The feasibility of measuring manganese concentrations in human liver using neutron activation analysis

Manganese is an element which is required by the human body. However, as with most metals, in large amounts manganese can be toxic. People who suffer from severe manganese intoxication have symptoms similar to those of Parkinson's disease. Preclinical symptoms of manganese intoxication have recently been detected in individuals working in industries which have manganese dioxide dust in the air. The concentration of many toxic elements can be measured in vivo using neutron activation. A small dose of neutrons is delivered to the organ of interest, the neutrons are readily captured by the target nuclei, and the gamma rays given off can be detected outside of the body. A neutron activation analysis system is being developed to measure manganese concentrations in humans. The McMaster KN-accelerator supplies the neutron beam and the thermal neutron capture reaction 55Mn(n,gamma)56Mn is used. The half-life of 56Mn is 2.58 hr and thus counting can occur after irradiation. The 847 keV gamma ray given off when 56Mn decays is detected using a Nal detector. Calibration curves are made using phantoms with known concentrations of Mn. This system will be used to monitor manganese levels in individuals who have occupational exposure to the element. Preliminary measurements, using liver phantoms, give a minimum detectable limit for Mn in the liver of less than one part per million, which is well below normal levels.