目的：本前瞻性之研究，主要利用CIRS 成人假體與金氧半場效電晶體（MOSFET）劑量計，去 評估乳癌病患使用兩不同治療計劃方式，其表面劑量與內部劑量的差異性。 材料與方法：本實驗使用MOSFET 劑量計作為劑量量測工具，並利用CIRS 假體與乳房假體來 模擬真實乳癌病患。在取得假體電腦斷層模擬定位影像後，將影像傳至計劃系統製作照野中照 野（Field in Field, FIF）與混合強度調控（Hybrid-IMRT）治療計劃，再利用直線加速器收集 MOSFET 劑量計所量測的劑量數據，也同時收集計劃系統上的劑量數據，再針對收集到的數據結 果作比較。 結果：表面劑量測量點1~20 數據結果在單次處方劑量為180 cGy 時，FIF 數值平均為142.8 ± 2.74 cGy，Hybrid-IMRT 的數值平均為136.3 ± 1.98 cGy，內部劑量測量點數據結果顯示，FIF 的5 個 測量點劑量平均值為202.3 ± 2.01 cGy，Hybrid-IMRT 的5 個測量點劑量平均值為194.3 ± 2.64 cGy，另一方面，在治療計劃系統上，所得到的數據結果顯示FIF 平均劑量為195.5 ± 9.7 cGy， Hybrid-IMRT 平均劑量為187.6 ± 5.7 cGy，FIF V95 為97.5%，Hybrid-IMRT V95 為 97.9%，FIF 正 常肺部組織劑量V5 為 0.84%，Hybrid-IMRT 正常肺部組織劑量V5 為 4.13%，FIF 110% 高劑量區 域的體積為107 cm3，Hybrid-IMRT 110% 高劑量區域的體積為0.8 cm3，此外，由治療計劃系統 顯示，表面劑量測量點1~20 數據的結果，FIF 的數值平均為117.1 ± 8.1 cGy，而Hybrid-IMRT 的 數值平均為113.5 ± 7.9 cGy，內部劑量測量點數據，結果則顯示FIF 的5 個測量點劑量平均值為 202.3 ± 0.37 cGy，而 Hybrid-IMRT 的5 個測量點劑量平均值為189.7 ± 0.15 cGy。 結論：由本實驗得知Hybrid-IMRT 比起FIF 的方式可以改善劑量均勻度，較低之表面劑量可使病 患在治療過程當中能有較輕微的皮膚反應，另外做計劃所需時間也較短，對臨床物理師而言是較 有效率的計劃方式。

Purpose : This prospective study used the Computed Imaging Reference System (CIRS) phantom and Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeters to evaluate internal dose and surface dose differences between two different types of treatment plans in radiotherapy for breast cancer patients. Materials and Methods : In this study, we used MOSFET dosimeters as a measurement tool. To simulate the real breast cancer patients, we used CIRS phantom to make prosthesis. After CT simulation, images were transmitted to the Pinnacle planning system, and then field-in-field (FIF) and hybridintensity modulated radiotherapy (IMRT) treatment plans were conducted. Irradiation through a linear accelerator to collect dose data by MOSFET dosimeters. The dose data calculated by the Pinnacle planning system were also collected. We compared the dosimetry differences between FIF and hybrid- IMRT techniques. Result : The mean measured surface dose from 1 to 20 points, in a single dose of prescription 180 cGy, was 142.8 ± 2.74 cGy and 136.3 ± 1.98 cGy for FIF and Hybrid-IMRT technique, respectively. The mean measured internal dose from 5 internal dose points was 202.3 ± 2.01 cGy and 194.3 ± 2.64 cGy for FIF and Hybrid-IMRT technique, respectively. On the other hand, treatment planning system revealed that the mean dose for FIF and Hybrid-IMRT technique was 195.5 ± 9.7 cGy and 187.6 ± 5.7 cGy, respectively. The V95 for FIF and Hybrid-IMRT technique was 97.5% and 97.9%, respectively. Normal lung tissue dose V5 for FIF and Hybrid-IMRT technique was 0.84% and 4.13%, respectively. The 110% volume of high-dose region for FIF and Hybrid-IMRT technique was 107 cm3 and 0.8 cm3, respectively. In addition, treatment planning system showed that the mean surface dose of 1 to 20 points was 117.1 ± 8.1 cGy and 113.5 ± 7.9 cGy for FIF and Hybrid-IMRT technique, respectively; the mean internal dose of five measurement points FIF dose was 202.3 ± 0.37 cGy and 189.7 ± 0.15 cGy for FIF and Hybrid-IMRT technique, respectively. Conclusions : Our study suggested that compared to FIF, Hybrid-IMRT technique can improve dose uniformity and decrease surface dose, and lower skin reactions can be expected. Furthermore, shorter time is required for Hybrid-IMRT plan, which is more efficient in terms of the program approach.