Pressure and Flow Rate Changes During Contrast Injections in Cerebral Angiography: Correlation to Reflux Length

Abstract

Cerebral angiography involves the antegrade injection of contrast media through a catheter into the vasculature to visualize the region of interest under X-ray imaging. Depending on the injection and blood flow parameters, the bolus of contrast can propagate in the upstream direction and proximal to the catheter tip, at which point contrast is said to have refluxed. In this in vitro study, we investigate the relationship of fundamental hemodynamic variables to this phenomenon. Contrast injections were carried out under steady and pulsatile flow using various vessel diameters, catheter sizes, working fluid flow rates, and injection rates. The distance from the catheter tip to the proximal edge of the contrast bolus, called reflux length, was measured on the angiograms; the relation of this reflux length to different hemodynamic parameters was evaluated. Results show that contrast reflux occurs when the pressure distal to the catheter tip increases to be greater than the pressure proximal to the catheter tip. The ratio of this pressure difference to the baseline flow rate, called reflux resistance here, was linearly correlated to the normalized reflux length (reflux length/vessel diameter). Further, the ratio of blood flow to contrast fluid momentums, called the Craya-Curtet number, was correlated to the normalized reflux length via a sigmoid function. A sigmoid function was also found to be representative of the relationship between the ratio of the Reynolds numbers of blood flow to contrast and the normalized reflux length. As described by previous reports, catheter based contrast injections cause substantial increases in local flow and pressure. Contrast reflux should generally be avoided during standard antegrade angiography. Our study shows two specific correlations between contrast reflux length and baseline and intra-injection parameters that have not been published previously. Further studies need to be conducted to fully characterize the phenomena and to extract reliable indicators of clinical utility. Parameters relevant to cerebral angiography are studied here, but the essential principles are applicable to all angiographic procedures involving antegrade catheter injections.

Angiographic assessment of the efficacy of flow diverter treatment for cerebral aneurysms

“…The power injector artifact is a larger issue that may need to be addressed by future evaluation of the injection technique and parameters. Antegrade contrast injections into the vasculature result in complex mixing phenomena at the catheter tip, and depending on the relative fluid momentums of contrast and blood, 4,5,7 injections can cause substantial hemodynamic disturbances 12 during the period of injection. Additionally, as stated above, when using a power injector, the inertia of the fluid in the large bore syringe causes contrast to emanate continually from the catheter tip, even after the injection.…”

“…While the literature body is vast, functional angiography is not yet used routinely in patients because catheter-based contrast injections can cause complex and substantial hemodynamic disturbances in the vessel of interest. [4][5][6][7] However, the growth in neuro-endovascular treatment has rekindled interest in the use of angiographic techniques for flow assessment in various pathologies. [8][9][10][11][12][13][14] The treatment of aneurysms with flow diverters is particularly amenable to such analysis because (a) the reduction of intraaneurysmal flow remains a central hypothesis of treatment success; (b) flow diversion does not require (dense) intra-saccular device implantation, thus allowing for X-ray visualization of contrast transport within the aneurysm; and (c) instead of the need for extraction of absolute flow parameters, the change in intraaneurysmal contrast transport from pre-device implantation to post-device implantation can potentially be used to predict aneurysm occlusion.…”

E-210 An in vitro study of intraneurysmal pressure increases during contrast injections in cerebral angiography

“…Introduction During angiography, the contrast bolus injected into a vessel can cause substantial changes in baseline pressures and flows. 1 There have been sparse case reports about aneurysmal re-bleeds during angiography. 2 A physician survey of injection rates used during angiography showed that 81% of respondents considered the impact of injection rate on aneurysm rupture to be negligible .…”

E-161 A novel angiographic method to measure arterial blood flow rates using contrast reflux

“…Introduction Several methods of extracting arterial blood flow rates from angiography have been attempted over the past decades. 1 2 However, catheter-based contrast injections in arteries can cause substantial disturbances to the baseline blood flow, 3 which has limited the utilization of these methods in the clinical setting. Contrast reflux, which is the movement of contrast proximal to the catheter tip is frequently observed during antegrade angiography.…”