Monte Carlo radiography simulation for assessment of absorbed radiation dose in femur bone marrow during X-ray radiography for constant mAs and AEC techniques

Background: The purpose of this study was to find the accurate absorbed dose in the femur bone marrow during the X-ray radiography for constant mAs and AEC techniques. Materials and Methods: The DOSXYZnrc was used to simulate radiation doses in two human femurs during diagnostic radiography. EGSnrc phantoms produced from actual CT images of human femurs were modified by adding seven micrometre layers of marrow tissues. The X-ray machine was simulated using BEAMnrc using 30 billions particles for different combinations of energies and filters. The resultant data was used to in DOSXYSnrc simulations to evaluate the absorbed dose in the human femur. Results: In the head of the femur, for 2.5 mm aluminium filtered 85 kVp X-ray set at 50 mAs, the absorbed dose in the marrow was found to be 1.360 mGy, ~ 36% of the absorbed dose in the cortical bone. It was also found that for the constant mAs technique, the radiation dose in the marrow over the studied energies and filter combination, ranges from 0.356 mGy to 2.403 mGy, with higher dose recorded for higher kVp settings. However, for the AEC technique, the dose is lower for higher kVp settings. For a typical setting, viz. 85 kVp, 6 mAs at 48 inches SID, the bone marrow absorbed dose was found to be 0.186 mGy for the constant mAs technique and 0.0308 mGy for the AEC technique. Conclusion: It was confirmed that the radiation dose is lower when the AEC exposure technique is used as opposed to using constant mAs technique. For the AEC technique, typical dose to the bone marrow was found to be ~ 0.05 mGy, decreasing with both kVp settings and beam filtration. For constant mAs technique, the typical dose to bone marrow is found to be higher, ~ 0.2 mGy, decreasing with the amount of filtration used but increasing with the kVp setting.