Abstract
A review is provided of early attempts at determining the elemental composition of the body by radioactive isotope dilution techniques. The development and the current status of in-vivo neutron activation analysis is presented and the ways in which it supersedes or supplements certain of the former techniques is outlined. A description is given of an irradiation facility which employs a 5 Ci neutron source. The facility was designed to be flexible and it is capable of performing prompt and delay gamma-ray measurements as well as cyclic activation. Personnel and gamma-ray detectors are shown to be adequately shielded from the mixed radiation field from the source. The uniformity of thermal neutron flux in a phantom is demonstrated by flux profiles obtained experimentally. Principles and techniques of dosimetry are given and the relationship between radiation quality and radiobiological effect is examined. The neutron spectrum at a depth in the phantom has been obtained by means of the activities induced in a set of threshold detectors. An examination is made of the possible applications of the Monte Carlo method to the design of irradiation and detection facilities and in yielding information about areas which are inaccessible to the experimenter. Detection limits for the bulk body elements have been determined by measurement of prompt and delay gamma rays and cyclic activation. Detection limits are also presented for trace elements using cyclic activation and prompt gamma ray analysis. It is shown that the depth of an organ or region of the body can be determined from information present in a prompt gamma ray spectrum. This technique can be used to correct measurements when it is known that activation and detection is non-uniform. Computed tomography scanning offers the possibility of determining the amount of bone mineral per unit volume of bone. The feasibility of using a C.T. whole body scanner to measure bone demineralisation is explored. Finally, the advantages and problems of each of the techniques mentioned above is discussed and suggestions are made for further work.