目的：研究評估肩部位移量對頭頸癌病患頸部劑量的影響，並在臨床上觀察肩部位置的再現性與 穩定性。 材料與方法：本研究分成假體實驗與臨床分析兩部分，先用假體模擬不同的肩部位移量，分析 相對於原始治療計畫中對頸部劑量的影響。再經本院人體試驗委員會許可下，自2010 年5 月 至2012 年12 月222 位病患分成頭頸模具（head mask, HM）、頭頸模具加肩牽引器（head mask+shoulder tractor, HM+T）；頭頸肩模具（head shoulder mask, HSM）及頭頸肩模具加肩牽 引器（head shoulder mask+shoulder tractor, HSM+T）四個族群，治療時經影像導引系統修正擺 位誤差後，以錐狀射束電腦斷層記錄每週一次治療前肩部位置（inter-fraction）的再現性和治療過 程中（intra-fraction）的穩定性來分析臨床上的意義。 結果：假體依序增加肩部高度 0 cm、1 cm、2 cm、3 cm，頸部劑量的變化在劑量百分比D100 及D95 分別為102%、97.5%、94.4%、91.2% 及 103%、99.3%、95%、92.5%；體積百分比 V100 及V95 分別為97.4%、87.5%、52.2%、31.2% 及99.5%、99%、90%、75.8%。可知頸部 劑量會隨著肩部位移量變化而產生差異。用HM、HM+T、HSM、HSM+T 四種模具來探討對於肩 部的相關影響性，其中inter-fraction 再現性的3D vector 值分別是右肩11.6±4.1 mm、10.1±4.1 mm、5.5±2.0 mm、5.6±2.6 mm；左肩9.7±3.3 mm、10.9±3.9 mm、5.3±1.9 mm、5.9±2.3 mm。intra-fraction 穩定性的3D vector 值（mm）分別是右肩4.4±2.6 mm、4.3±1.5 mm、 2.2±0.8 mm、2.9±1.3 mm；左肩3.9±1.8 mm、4.1±1.3 mm、2.1±1.1 mm、3.1±1.5 mm。 結論：肩部位置的改變確實會影響放射治療時頭頸癌病患的頸部劑量分布均勻性，HSM 模具不論 是再現性或是穩定性都優於其他模具，拉肩牽引器並無觀察到牽引器的助益。建議模具固定宜選 擇可以降低肩部位移量的模具，以維持放射治療時的再現性與穩定性。

Purpose : This study evaluated the impact of the shoulder displacement in head and neck cancer and observed the reproducibility and stability of the shoulder position in clinical practice. Materials and Methods : This study was divided into the experimental and clinical parts. The experimental displacement of shoulder was evaluated with the Rando phantom. From May 2010 to Dec 2012, four mold groups of 222 patients were HM (head mask), HM + T (head mask with tractor), HSM (head shoulder mask), and HSM + T (head shoulder mask with shoulder tractor) after IRB approval. Setup error was corrected by image-guided system before treatment. Recording to the shoulder displacement error values before and after treatment were determined once a week by conebeam computed tomography (CBCT). Results : After gradual increasing the shoulder height with 0 cm, 1 cm, 2 cm, 3 cm, the neck dose measured by Rando phantom are 102%, 97.5%, 94.4%, 91.2% and 103%, 99.3% , 95%, 92.5% in D100 and D95, and are 97.4%, 87.5%, 52.2%, 31.2% and 99.5%, 99%, 90%, 75.8% in V100 and V95, respectively. The neck dose is related to the displacement of shoulder. The reproducibility and stability of right and left shoulders displacement were determined as 3D vector during head and neck cancer radiation therapy. The results of right and left shoulders are 11.6±4.1 mm, 10.1±4.1 mm, 5.5±2.0 mm, 5.6±2.6 mm and 3.9±1.8 mm, 4.1±1.3 mm, 2.1±1.1 mm, 3.1±1.5 mm. Conclusion : Compared to HM or HM + T, HSM was more superior. It was recommended that the mold should be chosen approximately to reduce the shoulder displacement and to maintain the stability and reproducibility of radiation therapy. Using a suitable mold can reduce the displacement.