Dose mapping of complex-shaped foods using electron-beam accelerators

Obtaining a uniform dose in inherently irregularly shaped foods, such as an apple, is very difficult, and development of accurate dose calculation methodologies is needed. The objective was to determine the most uniform irradiation treatment on apple surrogates and GAFCHROMIC® HD-810 films using electron beams from a 2 MeV Van de Graaff (VDG) accelerator, a l0 MeV Linear Accelerator (LINAC), and X-rays from a 5 MeV LINAC. We manufactured a solid 3-D apple-surrogate from a mixture of paraffin wax, chloroform, and methyl yellow biological indicator. The surrogate showed electron interaction characteristics very similar to an actual apple. Evaluation of food positioning strategies in front of the e-beam source of the VDG demonstrated that tilting axial rotation ensure uniform dose distribution of the entire surface of the surrogate, even reaching the critical regions of the stem and calyx ends.Irradiation with 10 MeV dual e-beam showed uniform penetration (top to bottom) in the HD-810 film and surrogates. X-ray irradiation completely penetrated the apple surrogate (top to bottom) showing excellent lateral uniformity at different penetration depths. The measured dose distributions in the surrogate showed good agreement with the calculated doses. These results support the validity of using chemical surrogate techniques for accurate planning of food irradiation treatments.