A dosimetric phantom study of thoracic radiotherapy based on three-dimensional modeling of mediastinal lymph nodes

Ji-Bin Zhang; Li-Rong Zhao; Tian-Xiang Cui; Xie-Wan Chen; Qiao Yang; Yi-Bing Zhou; Zheng-Tang Chen; Shao-Xiang Zhang; Jian-Guo Sun

doi:10.3892/ol.2018.8084

A dosimetric phantom study of thoracic radiotherapy based on three-dimensional modeling of mediastinal lymph nodes

Oncol Lett. 2018 Apr;15(4):5634-5642. doi: 10.3892/ol.2018.8084. Epub 2018 Feb 16.

Authors

Ji-Bin Zhang¹, Li-Rong Zhao¹, Tian-Xiang Cui¹, Xie-Wan Chen², Qiao Yang¹, Yi-Bing Zhou¹, Zheng-Tang Chen¹, Shao-Xiang Zhang³, Jian-Guo Sun¹

Affiliations

¹ Cancer Institute of The People's Liberation Army, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, P.R. China.
² Department of Medical English, College of Basic Medicine, Third Military Medical University, Chongqing 400038, P.R. China.
³ Department of Digital Medicine, College of Basic Medicine, Third Military Medical University, Chongqing 400038, P.R. China.

Abstract

The aim of the present study was to investigate the optimal strategy and dosimetric measurement of thoracic radiotherapy based on three-dimensional (3D) modeling of mediastinal lymph nodes (MLNs). A 3D model of MLNs was constructed from a Chinese Visible Human female dataset. Image registration and fusion between reconstructed MLNs and original chest computed tomography (CT) images was conducted in the Eclipse™ treatment planning system (TPS). There were three plans, including 3D conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT), which were designed based on 10 cases of simulated lung lesions (SLLs) and MLNs. The quality of these plans was evaluated via examining indexes, including conformity index (CI), homogeneity index and clinical target volume (CTV) coverage. Dose-volume histogram analysis was performed on SLL, MLNs and organs at risk (OARs). A Chengdu Dosimetric Phantom (CDP) was then drilled at specific MLNs according to 20 patients with thoracic tumors and of a medium-build. These plans were repeated on fused MLNs and CDP CT images in the Eclipse™ TPS. Radiation doses at the SLLs and MLNs of the CDP were measured and compared with calculated doses. The established 3D MLN model demonstrated the spatial location of MLNs and adjacent structures. Precise image registration and fusion were conducted between reconstructed MLNs and the original chest CT or CDP CT images. IMRT demonstrated greater values in CI, CTV coverage and OAR (lungs and spinal cord) protection, compared with 3D-CRT and VMAT (P<0.05). The deviation between the measured and calculated doses was within ± 10% at SLL, and at the 2R and 7th MLN stations. In conclusion, the 3D MLN model can benefit plan optimization and dosimetric measurement of thoracic radiotherapy, and when combined with CDP, it may provide a tool for clinical dosimetric monitoring.

Keywords: dosimetric measurement; mediastinal lymph nodes; plan optimization; radiation phantom; thoracic radiotherapy; three-dimensional reconstruction.