多模式螺旋斷層放射治療儀對鼻咽癌治療在照野外散射劑量之測量

目的：利用Rando人形假體執行多模式螺旋斷層放射治療儀的強度調控放射治療時，測量各部位的器官照野外可能接受的散射劑量，並探討誘發另一個癌症之可能性及致死癌病機率。材料與方法：將校正完成的TLD-100H按照各不同器官的位置置入於Rando人形假體中，以實際鼻咽癌病患治療的情況，利用多模式螺旋斷層放射治療儀作照射及評估，並參酌ICRP60號報告，以總劑量72Gy來求得個別組織或器官的致死癌病機率與總體損害的危險度。結果：眼球水晶體的平均總吸收劑量為3.91Gy，心臟及腎臟分別是0.49及0.11Gy，遠低於它們所能接受的耐受劑量。根據ICRP60號報告，食道及肺部可能有0.7~4.45%的危險度，而其他器官的危險度約略為0.2~0.08%，而全身有效劑量約為0.52Sv，其致死癌病機率約為2.6%。結論：儘管多模式螺旋斷層放射治療儀在治療鼻咽癌病患有很高M.U.輸出，但致死癌病機率結果及正常的組織誘發第二個癌症的危險度很低。借此研究能提供給臨床醫師對於病患日後可能誘發第二個癌症追蹤的依據。

關鍵字

致死癌病機率；照野外的散射劑量；多模式螺旋斷層放射治療儀； Rando人形假體

並列摘要

Purpose: To study associated cancer risks by measurements from out-of-field scatter doses with IMRT techniques such as helical tomotherapy with the use of an anthropomorphic Rando phantom. Materials and Methods: A commercially available Rando phantom was placed on the treatment couch to simulate the patient treatment delivery under tomotherapy. Various calibrated TLD chips were placed at different anatomical locations for the dosimetry measurements. For nasopharyngeal cancer patient, tomotherapy was generated to deliver the radiation doses for evaluation. The clinical comparison is based on the ICRP-60 risk model analysis of critical organ doses after evaluation of the helical-IMRT techniques using 72Gy dose prescription and optimization criteria. Results: Len, heart and kidney received 3.91Gy, 0.49 and 0.11Gy respectively, which were far less than their maximal tolerance dose. According to the data calculation from ICRP Publication No.60 the lung and esophagus have about 0.7~4.45% risks, the risks for others organs were 0.2~0.08%. The whole body dose and fatal cancer probability rate recevied about 0.52Sv and 2.6% respectively. Conclusion: Despite the overall higher M.U. delivery in tomotherapy, the overall whole body dose is lower risk probability of secondary malignancies induced by low dose radiation.

並列關鍵字

Cancer risks ； Out-of-field scatter doses ； Helical tomotherapy ； Rando phantom

國際替代計量

多模式螺旋斷層放射治療儀對鼻咽癌治療在照野外散射劑量之測量

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