In vivo measurement of calcium by prompt-gamma neutron activation analysis

This paper describes phantom experiments to assess the feasibility of measuring both part- and total-body calcium by the prompt - as opposed to the more usual delayed - neutron activation technique. The results indicate that a 30 min irradiation of a 20 cm length of the lumbar spine with a collimated beam of 252Cf neutrons, would yield approximately 2500 counts in the 6.420 MeV main and escape peaks, with a statistical precision of less than 5%, for a dose equivalent of 20 mSv. The proposed detection system, consisting of two 20% efficient germanium detectors positioned above the subject, i.e. on the side opposite the incident neutron beam, would provide improved uniformity of measurement compared with the usual situation where activation and counting are performed from the same side. The on-line technique also enables the subject to be scanned across the neutron beam to provide a measure of total-body calcium. In this case it would be possible to make an analysis to the same degree of precision for an average whole-body dose equivalent of only 1 to 1.3 mSv. 10 references, 3 figures, 1 table