity and adhesion to living bodies. No toxicity. No change in energy. The shape must be stable and uniformity can be maintained. No air ingress. It is also desirable to have transparency and to withstand various sterilizations, sterilization treatments, and chemical solutions. Here, "equivalent to a human body tissue" means strictly the same atomic composition as that of the human body, but here, it indicates the same properties as radiation absorption or scattering as those of a substantial tissue.

[0004]

Since the bolus of the prior art is covered with a soft plastic film of a composition different from that of the encapsulating material, each composition has a different expansion and contraction rate. Depending on the degree of local unevenness of the affected part, countless wrinkles enter the surface in contact with the affected part of the bolus,
Creates a layer of air. For this reason, when used for treatment with charged particles such as an electron beam, for example, there is a disadvantage that the reaching depth (range) changes. In addition, since the coating material is non-adhesive, there is a disadvantage that the bolus easily shifts from the position during irradiation due to slight movement of the patient.

[0005] Furthermore, the bolus of the prior art is often expensive, so it is not practical to dispose it as a one-time use and disposable, considering the economic burden, and it is common to use it repeatedly. there were. For that purpose, various sterilization treatments such as sterilization washing with boiling water and steam, disinfection sterilization with alcohol, disinfectant, etc., and radiation sterilization with γ-ray are necessary. In many cases, it was not able to be used repeatedly.

On the other hand, in the case of water, there is a problem in manufacturing technology that it is difficult to enclose water in a container.

The present invention has been made to solve these problems. The bolus is fully satisfactorily satisfactorily satisfactorily satisfactorily in its various properties, and adheres well to an affected part, hardly causes wrinkles, and is used repeatedly for various sterilizations. An object of the present invention is to provide a silicone bolus having excellent durability to processing.

[0008]

The inventor of the present invention has conducted various studies on a bolus that meets the above-mentioned problems, and as a result, has found that a transparent silicone gel is used as an inner wrapping material, a silicone rubber is used for an outer layer coating portion, and a blend material of the two is used. It has been found that a silicone elastomer having a five-layer structure in which is provided as an intermediate layer between the inner encapsulant and the outer layer coating portion satisfies these requirements sufficiently, and has completed the present invention.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The silicone bolus of the present invention
Because the bolus of the prior art is coated with a film of a composition different from that of the encapsulating material, the drawback of wrinkling due to the difference in the expansion and contraction rate of each composition is a disadvantage of blending the composition used for the encapsulating material and the outer layer coating. This problem was solved by providing the prepared material as an intermediate layer between the inner wrapping material and the outer layer coating, and alleviating the difference in expansion and contraction between the inner wrapping material and the outer layer coating. Here, the silicone rubber used for the outer layer coating portion preferably has a slight tackiness, and is flexible and high in strength in order to improve the adhesion to the affected part and the durability during use.

The silicone bolus of the present invention is obtained by curing a silicone rubber and a silicone gel material by leaving them at room temperature or heating for a certain period of time. The heating temperature is not particularly limited, but in order to obtain a silicone bolus that does not wrinkle more, thermal stress generated during heating and curing of the silicone rubber used for each structural part, distortion applied to a molded product caused by difference in stress, inflection The heating temperature is preferably from 15 to 50 ° C, more preferably from 25 to 40 ° C, in order to alleviate the like.

Since the silicone elastomer of the present invention is intended to be used as a bolus for radiation therapy, it is necessary to minimize bubbles in the silicone gel and silicone rubber. When the bubbles are large or large, for example, when used for treatment with a charged particle beam such as an electron beam or a proton beam, this causes a change in the reaching depth (range).

The silicone bolus of the present invention has flexibility,
It has moderate elasticity and adhesion to living organisms, and is excellent in shape conformity and adhesion to living organisms, equivalent to human tissue, durability against repeated use and various sterilization treatments. Further, at the time of radiotherapy, the skin mark is easily aligned due to its high transparency, and wrinkles are hardly formed. By stacking silicone boluses of various thicknesses, the radiation dose distribution can be easily adjusted. Therefore, the silicone elastomer of the present invention is suitable as a bolus material used for radiotherapy.

[0013]

EXAMPLES Polysiloxane as a main ingredient having a reactive vinyl group (viscosity at 25 ° C .: 1200 cp) 398.4
Part, methylhydrogenpolysiloxane which is a crosslinking agent having a hydrogen-silicon bond (viscosity at 25 ° C. 20 c
p) 1.6 parts and 0.06 part of a 1% chloroplatinic acid alcohol solution as a curing catalyst were mixed, stirred, completely degassed at room temperature, and added to a silicone gel of an addition reaction type used for an encapsulating material. Material. Further, a main agent (2) containing 4% of fumed silica with respect to a polysiloxane having a reactive vinyl group.
99.6 parts of a viscosity at 5 ° C. of 150,000 cp, and 0.4 of a methylhydrogenpolysiloxane (viscosity at 25 ° C. of 20 cp) which is a crosslinking agent having a hydrogen-silicon bond.
Parts, 1% chloroplatinic acid alcohol solution as curing catalyst
After mixing and stirring, the mixture was completely defoamed at room temperature, followed by stirring.
A silicone rubber material of an addition reaction type used for the outer layer coating portion was used. This is adjusted to 40 mm so that the film thickness becomes 0.6 mm.
It was left for 15 hours under the condition of ° C. to be cured to obtain an outer layer film. Next, the coating on the surface in contact with the gel material serving as the intermediate layer,
The material of the silicone rubber used for the outer layer portion and the material of the silicone gel used for the encapsulating material were mixed at a ratio of 1: 2, and the material which was stirred and defoamed was applied to the prepared outer layer film surface so as to have a thickness of 1.6 mm. And left to cure at 40 ° C. for 15 hours.

This was prepared on two sides for one sample,
It is fixed in a mold frame having a width of 20 m, a width of 20 cm and a thickness of 10 mm, and a silicone gel material serving as an encapsulating material is poured without bubbles and cured under the same conditions. After the curing of the inner packaging material was completed, the injection side surface was sealed with a silicone rubber material used for the outer layer coating portion, and cured under the same conditions to obtain a silicone bolus having a thickness of 10 mm. A silicone bolus having an appropriate adhesion to a living body and having excellent transparency, flexibility, and adhesion was obtained, and the specific gravity of the obtained silicone bolus was 1.
02, hardness was 43 by Asker hardness tester FP.

[0015] In order to evaluate that the absorption or scattering of ionizing radiation of the hydrogel obtained in the example shows the same properties as those of the substantial tissue, the deep volume percentage curve was measured with an electron beam (6 Me).
V, 9MeV, 12MeV, 15MeV, 18MeV,
100 cm from launch window, electron beam irradiation field 15 × 15
cm ² ) according to a standard measurement method using a UNIDOS dosimeter (manufactured by PTW). Cli for generating electron beam
NAP CL-2100C (manufactured by VARIAN) was used, and JARP type, Ma
rks type (manufactured by PTW) was used, and RW3 (manufactured by PTW) was used as a phantom for measuring absorbed dose.
Further, the electron beam causes multiple scattering of the electron beam with depth in the substance, resulting in an increase in the amount of ionization per unit length. Then, a peak of the amount of ionization occurs at a depth where most of the incident electron flux is scattered. The position of this peak is 10
0% and 80% of the ionization amount is D80.

FIG. 1 shows 6 MeV, 9 MeV, 12 MeV,
The depth curve of the silicone bolus with respect to the electron beams of 15 MeV and 18 MeV is shown.

Table 1 shows 6Me obtained from the results of this measurement.
The required bolus thickness when the ionization amount is 80% with electron beams of V, 9 MeV, 12 MeV, 15 MeV, and 18 MeV is shown.

As a control for evaluation, the measured value was compared with the measured value of a phantom. Here, a phantom is a substance whose interaction, such as absorption and scattering of radiation, is equivalent to human tissue and whose density is as close as possible to human tissue (tissue equivalent material), similar to a bolus. Was used. As is evident from Table 1, the required bolus thickness for 80% ionization at each electron dose is:
The difference from the thickness required for the phantom was very small, and the value was within the error range. From these facts, the silicone bolus of the present invention can obtain almost the same radiation absorption as the phantom. In other words, it can be understood that the bolus for radiation therapy is highly equivalent to human body tissue and useful.

[0019]

[Table 1]

The above embodiment is an exemplification, and it is a matter of course that the scope of the present invention is not limited thereby.

[0021]

The silicone bolus of the present invention is hardly wrinkled, has moderate flexibility, elasticity, and adhesion to a living body, is transparent, conforms to a living body, is equivalent to human tissue,
It has excellent durability against repeated use and various sterilization treatments, and is useful as a bolus for radiation therapy.

[Brief description of the drawings]

FIG. 1 is a model diagram in which a side surface of a silicone bolus according to the present invention is cut.

FIG. 2 is a graph showing the relationship between the depth of the silicone bolus and the depth of the silicone bolus according to the present invention.

Continued on the front page (72) Inventor Yoshinori Koga 3-20-22 Maekawa, Kawaguchi City, Saitama Prefecture Mochida Shoko Lab.

Claims (1)

[Claims] 1. A gel material of transparent silicone rubber is used as an encapsulating material, and a transparent silicone rubber is used as a material for coating the encapsulating material. A method for producing a silicone bolus having a five-layer structure in which materials are blended and provided as an intermediate layer.