Measurements of Setup Error and Physiological Movement of Liver by Using Electronic Portal Imaging Device in Patients with Hepatocellular Carcinoma

Keum, Ki Chang; Lee, Sang wook; Shin, Hyun Soo; Kim, Gwi Eon; Seong, Jinsil; Lee, Chang Geol; Chu, Sung Sil; Chang, Sei Kyung; Suh, Chang Ok

Abstract

PURPOSE
The goal of this study was to improve the accuracy of three-dimensional conformal radio therapy (3-D CRT) by measuring the treatment setup error and physiological movement of liver based on the analysis of images which were obtained by electronic portal imaging device (EPID).
MATERIALS AND METHODS
For 10 patients with hepatocellular carcinoma, 4-7 portal images were obtained by using EPID during the radiotherapy from each patient daily. We analyzed the setup error and physiological movement of liver based on the verification data. We also determined the safety margin of the tumor in 3-D CRT through the analysis of physiological movement.
RESULTS
The setup errors were measured as 3 mm with standard deviation 1.70 mm in x direction and 3.7 mm with standard deviation 1.88 mm in y direction respectively. Hence, deviation were smaller than 5 mm from the center of each axis. The measured range of liver movement due to the physiological motion was 8.63 mm on the average. Considering the motion of liver and setup error, the safety margin of tumor was at least 15 mm.
CONCLUSION
EPID is a very useful device for the determination of the optimal margin of the tumor, and thus enhance the accuracy and stability of the 3-D CRT in patients with hepatocellular carcinoma.