Population-based dosimetry in nuclear medicine and pet: Development of Portuguese female and male anthropomorphic models

Internal organ dose estimates have always depended on standard reference models that mimic the interior and exterior anatomical features of the human body. These models are based on 20–30 year-old and healthy average European and North American populations, their organ masses and body weights and heights corresponding to the 50th percentile data [1]. However, if an individual patient deviates greatly from the reference anatomy, the use of a standard phantom can hinder the precision of the dose assessment being performed. Published anthropometric studies [2] suggest that the Portuguese population deviates from the parameters defined for the reference dosimetric models [3]. The general aim of the present research is to develop and validate two new anthropomorphic models of the human body (one male and one female), that specifically represent Portuguese adult patients who undergo PET/CT examinations. A secondary goal of this project is to profile the Portuguese patients undergoing PET/CT examinations, in respect to their age and internal and external anatomical features. In order to achieve this goal, anthropometric patient data regarding ¹⁸F-FDG PET/CT examinations performed at the Institute of Nuclear Sciences Applied to Health (ICNAS) were collected and analyzed. Statistical hypothesis tests (sign-tests) confirmed that the Portuguese adult patient population anatomy deviates greatly from that of the reference anthropometric phantoms most commonly used in internal dosimetry, at least where age, weight and height are concerned. This supports recent approaches in Internal Radiation Dosimetry, which challenge the “Reference Man paradigm”, that is, the application of reference computational phantoms to the overall population [1]. New anthropomorphic models of the human body, representing Portuguese adult patients who undergo PET/CT examinations, will be created by combining Monte Carlo simulation of the radiation transport and image quantification techniques. These models will facilitate an accurate estimation of internal radiation doses.