부산대학교 도서관

Purpose: The conventional verification films and electronic portal images are widely used in the verification of patients' position and the reproducibility of the multi-leaf collimator and block, custom block or cerroben block. The use of verification film is often accompanied by the inconvenience of storing and retrieving. In addition, the importance of using digital images cannot be overemphasized in the modem radiotherapy. We intended to compare digital portal images obtained from computed radiography (CR) system with conventional portal films and the images from electronic portal imaging devices (EPID). Materials ＆ Methods: The quality of the verification images was based on the contrast of different thickness or density. We took conventional portal films and digital images of a step wedge and an anthropomorphic RANDO Phantom under a 21 EX Varian linear accelerator. Those images were then compared by visual inspection and quantitative analysis method. Results: Based on the step wedge study, CR system could obtain the full gray-scale of images with least MU. In each treatment site (i.e. Head ＆ Neck, Chest ＆ Pelvis), the quality of the CR images was judged to be superior to conventional portal films. Conclusion: The operation for the CR system is similar to the tradition verification film. Since they are digital images, they ca be post processed and the anatomic structure can be enhanced in different ways, especially in the lateral fields of pelvis. It provides a better quality of image to verify the accuracy of the treatment position. It seems that the CR system ca provide a better solution for the radiation treatment of cancer.