Iodinated contrast opacification gradients in normal coronary arteries imaged with prospectively ECG-gated single heart beat 320-detector row computed tomography

Abstract

Background: To define and evaluate coronary contrast opacification gradients using prospectively ECG-gated single heart beat 320-detector row coronary angiography (CTA).

Methods and results: Thirty-six patients with normal coronary arteries determined by 320 x 0.5-mm detector row coronary CTA were retrospectively evaluated with customized image postprocessing software to measure Hounsfield Units at 1-mm intervals orthogonal to the artery center line. Linear regression determined correlation between mean Hounsfield Units and distance from the coronary ostium (regression slope defined as the distance gradient G(d)), lumen cross-sectional area (G(a)), and lumen short-axis diameter (G(s)). For each gradient, differences between the 3 coronary arteries were analyzed with ANOVA. Linear regression determined correlations between measured gradients, heart rate, body mass index, and cardiac phase. To determine feasibility in lesions, all 3 gradients were evaluated in 22 consecutive patients with left anterior descending artery lesions > or =50% stenosis. For all 3 coronary arteries in all patients, the gradients G(a) and G(s) were significantly different from zero (P<0.0001), highly linear (Pearson r values, 0.77 to 0.84), and had no significant difference between the left anterior descending, left circumflex, and right coronary arteries (P>0.503). The distance gradient G(d) demonstrated nonlinearities in a small number of vessels and was significantly smaller in the right coronary artery when compared with the left coronary system (P<0.001). Gradient variations between cardiac phases, heart rates, body mass index, and readers were low. Gradients in patients with lesions were significantly different (P<0.021) than in patients considered normal by CTA.

Conclusions: Measurement of contrast opacification gradients from temporally uniform coronary CTA demonstrates feasibility and reproducibility in patients with normal coronary arteries. For all patients, the gradients defined with respect to the coronary lumen cross-sectional area and short-axis diameters are highly linear, not significantly influenced by the coronary artery (left anterior descending artery versus left circumflex versus right coronary artery), and have only small variation with respect to patient parameters. Preliminary evaluation of gradients across coronary artery lesions is promising but requires additional study.

Figure 1

Linear fit of the distance (a), short axis diameter (b), and cross-sectional area (c) gradients in the left anterior descending (LAD) for a patient without and a patient with CT evidence of CAD, with results of linear regression.

Figure 1

Linear fit of the distance (a), short axis diameter (b), and cross-sectional area (c) gradients in the left anterior descending (LAD) for a patient without and a patient with CT evidence of CAD, with results of linear regression.

Figure 1

Linear fit of the distance (a), short axis diameter (b), and cross-sectional area (c) gradients in the left anterior descending (LAD) for a patient without and a patient with CT evidence of CAD, with results of linear regression.

Figure 2

Mean and standard deviation of the distance (a), short axis diameter (b), and cross-sectional area (c) gradients for the three major coronary arteries in 36 normal RCA, LAD, and LCx arteries, as well as corresponding gradients in 20 patients with LAD disease. Only the distance gradient has a significant difference between normal coronary arteries; the RCA is significantly closer to zero than the LAD and LCx (ANOVA p < 0.001). Patients with LAD stenosis have significantly different gradient magnitudes than normals (p < 0.011).

Figure 2

Mean and standard deviation of the distance (a), short axis diameter (b), and cross-sectional area (c) gradients for the three major coronary arteries in 36 normal RCA, LAD, and LCx arteries, as well as corresponding gradients in 20 patients with LAD disease. Only the distance gradient has a significant difference between normal coronary arteries; the RCA is significantly closer to zero than the LAD and LCx (ANOVA p < 0.001). Patients with LAD stenosis have significantly different gradient magnitudes than normals (p < 0.011).

Figure 2

Mean and standard deviation of the distance (a), short axis diameter (b), and cross-sectional area (c) gradients for the three major coronary arteries in 36 normal RCA, LAD, and LCx arteries, as well as corresponding gradients in 20 patients with LAD disease. Only the distance gradient has a significant difference between normal coronary arteries; the RCA is significantly closer to zero than the LAD and LCx (ANOVA p < 0.001). Patients with LAD stenosis have significantly different gradient magnitudes than normals (p < 0.011).

Figure 3

Variation of area gradient with respect to cardiac phase in diastole in one RCA (a) and through the entire cardiac cycle in the LAD of a different patient (b). Linear regression results are shown for the RCA, where the trend was significant (Table 5, p < 0.05).

Figure 3

Variation of area gradient with respect to cardiac phase in diastole in one RCA (a) and through the entire cardiac cycle in the LAD of a different patient (b). Linear regression results are shown for the RCA, where the trend was significant (Table 5, p < 0.05).

Figure 4

Standard deviation of the magnitude for all three gradients for the 36 patients with no CT evidence of CAD (blue bars), 60-85% cardiac phase in one patient (red bars), 5-95% cardiac phase at 5% intervals in a single LAD in one patient (purple bars), and between cardiovascular imagers performing the segmentation for 9 cardiac phases in one patient (green bars).