Identification of carotid artery atherosclerosis is conventionally based on measurements of luminal stenosis and surface irregularities using in vivo imaging techniques including sonography, CT and MR angiography, and digital subtraction angiography. However, histopathologic studies demonstrate considerable differences between plaques with identical degrees of stenosis and indicate that certain plaque features are associated with increased risk for ischemic events. The ability to look beyond the lumen using highly developed vessel wall imaging methods to identify plaque vulnerable to disruption has prompted an active debate as to whether a paradigm shift is needed to move away from relying on measurements of luminal stenosis for gauging the risk of ischemic injury. Further evaluation in randomized clinical trials will help to better define the exact role of plaque imaging in clinical decision-making. However, current carotid vessel wall imaging techniques can be informative. The goal of this article is to present the perspective of the ASNR Vessel Wall Imaging Study Group as it relates to the current status of arterial wall imaging in carotid artery disease.

Purpose:To compare the diagnostic performances of three T1-weighted 3.0-T magnetic resonance (MR) sequences at carotid intraplaque hemorrhage (IPH) imaging, with histologic analysis as the reference standard. Materials and Methods:Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Twenty patients scheduled for carotid endarterectomy underwent 3.0-T carotid MR imaging, including two-dimensional fast spin-echo, three-dimensional time-of-fl ight (TOF), and three-dimensional magnetization-prepared rapid acquisition gradient-echo (RAGE) sequences. Two reviewers blinded to the histologic fi ndings assessed the presence, area, and signal intensity of IPH with each sequence. Detection statistics (sensitivity, specifi city, and Cohen k values) and agreement between area measurements (Pearson correlation coeffi cient [r] values) were calculated for each sequence. Results:When all 231 available MR sections were included for analysis, the magnetization-prepared RAGE ( k = 0.53) and fast spin-echo ( k = 0.42) sequences yielded moderate agreement between MR and histologic measurements, while the TOF sequence yielded fair agreement (k = 0.33). However, when 47 sections with either small IPHs or heavily calcifi ed IPHs were excluded, sensitivity, specifi city, and k values, respectively, were 80%, 97%, and 0.80 for magnetizationprepared RAGE imaging; 70%, 92%, and 0.63 for fast spinecho imaging; and 56%, 96%, and 0.57 for TOF imaging. MR imaging-histologic analysis correlation for IPH area was highest with magnetization-prepared RAGE imaging ( r = 0.813), followed by TOF ( r = 0.745) and fast spin-echo ( r = 0.497) imaging. The capability of these three sequences for IPH detection appeared to be in good agreement with the quantitative contrast of IPH versus background plaque tissue. Conclusion:The magnetization-prepared RAGE sequence, as compared with the fast spin-echo and TOF sequences, demonstrated higher diagnostic capability for the detection and quantifi cation of IPH. Potential limitations of 3.0-T IPH MR imaging are related to hemorrhage size and coexisting calcifi cation.q RSNA, 2010

Background and Purpose There have been few neuroimaging studies of pediatric cerebral malaria (CM), a common, often fatal tropical condition. We undertook a prospective study of pediatric CM to better characterize the MRI features of this syndrome, comparing findings in children meeting a stringent definition of CM to those in a control group who were infected with malaria but who were likely to have a non-malarial cause of coma. Materials and Methods Consecutive children admitted with traditionally defined CM (parasitemia, coma and no other coma etiology evident) were eligible for this study. The presence or absence of malaria retinopathy was determined. MRI findings in patients with retinopathy-positive (ret+) CM (cases) were compared to those with retinopathy-negative (ret−) CM (controls). Two radiologists blinded to retinopathy status jointly developed a scoring procedure for image interpretation and provided independent reviews. MRI findings were compared between patients with and without retinopathy, to assess the specificity of changes for patients with very strictly defined CM. Results Of 152 children with clinically defined CM, 120 were ret+, and 32 were ret −. Abnormalities were much more common in the ret + cases, and included severe edema, abnormal T2 signal, and DWI abnormalities in the cortical, deep gray and white matter structures. Focal abnormalities rarely respected vascular distributions. Most of the scans in the more clinically heterogeneous ret− group were normal, and none of the abnormalities noted were more prevalent in controls. Conclusions Distinctive MRI findings present in patients meeting a stringent definition of CM may offer insights into disease pathogenesis and treatment.

Current diagnosis and monitoring of sports-related concussion rely on clinical signs and symptoms, and balance, vestibular, and neuropsychological examinations. Conventional brain imaging often does not reveal abnormalities. We sought to assess if the longitudinal change of functional and structural connectivity of the default-mode network (DMN) can serve as a potential biomarker. Eight concussed Division I collegiate football student-athletes in season (one participated twice) and 11 control subjects participated in this study. ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) was administered over the course of recovery. High-resolution three dimensional T1-weighted, T2*-weighted diffusion-tensor images and resting-state functional magnetic resonance imaging (rs-fMRI) scans were collected from each subject within 24 h, 7±1 d and 30±1 d after concussion. Both network based and whole-brain based functional correlation analyses on DMN were performed. ImPACT findings demonstrated significant cognitive impairment across multiple categories and a significant increase of symptom severity on Day 1 following a concussion but full recovery by 6.0±2.4 d. While the structural connectivity within DMN and gross anatomy appeared unchanged, a significantly reduced functional connectivity within DMN from Day 1 to Day 7 was found in the concussed group in this small pilot study. This reduction was seen in eight of our nine concussion cases. Compared with the control group, there appears a general trend of increased DMN functional connectivity on Day 1, a significant drop on Day 7, and partial recovery on Day 30. The results of this pilot study suggest that the functional connectivity of DMN measured with longitudinal rs-fMRI can serve as a potential biomarker to monitor the dynamically changing brain function after sports-related concussion, even in patients who have shown clinical improvement.

Carotid atherosclerotic plaques represent both stable and unstable atheromatous lesions. Atherosclerotic plaques that are prone to rupture owing to their intrinsic composition such as a large lipid core, thin fibrous cap and intraplaque hemorrhage are associated with subsequent thromboembolic ischemic events. At least 15–20% of all ischemic strokes are attributable to carotid artery atherosclerosis. Characterization of plaques may enhance the understanding of natural history and ultimately the treatment of atherosclerotic disease. MRI of carotid plaque and embolic signals during transcranial Doppler have identified features beyond luminal stenosis that are predictive of future transient ischemic attacks and stroke. The value of specific therapies to prevent stroke in symptomatic and asymptomatic patients with severe carotid artery stenosis are the subject of current research and analysis of recently published clinical trials that are discussed in this article.