Ahmad M, Liu W, Deng J, Nguyen K, Wu D, Chen Z, Moran M, Nath R
Yale School of Medicine, New Haven, CT.
Yale- New Haven Hospital, New Haven, CT.
Med Phys. 2012 Jun;39(6Part14):3770. doi: 10.1118/1.4735357.
To present a validation study of enhanced dynamic wedges (EDWs) implemented into Pinnacle3 treatment planning system (TPS) using a diode array, Monte Carlo (MC) simulation, and measurements.
Modeling of EDW dose distribution in the Pinnacle3 TPS is based on a combination of open-field beam data and the Varian 'Golden Segmented Treatment Table' (GSTT) unique to each photon beam. To validate the EDW models, dose profiles of 6- and 10-MV photon beams from a Clinac 2100C/D were measured in virtual water at depths from near- surface to 30 cm for a wide range of asymmetric field sizes and wedge angles using the Profiler-2 diode array system. The EDW output factors for asymmetric fields were measured in solid water using a small-volume cylindrical ionization chamber placed at a depth of 10 cm on the central axis. In addition, absolute doses on central axis at depths of 5, 10, 15 and 20 cm were measured in virtual water using a small-volume cylindrical chamber for comparison with the collapsed-cone convolution (CCC) calculations. The 6- and 10-MV photon beams emerging from the treatment head of the Clinac 2100C/D were fully simulated using the Monte Carlo code BEAMnrc and DOSXYZnrc. This code was used to calculate the central-axis percentage depth doses and dose profiles for the open and dynamically-wedged fields in a water phantom.
The off-axis dose profiles of various EDWs computed with the CCC dose model and MC simulations agreed with measured EDW dose distributions to an accuracy of better than 2%/2 mm. Measured EDW output factors used for MU calculations in Pinnacle3 TPS agreed with MC predictions within 1-2%.
The utility of Profiler-2 diode array system to measure dose profiles for commissioning of EDWs into the Pinnacle3 TPS has been demonstrated to have acceptable accuracy for clinical implementation.
使用二极管阵列、蒙特卡罗（MC）模拟和测量方法，对Pinnacle3治疗计划系统（TPS）中实现的增强动态楔形野（EDW）进行验证研究。
Pinnacle3 TPS中EDW剂量分布的建模基于开放野束数据与每个光子束特有的瓦里安“黄金分割治疗表”（GSTT）的组合。为了验证EDW模型，使用Profiler-2二极管阵列系统，在虚拟水中，针对各种不对称野大小和楔形角，在从近表面到30 cm的深度处，测量了Clinac 2100C/D的6和10 MV光子束的剂量分布。使用置于中心轴上10 cm深度处的小体积圆柱形电离室，在固体水中测量不对称野的EDW输出因子。此外，使用小体积圆柱形电离室在虚拟水中测量5、10、15和20 cm深度处中心轴上的绝对剂量，以便与坍缩圆锥卷积（CCC）计算结果进行比较。使用蒙特卡罗代码BEAMnrc和DOSXYZnrc对Clinac 2100C/D治疗头出射的6和10 MV光子束进行了全模拟。该代码用于计算水模体中开放野和动态楔形野的中心轴百分深度剂量和剂量分布。
使用CCC剂量模型和MC模拟计算的各种EDW的离轴剂量分布与测量的EDW剂量分布相符，精度优于2%/2 mm。在Pinnacle3 TPS中用于MU计算的测量EDW输出因子与MC预测结果在1%-2%以内相符。
已证明Profiler-2二极管阵列系统用于测量剂量分布以将EDW引入Pinnacle3 TPS进行调试，在临床应用中具有可接受的精度。
