Protecting a CT simulator room to accommodate a cyberknife facility

In 2012, a plan to develop Stereotactic treatments using a Cyberknife was unveiled at the Hermitage Medical Clinic, Dublin. Due to planning restrictions the new facility had to be contained in the existing hospital's blue print with the only available location being an unused CT simulation room. The room design would be different from conventional radiotherapy bunkers due to the fact the Cyberknife can fire an unfiltered beam in any direction bar the roof (restriction of 22° above the horizontal). Therefore all walls must be primary barriers with the roof designed to protect against the large leakage radiation resulting from the high MU's used during the treatments. Space consideration indicated that concrete alone could not be used to restrict the radiation beam to acceptable limits. To this end a combination of steel, lead, normal and heavy concrete were used to meet the dose constraints established by the Irish licensing authorities.