Radiation Shielding for Gamma Stereotactic Radiosurgery Units

Abstract

Shielding calculations for gamma stereotactic radiosurgery units are complicated by the fact that the radiation is highly anisotropic. Shielding design for this device is unique. Although manufacturers will answer questions about the data they provide for shielding evaluation, they will not perform such calculations for customers. There are now over 220 gamma knife centers worldwide. Those centers installing a gamma knife find themselves in a position requiring them to either invent or re-invent a method for performing shielding design. A rigorous and conservative method for barrier design for gamma knife treatment rooms is presented. This method should be useful to centers planning to either install a new gamma knife unit or replace an existing unit. The method described here is consistent with the principles outlined in the US NCRP Report No. 151. A simple electronic spreadsheet can be set up in as little as one hour which will provide radiation levels on planes parallel to the barriers and 0.3 m outside the barriers.