Results are presented comparing Monte Carlo (MC) calculations for dynamic IMRT treatments of tumors in the sinus region with Eclipse treatment planning system dose calculations, and ion chamber measurements. The EGS4nrc MC code, BEAMnrc, was commissioned to simulate a Varian 21Ex Linac for both open and IMRT fields. The accuracy of the simulation for IMRT plans was evaluated using a head phantom by comparing MC, Eclipse, TLD results, and ion chamber in solid water phantom measurements. The MC code was then used to simulate dose distributions for five patients who were treated using dynamic IMRT for tumors in the sinus region. The results were compared with absolute and relative dose distributions calculated using Eclipse (pencil beam, modified-Batho inhomogeneity correction). Absolute dose differences were also compared with ion chamber results. Comparison of the doses calculated on the head phantom using MC, compared with Eclipse, ion chamber, and TLD measurements showed differences of -3.9%, -1.4%, and -2.0%, respectively (MC is colder). Relative dose distributions for the patient plans calculated using MC agreed well with those calculated using Eclipse with respect to targets and critical organs, indicating the modified-Batho correction is adequate. Average agreement for mean absolute target doses between MC and Eclipse was -3.0 +/-; 2.3% (1 s.d.). Agreement between ion chamber and Eclipse for these patients was -2.2 +/- 1.9%, compared with 0.2 +/- 2.0% for all head and neck IMRT patients. When Eclipse doses were corrected based on ion chamber results, agreement between MC and Eclipse was -0.7 +/- 2.0%, indicating a small systematic uncertainty in the doses calculated using the treatment planning system for this subset of patients.

译文

:结果比较了用蒙特卡洛(MC)计算窦道区域肿瘤的动态IMRT治疗与Eclipse治疗计划系统剂量计算和离子室测量值的比较结果。委托EGS4nrc MC代码BEAMnrc模拟开放域和IMRT域的Varian 21Ex Linac。通过比较MC,Eclipse,TLD结果和固体水体模测量中的离子室,使用头部体模评估了IMRT计划仿真的准确性。然后,将MC代码用于模拟五名使用动态IMRT进行鼻窦区域肿瘤治疗的患者的剂量分布。将结果与使用Eclipse计算出的绝对和相对剂量分布(铅笔束,改良的Batho不均匀性校正)进行比较。还将绝对剂量差异与离子室结果进行了比较。与使用Eclipse,离子室和TLD进行测量相比,使用MC在头部模型上计算的剂量进行了比较,分别显示出-3.9%,-1.4%和-2.0%的差异(MC更冷)。对于目标和关键器官,使用MC计算的患者计划的相对剂量分布与使用Eclipse计算的相对剂量分布非常吻合,表明改良的Batho校正是足够的。 MC和Eclipse之间的平均绝对目标剂量的平均一致性为-3.0 /-; 2.3%(1 s.d.)。对于这些患者,离子室和Eclipse之间的一致性为-2.2 /-1.9%,而所有头颈部IMRT患者的一致性为0.2 /-2.0%。根据离子室结果校正Eclipse剂量后,MC和Eclipse之间的一致性为-0.7 /-2.0%,这表明使用治疗计划系统为该患者子集计算的剂量存在系统性的不确定性。

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