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The authors present phantom validation of a method for computing pulsatile flow waveforms in arterial vessels from high–frame-rate biplane x-ray angiograms.The three-dimensional course of a blood vessel is constructed from biplane digital x-ray angiograms. A parametric image of contrast mass versus time and true three-dimensional path length is generated. Adjacent contrast mass-distance profiles are matched to compute instantaneous velocity, which is multiplied by cross-sectional area to yield volume flow. An electromagnetic flowmeter was used to validate flow estimates in a phantom consisting of 150-mm tubes 3, 4, and 6 mm in diameter, orientated 15°, 30°, and 35° to the imaging plane, with flow rates and waveforms expected in vivo.Mean and peak flows were accurate to within 9% and 10%, respectively, for velocities of less than 1 meter/second at a frame rate of 25 frames per second.A practical method for computing highly pulsatile flow waveforms in vivo in tortuous vessels is presented.