BACKGROUND: Hemodynamic factors play a crucial role in the recurrence of intracranial aneurysms after coiling. However, the strongest factor for predicting recurrence remains unclear because each risk factor has been investigated and reported separately. OBJECTIVE: To clarify the strongest predictor of recurrence with computational fluid dynamics (CFD). METHODS: Using pretreatment patient-specific 3-dimensional rotational angiography data of 50 internal carotid artery (ICA) aneurysms (7 recanalized, 43 stable) treated with endovascular coiling, we created a precoiling model and a virtual postcoiling model produced by manually cutting the aneurysm by the flat plane corresponding to the virtual coil surface. We conducted CFD analysis to investigate inflow dynamics in the precoiling model and pressure difference and wall shear stress on the virtual coil surface. The pressure difference was calculated by subtracting average pressure at the proximal ICA from the maximum pressure at the coil surface and dividing by dynamic pressure at the proximal ICA for normalization. We compared hemodynamic parameters in both models between recanalized and stable aneurysms. RESULTS: Compared with stable aneurysms, recanalized aneurysms showed a significantly larger inflow area and higher inflow rate in the precoiling model (P = .016, .028), and higher pressure difference at the coil surface in the postcoiling model (P < .001). The receiver-operating characteristic analysis showed that the area under the curve value for the pressure difference (0.967) was superior to that of other evaluated parameters. CONCLUSION: The pressure difference in the virtual postcoiling model may be a strong predictor of recurrence after coiling.

During endovascular treatment of an aneurysm, the importance of the initial coil volume for facilitating tight packing is unclear. We retrospectively studied the relationships between initial packing density (PD; initial coil volume divided by aneurysm volume), final PD (volume of all coils divided by aneurysm volume). We reviewed 105 aneurysms in 98 patients who underwent endovascular coiling between April 2011 and March 2014. The initial coil was defined as the first coil in the single-catheter method and the first 2 coils in the double-catheter method. The patient data were divided into groups with or without a final PD ≥20%, and the significant predictors of a final PD ≥20% were determined using multivariable logistic regression. The optimal cutoff value for the initial PD was determined using a receiver operating characteristic curve. Of 105 aneurysms, 56 and 49 were treated with single- and double-catheter methods, respectively. Statistically significant differences in rupture status, neck size, dome/neck ratio, and initial PD were observed between aneurysms with and without a final PD ≥20% (all P < 0.05). Multivariate analysis showed that initial PD (P = 0.025; odds ratio, 1.22) and rupture status (P = 0.002; odds ratio, 0.19) were significantly associated with a final PD ≥20%. Using receiver operating characteristic curve analysis, the cutoff points of initial PD to achieve a final PD ≥20% were 8.0% and 10.0% in single- and double-catheter groups, respectively. Initial PD appears to be a critical factor for achieving tight packing.

BACKGROUND AND PURPOSE: Inflow jet characteristics may be related to aneurysmal bleb formation and rupture. We investigated the visualization threshold on the basis of the flow velocity in the parent artery to classify the inflow jet patterns observed on 4D flow MR imaging. MATERIALS AND METHODS: Fifty-seven unruptured aneurysms (24 bifurcation and 33 sidewall aneurysms) were subjected to 4D flow MR imaging to visualize inflow streamline bundles whose velocity exceeded visualization thresholds corresponding to 60%, 75%, and 90% of the maximum flow velocity in the parent artery. The shape of the streamline bundle was determined visually, and the inflow jet patterns were classified as concentrated, diffuse, neck-limited, and unvisualized. RESULTS: At the 75% threshold, bifurcation aneurysms exhibited a concentrated inflow jet pattern at the highest rate. At this threshold, the inflow jets were concentrated in 13 aneurysms (group C, 22.8%), diffuse in 18 (group D, 31.6%), neck-limited in 11 (group N, 19.3%), and unvisualized in 15 (group U, 26.3%). In 16 (28.1%) of the 57 aneurysms, the inflow jet pattern was different at various thresholds. Most inflow parameters, including the maximum inflow velocity and rate, the inflow velocity ratio, and the inflow rate ratio, were significantly higher in groups C and D than in groups N and U. CONCLUSIONS: The inflow jet pattern may depend on the threshold applied to visualize the inflow streamlines on 4D flow MR imaging. For the classification of the inflow jet patterns on 4D flow MR imaging, the 75% threshold may be optimal among the 3 thresholds corresponding to 60%, 75%, and 90% of the maximum flow velocity in the parent artery.

BACKGROUND AND PURPOSE: The complexity and instability of the vortex flow in aneurysms are factors related to the rupture risk of unruptured cerebral aneurysms. We identified aneurysm vortex cores on 4D flow MR imaging and examined the relationship of these factors with the characteristics of cerebral aneurysms. MATERIALS AND METHODS: We subjected 40 aneurysms (37 unruptured, 3 ruptured) to 4D flow MR imaging. We visualized streamlines with velocities below the threshold—that is, a percentage value of the aneurysm maximum inflow velocity—and progressively decreased the threshold to identify vortex cores as thin, streamline bundles with minimum velocities. Complexity and stability were compared in aneurysms with a smooth surface and those with blebs or daughter sacs. RESULTS: The threshold for visualizing vortex cores ranged from 3% to 13% of the maximum inflow velocity. Vortex cores could be visualized in 38 aneurysms; in 2, they were not visualized through the cardiac cycle. A simple flow pattern (single vortex core) was identified in 27 aneurysms; the other 13 exhibited a complex flow pattern. The cores were stable in 32 and unstable in 8 aneurysms. Significantly more aneurysms with-than-without blebs or daughter sacs had a complex flow pattern (P = .006). Of the 3 ruptured aneurysms, 1 aneurysm had an unstable vortex core; in the other 2, the vortex core was not visualized. CONCLUSIONS: The identification of vortex cores on 4D flow MR imaging may help to stratify the rupture risk of unruptured cerebral aneurysms.