Zimmermann Leonard W, Amoush Ahmad, Wilkinson Douglas A
Cleveland State University.
J Appl Clin Med Phys. 2015 Nov 8;16(6):226-239. doi: 10.1120/jacmp.v16i6.5659.
This work is a comparative study of the dosimetry calculated by Plaque Simulator, a treatment planning system for eye plaque brachytherapy, to the dosimetry calculated using Monte Carlo simulation for an Eye Physics model EP917 eye plaque. Monte Carlo (MC) simulation using MCNPX 2.7 was used to calculate the central axis dose in water for an EP917 eye plaque fully loaded with 17 IsoAid Advantage (125)I seeds. In addition, the dosimetry parameters Λ, gL(r), and F(r,θ) were calculated for the IsoAid Advantage model IAI-125 (125)I seed and benchmarked against published data. Bebig Plaque Simulator (PS) v5.74 was used to calculate the central axis dose based on the AAPM Updated Task Group 43 (TG-43U1) dose formalism. The calculated central axis dose from MC and PS was then compared. When the MC dosimetry parameters for the IsoAid Advantage (125)I seed were compared with the consensus values, Λ agreed with the consensus value to within 2.3%. However, much larger differences were found between MC calculated gL(r) and F(r,θ) and the consensus values. The differences between MC-calculated dosimetry parameters are much smaller when compared with recently published data. The differences between the calculated central axis absolute dose from MC and PS ranged from 5% to 10% for distances between 1 and 12 mm from the outer scleral surface. When the dosimetry parameters for the (125)I seed from this study were used in PS, the calculated absolute central axis dose differences were reduced by 2.3% from depths of 4 to 12 mm from the outer scleral surface. We conclude that PS adequately models the central dose profile of this plaque using its defaults for the IsoAid model IAI-125 at distances of 1 to 7 mm from the outer scleral surface. However, improved dose accuracy can be obtained by using updated dosimetry parameters for the IsoAid model IAI-125 (125)I seed.
本研究对用于眼部敷贴近距离放射治疗的治疗计划系统——斑块模拟器（Plaque Simulator）所计算的剂量测定法，与针对Eye Physics模型EP917眼部敷贴使用蒙特卡罗模拟计算的剂量测定法进行了比较。使用MCNPX 2.7进行蒙特卡罗（MC）模拟，以计算完全装载17颗IsoAid Advantage（125）I种子的EP917眼部敷贴在水中的中心轴剂量。此外，还针对IsoAid Advantage模型IAI - 125（125）I种子计算了剂量测定参数Λ、gL(r)和F(r,θ)，并与已发表数据进行了基准比较。使用Bebig斑块模拟器（PS）v5.74，根据美国医学物理师协会更新的任务组43（TG - 43U1）剂量形式计算中心轴剂量。然后比较了MC和PS计算得到的中心轴剂量。当将IsoAid Advantage（125）I种子的MC剂量测定参数与共识值进行比较时，Λ与共识值的一致性在2.3%以内。然而，发现MC计算的gL(r)和F(r,θ)与共识值之间存在更大差异。与最近发表的数据相比，MC计算的剂量测定参数之间的差异要小得多。从距巩膜外表面1至12毫米的距离来看，MC和PS计算得到的中心轴绝对剂量差异在5%至10%之间。当将本研究中（125）I种子的剂量测定参数用于PS时，从距巩膜外表面4至12毫米的深度来看，计算得到的绝对中心轴剂量差异减少了2.3%。我们得出结论，PS使用其IsoAid模型IAI - 125的默认值，在距巩膜外表面1至7毫米的距离处，能够充分模拟该敷贴的中心剂量分布。然而，通过使用IsoAid模型IAI - 125（125）I种子的更新剂量测定参数，可以提高剂量准确性。
