[New principles and theories for improving angio-cinedensitometry. I. The physical principles of quotient densitometry(author's transl)].

The physical basis of quotient densitometry is described. All stages are discussed, beginning with the production of the x-rays, their attenuation by the patient, their effect on the radiographic film, and the evaluation of the film by projection and its measurements by a photo cell in a Wheatstone bridge. Two values were obtained, one consisting of the signal together with background fog, the other of the background alone. By an analysis of the relationships of these measurements, obtained from specially separated points on the radiograph, it is possible to eliminate artefacts to a large extent.