An image-based rat model for Monte Carlo organ dose calculations.

An anatomically realistic rat model was developed from color images of successive cryosections of a mature Sprague-Dawley rat. Images were obtained, by digital scanning, of 9475 slices with thickness of 0.02 mm. A total of 13 major organs and tissues were selected, and models of these organs and tissues constructed from the images were used for calculations of absorbed dose from external photon sources. A detailed set of conversion coefficients from kerma free-in-air to organ absorbed dose have been calculated for external monoenergetic photon beams with energies ranging from 10 keV to 10 MeV under five idealized irradiation conditions (left lateral, right lateral, dorsal-ventral, ventral-dorsal, and isotropic) using the Monte Carlo code MCNPX. Dose results are presented in form of tables as supplemental data for practical use and comparison. The influence of anatomical characteristics, including organ volume, shape, location, and orientation, on dose distributions were evaluated. It would also be possible to make internal dose assessments using the computational rat model.