McDonald Daniel G, Jacqmin Dustin J, Mart Christopher J, Koch Nicholas C, Peng Jean L, Ashenafi Michael S, Fugal Mario A, Vanek Kenneth N
Department of Radiation Oncology, Medical University of South Carolina, Charleston, SC, USA.
J Appl Clin Med Phys. 2017 Jan;18(1):170-177. doi: 10.1002/acm2.12025.
To evaluate the Mobius second-check dosimetry system by comparing it to ionization-chamber dose measurements collected in the recently released Mobius Verification Phantom™ (MVP). For reference, a comparison of these measurements to dose calculated in the primary treatment planning system (TPS), Varian Eclipse with the AcurosXB dose algorithm, is also provided. Finally, patient dose calculated in Mobius is compared directly to Eclipse to demonstrate typical expected results during clinical use of the Mobius system.
Seventeen anonymized intensity-modulated clinical treatment plans were selected for analysis. Dose was recalculated on the MVP in both Eclipse and Mobius. These calculated doses were compared to doses measured using an A1SL ionization-chamber in the MVP. Dose was measured and analyzed at two different chamber positions for each treatment plan. Mobius calculated dose was then compared directly to Eclipse using the following metrics; target mean dose, target D95%, global 3D gamma pass rate, and target gamma pass rate. Finally, these same metrics were used to analyze the first 36 intensity modulated cases, following clinical implementation of the Mobius system.
The average difference between Mobius and measurement was 0.3 ± 1.3%. Differences ranged from -3.3 to + 2.2%. The average difference between Eclipse and measurement was -1.2 ± 0.7%. Eclipse vs. measurement differences ranged from -3.0 to -0.1%. For the 17 anonymized pre-clinical cases, the average target mean dose difference between Mobius and Eclipse was 1.0 ± 1.1%. Average target D95% difference was -0.9 ± 2.0%. Average global gamma pass rate, using a criteria of 3%, 2 mm, was 94.4 ± 3.3%, and average gamma pass rate for the target volume only was 80.2 ± 12.3%. Results of the first 36 intensity-modulated cases, post-clinical implementation of Mobius, were similar to those seen for the 17 pre-clinical test cases.
Mobius correctly calculated dose for each tested intensity modulated treatment plan, agreeing with measurement to within 3.5% for all cases analyzed. The dose calculation accuracy and independence of the Mobius system is sufficient to provide a rigorous second-check of a modern TPS.
通过将莫比乌斯二次检查剂量测定系统与最近发布的莫比乌斯验证体模（MVP）中收集的电离室剂量测量值进行比较，来评估该系统。作为参考，还提供了这些测量值与在主要治疗计划系统（TPS）瓦里安医科达直线加速器（Varian Eclipse）中使用AcurosXB剂量算法计算的剂量之间的比较。最后，将莫比乌斯中计算的患者剂量直接与医科达直线加速器进行比较，以展示莫比乌斯系统临床使用期间的典型预期结果。
选择17个匿名的调强放射治疗临床治疗计划进行分析。在医科达直线加速器和莫比乌斯中均在MVP上重新计算剂量。将这些计算出的剂量与在MVP中使用A1SL电离室测量的剂量进行比较。对于每个治疗计划，在两个不同的电离室位置测量并分析剂量。然后使用以下指标将莫比乌斯计算的剂量直接与医科达直线加速器进行比较；靶区平均剂量、靶区D95%、全局三维伽马通过率和靶区伽马通过率。最后，在莫比乌斯系统临床应用后，使用相同的指标分析前36例调强病例。
莫比乌斯与测量值之间的平均差异为0.3±1.3%。差异范围为-3.3%至+2.2%。医科达直线加速器与测量值之间的平均差异为-1.2±0.7%。医科达直线加速器与测量值的差异范围为-3.0%至-0.1%。对于17个匿名的临床前病例，莫比乌斯与医科达直线加速器之间的平均靶区平均剂量差异为1.0±1.1%。平均靶区D95%差异为-0.9±2.0%。使用3%、2毫米标准的平均全局伽马通过率为94.4±3.3%，仅靶区体积的平均伽马通过率为80.2±12.3%。在莫比乌斯临床应用后的前36例调强病例的结果与17例临床前测试病例的结果相似。
莫比乌斯为每个测试的调强治疗计划正确计算了剂量，在所有分析的病例中与测量值的一致性在3.5%以内。莫比乌斯系统的剂量计算准确性和独立性足以对现代TPS进行严格的二次检查。
