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題 名 | Neutron Dose Meaurement for Medical Linear Accelerator=醫用直線加速器中子劑量之量測 |
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作 者 | 黃文松; 李振弘; 邱垂煥; 陳為立; | 書刊名 | 放射治療與腫瘤學 |
卷 期 | 4:4 1997.12[民86.12] |
頁 次 | 頁265-270 |
分類號 | 414.93 |
關鍵詞 | 活化; 醫用直線加速器; 中子吸收劑量; Activation; Medical linear accelerator; Neutron absored dose; |
語 文 | 英文(English) |
中文摘要 | 目的:建立中子劑量量測技術以評估醫用直線加速器產生之X光中之中子劑量。 材料與方法:將3.2公克純度98%以上的五氧化二磷(P□O□)裝入小玻璃瓶內,並置於射柱內 距離X射線靶1公尺處,照野面積40公分x40公分,照射劑量為40戈雷(10-18MV)。五氧化 二磷經過光子與中子混合場照射後而產生活化反應,如□P(n, □)□及□P(n, p)□Si。活化 物用蒸餾水溶解後,以計測效率趨近100%之液體閃爍器計測。最後利用活化物飽和活度及劑 量轉換因子之乘積,則可決定快中子與熱中子的吸收劑量。 結果:加速器產生中子輻射的多寡與加速器的照野有關,當照野面積愈大時產生的中子輻射也 愈多。照野40公分x40公分,照射劑量40戈雷的條件下,對10MV至18MV之X射線所產生 的中子通量率範圍在10□至10□n cm□s□之間。 結論:醫用直線加速器產生之中子與病人治療劑量的比值在0.002%至0.071%之間。此結果符 合原子能委員會規定中子劑量與病人治療劑量的比值必須小於0.1%之要求。 |
英文摘要 | Purpose: To develop a technique to measure neutron dose in a high-energy photon field generated by a linear accelerator. Materials and Methods: Approximately 3.2 g of phosphorus pentoxide P□O□ powder with purity over 98% was placed into a 5 mL glass vial and capped. The vial was then placed in the radiation beam at 1 m against the target and irradiated to 40 Gy for 10 MV to 18 MV x-ray under the field size of 40 cm X 40 cm. Samples of P□O□ were exposed to a mixed photon-neutron field with the reactions of □P(n, □) □P and □P(n, p) □Si. The irradiated samples were then dissolved in distilled water and the activation products were counted using the liquid scintillation counting techique with a counting efficiency approaching 100%. The decay characteristics of the sample was then analyzed to determine the fast and thermal neutron absorbed dose. Results: Measurements for neutron contribution related to field size showed that the larger field size for irradiation, the more neutron contamination was generated. The total neutron fluence rate generated by five accelerators were in the range from 10 □ to 10□n□□MV to 18 MV x-ray machines with photon dose of 40 Gy and field size 40 cm X40cm. Conclusion: The total neutron absorbed dose was about 0.002% to 0.071 % compared with treatment x-ray dose to the patient. It meets the criteria as set by the Atomic Energy Council. The requirement is that the neutron dose due to neutron contamination produced by a linear accelerator with voltage above 7 MV should be less than 0.1% of radio-therapeutical dose to the patient. |
本系統中英文摘要資訊取自各篇刊載內容。