CR Portal Images for High Energy Electron Therapy

Abstract

The field verification is very important in the high energy electron therapy as well as in the high energy photon irradiation.
Bremsstrahlung X - rays, range from 1 to 5% of the total dosage, are produced in the high energy electron irradiation with ordinary energy (6 to 18MeV). Using these bremsstrahlung X - rays and a computed radiography system (abbreviated as CR hereafter), the following were investigated; (1) the relationship between the electron energy and the image contrast and (2) the clinical application of the CR - electrogram (abbreviated as CR - EG hereafter). The image contrast decreased with an increase of electron energy. However, the difference in the contrast with the change of electron energy became smaller when proper reading latitude of the CR was selected. Field trimming conditions in the CR - EGs and organs surrounding the applicator were clearly defined. Our new method turned out to be very useful in clinical use.