J. Kevin DeMarco

Carotid intraplaque hemorrhage imaging at 3.0-T MR imaging: comparison of the diagnostic performance of three T1-weighted sequences.

PURPOSE To compare the diagnostic performances of three T1-weighted 3.0-T magnetic resonance (MR) sequences at carotid intraplaque hemorrhage (IPH) imaging, with histo logic 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-flight (TOF), and three-dimensional magnetization-prepared rapid acquisition gradient-echo (RAGE) sequences. Two reviewers blinded to the histologic findings assessed the presence, area, and signal intensity of IPH with each sequence. Detection statistics (sensitivity, specificity, and Cohen kappa values) and agreement between area measurements (Pearson correlation coefficient [r] values) were calculated for each sequence. RESULTS When all 231 available MR sections were included for analysis, the magnetization-prepared RAGE (kappa = 0.53) and fast spin-echo (kappa = 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 calcified IPHs were excluded, sensitivity, specificity, and kappa values, respectively, were 80%, 97%, and 0.80 for magnetization-prepared RAGE imaging; 70%, 92%, and 0.63 for fast spin-echo 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 quantification of IPH. Potential limitations of 3.0-T IPH MR imaging are related to hemorrhage size and coexisting calcification.

An optimized 3D inversion recovery prepared fast spoiled gradient recalled sequence for carotid plaque hemorrhage imaging at 3.0 T

An optimized 3D inversion recovery prepared fast spoiled gradient recalled sequence (IR FSPGR) on a 3-T scanner for carotid plaque imaging is described. It offers clear blood and fat signal suppression at the carotid artery bifurcation and highlights the regions of carotid plaque affected by hemorrhage at 3 T with high contrast and contrast-to-noise ratio compared with other sequences. It can potentially be used to replace the more traditional noncontrast T(1)-weighted 2D black-blood imaging for hemorrhage detection and offers additional benefits of high-resolution 3D volumetric visualization.

A Potential Biomarker in Sports-Related Concussion: Brain Functional Connectivity Alteration of the Default-Mode Network Measured with Longitudinal Resting-State fMRI over Thirty Days

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.

Symptomatic and asymptomatic carotid artery plaque

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.

Neuroimaging findings in children with retinopathy-confirmed cerebral malaria.

PURPOSE To describe brain CT findings in retinopathy-confirmed, paediatric cerebral malaria. MATERIALS AND METHODS In this outcomes study of paediatric cerebral malaria, a subset of children with protracted coma during initial presentation was scanned acutely. Survivors experiencing adverse neurological outcomes also underwent a head CT. All children had ophthalmological examination to confirm the presence of the retinopathy specific for cerebral malaria. Independent interpretation of CT images was provided by two neuroradiologists. RESULTS Acute brain CT findings in three children included diffuse oedema with obstructive hydrocephalus (2), acute cerebral infarctions in multiple large vessel distributions with secondary oedema and herniation (1), and oedema of thalamic grey matter (1). One child who was reportedly normal prior to admission had parenchymal atrophy suggestive of pre-existing CNS injury. Among 56 survivors (9-84 months old), 15 had adverse neurologic outcomes-11/15 had a follow-up head CT, 3/15 died and 1/15 refused CT. Follow-up head CTs obtained 7-18 months after the acute infection revealed focal and multifocal lobar atrophy correlating to regions affected by focal seizures during the acute infection (5/11). Other findings were communicating hydrocephalus (2/11), vermian atrophy (1/11) and normal studies (3/11). CONCLUSIONS The identification of pre-existing imaging abnormalities in acute cerebral malaria suggests that population-based studies are required to establish the rate and nature of incidental imaging abnormalities in Malawi. Children with focal seizures during acute cerebral malaria developed focal cortical atrophy in these regions at follow-up. Longitudinal studies are needed to further elucidate mechanisms of CNS injury and death in this common fatal disease.

Sex Differences in Patients With Asymptomatic Carotid Atherosclerotic Plaque In Vivo 3.0-T Magnetic Resonance Study

Background and Purpose— Stroke prevention with carotid endarterectomy in asymptomatic men with carotid stenosis is greater than in women. Men have a higher incidence of stroke <75 years of age. Sex differences in plaque characteristics may help explain this, because several plaque features, including a thin/ruptured fibrous cap, larger lipid-rich/necrotic core, and hemorrhage, are associated with increased risk of stroke. We hypothesize that MRI carotid plaque features will demonstrate sex differences indicative of higher-risk plaque in men. Methods— One hundred thirty-one patients (men, 67; women, 64) with ≥50% asymptomatic carotid stenosis on duplex ultrasound were included. Two blinded reviewers interpreted multicontrast MRI. Presence of a thin/ruptured fibrous cap, plaque components (lipid-rich/necrotic core, hemorrhage, and calcification), and percent component volume were documented. The associations between sex and individual plaque characteristics were examined using logistic and linear regression models (2-part models) controlling for demographic characteristics and MR angiographic findings. Results— Presence of a thin/ruptured fibrous cap (48% versus 17%, adjusted OR=4.41, P<0.01) and lipid-rich/necrotic core (73% versus 50%, adjusted OR=3.66, P=0.01) were more common in men. There was a trend for more highly prevalent hemorrhage (33% versus, 17%, adjusted OR=2.15, P=0.07) in men. Calcification was not significantly associated with sex. Men demonstrated larger volumes of percent lipid-rich/necrotic core (median, 7.7% versus 3.2%, P=0.01), and percent hemorrhage (median, 6.1% versus 1.5%, P<0.01). Conclusion— In patients with asymptomatic ≥50% carotid stenosis by duplex ultrasound, men had higher-risk plaque features compared with women after controlling for potential confounders. These findings may help explain sex differences in stroke incidence and prevention.

An optimized 3D spoiled gradient recalled echo pulse sequence for hemorrhage assessment using inversion recovery and multiple echoes (3D SHINE) for carotid plaque imaging

Intraplaque hemorrhage into the carotid atherosclerotic plaque has been shown to create instability and progression. We have developed an optimized 3D Spoiled Gradient recalled echo pulse sequence for Hemorrhage assessment using INversion recovery and multiple Echoes (3D SHINE) for carotid plaque imaging. The sequence was developed by incorporating multiecho acquisition to its clinically validated optimized single‐echo counterpart 3D inversion recovery prepared fast spoiled gradient recalled sequence. With similar scan time (4 min), 3D spoiled gradient recalled echo pulse sequence for hemorrhage assessment using inversion recovery and multiple echoes maintained comparable high‐resolution volumetric coverage, black‐blood effect, contrast, signal‐to‐noise and contrast‐to‐noise ratios, and similar sensitivity and specificity in detecting whether intraplaque hemorrhage was present on an artery. The multiple echoes acquired with 3D SHINE allowed the estimation of intraplaque hemorrhage T*2 and then the subsequent characterization of intraplaque hemorrhage (T*2 for type I < 14 msec, and for type II > 14 msec). The type I intraplaque hemorrhage size estimated by 3D SHINE was significantly and positively correlated with the size estimated manually by an expert reviewer using the histology‐validated multicontrast MRI technique (r = 0.836 ± 0.080, p < 0.001). With only one fast sequence, 3D SHINE can detect and characterize intraplaque hemorrhage that has previously required a multicontrast approach using a combination of black‐blood T1‐weighted, black‐blood T2‐weighted, and time‐of‐flight imaging techniques. Magn Reson Med, 2010.

Imaging of high-risk carotid artery plaques: current status and future directions

In this paper, the authors review the definition of high-risk plaque as developed by experienced researchers in atherosclerosis, including pathologists, clinicians, molecular biologists, and imaging scientists. Current concepts of vulnerable plaque are based on histological studies of coronary and carotid artery plaque as well as natural history studies and include the presence of a lipid-rich necrotic core with an overlying thin fibrous cap, plaque inflammation, fissured plaque, and intraplaque hemorrhage. The extension of these histologically identified high-risk carotid plaque features to human in vivo MRI is reviewed as well. The authors also assess the ability of in vivo MRI to depict these vulnerable carotid plaque features. Next, the ability of these MRI-demonstrated high-risk carotid plaque features to predict the risk of ipsilateral carotid thromboembolic events is reviewed and compared with the risk assessment provided by simple carotid artery stenosis measurements. Lastly, future directions of high-risk carotid plaque MRI are discussed, including the potential for increased clinical availability and more automated analysis of carotid plaque MRI. The ultimate goal of high-risk plaque imaging is to design and run future multicenter trials using carotid plaque MRI to guide individual patient selection and decisions about optimal atherosclerotic treatment strategies.

Current State-of-the-Art 1.5 T and 3 T Extracranial Carotid Contrast-Enhanced Magnetic Resonance Angiography

Recent advances in magnetic resonance (MR) hardware and software have improved the resolution and spatial coverage of head and neck first-pass contrast-enhanced (CE) MR angiography. Despite these improvements, high-quality submillimeter-resolution 1.5 T and 3 T carotid CE MR angiography is not consistently available in the general radiology practice. This article reviews the important imaging parameters and potential pitfalls that affect carotid CE MR angiography image quality, and the dose and timing of the gadolinium-based contrast agent, and summarizes vendor-specific protocols for high-quality submillimeter-resolution carotid CE MR angiography at 1.5 and 3 T.

Initial experience with balanced turbo field echo in depicting carotid artery stenosis: comparison with multiple overlapping thin slab acquisition and 3D contrast-enhanced magnetic resonance angiography.

To compare balanced turbo field echo (bTFE) with multiple overlapping thin slice acquisition (MOTSA) and contrast‐enhanced MR angiography (CE‐MRA) in depicting carotid artery stenosis.