Introduction Several methods of extracting arterial blood flow rates from angiography have been attempted over the past decades.1 However, such methods are not used clinically, primarily because catheter-based contrast injections in arteries can result in substantial pressure and flow disturbances during the injection.2 We hypothesize that injections which cause minimal hemodynamic disturbance in the vessel of interest would result in greater accuracy of angiographically calculated mean flow rates. We conducted an in vitro study under various injection conditions to evaluate this hypothesis.
Methods Angiography at 15 FPS was acquired in a Circle of Willis silicone replica assembled on a pulsatile flow simulator (figure 1, Vascular Simulations, Stony Brook, NY). Injection conditions included (total n=72): catheter-tip position (right carotid, ascending aorta), catheter type (6F end-hole, 6F side-holes), baseline internal carotid flow (4.3, 5.3, 8.3 cc/s), injection rate (carotid: 2, 6 cc/s; aorta: 10, 20 cc/s). Contrast concentration-time curves were recorded at proximal and distal locations on the right internal carotid artery (figure 1) and the bolus transit-time between these two locations was calculated using three different methods (Mean Transit Time, Time to Peak, Cross Correlation). Then, arterial mean flow rate (ml/s)=arterial segment volume(ml)/transit-time(s). Actual flow in the vessel was measured with a flow meter.
Results Statistically significant linear correlations were observed between measured and angiographically calculated flow rates under nearly all injection conditions. Cross correlation was substantially superior to the other two methods (p<0.0001). The error between measured and calculated flows was significantly (p=0.001) lower with the side-hole catheter (11%±11%) as compared to the end-hole catheter (22%±15%). Similarly, the aortic injections showed lower error (13%±11%) than the carotid injections (20%±17%), but without statistical significance (p=0.64).
Conclusions Calculation of mean arterial flow rates by angiography is feasible. The accuracy is higher when the injection causes the least hemodynamic disturbance (side-hole catheter, aortic injection). Improvements to the technique need to be made in order to achieve reliable accuracy in patients, especially under standard (˜4 FPS) frame rate acquisitions.
Lieber BB, et al. Crit Rev Biomed Eng. 2005;33(1):1–1022.
Kovarovic B, et al. Cardiovasc Eng Technol. 2018. doi:10.1007/s13239-018-0344-3
Disclosures M. Gross: None. B. Kovarovic: None. H. Woo: 4; C; Vascular Simulations. 6; C; Cerenovus, JnJ. D. Fiorella: 2; C; Penumbra, Microvention, Medtronic. 4; C; Vascular Simulations. 6; C; Cerenovus JnJ. C. Sadasivan: 4; C; Vascular Simulations.
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