A practical approach to transverse-section gamma-ray imaging.

The object of transverse-section gamma-ray imaging is to display the concentration of radioactive material in a thin transverse slice of the body. The technique is essentially that of reconstructing a density distribution from its projections, and many methods have been developed to perform the reconstruction. This report describes the realization of three such methods, using a small digital computer PDP8 I, and their application to experimental and clinical data obtained from the Aberdeen Section Scanner: (1) simple back projection; (2) the convolution method of Bracewell and Riddle; (3) the linear integral transform method of Radon. The problems of sensitivity variation and attenuation are examined. An approximate attenuation correction procedure is described. The reconstruction method of Bracewell and Riddle was found convenient since then the data were manipulated in a manner where smoothing to reduce statistical noise and correction for absorption could both be readily incorporated.