RATIONALE AND OBJECTIVES.Timendash;dependent fluid flow is computed from projection radiographs without bolus tracking by applying the fluid equations of continuity and incompressibility.METHODS.The fluid equations are combined and integrated to yield an equation that describes instantaneous mass conservation within a vessel segment. The technique is demonstrated using phantom images and patient data obtained using a digital subtraction angiography (DSA) system.RESULTS.Instantaneous and mean flow rates are successfully computed with this algorithm, but the uncertainties are overestimated. In a 1.0ndash;cm diameter tube, instantaneous and mean velocities corresponding to 7.3 cm per frame are computed within 13percnt; uncertainty using a 4.0ndash;cm segment length. Mean flow rates computed from standard diagnostic angiograms taken from three different projections agree within 16percnt;.CONCLUSIONS.This technique can successfully compute timedependent flow rates from DSA image sequences with large fluid displacements between frames. The accuracy is strongly dependent on the magnitude of the contrast density gradient.
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