Dose kernels and dose clouds
tumor, SRS
TUMOR
Using the Leksell Gamma Knife Perfexion (Elekta, Stockholm, Sweden) as our SRS device, three‐dimensional (3D) dose distributions were calculated using GammaPlan treatment planning software (10.1) (Elekta, Stockholm, Sweden). A single‐shot dose distribution was created using each of the three GammaKnife Perfexion collimator sizes (4, 8, and 16 mm) at the center of mass of the brain. In addition, a fourth and a fifth dose distribution (24 and 36 mm) were created from a composite of 8‐ and 16‐mm shots. The five resulting dose distributions were exported with 1‐mm resolution in DICOM format into our in‐house simulation program, written in Matlab (MathWorks, Natick, MA). These 3D dose distributions were then used as pre‐calculated dose kernels in the Matlab simulation. Instead of recalculating the doses for every shot placement, the dose kernels were translated to the actual shot positions, summed together, and then renormalized to give each tumor its prescribed dose. From the dose‐volume histogram (DVH) of the summed distribution, the mean dose to the brain was calculated.