Background Contrast reflux, which is the retrograde movement of contrast against flow direction, is commonly observed during angiography. Despite a vast body of literature on angiography, the hemodynamic factors affecting contrast reflux have not been studied. Numerous methods have been developed to extract flow from angiography, but the reliability of these methods is not yet sufficient to be of routine clinical use. Purpose To evaluate the effect of baseline blood flow rates and injection conditions on the extent of contrast reflux. To estimate arterial flow rates based on measurement of contrast reflux length. Materials and methods Iodinated contrast was injected into an idealized tube as well as a physiologically accurate model of the cervico‐cerebral vasculature. A total of 194 high‐speed angiograms were acquired under varying “blood” flow rates and injection conditions (catheter size, injection rate, and injection time). The length of contrast reflux was compared to the input variables and to dimensionless fluid dynamics parameters at the catheter‐tip. Arterial blood flow rates were estimated using contrast reflux length as well as a traditional transit‐time method and compared to measured flow rates. Results Contrast reflux lengths were significantly affected by contrast injection rate (p < 0.0001), baseline blood flow rate (p = 0.0004), and catheter size (p = 0.04), but not by contrast injection time (p = 0.4). Reflux lengths were found to be correlated to dimensionless fluid dynamics parameters by an exponential function (R2 = 0.6–0.99). When considering the entire dataset in unison, flow estimation errors with the reflux‐length method (39% ± 33%) were significantly higher (p = 0.003) than the transit‐time method (33% ± 36%). However, when subgrouped by catheter, the error with the reflux‐length method was substantially reduced and was significantly lower (14% ± 14%, p < 0.0001) than the transit‐time method. Conclusion Results show correlations between contrast reflux length and baseline hemodynamic parameters that have not been reported previously. Clinically relevant blood flow rate estimation is feasible by simple measurement of reflux length. In vivo and clinical studies are required to confirm these correlations and to refine the methodology of estimating blood flow by reflux.

Background During diagnostic cerebral angiography, the contrast bolus injected into a vessel can cause substantial changes in baseline pressures and flows. One potential, and serious complication is the re-rupture of aneurysms due to these injections. The goals of this in vitro study were to evaluate the effect of injection conditions on intraneurysmal pressure changes during angiography. Methods A silicone replica of a complete circle of Willis model with ophthalmic, anterior communicating, and basilar tip aneurysms was connected to a physiologically accurate flow pump. Contrast injections were performed under different conditions (carotid or vertebral vessel imaging, catheter diameter, injection rate, injection time, and arterial blood flow rate) and the pressure in each aneurysm was recorded before and during each injection. The effect of injection conditions on percentage increase in aneurysm pressures was statistically assessed. Additionally, the effect of the distance between the aneurysm and the catheter-tip on aneurysmal pressures was assessed. Results Mean intraneurysmal pressures during injection (84.5 ± 10.8 mmHg) were significantly higher than pre-injection pressures (80.4 ± 10.6 mmHg, p < 0.0001). Only 3 of the 5 conditions – carotid injections, higher injection rates, and smaller catheter diameters – significantly increased intraneurysmal pressures. The catheter-tip distance showed no correlation to pressure increases. Conclusions Increasing contrast injection rates and decreasing catheter diameters are correlated to intraneurysmal pressure increases during angiography irrespective of the distance to the catheter tip. Future in vivo studies are required to confirm these findings and determine whether the amplitude of pressure increases with commonly used injection rates can be clinically detrimental.

outcome, occlusion rate and reoperation. Moreover, clipping and stent-assisted coiling all showed higher occlusion rates compared with coiling alone. Conclusion Definitely, EVT is the mainstream treatment for paraclinoid aneurysms. Surgical clipping showed a higher complication risk than EVT. Clipping might be considered to be an alternative option for paraclinoid aneurysms if EVT are for hard hurdle because many complications were temporary, and occlusion tendency of clipping was also good. Disclosures S. Chung: None. S. Chang: None.

reflected inverse correlation between thrombus-T2* relaxation time and red blood cell content (figures A to E). Conclusion FSE T2 WI and quantitative T2* mapping MR can help in characterization of emboli in large vessel occlusion patients.

BackgroundLiquid embolic agents and polyvinyl alcohol (PVA) particles have been used for the embolization of the middle meningeal artery (MMA) for the treatment of chronic subdural hematomas. However, the vascular penetration and distribution of these embolic agents have not yet been compared. The current study compares distribution of a liquid embolic agent (Squid) to PVA particles (Contour) in an in vitro model of the MMA.MethodsMMA models were embolized with Contour PVA particles 45–150 µm, Contour PVA particles 150–250 µm, and Squid-18 liquid embolic agent (n=5 each). The models were scanned and every vascular segment with embolic agent was manually marked on the images. Embolized vascular length as a percentage of control, average embolized vascular diameter, and embolization time were compared between the groups.ResultsThe 150–250 µm Contour particles primarily accumulated close to the microcatheter tip, yielding proximal branch occlusions. The 45–150 µm Contour particles achieved a more distal distribution, but in a patchy segmental pattern. However, the models embolized with Squid-18 had a consistently distal, near-complete and homogenous distribution. Embolized vascular length was significantly higher (76±13% vs 5±3%, P=0.0007) and average embolized vessel diameter was significantly smaller (405±25 µm vs 775±225 µm, P=0.0006) with Squid than with Contour. Embolization time with Squid was also lower (2.8±2.4 min vs 6.4±2.7 min, P=0.09).ConclusionsSquid-18 liquid results in a considerably more consistent, distal and homogeneous pattern of embolysate distribution than Contour PVA particles in an anatomical model of the MMA tree.