Aortic root catheter-directed coronary CT angiography in swine: coronary enhancement with minimum volume of iodinated contrast material.

OBJECTIVE

The purpose of this study was to evaluate the minimum amount of contrast material for coronary imaging with aortic root catheter-directed enhancement and 64-MDCT angiography (MDCTA).

MATERIALS AND METHODS

A 64-MDCT scanner was used after animal institutional review board approval to study four swine (40-60 kg). Heart rate reduction to 65 beats per minute was achieved with atenolol by mouth and i.v. Cardizem. Common femoral artery access was obtained with a 5-French micropuncture kit and sonographic guidance. A diffusiontip (640 side holes), 5-French pigtail catheter was positioned in the aortic root on the CT table with a retrofitted C-arm fluoroscopy unit and connected to an arterial power injector. Aortic root MDCTA (retrospective ECG gating; collimation, 0.6 mm; tube rotation time, 0.33 second; scanning time, 10-12 seconds; tube voltage, 120 kVp; effective mAs, 850 mAs; pitch, 0.2; field of view, 109-123 mm; slice thickness and increment, 0.6 and 0.3 mm) was begun 1 second after the injection of 100 mL of various Visipaque (iodixanol) concentrations (10%, 20%, 30%, 40%) at 10 mL/s. Coronary mean and peak densities, 3D maximum intensity projections, and 4D projections were obtained.

RESULTS

The mean pooled coronary attenuation values (H +/- SD) for the right (RCA), left anterior descending (LAD), and left circumflex (LCx) coronary arteries at various concentrations (10%, 20%, 30%, 40%) were as follows: 10% (RCA [232.6 +/- 64.0], LAD [180.4 +/- 45.1], and LCx [176.6 +/- 56.2]); 20% (RCA [383.0 +/- 98.7], LAD [324.3 +/- 60.1], and LCx [331.8 +/- 105.5]); 30% (RCA [441.8 +/- 137.6], LAD [401.3 +/- 125.8], and LCx [418.5 +/- 173.0]); and 40% (RCA [717.3 +/- 377.7], LAD [573.3 +/- 233.3], and LCx [584.8 +/- 189.0]). Coronary imaging with aortic root MDCTA was feasible at all concentrations, and the attenuation values were statistically significantly greater than 250 H at 20%, 30%, and 40% (p < 0.05). The attenuation values with aortic root MDCTA using one fifth of the volume of contrast material are comparable to those currently achieved both clinically and experimentally with peripheral i.v. MDCTA.

CONCLUSION

Aortic root MDCTA can depict the coronary arteries with as little as 20 mL of contrast material. This may provide an alternative means of coronary evaluation in patients with renal insufficiency.