JPH11255958A - Bolus for radiotherapy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bolus disposable besides sufficiently satisfying various characteristics required for the bolus, capable of being produced at a low cost compared to the conventional one, and excellent in cleanliness and processability. SOLUTION: This method for producing a hydrated gel of a natural organic polymer compound comprises adding one or more kinds of natural organic polymers (e.g. a carrageenan, a Locust bean gum, a glucomannan, a starch, a curdlan, a guar gum, an agar, a cassia gum, a dextran, an amylose, a gelatin, a pectin, a xanthan gum, a Tara gum and a gellan gum) as gelatinizing agents so as to form the hydrated gel having a concentration thereof higher than the gelatinizing concentration, preferably of <=10%, more preferably of 2-5% based on water. The bolus obtained thereby is capable of being disposable, produced in a lower cost compared to the conventional one, and excellent in cleanliness and processability.

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 correct the distribution of an absorbed dose in radiation therapy, and more particularly to a disposable bolus.

[0002]

2. Description of the Related Art It is widely practiced to irradiate the human body with radiation such as X-rays, γ-rays, and electron beams and use it for treating diseases such as cancer. Generally, when a substance is irradiated with radiation,
The amount of the original radiation decreases as going deeper, but the scattered radiation increases relatively deeper and in different directions. Therefore, the depth decreases exponentially (the dose) as shown in FIGS. However, in high-energy radiation, the recoil electrons (scattered rays) are mainly in the forward direction, so scattering to the side is reduced, and the dose at a certain depth is higher than the surface dose, and thereafter, It decreases exponentially as shown in FIGS. If treatment is performed without considering the nature of such radiation in the skin, unnecessary radiation may have harmful effects on normal tissues other than the affected area.

For example, as shown in FIG.
It is assumed that there is a lesion in the area. When this lesion is irradiated for treatment with radiation that has a maximum absorption line at a position 10 mm below the skin surface, the radiation is also applied to the lesion, but unnecessary to normal parts other than the lesion. In this case, excessive radiation is irradiated. In particular, the absorbed dose reaches a maximum value at a position 10 mm below the skin surface, and the risk of causing radiation damage in this portion becomes extremely large. The bolus plays a role in adjusting the dose distribution so that the amount of the absorbed dose applied to the affected part is maximized. This bolus is used by being interposed between the irradiation device and the human body as shown in FIG. By using the bolus in this manner, a required amount of radiation can be efficiently given to the affected area to be treated.

[0004] As shown in Fig. 7 (A), when radiation treatment is applied to an affected part in the brain, the distribution of the radiation in the brain is rounded to reflect the outer shape of the head. It becomes something. In such a state, the distribution of the maximum absorption line for a flat plate-shaped diseased part becomes spherical. As a result,
As shown in FIG. 5, the maximum absorbed dose is applied to a part other than the affected part, which is very dangerous. Therefore, by using a bolus matching the shape of the head as shown in FIG. 7B, the distribution of the rounded radiation can be corrected.

In general, 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, good shape conformity to living organisms, and good adhesion. No toxicity. No change in energy. The thickness must be uniform. No air ingress. In addition, it is desirable to have transparency in addition to the above. Here, "equivalent to a human body tissue" means strictly the same atomic composition as that of the human body, but here indicates that the material exhibits substantially the same properties as radiation absorption or scattering as those of a tissue.

To date, bolus materials have been plastics, paraffin, synthetic rubber, silicone,
Water is used.

[0007]

In recent years, infection of bacteria and viruses in hospitals via medical devices and tools has become a serious problem. There is a growing demand for disposable devices that are disposable for limited use. However, conventionally used boluses using plastics, paraffin, silicone, and synthetic rubber as a base material are expensive, depending on the size, and the bolus after use cannot be easily disposed of as it is. For this reason, it has not been realistic to dispose it as a one-time use, because it must be disposed of as industrial waste. For this reason, the conventional bolus has to be used repeatedly, and it has to be disinfected in order to maintain cleanliness at the time of re-use. Furthermore, there is a problem that the subject is given a clean and uncomfortable feeling in terms of repeated use.

On the other hand, when water is used as a bolus, water itself can be easily discarded, but there is a problem in manufacturing technology that a container for enclosing the water cannot be easily discarded and that it is difficult to enclose.

The present invention has been made in view of the above-mentioned circumstances, and is capable of disposable after sufficiently satisfying various characteristics required for a bolus, and can be manufactured at a lower cost than a conventional bolus, and has a high cleanliness. The purpose of the present invention is to provide a bolus excellent in workability and workability.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a bolus used for radiotherapy, which is inexpensive, disposable, and excellent in processability. It is achieved by using a hydrogel using a gelling preparation of an organic polymer.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The bolus of the present invention has a rectangular plate shape as shown in FIG. 1, and is made of a hydrogel of an organic polymer substance. As a gelling preparation of a high molecular substance, a gelling preparation having sufficient strength and water retention for use and capable of obtaining a hydrogel having a water content of 80% or more is desirable. Examples of such gelled preparations include natural organic polymers such as carrageenan, locust bean gum, glucomannan, starch, curdlan, guar gum, agar, cassia gum, dextran, amylose, gelatin, pectin, xanthan gum, cod gum, gellan gum, and the like. Is mentioned. One or more of these can be used in combination for producing a hydrogel of a natural organic polymer.

The amount of the gelling preparation to be added may be in the range of not less than the concentration at which gelation is caused and not more than the concentration not too hard as a bolus, and is preferably 10% or less with respect to water, more preferably Is suitably 2 to 5%. However, some of the natural organic high molecular substances such as gellan gum and pectin in the above examples do not gel by the above method. Therefore, a gelling preparation can be gelled by adding a metal salt such as calcium, potassium, sodium, or barium after adding the gelling preparation to water, dissolving with heat, stirring, and then adding the metal salt. The process of adding the metal salt is effective even in the preparation of a gelled preparation that easily gels.
Metal salts such as calcium, potassium, sodium, barium and the like can be added after adding the gelling preparation to water, dissolving with heating, and stirring. At this time, the produced natural organic polymer hydrogel has higher strength than when no metal salt is added. Some natural organic high molecular substances such as pectin may or may not gel depending on the pH value. Therefore, a pH adjuster must be added in order to change the pH from alkaline or acidic conditions, which are difficult to gel, to a range in which gelation is easy. p
In addition, the H adjuster also has a role of being able to stabilize the gelled substance over time by being added.
Also when adding a pH adjuster, a gelling preparation is added to water and dissolved by heating in the same manner as when a metal salt is added, and after stirring, the pH adjuster is added. The bolus is desirably colorless and transparent. However, in some cases, a coloring agent may be added to make the bolus transparent.

The method for producing the bolus for radiotherapy of the present invention will be described by taking carrageenan and locust bean gum as examples. First, carrageenan and locust bean gum are heated and dissolved in water at a temperature of 70 to 100 ° C., immediately poured into an appropriate mold, and cooled. Then, it gels and a bolus is obtained. The strength of the gel, the degree of hardness of the gel, and the like can be varied over a wide range by variously combining the types and amounts of the gelling preparations. The size of the gel can also be changed by selecting the shape of the mold,
The shape is not limited to the shape shown in FIG. 1 and may be a circle as shown in FIG. 2A, a triangular prism as shown in FIG. 2B, or a shape as shown in FIG. It may have a complicated shape as described above, or may have another shape.
Also, the size of the gel after molding can be freely changed by easily cutting it with a knife or the like.

As described above, the natural organic polymer hydrogel according to the present invention can be easily molded and its size can be freely changed, so that different types of radiation can be used or the depth of the affected part from the skin surface can be reduced. Various boluses can be easily produced depending on the difference and the shape of the human body due to the difference in the part to be treated.

According to this method, there is an advantage that a uniform hydrogel can be obtained without requiring special equipment and operation, and it is useful for energy saving measures and stabilization of quality.

When the hydrogel of the present invention is stored for a long period of time, molds and bacteria may adhere thereto and propagate there. Therefore, it is necessary to add a preservative, a fungicide or the like in advance during the production of the hydrogel. preferable. These preservatives and fungicides are added after adding a gelled preparation to water, heating and dissolving, and stirring.

Since the water-containing gel of the present invention is intended to be used as a bolus for radiotherapy, it is necessary to minimize bubbles in the gel. This is because, when the bubbles are large or large, when they are used in the treatment of charged particles such as electron beams and proton beams, for example, they cause a change in the reaching depth (range).

The bolus for radiotherapy of the present invention is characterized in that it is nontoxic, has an appropriate flexibility and elasticity, and is excellent in adhesion to a living body, homogeneity of a material, and human body tissue equivalent. Further, at the time of radiotherapy, the skin mark is easily aligned due to high transparency, and the radiation dose distribution can be easily adjusted by stacking radiotherapy boluses of various thicknesses. Therefore, the natural organic polymer hydrogel of the present invention is suitable as a material for a bolus used for radiotherapy.

[0019]

EXAMPLE An example of the preparation of a bolus for radiation therapy having a total volume of 400 cm ³ is shown below. 3. Carrageenan in 390 g of water
0 g, locust bean gum 3.0 g, and xanthan gum 3.0 g were added, and the mixture was heated and dissolved at 80 ° C. for 10 minutes with stirring. Thereafter, all the liquid was poured into a container having a length of 200 mm, a width of 200 mm and a thickness of 10 mm while being careful not to include bubbles, and the container was immersed in cooling water at 5 ° C. to be cooled and solidified.
A hydrogel having a thickness of 10 mm was obtained. As a result, a homogeneous hydrated gel having excellent transparency and plasticity and appropriate elasticity was obtained, and the specific gravity of the obtained gel was 1.01 and the hardness was 34 with an Asker hardness tester FP.

In order to evaluate that the absorption or scattering of radiation shows the same properties as those of a substantial tissue, the deep gel percentage curve for X-rays and electron beams was obtained for the hydrogel obtained in the example. It was measured. X-rays of 4 MV and 10 MV were used, and the distance from the focus of generation to the bolus surface was 10
0 cm and the irradiation field was 10 × 10 cm ² . The electron beams used were 6 MeV, 9 MeV, 12 MeV, 15 MeV, and 18 MeV, and the distance from the generation window to the bolus surface was 100 cm, and the irradiation field was 15 × 15 cm ² . The measurement method is UNIDOS, according to the standard measurement method.
It was measured with a dosimeter (manufactured by PTW).

X-rays and electron beams are generated by Clinac
CL-2100C (manufactured by VARIAN) was used, and JARP type, Markus was used in the ionization chamber for measurement.
Type (both manufactured by PTW) was used, and RW3 (manufactured by PTW) was used as a phantom for measuring absorbed dose. Here, the phantom is made of a material (tissue equivalent material) 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, like a bolus.

FIG. 3 shows the deep percentage curves of the hydrogel and the phantom for X-rays of 4 MV and 10 MV. In each deep part, the deep percentages of the natural organic polymer hydrogel and the phantom show almost the same values, and for X-rays,
It can be seen that the equivalence with human body tissue is high.

FIG. 4 shows 6 MeV, 9 MeV, 12 MeV,
The deep percentage curves of the hydrogel and the phantom for 15 MeV and 18 MeV electron beams are shown. Also for the electron beam, the hydrogel of natural organic polymer at each deep part showed a value almost consistent with the deep percentage curve of the phantom, indicating that the equivalence with human body tissue was high.

From these facts, the water-containing gel of the present invention can obtain radiation absorption substantially similar to that of the phantom. In other words, it can be understood that the bolus for radiation therapy is highly equivalent to human body tissue and useful.

The above embodiments are merely examples, and the scope of the present invention is, of course, not limited thereby.

[0026]

The bolus for radiotherapy of the present invention having the above-mentioned structure has the following specific effects.

Since natural organic high molecular substances and water are used as materials, after use, unlike the conventional bolus which had to be treated as industrial waste,
It can be disposed of by incineration.

Since natural organic high molecular substances and water are used as materials, the material cost is low and the molding is easy, so that the cost is extremely low.

From the above characteristics, it is possible to realize a disposable bolus for one-time use, eliminating the need for complicated disinfection such as the bolus of the prior art. Can be given.

Further, as described in detail in the section of the embodiment,
A bolus with excellent human tissue equivalent, transparency, flexibility and uniformity can be obtained.

[Brief description of the drawings]

FIG. 1 is an external view showing an example of a bolus of the present invention.

FIG. 2 shows another embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the depth of the bolus of the present invention and the percentage of the depth with respect to X-rays.

FIG. 4 is a graph showing the relationship between the depth and the depth percentage of the bolus of the present invention with respect to the electron beam.

FIG. 5 is a schematic diagram showing the relationship between the intensity of radiation in the body and the lesion in radiation therapy.

FIG. 6 is a schematic diagram showing a relationship between a radiation intensity and a lesion when a bolus is inserted between the skin and a radiation source in radiation therapy.

FIG. 7 is a schematic diagram showing a difference in radiation distribution depending on the presence or absence of a bolus during radiation treatment of the head.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshinori Koga 3-20-22 Maekawa, Kawaguchi City, Saitama Prefecture Mochida Shoko Laboratory

Claims (10)

[Claims] 1. One or more natural organic polymers (carrageenan, locust bean gum, glucomannan,
Starch, curdlan, guar gum, agar, cassia gum, dextran, amylose, gelatin, pectin,
Xanthan gum, cod gum, gellan gum) as a gelling preparation, at a gelling concentration or higher, preferably 10% or less, more preferably 2 to 5% of the gelling preparation with respect to water.
A method for producing a water-containing gel of a natural organic polymer compound prepared by adding an amount. 2. For natural organic polymers which are difficult to gel,
The method for producing a hydrogel of a natural organic polymer according to claim 1, wherein a metal salt, a coloring agent, and a pH adjuster are added after dissolution with water and heated to facilitate gelation. 3. To increase the strength, use a metal salt with a natural organic polymer (carrageenan, locust bean gum, glucomannan, starch, curdlan, guar gum, agar, cassia gum, dextran, amylose, gelatin, pectin, xanthan gum, tara gum). , One of gellan gum
2. The method for producing a hydrogel of a natural organic polymer according to claim 1, wherein the hydrous gel is added after water is added thereto and dissolved after heating. 4. A natural organic polymer (carrageenan, locust bean gum, glucomannan, starch, curdlan, guar gum, agar, cassia gum, dextran, etc.) so that the hydrogel of natural organic polymer does not rot or mold. , Amylose, gelatin, pectin, xanthan gum, cod gum, gellan gum, or a combination of two or more thereof), added to water, heated and dissolved, and then added with a preservative and a fungicide. A method for producing a polymer hydrogel. 5. A natural organic polymer (one or two of carrageenan, locust bean gum, glucomannan, starch, curdlan, guar gum, agar, cassia gum, dextran, amylose, gelatin, pectin, xanthan gum, tarara gum, gellan gum) A bolus for radiotherapy, comprising a hydrogel. 6. The bolus for radiotherapy according to claim 5, wherein a metal salt is added. 7. The bolus for radiation therapy according to claim 5, further comprising a coloring agent. 8. The bolus for radiotherapy according to claim 5, further comprising a pH adjuster. 9. The bolus for radiation therapy according to claim 5, further comprising a preservative. 10. The bolus for radiotherapy according to claim 5, further comprising a fungicide.