Some physical problems associated with clinical radioisotope imaging

A thesis has been presented which has investigated some of the important physical factors which control the detection of tumours with radioisotope imaging systems. Using phantoms, the physical factors investigated include a) the dead time of the system, b) the concentration ratio of the isotope in the target to that in the background, c) the size and shape of the target, d) the depth of the target in the medium, e) the absorption coefficients for the gamma ray energies of the intervening tissues between the target and the surface, f) the size of the background region, g) the energies accepted by the system (pulse height analyser settings), h) the type of collimator, i) the shape of the profile curve, j) the display system employed to output the data, k) the nature of any data processing or 'smoothing' employed prior to displaying the information and l) the decision criterion adopted by the observer. The conclusions deduced from these investigations are presented. (U.K.)