Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA.
Phys Med Biol. 2011 Nov 7;56(21):6935-49. doi: 10.1088/0031-9155/56/21/011.
Tumor trailing techniques have been proposed as a method of reducing the problem of intrafraction motion in radiotherapy. However the dosimetric assessment of trailing strategies is complicated by the requirement to study dose deposition over a full fraction delivery. Common 4D planning strategies allowing assessment of dosimetric motion effects study a single cycle acquired with 4DCT. In this paper, a methodology to assess dose deposited over an entire treatment course is advanced and used to assess the potential benefit of tumor trailing strategies for lung cancer patients. Two digital phantoms mimicking patient anatomy were each programmed to follow the tumor respiratory trajectory observed from 33 lung cancer patients. The two phantoms were designed to represent the cases of a small (volume = 13.6 cm3) and large (volume = 181.7 cm3) lung lesion. Motion margins required to obtain CTV coverage by 95% of the prescription dose to 90% of the available cases were computed for a standard treatment strategy and a trailing treatment strategy. The trailing strategy facilitated a margin reduction of over 30% relative to the conventional delivery. When the dose was computed across the entire delivery for the 33 cases, the trailing strategy was found to significantly reduce the underdosage to the outlier cases and the reduced trailing margin facilitated a 15% (small lesion) and 4% (large lesion) reduction for the mean lung dose and 7% (small lesion) and 10% (large lesion) for the mean esophagus dose. Finally, for comparison an ideal continuous tracking strategy was assessed and found to further reduce the mean lung and esophagus dose. However, this improvement comes at the price of increased delivery complexity and increased reliance on tumor localization accuracy.
肿瘤跟踪技术被提议作为减少放射治疗中分次内运动问题的一种方法。然而，跟踪策略的剂量评估受到需要研究整个分次递送过程中剂量沉积的要求所复杂化。常见的允许评估剂量运动效应的 4D 计划策略研究使用 4DCT 获取的单个周期。在本文中，提出了一种评估整个治疗过程中沉积剂量的方法，并用于评估肺癌患者肿瘤跟踪策略的潜在益处。两个模拟患者解剖结构的数字体模分别被编程为跟随从 33 例肺癌患者中观察到的肿瘤呼吸轨迹。这两个体模旨在代表体积分别为 13.6cm3 和 181.7cm3 的小（体积=13.6cm3）和大（体积=181.7cm3）肺病变的情况。对于标准治疗策略和跟踪治疗策略，计算了获得 CTV 覆盖率所需的运动边界，以满足 95%处方剂量的 90%可用病例。与常规递送相比，跟踪策略可将边界减少 30%以上。当在 33 例患者的整个递送过程中计算剂量时，发现跟踪策略可显著减少离群值病例的剂量不足，并且减少的跟踪边界可使平均肺剂量降低 15%（小病变）和 4%（大病变），平均食管剂量降低 7%（小病变）和 10%（大病变）。最后，为了进行比较，评估了理想的连续跟踪策略，并发现它进一步降低了平均肺和食管剂量。然而，这种改进是以增加的交付复杂性和对肿瘤定位准确性的更高依赖为代价的。
