使用放射物理中心的头颈部 phantom 对 Acuros XB 算法进行 IMRT 和 VMAT 剂量计算的确定性实验验证。
Experimental validation of deterministic Acuros XB algorithm for IMRT and VMAT dose calculations with the Radiological Physics Center's head and neck phantom.
机构信息
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
出版信息
Med Phys. 2012 Apr;39(4):2193-202. doi: 10.1118/1.3692180.
PURPOSE
The purpose of this study was to verify the dosimetric performance of Acuros XB (AXB), a grid-based Boltzmann solver, in intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT).
METHODS
The Radiological Physics Center (RPC) head and neck (H&N) phantom was used for all calculations and measurements in this study. Clinically equivalent IMRT and VMAT plans were created on the RPC H&N phantom in the Eclipse treatment planning system (version 10.0) by using RPC dose prescription specifications. The dose distributions were calculated with two different algorithms, AXB 11.0.03 and anisotropic analytical algorithm (AAA) 10.0.24. Two dose report modes of AXB were recorded: dose-to-medium in medium (D(m,m)) and dose-to-water in medium (D(w,m)). Each treatment plan was delivered to the RPC phantom three times for reproducibility by using a Varian Clinac iX linear accelerator. Absolute point dose and planar dose were measured with thermoluminescent dosimeters (TLDs) and GafChromic® EBT2 film, respectively. Profile comparison and 2D gamma analysis were used to quantify the agreement between the film measurements and the calculated dose distributions from both AXB and AAA. The computation times for AAA and AXB were also evaluated.
RESULTS
Good agreement was observed between measured doses and those calculated with AAA or AXB. Both AAA and AXB calculated doses within 5% of TLD measurements in both the IMRT and VMAT plans. Results of AXB_D(m,m) (0.1% to 3.6%) were slightly better than AAA (0.2% to 4.6%) or AXB_D(w,m) (0.3% to 5.1%). The gamma analysis for both AAA and AXB met the RPC 7%/4 mm criteria (over 90% passed), whereas AXB_D(m,m) met 5%/3 mm criteria in most cases. AAA was 2 to 3 times faster than AXB for IMRT, whereas AXB was 4-6 times faster than AAA for VMAT.
CONCLUSIONS
AXB was found to be satisfactorily accurate when compared to measurements in the RPC H&N phantom. Compared with AAA, AXB results were equal to or better than those obtained with film measurements for IMRT and VMAT plans. The AXB_D(m,m) reporting mode was found to be closer to TLD and film measurements than was the AXB_D(w,m) mode. AXB calculation time was found to be significantly shorter (× 4) than AAA for VMAT.
目的
本研究旨在验证 Acuros XB（AXB）在调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）中的剂量学性能。
方法
本研究所有计算和测量均使用放射物理中心（RPC）头颈（H&N）体模。在 Eclipse 治疗计划系统（版本 10.0）中，根据 RPC 剂量处方规范，为 RPC H&N 体模创建临床等效的 IMRT 和 VMAT 计划。使用两种不同的算法（AXB 11.0.03 和各向异性解析算法（AAA）10.0.24）计算剂量分布。记录了两种 AXB 剂量报告模式：介质中剂量到介质（D(m,m)）和介质中剂量到水（D(w,m)）。使用瓦里安 Clinac iX 直线加速器将每个治疗计划重复三次输送到 RPC 体模，以确保重现性。使用热释光剂量计（TLD）和 GafChromic® EBT2 胶片分别测量绝对点剂量和平面剂量。使用轮廓比较和二维伽马分析来量化胶片测量结果与 AXB 和 AAA 计算的剂量分布之间的一致性。还评估了 AAA 和 AXB 的计算时间。
结果
在 AAA 或 AXB 计算的剂量与 TLD 测量值之间观察到良好的一致性。在 IMRT 和 VMAT 计划中，AAA 和 AXB 均计算出的剂量均在 TLD 测量值的 5%以内。AXB_D(m,m)（0.1%至 3.6%）的结果略优于 AAA（0.2%至 4.6%）或 AXB_D(w,m)（0.3%至 5.1%）。AAA 和 AXB 的伽马分析均符合 RPC 7%/4 mm 标准（超过 90%通过），而 AXB_D(m,m) 在大多数情况下符合 5%/3 mm 标准。对于 IMRT，AAA 的速度比 AXB 快 2 到 3 倍，而对于 VMAT，AXB 的速度比 AAA 快 4 到 6 倍。
结论
当与 RPC H&N 体模中的测量值进行比较时，AXB 被发现具有令人满意的准确性。与 AAA 相比，AXB 结果与 IMRT 和 VMAT 计划的胶片测量结果相等或更好。AXB_D(m,m) 报告模式被发现比 AXB_D(w,m) 模式更接近 TLD 和胶片测量值。AXB 的计算时间比 AAA 显著缩短（×4），对于 VMAT 更是如此。
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