A block localizer for easy and reproducible transfer of shielding block positions from simulator to treatment unit

For the localization of shielding blocks at the simulator a special tray called "block localizer" was constructed. It can be attached to the simulator head by means of magnets in the top frame. The "block localizer" provides a platform at a distance from the X-ray source corresponding to the source-to-block distance at the treatment unit. On the platform templates made from 0.5 mm brass to the size of the block bases can be positioned under fluoroscopy. Before taking the beam localization exposure a low sensitivity film is placed in a slit in the platform. On this film the template (block) position is recorded. For treatment the developed film is attached to the block tray and the shielding block inserted according to the light shadow of the template projected from the film onto the patient. An easy and reliable positioning of blocks during repeated irradiations is thus provided. The block (template) position is also recorded on the beam localization film of the patient as a transparent shadow.