Stereotactic dose perturbation from an aneurysm clip measured by Gafchromic EBT film

Aneurysm clips within stereotactic treatment volumes enhance spatial accuracy but perturb the dose distribution. The dose perturbations caused by a standard titanium alloy aneurysm clip (Ti6Al4V) have been measured with Gafchromic EBT film. The maximum dose perturbation was an increase of 6 % within 0.5 mm of the beam entry surface of the clip, and a decrease of 7 % within 0.5 mm of the beam exit surface of the clip. Results also showed perturbations to film readout due to the presence of micro dust particles on the film affecting optical properties at high spatial resolution (21um) scanning. Special procedures should be used when film is immersed in water, dried and then read at high spatial resolution. We recommend that films should be immersed only in distilled water and tools such as canned air puffs should be used to clean films without scratches.