6MV X-선의 조사조건과 피부반응에 관한 실험적 연구

Abstract

超高壓放射線은 build up 現象에 依해 最大吸收線量 部位가 皮下組織으로 移動됨에 따라 皮膚周圍 組織의 線量減少 現象이 나타나게 되었으며 이들의 正確한 線量分布 測定과 皮膚의 生物學的 反應을 觀察함으로서 臨床的으로 放射線 治療效果를 向上시킬 수 있다. 著者는 梨花女子大學校附屬病院 放射線治療室에서 使用하고 있는 6MV X-線과 組織과의 相互作用에서 皮膚 및 皮下組織에 대한 吸收線量을 物理的 側面에서 測定하고 一定한 理論式을 應用하였다. 實驗 對象으로는 기니아피그（guinea pig）60마리（120部位）를 使用하였으며, 이를 3群으로 大別하여 單一照射群에 10~60Gy를, bolus를 使用한 單一照射群에 10~40Gy를 各各 照射하였으며, 分割照射群에 20Gy를 1週에 3回, 30Gy를 1週 및 2週에 各各 2,3,5 回 分割照射한 後 5週間 皮膚反應을 觀察하여 다음과 같은 結論을 얻었다. 1）6MV X-線의 吸收線量은 皮膚面에서부터 1.5㎝까지 점차 增加하여 1.5㎝에서 最高點이 되었다. 2）放射線 單一照射時 皮膚反應은 照射線量에 比例하여 增加하였고 皮膚反應點數가 1.5에 해당하는 照射線量（D1.5）은 25Gy였다. 3）放射線 單一照射에서 最大 皮膚反應은 照射 後 24日 前後에 發生하였고 照射線量이 클수록 皮膚反應은 多少 빨리 나타났다. 4）0.5㎝, 1.0㎝, 1.5㎝ 두께의 bolus를 使用하여 各各 53%, 78%, 100%의 線量增加에 해당하는 皮膚反應點數를 나타냈다. 5）bolus를 使用하지 않은 單一照射群의 光學顯微鏡學的 組織變化는 表皮보다 眞皮에 더욱 甚하였다. 6）bolus를 使用한 單一照射群의 電子顯微鏡學的 組織變化는 眞皮의 甚한 浮重과 콜라겐의 變質된 病巢를 나타냈다. 7）分割照射에 의한 皮膚反應點數는 全體線量의 分割回數와 照射期間의 增加에 따라 減少되었다. 8）表皮의 皮膚反應은 表面으로부터 깊이 0.4㎝의 吸收線量에 해당하는 生物學的 效果를 나타냈다. 9）6MV X-線의 分割照射에 의해 生物學的 等價效果는 Ellis公式과 比較하여 分割回數와는 一致하나 照射期間에 의한 變化는 照射期間이 增加됨에 따라 多少 減少되었다（T0.08）. ; The maximum ionization point of supervoltage X-ray radiation modality is moved to subcutaneous tissue by the build up effect, as the result, the surface dose of the skin is decreased. It is necessary to measure the accurate dose distribution of supervoltage X-ray radiation modality and determine its biological effect on the skin in order to increase the effect of radiation therapy. By using 6 MV Linear accelerator, the absorbed dose of the skin and subcutaneous tissue was determined by physical aspect in relationship of 6 MV X-ray and tissue and a uniform formula was developed. For the experiment, guinea pigs were divide into 3 groups. A single irradiation group was irradiated with 10-60Gy, and a single irradiation group with 1.5cm, 1.0cm and 1.5cm bolus was irradiated with 10-40Gy, and fractionation group was irradiated with 20Gy by 3 fractionation for 1week and with 30Gy 2,3,5 fractionation for 1week and 2weeks respectively. The results were as follows: 1. The absorbed dose of 6MV X-ray was increased depending on the depth of skin and its maximum point was 1.5cm from skin surface. 2. The skin score by a single dose irradiation was proportionally increased by the dose and D1.5 dose at the point of skin score 1.5 was 25Gy. 3. The maximum skin reaction by a single dose irradiation was developed about 24th day after irradiation and generally the maximum reaction was developed earlier in higher dose. 4. By using the bolus, the skin score was increased by the ratio of 53%, 78% and 100% of dose increment depending on the thickness of the bolus 0.5cm, 1.0cm and 1.5cm respectively. 5. The light microscopic finding of a single dose irradiation without bolus showed more prominent changes in the dermis than epidermis, whereas a single dose irradiation with bolus showed prominent epidermal change. 6. Electron microscopic finding of a single dose irradiation with bolus were sever edema and degenerative change of collagen and dermal appendages in dermis. 7. The skin score of fractionation group was decreased by increasing number of fractionation and duration of overall time in the same total dose. 8. The skin reaction in epidermis was correspond to depth dose of 0.4cm from the surface in biological effect. 9. The biological isodose effect by fractionation irradiation of 6 MV X-ray was correspond to number of fractionation of Ellis formula, but the change by overall time is slightly decreased in longer time（T0.08）.