Validation of GATE for bone and bone marrow with calculation specific absorbed fraction for photons.

Purpose: GATE/GEANT is a Monte Carlo code dedicated to nuclear medicine that allows calculation of the dose to organs (bone and bone marrow) of voxel phantoms. On the other hand, Medical Internal Radiation Dose (MIRD) is a well-developed system for estimation of the dose to human organs. In this study, results obtained from GATE/GEANT using leg of Snyder phantom is compared to published MIRD data.

Materials and Methods: For this, the mathematical leg of Snyder phantom was discretized and converted to a digital phantom of 100 × 100 × 200 voxels. The activity was considered uniformly distributed within bone and bone marrow. The GATE/GEANT Monte Carlo code was used to calculate the dose to the bone and bone marrow of the leg phantom from mono-energetic photons of 10, 15, 20, 30, 50, 100, 200, 500, and 1000 keV. The dose was converted into a specific absorbed fraction (SAF) and the results were compared to the corresponding published MIRD data.

Results: On average, there was a good correlation between the two series of data for self-absorption (r 2 = 0.99) and for cross-irradiation (r 2 = 0.99). However, the GATE/GEANT data were on average 1.01 ± 0.79% higher than the corresponding MIRD data for self-absorption. As for cross-irradiation, the GATE/GEANT data were on average 8.11 ± 7.95% higher than the MIRD data.

Conclusion: In this study, the SAF values derived from GATE/GEANT and the corresponding MIRD published data were compared. On average, the SAF values derived with GATE/GEANT showed an acceptable correlation and agreement with the MIRD data for the photon energies of 50-1000 keV. For photons of 10-30 keV, there was an only poor agreement between the GATE/GEANT results and MIRD data.