Digital densitometric determination of relative coronary flow distributions

In cardiology coronary stenoses are in most case diagnosed by subjective visual interpretation of coronary artery structures in which contingent stenoses are assessed in terms of percentage luminal area reduction. This results in large intra and interobserver variability in readings. Besides, also the correlation between the anatomical severity of coronary stenoses and their physiological significance is rather poor.

A far better indication for the functional severity of coronary stenoses is coronary flow reserve (CFR). Although good results with densitometric CFR methods have been reported, in clinical practice the current techniques are time consuming and difficult in procedure.

This paper presents a less demanding approach to determine densitometrically the relative flow distribution between the two main branches of the left coronary artery. The hypotheses is that comparison of the flow distributions under basal and hyperemic conditions of the heart muscle will provide useful clinical information concerning the physiological relevance of coronary stenoses.

The hypotheses is tested by means of in vitro flow experiments with a glass flow phantom representing the proximal part of the left coronary artery. From properly positioned regions of interest (ROIs) within a sequence of temporal digital images time-density curves have been extracted. It is investigated whether the centre of gravity of the density curves is a useful parameter to calculate relative flow rate differences. The flow study results together with a discussion will be presented in this paper.