模擬攝影照射方向之一些考量

Some Considerations in the Direction of Simulation Beams

10.6316/TRO/199603(4)251

孫立民(Li-Min Sun)；梁雲(Stephen Wan Leung)；葉世安(Shyh-An Yeh)；康瑋篁(Wei-Huang Kang)

模擬攝影 ； 照野 ； 發散效應 ； Simulation ； Field ； Divergency effect

放射治療與腫瘤學

3卷4期（1996 / 12 / 01）

251 - 256

繁體中文

臨床上，對於放射治療照野大小之取決，往往得先借助模擬攝影(simulation)之技術於治療前拍攝模擬攝影片，再由片上清晰之解剖相關位置決定治療的範圍，並在病患身上或模具(cast)上做好體表之相對四周與中心點的記號。但有時想照射之某些部位（如肛門，頸部淋巴結），或是想避開之某些區域（如眼球之水晶體，腸造口），並非在照野體厚一半之中心深度且遠離射束之中心點（接近照野之四周邊緣），則此時應清晰地標明出來，並特別考慮模凝攝影照射之方向，以免在照野邊綠因射束之發散效應(divergency)而造成涵蓋不夠或過多，引起治療之失敗。

Simulation is a technique to determine the treatment field via diagnostic films before radiotherapy. By radiographic visualization of internal organs, the correct position of fields can be obtained by physicians in relation to external landmarks. Some of areas we would like to include in treatment fields (eg. anus, neck lymph node) or to spare (eg. lens, colostomy) by cerrobend block are not located exactly at the midline of body thickness and are far from the central beam axis (near the field margin). Because of the beam divergency effect, the field margin may be too extended or too limited by different beam directions. Therefore, those areas should be marked clearly and we should especially consider the direction of simulation beam. It may be one of the crucial factors of marginal failure of treatment if we do not pay attention to it.