A novel transportable neutron activation analysis system to quantify manganese in bone in vivo: system setup and validation.
Liu-Y; Koltick-D; Zheng-W; Nie-HL
Toxicologist 2014 Mar; 138(1):342
Overexposure to manganese (Mn) can lead to"manganism", a devastating neurological disorder with symptoms closely resembling Parkinson's disease. The progressive and irreversible characteristics of manganism, even after exposure cessation, make early diagnosis of body Mn burden an urgent issue. Data in literature suggests that the amount of Mn in bone accounts for ~40% of total body burden. We hypothesize that bone Mn (MnBn) may serve as a valuable biomarker for long-term cumulative Mn exposure. To test this hypothesis, we have constructed a neutron activation analysis system and validated its usefulness for non-invasive quantification of Mn in bone. Thermal neutrons have a high cross section to interact with 55Mn; the resulting 847 keV characteristic gamma-rays can then be captured. By measuring those gamma counts from the irradiated bone, MnBn concentration can be calculated. Based on simulation work, a deuterium-deuterium (DD) neutron generator system was selected, and optimal materials and thicknesses for neutron moderation, reflecting, and shielding were also determined in order to provide the highest yield of thermal neutrons. Hand bone has been chosen as the irradiation site to minimize the irradiation dose to human subjects. More recently, we have constructed a DD neutron generator with a flux up to 3 X10(9) neutrons/sec. Hand phantoms doped with different Mn concentrations were irradiated using the optimized irradiation system. The Mn characteristic gamma-rays were collected by a HPGe detector system with 100% relative efficiency and analyzed by a digital spectral processor. The detection limit was calculated to be about 1.5 ug Mn/g dry bone (ppm) with an irradiation dose of 50 mSv to the hand. The whole body effective dose was about 31 uSv. The current effort is devoted to reduce the detection limit to 0.75 ppm with a combination of four 100% HPGe detectors. Given the normal MnBn concentration of ~1 ppm in general population, this system appears to be useful in MnBn quantification in humans.
Toxicology; Air-quality; Exposure-levels; Chemical-composition; Workers; Work-environment; Manganese-compounds; Bone-disorders; Biomarkers; Analytical-processes; Irradiation
The Toxicologist. Society of Toxicology 53rd Annual Meeting and ToxExpo, March 23-27, 2014, Phonex, Arizona
Purdue University, West Lafayette, Indiana