Abstract

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Title:: Volumetric and dosimetric effects of 4D-CT on internal target areas in stereotactic body radiotherapy

Author(s):: ZOU Jinhua; LIU Zhongqiang; XU Jinfeng; Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China

Keywords:: Keywords: lung cancer internal target area stereotactic body radiotherapy four-dimensional computed tomography volumetric modulated arc therapy radiation dose

Abstract:: Abstract: Objective To investigate the volumetric and dosimetric effects on internal target volume (ITV) delineations based on the tumor motions measured by four-dimensional computed tomography (4D-CT) in the stereotactic body radiotherapy (SBRT) of lung cancers. Methods Two ITV definition methods for 6 lung cancer patients were investigated. One of the definition is the ITVall combining all gross tumor volumes (GTV) in the 4D-CT sequences of 10 respiratory phases and the other was ITVmotion which was obtained by adding the measured tumor motions in anterior-posterior, left-right and cranial-caudal directions from 4D-CT to the GTV in free-breathing CT. The volumes and dosimetric differences resulted from different ITV definitions were analyzed. Results In the term of volume, the average ratios of ITVmotion to ITVall were 2.36, and the two ITV definitions had similar PTV coverage. The lung mean dose (Dmean) was decreased as the TIV decreased, and the Dmean of ITVall was 77.4 cGy less than that of ITVmotion. Conclusion Due to the relative small tumor size for SBRT, no significant dosimetric differences were observed between two ITV definitions. Considering the workload and time required to generate ITVall, ITVmotion may be a preferred option.