 The purpose of this study is to test a new technology for obtaining x-ray images of your treatment fields when you are positioned on the treatment machine, to determine whether this new system is as reliable and easy to use as conventional systems.. These so-called portal images are normally taken on a weekly basis, prior to your radiation treatment. The new portal imaging system to be tested is designed to produce better quality images than are currently achievable, but with no additional dose or added treatment time. 