The role of fan-shaped complete block on Helical Tomotherapy for esophageal cancer: a phantom study

• Main Authors: Chiu-Han Chang, 張秋涵
• Other Authors: Tung-Hsin Wu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/66419247807595550727

碩士 === 國立陽明大學 === 生物醫學影像暨放射科學系 === 103 === 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 (V20) 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 non-block design and FSCB with different fan angles, i.e., 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 (V5, V10, V15, V20) were determined for each treatment scheme. There was a substantial reduction in the mean lung dose, V5, V10, V15 and V20 when using different types of FSCB as compared to the non-block design. The reduction of V20, V15, V10 and V5 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, V20 and relative lung volume in low dose region, especially in V5 and V10 for esophageal cancer. More dose reduction was observed for FSCB design with larger fan angles.