Yang Yun, Rivard Mark J
Department of Biomedical Engineering and Biotechnology, University of Massachusetts Lowell, Massachusetts 01854, USA.
Med Phys. 2009 Mar;36(3):809-15. doi: 10.1118/1.3075818.
Conformal dose coverage for accelerated partial breast irradiation or radiotherapy boost can be obtained with AccuBoost D-shaped brachytherapy applicators using a flattened surface positioned near the patient. Three D-shaped applicators (D45/D53/D60) were dosimetrically characterized using Monte Carlo methods (MCNP5), air ionization chambers (Farmer and Markus), and radiochromic film (GafChromic EBT) in polystyrene and ICRU 44 breast tissue. HDR 192Ir source dwell times were either constant or optimized to improve skin dose uniformity. Scatter dose decreased as depth decreased. 10 mm beyond the applicator aperture, dose reductions of 90% and 51% were observed at depths of 0 and 30 mm, respectively. Similarly, planar dose uniformity improved as depth decreased and was also due to scatter and applicator geometry. Dose uniformity inside the applicator aperture was approximately 11% and 15% for all three applicators at the skin and 30 mm deep, respectively. Depth dose measurements in polystyrene using ion chamber and radiochromic film agreed with Monte Carlo results within 2%. Discrepancies between film and Monte Carlo dose profiles at 30 mm depth were within 1%.
使用AccuBoost D形近距离放射治疗施源器，将其扁平表面靠近患者放置，可实现加速部分乳腺照射或放疗增敏的适形剂量覆盖。使用蒙特卡罗方法（MCNP5）、空气电离室（Farmer和Markus）以及放射性色胶片（GafChromic EBT），在聚苯乙烯和ICRU 44乳腺组织中对三个D形施源器（D45/D53/D60）进行了剂量学表征。高剂量率192Ir源驻留时间要么恒定，要么经过优化以改善皮肤剂量均匀性。散射剂量随深度减小而降低。在施源器孔径外10 mm处，在0和30 mm深度处分别观察到剂量降低了90%和51%。同样，平面剂量均匀性也随深度减小而改善，这也是由于散射和施源器几何形状所致。对于所有三个施源器，在皮肤处和30 mm深处，施源器孔径内的剂量均匀性分别约为11%和15%。使用电离室和放射性色胶片在聚苯乙烯中进行的深度剂量测量结果与蒙特卡罗结果的偏差在2%以内。在30 mm深度处，胶片和蒙特卡罗剂量分布之间的差异在1%以内。
