New angiographic technique for measurement of instantaneous blood flow rates using distance-density curves

Accurate measurement of blood flow rates can provide a useful means for evaluation of functional significance of stenoses, coronary flow reserve, and changes in flow rates resulting from interventional procedures. However, for pulsatile flow conditions, blood flow rates determined by analysis of conventional time-density curves are unreliable. Therefore, we are developing a new method based on an analysis of the distribution of contrast material along the length of the vessel, i.e., the 'distance-density' curve, in digital subtraction angiographic (DSA) images. The distance that the contrast material travels during the time between two image acquisitions is determined by comparison of the two distance-density curves. The flow rate between the image acquisitions is calculated by multiplying this distance by the frame rate and the vessel cross-sectional area which is estimated from the vessel size. Thus, for high frame-rate acquisitions, 'instantaneous' blood flow rates can be determined. From angiograms obtained at 15 frames/sec, the instantaneous flow rates measured with our technique agreed with those measured with an electromagnetic method to within an average of 2.3 cc/sec for pulsatile flow conditions with peak flow rates of up to 30 cc/sec, and average flow rates agreed to within an average of 11%.