In 1958 Rejali, MacIntyre, and Friedell suggested the application of radioisotopic scanning methods to visualization of the cardiac blood pool.1 Since that time, several different radioisotopic scanning devices have been developed and applied to problems in medical diagnosis. Using an automatic photoscanning technique developed at this hospital, we have studied a series of 40 patients in whom differentiation of cardiac dilatation from pericardial effusion was not certain by clinical means.
Principles of Radioisotope Scanning
Radioisotope scanning is the visualization of an internal organ or tumor by determining the spatial distribution of a γ-emitting radioisotope within the body. Cassen and his associates introduced the method in 1950 by utilizing newly developed scintillation counters to print mechanically the distribution of radioactive iodine in the thyroid gland.2 In 1950, Anger improved the technique by replacing the mechanical stylus with a flashing light that activated photographic emulsion on x-ray film.3 In