Technical note: a transparent template system for positioning independent radiation-therapy shielding blocks.

To assist the radiation therapist/technologist with setting up patients for radiation therapy treatments, a set of accessories has been developed for placing a transparent template of the treatment-field border in the light-field of a radiation teletherapy unit. These accessories permit the efficient, accurate, and reproducible manual placement of independent lead-shielding blocks. Software has been developed to print templates on standard transparency sheets using a laser printer. A transparent template holder slides into the wedge slot of the teletherapy unit. The template holder features 2 alignment pegs to assure rapid, accurate, and reproducible placement of the template. A specially-developed hole-punch is used to cut, in the template, alignment holes that fit snugly over the pegs of the template holder. This system currently supports Siemens MX and KD units and the Theratronics Theratron 780C Co unit, as well as the Helax TMS block file format.