Quantitative evaluation of vessel tracking techniques on coronary angiograms

Accurate, automated determination of vessel center lines is essential for t wo- and three-dimensional analysis of the coronary vascular tree. Therefore , we have been developing techniques for vessel tracking and for evaluating their accuracy and precision in clinical images. After points in vessels a re manually indicated, the vessels are tracked automatically by means of a modified sector-search approach. The perimeters of sectors centered on prev ious tracking points are searched for the pixels with the maximum contrast. The sector size and radius are automatically adjusted based on local vesse l tortuosity. The performance of the tracking technique in regions of high- intensity background is improved by application of a nonlinear adaptive fil tering technique in which the vessel signal is effectively removed prior to background estimation. The tracking results were evaluated visually and by calculation of distances between the tracked and user-indicated centerline s, which were used as the "truth." Two hundred and fifty-six coronary vesse ls were tracked in 32 angiograms. Vessels as small as 0.6 mm in diameter we re tracked accurately. This technique correctly tracked 255/256 (>99%) vess els based on an average of 2-3 indicated points per vessel. The one incorre ct tracking result was due to a low signal-to-noise ratio (SNR<2). The dist ance between the tracked and the "true" centerlines ranged from 0.4 to 1.8 pixels, with an average of 0.8 pixels. These results indicate that this tec hnique can provide a reliable basis for 2D and 3D vascular analysis. (C) 19 99 American Association of Physicists in Medicine. [S0094-2405(99)02205-1].