MYOCARDIAL BLOOD FLOW: ROENTGEN VIDEODENSITOMETRY TECHNIQUES.

Roen videodensitometry is a technique for obtaining objective measurements of the dilution and transport of radiopaque indicator in the circulatory system. The continuous roentgen angiographic image is recorded on videotape during cardiac catheterization, and during replay of the videotape, digital computer analysis of roentgen density at selected sites within the recorded image can be performed. The image brightness or roentgen density at any point in the circulation is determined by the intensity radiation transmitted through that site. This x-ray transmission is altered by the presence of radiopaque indicator according to the Lambert-Beer law for monochromatic radiation. Because the specific absorption coefficient and incident radiation are constant during the angiographic procedure, measured changes in x-ray density (transmitted radiation) indicate the amount (concentration and depth) of the indicator - bloom mixture being transradiated. While conventional x-ray equipment does not generate monochromatic radiation, the use of suitable copper filters greatly narrows the spectral band of radiation employed.