Carotid artery hemodynamics: observing patient-specific changes with amlodipine and lisinopril by using MR imaging computation fluid dynamics.

PURPOSE: To assess whether using magnetic resonance (MR) imaging combined with computational fluid dynamics (CFD) could reveal changes in common carotid artery (CCA) flow and wall shear stress (WSS) that might contribute to differences in CCA remodeling between amlodipine, a calcium channel blocker, and lisinopril, an angiotensin-converting enzyme inhibitor, despite similar reductions in blood pressure (BP). MATERIALS AND METHODS: Institutional review board approval was obtained, and participants gave informed consent. Nine subjects with hypertension were recruited into a double-blind placebo-controlled randomized three-way crossover study to compare the hemodynamic effects of 7 days of treatment with placebo, amlodipine, or lisinopril. After each treatment period, patients underwent CCA ultrasonography, BP measurement, and MR imaging with CFD. Analyses were performed by using repeated-measures analysis of variance, followed by the Tukey test or the Wilcoxon matched-pairs test. RESULTS: Amlodipine and lisinopril lowered BP similarly, but CCA flow rate was significantly higher (P < .01) and distal vascular resistance was lower (P = .016) after amlodipine treatment than after lisinopril treatment. WSS on the inner wall of the CCA was significantly lower after lisinopril treatment than after amlodipine treatment (P = .03). The change in WSS in the CCA correlated with the change in vascular resistance (r = -0.85, P < .001). CONCLUSION: Amlodipine causes increased blood flow and increased time-averaged WSS in the CCA compared with lisinopril, despite similar reductions in BP. Differences in the subacute hemodynamic effects of amlodipine and lisinopril could contribute to the differences in CCA remodeling seen in long-term studies. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100788/-/DC1.

Reconstruction and quantification of the carotid artery bifurcation from 3-D ultrasound images.

Three-dimensional (3-D) ultrasound is a relatively new technique, which is well suited to imaging superficial blood vessels, and potentially provides a useful, noninvasive method for generating anatomically realistic 3-D models of the peripheral vasculature. Such models are essential for accurate simulation of blood flow using computational fluid dynamics (CFD), but may also be used to quantify atherosclerotic plaque more comprehensively than routine clinical methods. In this paper, we present a spline-based method for reconstructing the normal and diseased carotid artery bifurcation from images acquired using a freehand 3-D ultrasound system. The vessel wall (intima-media interface) and lumen surfaces are represented by a geometric model defined using smoothing splines. Using this coupled wall-lumen model, we demonstrate how plaque may be analyzed automatically to provide a comprehensive set of quantitative measures of size and shape, including established clinical measures, such as degree of (diameter) stenosis. The geometric accuracy of 3-D ultrasound reconstruction is assessed using pulsatile phantoms of the carotid bifurcation, and we conclude by demonstrating the in vivo application of the algorithms outlined to 3-D ultrasound scans from a series of patient carotid arteries.