Computer simulation of the propagation of contrast medium in a coronary artery during one cardiac cycle

Novel approaches to the measurement of arterial blood flow from dynamic digital X-ray images

We have developed two new algorithms for the measurement of blood flow from dynamic X-ray angiographic images. Both algorithms aim to improve on existing techniques. First, a model-based (MB) algorithm is used to constrain the concentration-distance curve matching approach. Second, a weighted optical flow algorithm (OP) is used to improve on point-based optical flow methods by averaging velocity estimates along a vessel with weighting based on the magnitude of the spatial derivative. The OP algorithm was validated using a computer simulation of pulsatile blood flow. Both the OP and the MB algorithms were validated using a physiological blood flow circuit. Dynamic biplane digital X-ray images were acquired following injection of iodine contrast medium into a variety of simulated arterial vessels. The image data were analyzed using our integrated angiographic analysis software SARA to give blood flow waveforms using the MB and OP algorithms. These waveforms were compared to flow measured using an electromagnetic flow meter (EMF). In total 4935 instantaneous measurements of flow were made and compared to the EMF recordings. It was found that the new algorithms showed low measurement bias and narrow limits of agreement and also out-performed the concentration-distance curve matching algorithm (ORG) and a modification of this algorithm (PA) in all studies.

A new densitometric approach to the assessment of mean coronary flow

RATIONALE AND OBJECTIVES

The authors present an angiographic method to measure absolute coronary blood flow in patients.

METHODS

The left or right coronary tree is three-dimensional (3D)-reconstructed from biplane coronary angiograms. This allows the determination of the intravascular volumes needed for flow measurement. The 3D distance traveled by the contrast medium during one cardiac cycle is determined by appropriately thresholding the "concentration-distance", curves computed on two pairs of images taken one cardiac cycle apart.

RESULTS

The angiographic flow measurements were compared with nearly simultaneous flow determinations obtained with an intracoronary ultrasonic Doppler flow velocity measuring device. The mean relative difference between the Doppler and the 3D measurements was 11% and the two sets of flow values correlated well (r = 0.81).

CONCLUSIONS

A method for the determination of mean coronary flow is presented. The procedure is simple and can be incorporated easily into clinical routine.