Lung density imaging in pulmonary edema: chest X-ray versus compton scatter tomography

In the course of pulmonary edema water accumulates in the extravascular space with a consequent increase of lung density- Therefore, the severity of the disease may be quantified and the time course followed if lung density changes can be measured. A tomographic technique was developed in order to visualize sectional chest planes by means of a collimated linear source of gamma rays and a gamma camera to detect Compton scattered photons at 90° to the primary beam. As the intensity of the Compton effect is a linear function of the scanned tissue density, the resulting image is a map of the distribution of a lung densities along the plane crossed by the incident beam. A computer processing of the original images was performed to clear the views of systematic and/or random acquisition errors. The application of this technique to the study of pulmonary edema and the comparison with x-ray findings are described.