Dosimetry study for a new in vivo X-ray fluorescence (XRF) bone lead measurement system

A new 109Cd γ-ray induced bone lead measurement system has been developed to reduce the minimum detectable limit (MDL) of the system. The system consists of four 16mm diameter detectors. It requires a stronger source compared to the “conventional” system. A dosimetry study has been performed to estimate the dose delivered by this system. The study was carried out by using human-equivalent phantoms. Three sets of phantoms were made to estimate the dose delivered to three age groups: 5-year old, 10-year old and adults. Three approaches have been applied to evaluate the dose: calculations, Monte Carlo (MC) simulations, and experiments. Experimental results and analytical calculations were used to validate MC simulation. The experiments were performed by placing Panasonic UD-803AS TLDs at different places in phantoms that representing different organs. Due to the difficulty of obtaining the organ dose and the whole body dose solely by experiments and traditional calculations, the equivalent dose and effective dose were calculated by MC simulations. The result showed that the doses delivered to the organs other than the targeted lower leg are negligibly small. The total effective doses to the three age groups are 8.45/9.37μSv (female/male), 4.20μSv, and 0.26μSv for 5-year old, 10-year old and adult, respectively. An approval to conduct human measurements on this system has been received from the Research Ethics Board based on this research.