Time and flow parameter extraction in digital angiography: principles and methods.

Indicator dilution techniques are used in the quantitative analysis of angiograms for time and flow measurements. In digital angiography the temporal changes of brightness are examined for each picture element. Certain functional parameters are evaluated and assembled in "parametric images". Flow distribution measurements are performed on the basis of two parametric images: A time parameter is used to define vascular segments that are passed by the blood flow in preselected time intervals. The depth parameter image provides for computation of the volume of each segment, which is used as the basis for regional blood flow calculation. Five time parameters and two depth parameters are described, differently suitable in various fields of application.