Rana S, Pokharel S
Suresh Rana, MS, Department of Medical Physics, ProCure Proton Therapy Center, 5901 West Memorial Road, Oklahoma City, OK 73142, USA. Email:
Gulf J Oncolog. 2013 Jul;1(14):63-9.
The development of advanced radiation treatment techniques such as intensity modulated radiation therapy (IMRT) and volumetric intensity modulated arc therapy (VMAT) require more accurate dose calculation algorithms within the treatment planning systems (TPS) considering that the human body is composed of tissues of widely differing radiological properties and the characteristics of a therapeutic radiation treatment beam along a heterogeneous path will be different. The objective of this study was to evaluate the accuracy of 2D-isodose distributions predicted by pencil beam convolution algorithm (PBC) and anisotropic analytic algorithm (AAA) in a heterogeneous slab phantom composed of media equivalent to air, water and bone density. The measurements were done by using the films at multiple depths in the phantom for open field sizes 5 × 5 cm2 and 10 × 10 cm2. The results from this study indicated that the AAA had better agreement with the measurement compared to PBC for both the test field sizes at all selected depths; however, the limitation of AAA in predicting doses within and beyond low-density medium was observed, especially for a smaller field size (up to 32.7% and 34.0% for AAA and PBC, respectively). Furthermore, discrepancies up to -4.8% for AAA and -14.6% for PBC was seen in the high-density medium as well. Dose prediction errors by the AAA and PBC were more pronounced for a smaller test field size, especially in the low-density medium.
IMRT, dose calculation algorithms, Anisotropic Analytical Algorithm (AAA), Pencil Beam Convolution (PBC), Varian's Eclipse treatment planning system.
先进的放射治疗技术如调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）的发展，要求治疗计划系统（TPS）中有更精确的剂量计算算法，因为人体是由具有广泛不同放射学特性的组织组成，并且治疗放射束沿非均匀路径的特性会有所不同。本研究的目的是评估在由等效于空气、水和骨密度的介质组成的非均匀平板体模中，铅笔束卷积算法（PBC）和各向异性解析算法（AAA）预测的二维等剂量分布的准确性。测量是通过在体模中多个深度处使用胶片，针对5×5 cm²和10×10 cm²的开放野尺寸进行的。本研究结果表明，对于所有选定深度的两种测试野尺寸，与PBC相比，AAA与测量结果的一致性更好；然而，观察到AAA在预测低密度介质内和之外的剂量时存在局限性，特别是对于较小的野尺寸（AAA和PBC分别高达32.7%和34.0%）。此外，在高密度介质中也观察到AAA高达-4.8%和PBC高达-14.6%的差异。对于较小的测试野尺寸，尤其是在低密度介质中，AAA和PBC的剂量预测误差更为明显。
调强放射治疗，剂量计算算法，各向异性解析算法（AAA），铅笔束卷积（PBC），瓦里安的Eclipse治疗计划系统
