Damrongkijudom N, Butson M, Rosenfeld A
Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia.
Australas Phys Eng Sci Med. 2007 Mar;30(1):46-51. doi: 10.1007/BF03178409.
Extrapolated surface dose measurements have been performed using radiographic film to measure 2-Dimensional maps of skin and surface dose with and without a magnetic deflector device aimed at reducing surface dose. Experiments are also performed using an Attix parallel plate ionisation chamber for comparison to radiographic film extrapolation surface dose analysis. Extrapolated percentage surface dose assessments from radiographic film at the central axis of a 6 MV x-ray beam with magnetic deflector for field size 10 x 10 cm2, 15 x 15 cm2 and 20 x 20 cm2 are 9 +/- 3%, 13 +/- 3% and 16 +/- 3%, these compared to 14 +/- 3%, 19 +/- 3%, and 27 +/- 3% for open fields, respectively. Results from Attix chamber for the same field size are 12 +/- 1%, 15 +/- 1% and 18 +/- 1%, these compared to 16 +/- 1%, 21 +/- 1% and 27 +/- 1% for open fields, respectively. Results are also shown for profiles measured in-plane and cross-plane to the magnetic deflector and compared to open field data. Results have shown that the surface dose is reduced at all sites within the treatment field with larger reductions seen on one side of the field due to the sweeping nature of the designed magnetic field. Radiographic film extrapolation provides an advanced surface dose assessment and has matched well with Attix chamber results. Film measurement allows for easy 2 dimensional dose assessments.
已使用射线照相胶片进行外推表面剂量测量，以测量有和没有旨在降低表面剂量的磁偏转器装置时皮肤和表面剂量的二维图。还使用Attix平行板电离室进行实验，以便与射线照相胶片外推表面剂量分析进行比较。对于6 MV X射线束中心轴上10×10 cm2、15×15 cm2和20×20 cm2射野尺寸，带有磁偏转器的射线照相胶片外推表面剂量百分比评估分别为9±3%、13±3%和16±3%，而开放射野分别为14±3%、19±3%和27±3%。相同射野尺寸的Attix电离室结果分别为12±1%、15±1%和18±1%，开放射野分别为16±1%、21±1%和27±1%。还给出了在与磁偏转器平面内和平面交叉方向测量的剂量分布结果，并与开放射野数据进行了比较。结果表明，治疗野内所有部位的表面剂量均降低，由于设计磁场的扫描特性，在射野一侧观察到更大程度的降低。射线照相胶片外推提供了一种先进的表面剂量评估方法，并且与Attix电离室结果匹配良好。胶片测量便于进行二维剂量评估。
