Page 40 - Fisica In Medicina n° 1/2017

ResultsWe chose a 0.5mMFe2+ gel composition, without XO. Spatial diffusion with no XO raised (~1.7times), even if it remained negligible, but on the contrary dose sensitivity increase (~2.4times). Best sensitivity was obtained for TR=4000ms, TI=400ms. FGd outcome didn’t depend on photon beam dose rate (Δ600-1000UM/min<1.6%). No image correction maps were needed, since GD and inhomogeneity were negligible. 3D spatial resolution (voxel dimension), was 1x1x3mm3. Dose accuracy was in the range 2-4% for 18-25Gy, but worst for lower doses. Dose resolution was about 1Gy, while LOD was 0.4Gy. Differences between FGd and Gafchromic profiles’ FWHMs were min=0.7mm– max=5.2mm. Max dose deviation in the profiles’ flat region was 2.3%, while penumbra differences were 2.3mm max.ConclusionThis feasibility study showed that FGd could be a suitable tool for SBRT and SRS pre-treatment QA, thanks to their optimal spatial resolution, their practicability and their capability to perform 3D dosimetry.^Äëíê~Åí=cáëáÅá= =31