Quantitative coronary angiography (QCA) provides more objective interpretation of coronary arteries than visual estimation by minimizing intraobserver and interobserver variability. QCA uses edge detection and densitometry techniques to measure parameters like percent diameter stenosis, lesion length, and area of obstruction. While more accurate than visual assessment, QCA does not always correlate well with functional flow assessments and has not been widely adopted in laboratories due to limitations in accounting for factors like vessel angle and vasomotor tone.

1. Quantitative CAG
• Dr Hiralal P

2. 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.

3. • Techniques

4. • 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

6. • 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

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

8. • 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.