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J Korean Soc Ther Radiol > Volume 14(1); 1996 > Article
Journal of the Korean Society for Therapeutic Radiology 1996;14(1): 69-76.
Objective Analysis of the Set-up Error and Tumor Movementin Lung Cancer Patients using Electronic Portal Imaging Device
Gwi Eon Kim, Eun Ji Chung, Chang Geol Lee, Sung Sil Chu, Woo Cheol Kim
1Department of Radiation Oncology, Yonsei University, College of Medicine, Korea.
2Yonsei Cancer Center, Yonsei University, College of Medicine, Seoul, Korea.
ABSTRACT
PURPOSE:
The aim of this study is to investigate the random and systematic errors and tumor movement using electronic portal imaging device in lung cancer patients for the adequate margin in the treatment planning of 3-dimensional conformal therapy. METHODS AND MATERIALS: The electronic portal imaging device is matrix ion chamber type(Portal Vision, Varian). Ten patients of lung cancer treated with chest irradiation were selected for this study. Patients were treated in the supine position without immobilization device. All treatments were delivered by an 10 MV linear accelerator that had the portal imaging system mounted to its gantry. AP or PA field portal images were only analyzed. Radiation therapy field included the tumor, mediastinum, and supraclavicular lymph nodes. A total of 103 portal images wereanalyzed for set-up deviation and 10 multiple images were analyzed for tumor movement because of respiration and cardiac motion.
RESULTS:
The average values of setup displacements in the x, y direction was 1.41 mm, 1.78 mm, respectively. The standard deviation of systematic component was 4.63 mm, 4.11mm along the x,y axis, respectively while the random component was 4.17 mm in the x direction and 3.31 mm in the y direction. The average displacement from respiratory movement was 12.2 mm with a standard deviation of 4.03 mm
CONCLUSION:
The overall set-up displacement includes both random and systematic component and respiratory movement. About 10 mm, 25 mm margins along x,y axis which considered the set-up displacement and tumor movement were required for initial 3-dimensional conformal treatment planning in the lung cancer patients and portal images should be madeand analyzed during first week of treatment, individually.
Key Words: 3-Dimensional conformal radiation therapy, Electronic portal imaging device, Set-up error
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