Peppa V, Pappas E P, Karaiskos P, Major T, Polgár C, Papagiannis P
Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Greece.
National Institute of Oncology, Budapest, Hungary.
Phys Med. 2016 Oct;32(10):1245-1251. doi: 10.1016/j.ejmp.2016.09.020. Epub 2016 Oct 5.
To investigate the clinical significance of introducing model based dose calculation algorithms (MBDCAs) as an alternative to TG-43 in Ir interstitial breast brachytherapy.
A 57 patient cohort was used in a retrospective comparison between TG-43 based dosimetry data exported from a treatment planning system and Monte Carlo (MC) dosimetry performed using MCNP v. 6.1 with plan and anatomy information in DICOM-RT format. Comparison was performed for the target, ipsilateral lung, heart, skin, breast and ribs, using dose distributions, dose-volume histograms (DVH) and plan quality indices clinically used for plan evaluation, as well as radiobiological parameters.
TG-43 overestimation of target DVH parameters is statistically significant but small (less than 2% for the target coverage indices and 4% for homogeneity indices, on average). Significant dose differences (>5%) were observed close to the skin and at relatively large distances from the implant leading to a TG-43 dose overestimation for the organs at risk. These differences correspond to low dose regions (<50% of the prescribed dose), being less than 2% of the prescribed dose. Detected dosimetric differences did not induce clinically significant differences in calculated tumor control probabilities (mean absolute difference <0.2%) and normal tissue complication probabilities.
While TG-43 shows a statistically significant overestimation of most indices used for plan evaluation, differences are small and therefore not clinically significant. Improved MBDCA dosimetry could be important for re-irradiation, technique inter-comparison and/or the assessment of secondary cancer induction risk, where accurate dosimetry in the whole patient anatomy is of the essence.
探讨引入基于模型的剂量计算算法（MBDCAs）作为Ir间质乳腺近距离放射治疗中TG-43替代方法的临床意义。
对57例患者进行回顾性比较，比较从治疗计划系统导出的基于TG-43的剂量测定数据与使用MCNP v. 6.1并结合DICOM-RT格式的计划和解剖信息进行的蒙特卡罗（MC）剂量测定。使用剂量分布、剂量体积直方图（DVH）以及临床上用于计划评估的计划质量指标和放射生物学参数，对靶区、同侧肺、心脏、皮肤、乳腺和肋骨进行比较。
TG-43对靶区DVH参数的高估具有统计学意义，但数值较小（平均而言，靶区覆盖指数小于2%，均匀性指数小于4%）。在靠近皮肤处以及距植入物相对较远的距离处观察到显著的剂量差异（>5%），导致TG-43对危及器官的剂量高估。这些差异对应于低剂量区域（<规定剂量的50%），小于规定剂量的2%。检测到的剂量差异在计算的肿瘤控制概率（平均绝对差异<0.2%）和正常组织并发症概率方面未引起临床显著差异。
虽然TG-43对大多数用于计划评估的指标显示出统计学上显著的高估，但差异较小，因此在临床上不显著。改进的MBDCA剂量测定对于再照射、技术相互比较和/或继发性癌症诱导风险评估可能很重要，在这些情况下，整个患者解剖结构中的准确剂量测定至关重要。
