Flow analysis with digital subtraction angiography: 2. Acquisition and accuracy of transit-flow measurements.

A steady-state flow model was used to optimize methods of data analysis, to investigate variables that affect the time-density curves, and to determine the accuracy of transit-flow measurements with digital subtraction angiography. The most accurate data were obtained by using a small region of interest placed within the vessel, averaged data acquisition, and a gamma-variate fit applied to the time-density curve. The integrated area of the curve depended on the flow, vessel size, amount of iodine injected, framing rate, and the kVp. The integrated area was not affected by the mAs; the matrix size; or the volume, concentration, or rate of injection of the contrast material. Subject density, image intensifier mode, and field size did not affect the curves except for their contribution to scatter and beam hardening. There was good correlation between digital subtraction angiographic transit-flow measurements and known flow values.