Magnetic Resonance Imaging (MRI)

BACKGROUND AND PURPOSE: Hemodynamic changes associated with acute ischemia cannot be measured with conventional nuclear magnetic resonance imaging. In this study, we used dynamic susceptibility-contrast magnetic resonance imaging to measure the changes in vascular transit time and relative cerebral blood volume in a feline occlusion-reperfusion model.

Using perfusion weighted imaging, we studied 28 spontaneous migraine episodes; 7 during visual aura (n = 6), 7 during the headache phase following visual aura (n = 3), and 14 cases of migraine without aura (n = 13). The data were analyzed using a region-of-interest-based approach. During aura, relative cerebral blood flow (rCBF) was significantly decreased (27% +/- 0.07) in occipital cortex contralateral to the affected hemifield. rCBV was decreased (15% +/- 0.12) and mean transit time increased (32% +/- 0.3), persisting up to 2.5 h into the headache phase.

Perfusion- and diffusion-weighted magnetic resonance imaging was performed during spontaneous visual auras in four migraineurs. Alterations in relative cerebral blood flow (16-53% decrease), cerebral blood volume (6-33% decrease), and tissue mean transit time (10-54% increase) were observed in the gray matter of occipital cortex contralateral to the affected visual hemifield. No changes in the apparent diffusion coefficient were observed either while the patients were symptomatic or after resolution of the visual symptoms but before the onset of headache.

Previous brain imaging studies suggest that stroke alters functional connectivity in motor execution networks. Moreover, current understanding of brain plasticity has led to new approaches in stroke rehabilitation. Recent studies showed a significant role of effective coupling of neuronal activity in the SMA (supplementary motor area) and M1 (primary motor cortex) network for motor outcome in patients after stroke. After a subcortical stroke, functional magnetic resonance imaging (fMRI) during movement reveals cortical reorganization that is associated with the recovery of function.

OBJECTIVE: Patent foramen ovale and pulmonary arteriovenous shunts are associated with serious complications such as cerebral emboli, stroke, and migraine with aura. The pathophysiological mechanisms that link these conditions are unknown. We aimed to establish a mechanism linking microembolization to migraine aura in an experimental animal model.

BACKGROUND: Migraine is an independent risk factor for stroke. Mechanisms underlying this association are unclear. Familial hemiplegic migraine (FHM), a migraine subtype that also carries an increased stroke risk, is a useful model for common migraine phenotypes because of shared aura and headache features, trigger factors, and underlying glutamatergic mechanisms.

INTRODUCTION: Neoangiogenesis is a critical feature that can differentiate high-grade from low-grade glioma. Conventional MR imaging does not assess this histological feature accurately. The goal of this study was to evaluate the gain in relative cerebral blood volume measurement using perfusion MRI in the management of cerebral gliomas.

The aim of this study was to implement a quantitative in vivo cardiac diffusion tensor imaging (DTI) technique that was robust, reproducible, and feasible to perform in patients with cardiovascular disease. A stimulated-echo single-shot echo-planar imaging (EPI) sequence with zonal excitation and parallel imaging was implemented, together with a novel modification of the prospective navigator (NAV) technique combined with a biofeedback mechanism. Ten volunteers were scanned on two different days, each time with both multiple breath-hold (MBH) and NAV multislice protocols.

BACKGROUND: The arrangement of myofibers in the heart is highly complex and must be replicated by injected cells to produce functional myocardium. A novel approach to characterize the microstructural response of the myocardium to ischemia and cell therapy, with the use of serial diffusion tensor magnetic resonance imaging tractography of the heart in vivo, is presented.

PURPOSE: To significantly enhance tumor MR imaging by using a contrast agent combining three components -- a long-circulating liposome, liposomal membrane-incorporated polychelating amphiphilic polymer heavily loaded with gadolinium, and cancer-specific monoclonal antibody 2C5 attached to the liposome surface.