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BioMed Research International
Volume 2015, Article ID 959504, 6 pages
http://dx.doi.org/10.1155/2015/959504
Research Article

Fan-Shaped Complete Block on Helical Tomotherapy for Esophageal Cancer: A Phantom Study

1Department of Biomedical Imaging and Radiological Sciences, National Yang Ming University, Taipei 112, Taiwan
2Division of Radiation Oncology, Department of Radiology, Far Eastern Memorial Hospital, New Taipei City 220, Taiwan
3Biomedical Imaging Laboratory, Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau
4Department of Radiation Oncology, Koo Foundation Sun Yat-Sen Cancer Center, Taipei 112, Taiwan

Received 10 November 2014; Revised 13 January 2015; Accepted 14 January 2015

Academic Editor: Xin-yuan Guan

Copyright © 2015 Chiu-Han Chang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Radiation pneumonitis (RP) is a common complication for radiotherapy of esophageal cancer and is associated with the low dose irradiated lung volume. This study aims to reduce the mean lung dose (MLD) and the relative lung volume at 20 Gy () and at low dose region using various designs of the fan-shaped complete block (FSCB) in helical tomotherapy. Hypothetical esophageal tumor was delineated on an anthropomorphic phantom. The FSCB was defined as the fan-shaped radiation restricted area located in both lungs. Seven treatment plans were performed with nonblock design and FSCB with different fan angles, that is, from 90° to 140°, with increment of 10°. The homogeneous index, conformation number, MLD, and the relative lung volume receiving more than 5, 10, 15, and 20 Gy (, , , and ) were determined for each treatment scheme. There was a substantial reduction in the MLD, , , , and when using different types of FSCB as compared to the nonblock design. The reduction of , , , and was 6.3%–8.6%, 16%–23%, 42%–57%, and 42%–66% for FSCB 90°–140°, respectively. The use of FSCB in helical tomotherapy is a promising method to reduce the MLD, , and relative lung volume in low dose region, especially in and for esophageal cancer.