title: Age-dependent small-animal internal radiation dosimetry.
abstract: Rats at various ages were observed to present with different radiosensitivity and bioavailability for radiotracers commonly used in preclinical research. We evaluated the effect of age-induced changes in body weight on radiation dose calculations. A series of rat models at different age periods were constructed based on the realistic four-dimensional digital rat whole-body (ROBY) computational model. Particle transport was simulated using the MCNPX Monte Carlo code. Absorbed fractions (AFs) and specific absorbed fraction (SAFs) of monoenergetic photons/electrons and S values of eight positron-emitting radionuclides were calculated. The SAFs and S values for most source-target pairs were inversely correlated with body weight. Differences between F-18 S values for most source-target pairs were between -1.5% and -2%/10 g difference in body weight for different computational models. For specific radiotracers, the radiation dose to organs presents a negative correlation with rat body weight. The SAFs for monoenergetic photons/electrons and S values for common positron-emitting radionuclides can be exploited in the assessment of radiation dose delivered to rats at different ages and weights. The absorbed dose to organs is significantly higher in the low-weight young rat model than in the adult model, which would result in steep secondary effects and might be a noteworthy issue in laboratory animal internal dosimetry.
authors: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva.
authors: Tianwu
authors: T
authors: Xie
authors: Habib
authors: H
authors: Zaidi
mesh_terms: D000367:Age Factors; D000818:Animals; D001835:Body Weight; D003198:Computer Simulation; D004195:Disease Models, Animal; D007668:Kidney / Q000502:physiology; D008954:Models, Biological; D009010:Monte Carlo Method; D009929:Organ Size; D011874:Radiometry / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D013270:Stomach / Q000502:physiology