Evaluation of Monte Carlo Simulation Accuracy to Calculate PDD in Femoral Bone Marrow During Exposure to Low Energy Rays

Due to the high sensitivity of the bone marrow to ionizing radiation as well as the large number of bone graphs, it is important to evaluate the absorbed dose in the bone marrow during exposure to radiographic rays. The aim of the present study was to determine and evaluate the accuracy of Monte Carlo simulations to calculate PDD in the femoral bone marrow during exposure to low energy rays.

The present descriptive study was conducted in 2020 at Yasuj University of Medical Sciences. 100 CT scan images of the femur were selected, of which 28 images were extracted from the beginning to the end of the femur. After simulating the head of the device with normal energies in femoral radiography using BEAMnrc simulator, the information obtained from CT scan images of patients with CT CREAT software, digital femoral phantom was designed. The phantom was digitally irradiated (using DOSXYX simulator) and the absorbed dose percentage (PDD) was calculated using STATE DOSE software. Finally, the data were analyzed using Image Java and Excel software.

The percentage of absorbed dose in femoral bone marrow at energies of 70, 80 and 90 was in the range of 2 to 78%, 5 to 79% and 5 to 76%, respectively. Also, with increasing depth in all energies, the percentage of absorbed dose decreases. For energies of 90 kV and to some extent for energies of 70 and 80 kV, the data show a sudden decrease in the percentage of absorbed dose from a depth of 6 mm to 9 mm. From a depth of 1.1 cm to 1.5 cm, the dose absorbed in the bone marrow varies according to energy.

Monte Carlo simulation method can be an effective method in calculating the absorbed dose in bone marrow tissue. The results show that the calculations of the percentage of absorbed dose up to a depth of 2 cm are significantly accurate. As the depth increases, the accuracy of the calculations (provided that the number of particles participating in the simulation does not increase) gradually decreases.