Evaluation of Cyberknife Treatment Planning for Prostate Cancer using the Conformal Index and the Tumor Control Probability

目的：本研究在於利用劑量包覆順型度數學模型，分析電腦刀放射治療技術輻照區域劑量與周圍器官體積彼此間順型度之關係。配合腫瘤控制機率公式運算分析攝護腺癌經放射治療後腫瘤控制機率，以期更能適用於電腦刀治療計畫的分析。材料與方法：本研究回溯性收集六名攝護腺腫瘤患者接受低分次電腦刀立體定位放射治療計畫。給予劑量分別為37.5Gy分五次治療，42Gy分五次治療，和32Gy分四次治療。計算劑量包覆順型度及腫瘤控制機率，並分析計算結果以作為評估電腦刀計畫系統的參考。結果：電腦刀治療計畫系統本身所提供的劑量包覆順型度計算值在腫瘤控制機率達98.3%以上時均在1.483以下。而經過以週遭重要器官加入考量的模式計算後，增加劑量包覆順型度的差異性提供作為治療計畫的評估。結論：放射線手術治療計畫給予較高的生物等效劑量，故適用於電腦刀劑量包覆順型度模式，必須能兼顧分析放射治療劑量區最佳的腫瘤體積包覆特性，和擴散到周圍的正常組織高劑量分佈。本文中所運算的模式可以用來評估及比較放射治療計畫。

關鍵字

腫瘤包覆順型度；腫瘤控制機率模式；立體定位放射線手術；電腦刀

並列摘要

Purpose: This study was to evaluate the feasibility of dose conformity and tumor control probability calculated for CyberKnife(superscript ®) hypofractionated planning for prostate cancer. Materials and Methods: Six patients with early prostate cancer were included in this retrospective study. They received stereotactic hypofractionation radiotherapy by CyberKnife(superscript ®). The dose prescriptions were 37.5 Gy in 5 fractions, 42 Gy in 5 fractions, or 32 Gy in 4 fractions. Dose conformity was calculated with three parameters: the conformity index (CI), the new conformity index (nCI) and the modified conformal index (mCOIN). A statistical analysis of the tumor control probability (TCP) was also calculated. Results: The CI and nCI of the CyberKnife(superscript ®) treatment planning system are all under 1.483. All the calculated TCP values were greater than 98.3%. We added the factors pertaining to the critical organ and obtained the mCOINs. The mCOIN values were listed to compare the quality of treatment plans. Conclusion: The conformity index value can be used to evaluate the quality of radiosurgery planning. The mCOIN values are also feasible to compare the plans.

並列關鍵字

Conformity index ； Tumor control probability ； Stereotactic radiosurgery ； CyberKnife

國際替代計量

Evaluation of Cyberknife Treatment Planning for Prostate Cancer using the Conformal Index and the Tumor Control Probability

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