Technical note: an aid to radiation therapy simulation

We have mounted a transmission liquid crystal display unit on the head of a radiotherapy simulator and projected, using the field light, a digitized fluoroscopic image with treatment prescription overlay. It is suggested that this approach (i) can aid visualization on the patient of complex field borders including those defined by multileaf collimators; (ii) could play a role in computed tomography or magnetic resonance based treatment planning and (iii) contributes to configuring non-coplanar beams.