目的：本試驗試圖以兩種不同軟硬程度的枕墊，來為即將接受頭頸部放射治療的病患製作模型，使用影像導引技術來測量並比較兩種枕墊在治療定位中的再現性，並試圖比較受試病患感受兩種不同枕墊主觀舒適度及軟硬程度。另外，本試驗將會探討定位再現性與枕墊舒適度或軟硬程度之間的相關性。材料與方法：自2011年三月開始，至2012年二月底止，總共有35位受試者進入本試驗。每位受試者皆會接受兩組模型的製作及分別的模擬電腦斷層掃描，其中一組模型的枕墊使用TIMO枕，另一組模型的枕墊使用壓克力枕。在療程一開始的三天內、療程中每隔三至五天、及療程結束的那一天利用影像導引放射治療技術來分別取得當日治療前的定位影像，藉此測量並計算出擺位再現性的相關參數，包括在中心點上的垂直角度面上的三軸位移。再者，在療程進行中的取像日當天以問卷方式調查受試者對於兩種枕墊的主觀感受舒適程度、軟硬程度、及偏好選擇。最後，定位再現性與枕墊舒適度或軟硬程度互相之間的相關性亦會被分析。結果：總共有351筆由即時影像導影所得的取像資料，可供我們做位移誤差的分析。一、兩枕墊之位移誤差分析：由結果可知雖然各項位移絕對差異相當小，但於前後軸（p=0.011，成對 t 檢定）與左右軸（p=0.004，成對 t 檢定）的位移差異，確實已達統計顯著意義，亦即壓克力枕的再現性較 TIMO 枕佳。在評估頸椎彎曲位移與下頷骨仰角變化，可得知不論是頸椎彎曲或下頷骨仰角的變動都可觀察到當治療到中後期後，兩枕墊的再現性呈現變差的趨勢。二、兩枕墊之舒適度問卷分析：從Spearman’s相關係數得知不論是壓克力枕或 TIMO 枕，受試者主觀感受枕墊愈軟，則給予該枕墊舒適度的評分有顯著愈高之趨勢（Spearman’s 相關係數=0.387，p＜0.001）。三、兩枕墊軟硬度評等及舒適度分數與位移誤差之間的關係：雖然兩種枕墊的軟硬程度與位移誤差之間毫無相關性，但若評估枕墊舒適度與定位誤差之間的相關性，只有壓克力枕在空間向量位移（Pearson’s 相關係數=0.153，p =0.006）和中軸旋轉上（Pearson’s 相關係數=0.213，p＜0.001）的定位誤差與病患感受舒適度之間存在著統計顯著的正相關性。結論：不論是在再現性或舒適度上，壓克力枕墊與 TIMO 枕墊差異皆不大。在未來，如何設計兼顧病患舒適性與準確性的模型，且在不影響治療準確度與再現性的狀況下，讓病患可採取舒適且不易變動的姿勢來做治療，是我們未來期許的重要目標。

Objectives/Hypothesis : To compare setup reproducibility, comfort level and hardness perceived bythe patients between two head suports employed in the same immobilization system in head-and neckradiotherapy. Additionally, the relationship between setup accuracy and patient comfort survey wasalso investigated.Methods : Between March 2011 and February 2012, there were 35 patients undergoing head-and-neckradiotherapy (RT) being recruited and all studied patients received the same immobilization device(a standard thermoplastic head-and-shoulder mask, Type S mask) twice, in which two different headsupports were employed. Both a TIMO support and a Silverman support were used to compare setupaccuracy/precision with several types of measurement respectively in each studied patient. All patientsunderwent planning computed tomography (CT). A series of on-board images (OBIs) were taken atthe start, during, and by the end of the radiotherapy course in each studied patient. The OBI imageswere subsequently co-registered and repositioning accuracy was examined by recording displacementincluding three axes at the isocenter and orthogonal planes. Furthermore, the patients’ subjectiveperception of comfort level, hardness, and preference for selecting between the two head supportswere analyzed and compared. Last but not least, we attempted to explore the association betweenrepositioning accuracy represented by several indicators and the patients’ subjective perception interms of comfort level and hardness.Results : A total of 351 OBI data sets were analyzed. Although the absolute difference was quitesmall between the two head supports (TIMO support vs. Silverman support) with regard to threedisplacement errors, total vector displacement errors, spine curve, and mandible angle, it was notedthat Silverman support was associated with more limited repositioning displacement in the anteroposterior(AP) and medio-lateral (ML) directions (paired t-test, p= 0.011, 0.004, respectively). Asthe RT course was proceeding, a trend was noted toward a greater variation in both spinal curve andmandible angle, suggesting that reproducibility should be paid more attention when the RT coursemoves forward. In the comfort survey, perception of hardness was positively correlated with comfortlevel in both head supports with weak but significant significance (Spearman’s correlation coefficient=0.387, p <0.001). As for the association between repositioning accuracy and comfort survey, althoughthere was no any correlation between hardness of head supports and repositioning accuracy, comfort level was positively correlated with repositioning displacement in rotation (Pearson’s correlationcoefficient =0.213, p <0.001) and total vector displacement error (Pearson’s correlation coefficient=0.153, p= 0.006) in Silverman head support only.Conclusions : The results of the current study have demonstrated that the available immobilizationsystem equipped with either TIMO head support or a Silverman head support provides satisfactoryand nearly equivalent repositioning-related outcomes. More limited repositioning displacementis positively associated with more satisfactory perception of comfort level exclusively in theimmobilization system equipped with Silverman head support. In the future, we might considerleaving the choice between the two different head supports to the individual patient according tosubjective perception of comfort level.