Display of the cross-sectional anatomy of radiation therapy patients has been approached by utilizing the mathematical theory of Ramachandran (1972) for the reconstruction of two-dimensional images from uni-dimensional gamma -ray transmission data. A collimated Co-60 beam is swept through a transverse plane above a patient, and a collimated NaI detector moving synchronously on the opposite side of the patient records the gamma -ray transmission. This process is repeated at various angulations of the Co-60 beam and the detector. The transmission data are processed by computer to obtain a two-dimensional density distribution describing the cross-sectional anatomy of the patient.
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