Sarkar Vikren, Huang Long, Huang Yu-Huei Jessica, Szegedi Martin W, Rassiah-Szegedi Prema, Zhao Hui, Hitchcock Ying J, Kokeny Kristine E, Wang Brian, Salter Bill J
Department of Radiation Oncology, University of Utah, Salt Lake City, UT 84112, USA.
Department of Radiation Oncology, University of Louisville, Louisville, KY 40292, USA.
J Radiosurg SBRT. 2016;4(2):125-132.
Abdominal compression has been shown to reduce the extent of lung tumor motion but the dosimetric impact of the approach is still in need of investigation. The current work analyzes the impact of various changes in PTV volume on key metrics of the final dose distribution to normal lung. To add clinical perspective, we also provide NTCP calculations for grade 2+ pneumonitis for each case. For a total of seventeen cases, the original ITV/PTV was reduced by systematically varied amounts and SBRT plans using dynamic conformal arc and VMAT techniques were created. DVH analysis for the normal lung comparing the original plan to the one with the ITV reduced by up to 10 mm shows that the average reduction of V5, V20 and mean lung dose is 3.8%, 2.0% and 1.1 Gy, respectively, for the conformal arc plans. Corresponding values for the VMAT plans were 3.9%, 1.9% and 1.2 Gy respectively. The mean NTCP drop for the conformal arc plans was 2.0% while it was 1.9% for the VMAT plans. These results suggest that abdominal compression has a modest impact on NTCP and on dosimetric parameters typically used to predict the risk of radiation pneumonitis in patients undergoing lung SBRT.
腹部压迫已被证明可减少肺部肿瘤的运动范围，但该方法对剂量学的影响仍有待研究。当前工作分析了计划靶体积（PTV）的各种变化对正常肺最终剂量分布关键指标的影响。为增加临床视角，我们还针对每个病例提供了2级及以上肺炎的正常组织并发症概率（NTCP）计算。对于总共17例病例，原始的内部靶体积（ITV）/PTV以系统变化的量减少，并使用动态适形弧和容积调强放疗（VMAT）技术创建了立体定向体部放疗（SBRT）计划。将原始计划与ITV减少多达10毫米的计划进行比较，对正常肺的剂量体积直方图（DVH）分析表明，对于适形弧计划，V5、V20和平均肺剂量的平均减少分别为3.8%、2.0%和1.1 Gy。VMAT计划的相应值分别为3.9%、1.9%和1.2 Gy。适形弧计划的平均NTCP下降为2.0%，而VMAT计划为1.9%。这些结果表明，腹部压迫对NTCP以及通常用于预测接受肺部SBRT患者放射性肺炎风险的剂量学参数有适度影响。
