Brachytherapy applicators incorporate various forms of selective shielding devices for controlling the direction and intensity of radiation directed at a patient's tissue. In some forms the applicators include a retractable sheath, in some a series of retractable fingers. In other forms the applicator,...http://www.google.ca/patents/US7686755?utm_source=gb-gplus-sharePatent US7686755 - Radiation therapy apparatus with selective shielding capability
