An optical edge detector for the accurate delineation of the light field in radiotherapy machines.

A hand-held detector was developed which allows for the unambiguous and consistent determination of the edge of the light (optical) field on treatment machines conveniently and practically. The design incorporates an electronic circuit using three miniature photodiodes. The complete module is housed conveniently in a hand-held box measuring 6 cm x 10 cm x 1.5 cm. The device eliminates any observer subjectivity on the position of the edge of the light field and hence facilitates greatly any commissioning and quality assurance procedures requiring light-radiation field coincidence. Other applications are possible, including alignment of the light field on patients.

Radiation protection design philosophy for a door interlock system for shared room remote afterloading brachytherapy.

A single remote afterloading system can sometimes be used for the radiation treatment of two or more patients in separate rooms simultaneously. This configuration poses certain radiation protection problems, especially in a busy clinic where some of the treatment rooms have to be used for other non-radiation related patients even though not all radiation treatments have been completed. In this report we describe a door interlock system that has been designed to allow for radiation protection purposes during radiation treatment but is disabled when the radiation treatment is completed--with enough safeguard built in to prevent accidental bypass of the interlock. In addition, the quality control procedures of the radiation monitor devices for these treatment rooms are described. These radiation protection procedures could be generalized to other remote afterloading systems.