Angiographic Quantification of Contrast Medium Washout from Cerebral Aneurysms after Stent Placement

Abstract

BACKGROUND AND PURPOSE: Endovascular stent placement is an emerging technique in treating cerebral aneurysms. Thus far, no quantitative method is available to determine the effectiveness of stent deployment in reducing intraaneurysmal flow circulation, and thereby, in excluding the aneurysm from the cerebral vasculature. Our purpose was to develop a mathematical model congruent with flow transport phenomena observed in cerebral aneurysms and based on the washout of angiographic contrast medium from these aneurysms to provide quantitative indices for predicting the likelihood of stable thrombus formation after stent placement.

METHODS: Angiographic data from an in vitro experiment involving an elastomer side-wall aneurysm model and data from five patients with cerebral aneurysms were collected and analyzed. A region of interest (ROI) delineating the aneurysm was selected in each case, and the temporal variation in average gray-scale intensity within this ROI was assessed. The mathematical model was fit to the gray-scale intensity curves by using least-squares minimization. Variations in model parameters before and after stent placement were studied.

RESULTS: A marked variation in the model parameters was observed in both in vitro cases and when data suitable for mathematical modeling were available from the clinical setting. This variation supported the hypothesis of the model.

CONCLUSION: On the basis of our results, we conclude that the model developed herein can be used to quantitatively depict and characterize alterations in aneurysmal blood-flow transport before and after endovascular stent placement. By inference, future versions of the model will be useful in predicting the long-term effectiveness of endovascular stent placement for cerebral aneurysms immediately after the procedure is performed.