Abstract
We introduced an image mixing camera system at Akita University Hospital in 1999. We evaluated portal film matching rate by using this mixing camera system from January to December 1998. Of 166 cases of radiation therapy, 17 cases were selected at random and we used this system and compared it with the visual verification of portfilms, a traditional way of examination. These 17 cases examined in a traditional way were the cases that were considerd to have no problem in terms of matching (within-10 mm distance). As a result of using this mixing camera system, we found that only 2 cases out of 17 were actually fully (100%) matched. We consider that difference in magnification of portfilm and linacgraphy was one of the reasons for mismatch. Our image mixing camera system can check each other at equal magnification. Therefore this device will play an important role in radiation therapy in terms of increasing the accuracy of treatment (Quality Assurance).
