A NEW APPROACH FOR THE QUANTIFICATION OF COMPLEX LESION MORPHOLOGY - THE GRADIENT FIELD TRANSFORM - BASIC PRINCIPLES AND VALIDATION RESULTS

Objectives. This report describes the basic principles and the results from clinical evaluation studies of a new algorithm that has been des igned specifically for the quantification of complex coronary lesions. Background. Currently used edge detection algorithms in quantitative coronary arteriography, such as the minimum cost algorithm, are limite d in the precise quantification of complex coronary lesions characteri zed by abruptly changing shapes of the obstruction. Methods. The new a lgorithm, the gradient field transform, is not limited in its search d irections and incorporates the directional information of the arterial boundaries. To evaluate its accuracy and precision, 11 tubular phanto ms (sizes 0.6 to 5.0 mm), were analyzed. Second, angiographic images o f 12 copper phantoms with U shaped obstructions were analyzed by both the gradient field transform and the minimum cost algorithm. Third, 25 coronary artery segments with irregularly shaped obstructions were se lected from 19 routinely acquired angiograms. Results. The plexiglass phantom study demonstrated an accuracy and precision of -0.004 and 0.1 14 mm, respectively. The U-shaped copper phantoms showed that the grad ient field transform performed very well for short, severe obstruction s, whereas the minimum cost algorithm severely overestimated the minim al lumen diameter. From the coronary angiograms, the intraobserver var iability in the minimal lumen diameter was found to be 0.14 mm for the gradient field transform and 0.20 mm for the minimum cost algorithm. Conclusions. The new gradient field transform eliminates the limitatio ns of the currently used edge detection algorithms in quantitative cor onary arteriography and is therefore particularly suitable for the qua ntification of complex coronary artery lesions.