目的：比較自創右側躺姿勢與一般傳統治療平躺姿勢之心臟和肺臟劑量，來評估自創固定裝置之 右側躺姿勢，對於早期左側乳癌放射治療病人之效益。 材料與方法：本研究集結二十一位和信治癌中心醫院早期左側乳癌病人的資訊結果，依據腫瘤床 的部位分類，可分為8 個上內側（UIQ）、5 個上外側（UOQ）、4 個中心部位（Center）、2 個下 內側（LIQ）與2 個下外側（LOQ）。每位病人皆收取右側躺姿勢與平躺姿勢之兩組影像。對於 右側躺姿勢，使用自製二十度傾斜之發泡劑模具（alpha cradle）及自製腳部固定設備；對於平 躺姿勢，使用一般治療之模具，病人雙手皆上舉，頭轉向非治療之對側方向。在相同之計畫靶 體積包覆程度下，經由(1) 乳房體積(2) 照野內最大心臟距離（MHD）；(3) 照野內最大心臟長度 （MHL）；(4) 照野中心肺距離（CLD）；(5) 腫瘤區域等方面，探討心臟劑量（V5, V10, V25 及平均 劑量）與肺部劑量（V5, V10, V20 及平均劑量）之差異，評估自創右側躺姿勢相較於一般傳統平躺 姿勢之優缺點。 結果：心臟劑量與乳房體積沒有相關聯性；但隨著右側躺姿勢，MHD、MHL 減少，心臟劑量皆 有減少之現象，平均劑量最大可減少約48.2%±14.0% 之比率，V5 可減少7.6%±6.0%，V10 可 減少4.2%±2.4%，V25 可減少1.9%±1.3%。然而，並非所有之右側躺姿勢相較於平躺姿勢，其 CLD 值皆會減小，故右側躺姿勢肺部劑量不一定會減少。腫瘤區域在下內側（LIQ）部位，隨右 側躺姿勢，心臟平均劑量與V5 、V10 、V25 都能更有效地減少；上側部位（UIQ, UOQ）心臟劑量 之V10 、V25 較低；腫瘤在中央區域位置（Central）之病人，其右側躺姿勢肺部劑量反而較平躺姿 勢增加，但增加幅度不多，平均劑量增加16.4 厘格雷（cGy），體積- 劑量因子增加在1% 範圍 內。 結論：本研究自製之右側躺姿勢能有效降低心臟之劑量，現今已普遍使用於和信治癌中心醫院， 早期左側乳癌病人之術後全乳放射治療。

Purpose : To evaluate the effectiveness of homemade immobilization equipment of right decubitus position for left breast cancer treatment by comparing the heart and lung doses of right decubitus position with those of supine position. Materials and Methods : Twenty-one early-stage left breast cancer patients of Koo Foundation Sun Yat-Sen Cancer Center (KFSYSCC) were collected in this study. Based on the location of the tumor bed, 8 Upper Inner Quadrant (UIQ), 5 Upper Outer Quadrant (UOQ), 4 Central, 2 Lower Inner Quadrant (LIQ) and 2 Lower Outer Quadrant (LOQ) sites were classified. Two sets of CT images (right decubitus and supine position) were acquired. Homemade alpha-cradle with 20 degrees tilt and homemade immobilization device of legs were used for the right decubitus position while the routine treatment position with both arms raised and head turned to the opposite side of treatment side was set for the supine position. Heart dose (V5, V10, V25 and mean dose) and lung dose (V5, V10, V20 and mean dose) of right decubitus position were compared with those of supine position by using parameters of breast volume, Maximum Heart Distance (MHD), Maximum Heart Length (MHL) and Central Lung Distance (CLD) in the same condition of Planning Target Volume (PTV) coverage. Results : There was no correlation between breast volume and heart dose. Heart dose could be decreased by using right decubitus position because of decreased MHD and MHL. Under this condition, the maximum decreased mean heart dose, V5, V10 and V25 were 48.2% ± 14.0%, 7.6% ± 6.0%, 4.2% ± 2.4% and 1.9% ± 1.3%, respectively. CLD was not always decreased in the right decubitus position compared to the supine position. Therefore, lung dose was not always decreased by using the right decubitus position. Heart dose was decreased effectively for tumor in the LIQ. Heart dose for tumor in the UIQ or UOQ was lower than that in other position. For tumor in the Central position, lung dose was a little bit increased by using the right decubitus position. The mean dose of lung was increased 16.4 cGy and the Dose-Volume value was increased within 1%. Conclusion : Heart dose can be decreased effectively by using right decubitus position. Homemade immobilization equipment for right decubitus position is now routinely used for early-stage left breast cancer treatment at KFSYSCC.