title: Optimum neutron source to subject distance (ONSSD) and the influence of air-gap on body irradiation in activation analysis.
abstract: An optimum neutron source to subject distance (ONSSD) for body irradiation with a 238Pu-Be neutron source is described. Results are presented which show that the influence of air gaps on the results of neutron activation analysis (NAA) is unimportant when irradiation is performed at the ONSSD. In addition, for subjects having similar bone volumes, differences in the thickness of the surrounding soft tissue may not significantly influence the NAA results. The ONSSD is dependent on the medium surrounding the sources. For 238Pu-Be sources in water, surrounding an air-filled or water-filled sample chamber of radius 6 cm, the ONSSD is about 12 cm from the centre of the chamber. A configuration such as described above will be suitable for in vivo studies of the human extremities in the course of investigation of metabolic bone diseases and also for whole body in vivo studies of small animal models in clinical situations. The technique can easily be extended to other neutron sources.
authors.affiliation: Department of Physics, University of Toronto, Ontario, Canada.
authors.forename: M E
authors.initials: ME
authors.lastname: Ebifegha
mesh_terms: D000201:Activation Analysis; D000388:Air; D001842:Bone and Bones / Q000032:analysis*; D006801:Humans; D008903:Minerals / Q000032:analysis*; D009501:Neutron Activation Analysis; D014867:Water
chemical_list: D008903:Minerals; D014867:Water