Dose calculation methodology for irradiation treatment of complex-shaped foods
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Dose calculation methodology was developed for irradiation treatment of complex-shaped foods. To obtain satisfactory electron beam irradiation of food products, a strict process control is required to ensure that the dose delivered to all parts of the treated product falls within some specified range. The Monte Carlo electron transport simulation and computer tomography (CT) scan technology were used to predict the dose distribution in complex shaped foods, an apple phantom composed of paraffin wax, chloroform, and methyl yellow, and a chicken carcass. The Monte Carlo code used was successfully tested against the experimental data, resulting in less than 5% discrepancy between the simulated and measured data. For 1.35 MeV electron beam simulation of apple phantom, tilting and axial rotation ensures dose distribution of the entire surface of the phantom, even reaching the critical regions of the apple stem and calyx ends. For 1 and 5 MeV X-ray simulations, both depth-dose curves show exponential attenuation after a build-up region. The depth to peak for the former is shorter than that of the latter. For 1.35 MeV electron beam simulation of a chicken carcass, dose adsorption occurred up to 5-7 mm deep, resulting in surface irradiation of the carcass. For 10 MeV electron beam simulation, the doses within the carcass reached a peak of 1.2 times the incident dose with increasing depth. Two-sided X-ray (5 MeV) irradiation significantly improved the dose uniformity ratio, from 2.5 to 1.8. A web-based integrated system was developed for data manipulation and management for irradiation treatment of foods. Based on CT scan, three dimensional geometry modeling was used to provide input data to the general Monte Carlo N-Particle (MCNP) code. A web-based interface provided the on-line capability to formulate input data for MCNP and to visualize output data generated by MCNP. The integrated Matlab and Matlab Web Server programs automatically functions through the steps and procedures for data input and output during simulation. In addition, a database having D10 values (decimal reduction value), food nutrition composition, and qualities was integrated into the dose planning system to support food irradiation treatment.