Carbon dioxide angiography: Effect of injection parameters on bolus configuration

PURPOSE: Predict the intravascular distribution of carbon dioxide during an giography. MATERIALS AND METHODS: Mathematical modeling was used to predict the flow p attern of CO2 in a pulsatile system as a function of the CO2 flow rate. Fin dings were validated in an in vitro pulsatile circuit. RESULTS: The annular flow pattern with filling of nearly the entire lumen w ith CO2 is the most desirable, followed by intermittent bubble flow (provid ed individual bubbles are large). Stratified flow relates to a continuous f loating CO2 bubble. Configuration of the CO2 bolus depends on fluid propert ies, fluid velocity, flow rates, mean intraluminal pressure, pressure ampli tude, pulse rate, and vessel diameter. In vessels with less than 10-mm inne r diameter, annular flow can be achieved relatively easily with injection r ates 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 clinical ly is intermittent flow with large bubbles. Bubbles size increases with inc reasing CO2 flow rate. In aneurysms, only stratified flow can be achieved w ith reasonable injection rates, Periodicity of the flow patterns is determi ned 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 d uring CO2 angiography.