Carbon dioxide angiography: effect of injection parameters on bolus configuration.

PURPOSE

Predict the intravascular distribution of carbon dioxide during angiography.

MATERIALS AND METHODS

Mathematical modeling was used to predict the flow pattern of CO2 in a pulsatile system as a function of the CO2 flow rate. Findings were validated in an in vitro pulsatile circuit.

RESULTS

The annular flow pattern with filling of nearly the entire lumen with CO2 is the most desirable, followed by intermittent bubble flow (provided individual bubbles are large). Stratified flow relates to a continuous floating CO2 bubble. Configuration of the CO2 bolus depends on fluid properties, fluid velocity, flow rates, mean intraluminal pressure, pressure amplitude, pulse rate, and vessel diameter. In vessels with less than 10-mm inner diameter, annular flow can be achieved relatively easily with injection rates above 20-30 mL/sec. Higher rates are not expected to produce superior results. When imaging a 2-cm artery, the best that can be realized clinically is intermittent flow with large bubbles. Bubbles size increases with increasing CO2 flow rate. In aneurysms, only stratified flow can be achieved with reasonable injection rates. Periodicity of the flow patterns is determined by the pulsatile circuit and can produce indentations in the CO2 bolus, which can be mistaken for stenoses.

CONCLUSIONS

Flow regime maps can be used to optimize bolus configuration during CO2 angiography.