瘤定息螺旋斷層放射治療儀與直線加速器對左側乳癌放射治療技術之比較

目的：乳癌自2003年起持續蟬聯國內女性好發癌症之首，放射治療在其療程中有著舉足輕重的地位。拜醫療科技進步所賜，現今放射治療的技術種類非常多且各有不同的特性，本研究針對左側乳癌規劃使用數種不同放射治療技術，比較在劑量上差異並分析不同技術之特性。材料與方法：使用女性擬人假體（Rando phantom）作為標準病患進行胸部電腦斷層掃描。規劃數種以直線加速器所執行各種形式之強度調控放射治療（intensity modulated radiation therapy, IMRT）、體積調控弧形放射治療（volumetric modulated arc therapy, VMAT），與瘤定息（Radixact）所執行的TomoDirect及TomoHelical等，進行不同治療技術的設計，並針對靶區劑量的順形指標（conformity index, CI）、均勻指標（homogeneity index, HI），以及危急器官與正常組織的接受劑量和總治療時間等各項參數，進行分析比較。結果：靶區劑量方面TomoDirect之CI為0.770，HI為0.072，V95%為99.8%，V98%為99.1%，皆為全部技術中最佳。同側器官劑量方面以FFF-VMAT左肺V20Gy的8.9%與心臟V20Gy的2.7%為全部技術中最低；對側器官與脊髓劑量方面，TomoDirect之右肺Dmax為88 cGy，右側乳房Dmean為34 cGy，脊髓Dmax為30 cGy，皆為全部技術中最低。總治療時間以FFF-VMAT的151±2.1秒為全部技術中最短。結論：由本研究結果得知，全部六種乳癌放射治療技術中，TomoDirect可提供最佳的靶區劑量分布，並使對側器官受到最低劑量，但較長的治療時間需要特別注意；FFF-VMAT對心臟及同側肺臟造成的劑量最低，脊髓和對側器官造成的劑量最高，其治療時間短最適合搭配呼吸調控技術降低呼吸因素而造成的誤差，能進一步提升治療精準度。

關鍵字

左側乳癌；放射治療技術；瘤定息；順形指標；均勻指標

並列摘要

Purpose：Breast cancer is the most common cancer in domestic women since 2003. Currently, radiation therapy may play an important role in breast cancer treatment. This study aimed to evaluated several radiotherapy techniques for dosimetric different and characteristic in left breast cancer irradiation. Methods and materials：Using Rando phantom as a standard patient, radiation therapy plans were created with linear accelerator for IMRT, FIMRT, Hybrid IMRT, FFF-VMAT; Radixact TomoDirect, TomoHelical techniques. Dose characteristics of planning target volume, and organs at risk, treatment time, conformity and homogeneity index were compared. Results：TomoDirect had higher target dose distribution (CI and HI), and target coverage (V95% and V98%). The lowest dose to ipsilateral lung and heart was FFF-VMAT. The lowest dose to contralateral breast, lung and spinal cord was TomoDirect. The shortest total treatment time was FFF-VMAT, and the longest total treatment time was TomoHelical. Conclusion：In whole left breast irradiation, TomoDirect generated in this study achieved higher dose coverage of the PTV, and the lowest dose on contralateral organs. The advantage of FFF-VMAT is the lowest dose on ipsilateral organs and the shortest treatment time. The choice of the radiotherapy should be considered by each hospital taking into account of the dose characteristics in different techniques, and whether it fits patient anatomy and keeps workload and treatment time acceptable.