Dose Level outside the Primary Beam of a Neutron Therapy Machine

中子治療機主射柱外的劑量水平

朱國龍(Guo-Long Chu)

《中華放射線醫學雜誌》 6卷3期 (1981/09) Pp. 225-234

摘要

病人于接受放射線治療的整個過程中所接受到的全身劑量是個很重要的課題之一，新近引用的中子放射治療已引起對其屏蔽要求的關切，因其已證實較傳統治療設備更難以處理。
爲了估計來自氘－氚中子發生器的14百萬電子伏中子主要射柱外的劑量水平，我們在空氣及水假體中做了一序列的測量。
我們使用雙游離腔法做劑量之測定，一為等組織游離腔，另一游離腔則以碳為腔壁材料再充以二氧化碳。另外再以中子靈敏度幾可忽略不計的蓋氏計數器做雙重之測量。
最後結果顯示，在主要的射柱內，空氣中伽瑪射線污染為10%，在水中則為15-20%,射柱外伽瑪線比例增加得很快，在離射柱中心80公分處可達80%。平均來說，水中伽瑪分量比空氣中約高出10%。

並列摘要

One of the most important problems is the whole body dose to the patient during the whole course of treatment. The recent introduction of therapy neutron sources has led to a concern about their shielding requirements which prove to be a more difficult problem than those encountered with conventional therapy equipments.
Hence a series of measurements were made both in air and in water phantom in attempting to estimate the dose level outside the primary beam of 14 Mev neutron from a D-T neutron generator.
In dosimetry, we used two chamber method, tissue-equivalent chamber and carbon wail carbon dioxide filled chamber, doubly checked by G. M. counter, of which neutron sensitivity is negligible.
Final results show that gamma ray contamination in air is about 10% and 15-20% in water in the main beam, outside it increases rapidly. It can be as high as 80% at the point 80cm off the beam center: Averagely, gamma component in water is 10% higher than in air.