Quantitative CAG

• Dr Hiralal P

1. INTRODUCTION — A reduction in the coronary artery luminal cross-sectional diameter, estimated by the visual inspection of the radiocontrast column or lumenogram during conventional angiography, has been utilized to formulate predictions about clinical presentations and stress-induced reductions in coronary blood flow.

2. Anatomic and physiologic approaches to coronary artery disease are complementary but because of numerous factors not evident from angiography (eg, length, entrance angle, coefficient of separation of laminar flow) comparison data yield contradictory results.

3. As a result, quantitative approaches to the angiographic evaluation of coronary anatomy are infrequently employed on a routine daily basis in most laboratories. The greatest advantage of quantitative coronary angiography is its theoretical freedom from observer influences and bias, thereby minimizing significant potential intraobserver and interobserver variability.

• Techniques

• Edge-detection — Once the image has been acquired and digitally processed, computer manipulation is performed. The most critical component of the computational analysis is the algorithm of boundary delineation within the area of interest. This method requires identification of the arterial segment to be analyzed and an accurate computer-assisted vessel edge delineation

• Densitometry — The densitometric methodology minimizes any distorting effect of lesional eccentricities upon those geometric assumptions that are required for area calculations by the edge-detection methods. With densitometry, assuming homogeneous distribution of radio-contrast in the blood pool, the errors in edge definition are minimized since the method utilizes the measurement of brightness profiles throughout the segmental diameters which surround the defined center line [9]. With application of this assumption, the difference in cross-sectional luminal area can be compared between normal and diseased vascular segments, using differences in the density of radio-contrast distributed within each cross-sectional area. These derived measurements must be corrected for radiation scatter by the subtraction of background activity. Additional radiographic variables can contribute to measurement inaccuracy, and convincing validation of this technique has not yet been forthcoming

• Ulceration,lesion morhology not detected• Vasomoter tone • Inhomogenious radioconrast• Angle• Side branches

• SUMMARY• ●Quantitative coronary angiography (QCA) is a method to provide more objective

interpretation of the coronary lumenogram than standard visual estimation. The greatest advantage of quantitative coronary angiography is its theoretical freedom from observer influences and bias, thereby minimizing significant potential intraobserver and interobserver variability.

• ●QCA reports the percent diameter stenosis as well as additional parameters, such as lesion length, area of obstruction, area of plaque, and minimal stenosis diameter.

• ●QCA attempts to standardize the measurement of stenosis severity.• ●QCA has been utilized to formulate predictions about clinical presentations and

prognosis.• ●QCA, while more accurate than visual assessment for gauging lesion severity, has

only weak correlation to translesional functional assessment in the cath lab.• ●Quantitative approaches to the angiographic evaluation of coronary anatomy are

infrequently employed on a routine daily basis in most laboratories.