Determination of instantaneous and average blood flow rates from digital angiograms of vessel phantoms using distance–density curves

We have developed a new method for quantitation of blood flow rates based on determination of the spatial shift of the distribution of contrast material in opacified vessels in digital angiograms that are acquired while the contrast material proceeds through the vessel. The distance that the contrast material travels during the time between image acquisitions is determined by comparison of density-vs.-distance curves, which represent the distribution of contrast material along the length of the vessel in the respective images. The flow rate between image acquisitions is calculated by multiplication of the distance traveled by the frame rate and the vessel cross-sectional area. Therefore, for high-frame-rate acquisitions, “instantaneous” flow rates can be determined. In these vessel-phantom studies, the root-mean-square (RMS) difference between instantaneous flow rates measured with our technique and those measured with an electromagnetic method was 2.9 ml/sec; the RMS difference for average flow rates was 0.8 ml/sec.