Optimization of Body Composition Analyzer Facility, Considering Operator Dosimetry

Abstract

Background: Changes in body composition may be used for monitoring progression/<br><br>regression of a disease. Prompt γ-rays in vivo neutron activation analysis<br><br>(IVNAA) has been widely used for the measurement of body composition in recent<br><br>years.<br><br>Objective: In this paper, we tried to improve the safety of IVNAA operator.<br><br>Methods: The most important factor for reducing the operator receiving dose is the<br><br>optimization of shields. An appropriate shield should not only reduce the operator receiving<br><br>dose, but it also must have the least effect on the detected spectrum. Because<br><br>all parts of setup, including the operator shield, can be activated, the emitted γ-rays<br><br>may be counted in detectors and increase the background level. In this research,<br><br>several shields have been considered for an IVNAA setup. 4 different shields—concrete,<br><br>epoxy colemanite resin, paraffin borated with bismuth layer (PE-Bi layer), and<br><br>paraffin borated uniformly mixed with bismuth (PE-Bi)—were simulated by MCNPX<br><br>code.<br><br>Results: We found that the PE-Bi shield decreases the absorbed dose to 77%<br><br>compared with “no shield” and 74% compared to concrete. Also, the reduction rate of<br><br>dose equivalent was 95% compared to “no shield” and 91% compared to colemanite<br><br>resin. The neutron flux decreased almost 400 times in the presence of PE-Bi; it had<br><br>less background in γ-spectrum compared to other suggested shields.<br><br>Conclusion: Among the tested shields, PE-Bi would be the best one.