%0 Journal Article %T Computational and Experimental Approaches for Evaluating Dose under a Block in TBI Geometry %A Laura Russell %A Jussi Sillanpaa %J International Journal of Medical Physics,Clinical Engineering and Radiation Oncology %P 77-83 %@ 2168-5444 %D 2022 %I Scientific Research Publishing %R 10.4236/ijmpcero.2022.111007 %X Total Body Irradiation (TBI) patients are often treated at extended distances of several meters, with blocking made from high-Z materials placed close to the patientsбп skin. Evaluating the dose under a block (e.g., for implanted medical device shielding purposes) in such a geometry is challenging. We compare the performance of two commonly used dose calculation algorithms, Anisotropic Analytical Algorithm (AAA) and Acuros XB, with Optically Stimulated Lumine- scence (OSLD) and ion chamber measurements in phantoms. The calculations and phantom measurements are also compared with in-vivo OSLD measure- ments. We find that OSLD and ion chamber measurements in phantom are good predictors of in-vivo measurements, while both AAA and Acuros XB sys- tematically overestimate the block transmission. We found Acuros XB to be accurate enough for a rough upper estimate (dose under block overestimated by 7% - 22%), while for AAA the overestimate was more severe (90% - 110%); the reason is that AAA does not account for the increase in pair production