Ehrbar Stefanie, Jöhl Alexander, Tartas Adrianna, Stark Luisa Sabrina, Riesterer Oliver, Klöck Stephan, Guckenberger Matthias, Tanadini-Lang Stephanie
Department of Radiation Oncology, University Hospital Zurich (USZ), Switzerland; University of Zurich, Switzerland.
Department of Radiation Oncology, University Hospital Zurich (USZ), Switzerland; Product Development Group Zurich, Department of Mechanical and Process Engineering, ETH Zurich, Switzerland.
Radiother Oncol. 2017 Jul;124(1):80-88. doi: 10.1016/j.radonc.2017.05.016. Epub 2017 Jun 3.
Respiratory motion-management techniques (MMT) aim to ensure tumor dose coverage while sparing lung tissue. Dynamic treatment-couch tracking of the moving tumor is a promising new MMT and was compared to the internal-target-volume (ITV) concept, the mid-ventilation (MidV) principle and the gating approach in a planning study based on 4D dose calculations.
For twenty patients with lung lesions, planning target volumes (PTV) were adapted to the MMT and stereotactic body radiotherapy treatments were prepared with the 65%-isodose enclosing the PTV. For tracking, three concepts for target volume definition were considered: Including the gross tumor volume of one phase (single-phase tracking), including deformations between phases (multi-phase tracking) and additionally including tracking latencies of a couch tracking system (reliable couch tracking). The accumulated tumor and lung doses were estimated with 4D dose calculations based on 4D-CT datasets and deformable image registration.
Single-phase tracking showed the lowest ipsilateral lung Dmean (median: 3.3Gy), followed by multi-phase tracking, gating, reliable couch tracking, MidV and ITV concepts (3.6, 3.8, 4.1, 4.3 and 4.8Gy). The 4D dose calculations showed the MidV and single-phase tracking overestimated the target mean dose (-2.3% and -1.3%), while it was slightly underestimated by the other MMT (<+1%).
The ITV concept ensures tumor coverage, but exposes the lung tissue to a higher dose. The MidV, gating and tracking concepts were shown to reduce the lung dose. Neglecting non-translational changes of the tumor in the target volume definition for tracking results in a slightly reduced target coverage. The slightly inferior dose coverage for MidV should be considered when applying this technique clinically.
呼吸运动管理技术（MMT）旨在确保肿瘤剂量覆盖，同时保护肺组织。对移动肿瘤进行动态治疗床跟踪是一种有前景的新型MMT，并在基于4D剂量计算的计划研究中与内靶区（ITV）概念、中期通气（MidV）原则和门控方法进行了比较。
对于20例肺部病变患者，将计划靶体积（PTV）适配于MMT，并使用包绕PTV的65%等剂量线进行立体定向体部放射治疗计划。对于跟踪，考虑了三种靶体积定义概念：包括一个时相的大体肿瘤体积（单相跟踪）、包括时相之间的形变（多相跟踪）以及另外包括治疗床跟踪系统的跟踪延迟（可靠治疗床跟踪）。基于4D-CT数据集和可变形图像配准，通过4D剂量计算估计累积肿瘤和肺剂量。
单相跟踪显示同侧肺平均剂量最低（中位数：3.3Gy），其次是多相跟踪、门控、可靠治疗床跟踪、MidV和ITV概念（3.6、3.8、4.1、4.3和4.8Gy）。4D剂量计算显示MidV和单相跟踪高估了靶区平均剂量（分别为-2.3%和-1.3%），而其他MMT略低估了靶区平均剂量（<+1%）。
ITV概念可确保肿瘤覆盖，但使肺组织接受更高剂量。MidV、门控和跟踪概念可降低肺剂量。在跟踪的靶体积定义中忽略肿瘤的非平移变化会导致靶区覆盖略有降低。临床应用该技术时应考虑MidV的剂量覆盖略差这一情况。
