3-D dose distributions for optimum radiation treatment planning of complex foods

To obtain satisfactory e-beam irradiation of fresh 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. As a basis of a dosimetry technique, assessment of the exact geometry of fresh products in a 3-D configuration is needed. Obtaining a uniform dose in inherently complex foods such as a chicken carcass is, however, difficult. The objective of this study was to obtain detailed, high-resolution dose distributions of a chicken carcass exposed to e-beam or X-ray irradiation using Monte Carlo simulation and Computer Tomography (CT) techniques. We obtained multi-sliced CT data of a frozen chicken carcass to extract exact product geometry and densities using image-processing methods. The type of source energy input spectrum and source size were entered into the Monte Carlo N-Particle radiation transport code (MNCP5) to obtain dose distributions in the product. For low energy treatment (1.35 MeV electrons, Van de Graaff accelerator), dose absorption occurred up to 5-7 mm deep, resulting in surface irradiation of the carcass. For high energy treatment (10 MeV, LINAC, bottom only), the doses within the carcass rose up to 1.2 times the incident dose with increasing depth and rapidly fell to low values. Two-sided (top and bottom) irradiation resulted in a dose uniformity ratio (D-max/D-min) of about 1.6. Two-sided X-ray irradiation significantly improved the uniformity ratio from 2.5 to 1.8. (c) 2006 Elsevier Ltd. All rights reserved.