Objectives This work aimed to refine a large animal in minimally invasive reversible middle cerebral artery (MCA) occlusion (MCAO) model to account for leptomeningeal collateral formation. Materials and Methods An angiographically based methodology allowed for transient MCA and carotid terminus occlusion in 12 mongrel dogs and assessment of pial collateral recruitment. Outcome measures included 1- and 24-hour magnetic resonance imaging-based infarct volume calculation, a behavioral scale and histopathologic sections. Results MCAO succeeded in 8 of 12 dogs (67% efficiency). One-hour postreperfusion infarct volume predicted 24-hour postreperfusion infarct volume (r2 = 0.997, P < 0.0001). Pial collateral recruitment varied with time and reproducibly assessed predicted infarct volume on 1-hour postre-perfusion mean diffusivity maps (P < 0.0001; r2 = 0.946) and 24-hour fluid-attenuated inversion recovery FLAIR magnetic resonance imaging (P < 0.0033; r2 = 0.961). The canine stroke scale score correlated with infarct volumes and pial collateral score. Conclusion This canine MCAO model produces defined cerebral infarct lesions whose volumes correlate with leptomeningeal collateral formation and canine behavior.

A wide variety of conditions may involve the splenium of the corpus callosum on magnetic resonance imaging in children. A single cause may present with different patterns of splenial involvement, and multiple diseases may have similar imaging findings. Keeping this limitation in mind, the goal of this text is to assist in the diagnostic process of pediatric neurological diseases that are characterized by prominent involvement of the splenium of the corpus callosum on imaging. The various pathologies will be reviewed and categorized based on etiology, reversibility, and pattern of additional or associated findings. Transient splenial lesions in children are an uncommon radiologic finding of unknown etiology in a long list of conditions that may present with altered consciousness, and it usually carries a favorable prognosis. The discussion continues with the presentation of diseases inflicting irreversible damage on the splenium. Familiarity with the various causes implicated in splenial injury may assist in the formulation of differential diagnosis in the appropriate clinical setting using an easily recognizable imaging finding.

Stroke is currently the third leading cause of death in the United States, with approximately 780,000 Americans affected by a new or recurring stroke each year. Although a variety of therapeutic approaches have shown promise in small-animal models of stroke, the vast majority of clinical trials to test the efficacy of such modalities have failed. To bridge the translational gap between laboratory and clinical research, we developed a preclinical model of acute ischemic stroke in dogs. Using a minimally invasive endovascular approach, a platinum coil was intravascularly guided through the vertebrobasilar system under C-arm fluoroscopy to occlude the M1 segment of the middle cerebral artery (MCA) for 1 h. The approach included femoral artery catheterization to access the MCA and therefore eliminated the occurrence of head trauma associated with other preclinical stroke models relying on transorbital or craniectomy approaches. After 1 h of focal MCA ischemia, the coil was retrieved to cause reperfusion, which was verified by arteriograms. At 24 h, T2-weighted coronal magnetic resonance (MR) images were acquired and processed for three-dimensional reconstruction of the brain and its vasculature. Infarction, limited to the area at risk, was noted. Two independent observers calculated the mean percentage hemispherical lesion volumes as follows: observer 1, 30.9 ؎ 2.1%; observer 2, 31.2 ؎ 4.3%. Infarctaffected changes in histology were determined by hematoxylin and eosin as well as by Fluoro-Jade staining. This work reports the successful development of a powerful preclinical model of stroke that lends itself to the study of biologic mechanisms as well as to testing experimental therapeutics.imaging ͉ therapeutics ͉ vascular ͉ stroke ͉ ischemia

Τhe accuracy of template‐based neuroimaging investigations depends on the template's image quality and representativeness of the individuals under study. Yet a thorough, quantitative investigation of how available standardized and study‐specific T1‐weighted templates perform in studies on older adults has not been conducted. The purpose of this work was to construct a high‐quality standardized T1‐weighted template specifically designed for the older adult brain, and systematically compare the new template to several other standardized and study‐specific templates in terms of image quality, performance in spatial normalization of older adult data and detection of small inter‐group morphometric differences, and representativeness of the older adult brain. The new template was constructed with state‐of‐the‐art spatial normalization of high‐quality data from 222 older adults. It was shown that the new template (a) exhibited high image sharpness, (b) provided higher inter‐subject spatial normalization accuracy and (c) allowed detection of smaller inter‐group morphometric differences compared to other standardized templates, (d) had similar performance to that of study‐specific templates constructed with the same methodology, and (e) was highly representative of the older adult brain.

Axial T2 screening can detect pediatric brain abnormalities with high sensitivity and specificity and can possibly replace CT as screening tool if the reading physician is aware of possible limitations/pitfalls. The level of experience influences sensitivity and specificity. Adding diffusion-weighted imaging and susceptibility-weighted imaging to a 3-dimensional T2-weighted sequence would most likely further increase sensitivity and specificity.

Objectives-This study assessed whether ultra-small particles of iron oxide (USPIO) intravascular contrast agent could enhance visualization of tumor microvascularity in F98 glioma bearing rats by means of ultra high field (UHF) high-resolution gradient echo (GRE) magnetic resonance imaging (MRI). In an effort to explain differences in visualization of microvascularity before and after USPIO administration, hypoxia and vessel diameters were assessed on corresponding histopathologic sections.Materials and Methods-F98 glioma cells were implanted stereotactically into the brains of syngeneic Fischer rats. Based on clinical criteria, rats were imaged 1 to 2 days before their death with and without USPIO contrast on an 8 Tesla MRI. To identify hypoxic regions of the brain tumor by immunohistochemical, a subset of animals also received a nitroimidazole-based hypoxia marker, EF5, before euthanasia. These sections then were compared with noncontrast enhanced MR images. The relative caliber of tumor microvasculature, compared with that of normal brain, was analyzed in a third group of animals.Results-After USPIO administration, UHF high-resolution GRE MRI consistently predicted increased microvascular density relative to normal gray matter when correlated with histopathology. The in-plane visibility of glioma microvascularity in 22 rats increased by an average of 115% and signal intensity within the tumor decreased by 13% relative to normal brain. Tumor microvascularity identified on noncontrast MR images matched hypoxic regions identified by immunohistochemical staining with a sensitivity of 83% and specificity of 89%. UHF GRE MRI was able to resolve microvessels less than 20 μ in diameter, although differences in tumor vessel size did not consistently account for differences in visualization of microvascularity.Conclusions-USPIO administration significantly enhanced visualization of tumor microvascularity on gradient echo 8 T MRI and significantly improved visualization of tumor microvascularity. Microvascularity identified on pre-contrast images is suspected to be partly associated with hypoxia. Keywords NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptImproved signal-to-noise ratio with ultra high field (UHF) 8 T magnetic resonance imaging (MRI) allows acquisition of high-resolution (HR) images of the central nervous system. One major advantage of UHF MRI has been its ability to delineate cortical vascular anatomy. 1 MRI (8 T) can resolve microvessels with a diameter as small as 100 μm, using gradient echo (GRE) sequences with an in-plane resolution of 196 μm in normal human brain 2-4 and in glial tumors. 5,6 This 100-micron dimension is smaller than the voxel size used in acquisition, although the paramagnetic properties of deoxyhemoglobin, combined with increasing magnetic susceptibility effects at high field, allow microvessels to be resolved on T2*-weighted images. 3,7 Ultra-small superparamagnetic particles of iron oxide (USPIO) are intravascular magnetic resonance (MR) contrast a...

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Conventional CT, MR, and digital subtraction angiography rely on the presence of luminal narrowing for the identification of vascular pathology offering limited insight into the offending pathophysiologic mechanism affecting the vessel. High-resolution MRI vessel wall imaging (VWI) has the potential to directly depict and characterize vessel wall pathology affecting the intracranial circulation increasing diagnostic accuracy for vasculopathies with similar angiographic findings.