Dose reconstruction method for photon external radiation accident based on human voxel phantom

Objective: To study the method of dose reconstruction in human body under the photon external radiation accident condition, and to verify the accuracy of the method for the local dose distribution. Methods: Based on the open source Monte Carlo tool kit Geant 4 and using the human voxel phantom recommended by ICRP Publication 103, the dose reconstruction method under the condition of external radiation accident was studied to evaluate the average absorbed dose, organ absorbed dose and local dose distribution. To validate the code, several irradiation experiments were implemented in some standard radiation fields by putting TLDs in the tissue equivalent physical phantom ART. A voxel phantom was used to reconstruct the radiation doses, which was created based on the CT scan image of the ART phantom with resolution of 1.57 mm × 1.57 mm × 10.00 mm. The result of experiment were compared with those of dose reconstruction simulation. Results: The relative uncertainty of the measured values was 10.9%. The relative uncertainty of the dose reconstruction simulation values was 7.10% at the non-tissue-interface area and 16.6% at the tissue-interface area. For 451 measuring points, the average of the simulated value divided by the measured value was 0.972, with the standard deviation of 0.0838. In the range of 0.95-1.05, 0.90-1.10 and 0.80-1.20, and the proportions were 49.2%, 79.4% and 96.4%, respectively. Conclusions: The method of Monte Carlo dose reconstruction based on human voxel phantom meets the accuracy requirement of actual uses both at the whole body or organ level and at the local dose distribution level. It can be used as a powerful tool for dose assessment of the exposed people in an external radiation accidents and provide support for diagnosis and treatment. (authors)