Given the rising number of older people with HIV (PWH) and the overlap in cognitive dysfunction profiles in HIV-associated neurocognitive disorders (HAND) and Alzheimer's disease and its precursor, ...amnestic mild cognitive impairment (aMCI), methods are needed to distinguish aMCI/Alzheimer's disease from HAND. As an early indicator of Alzheimer's disease, we examined whether olfactory dysfunction could help to distinguish between aMCI/Alzheimer's disease and HAND among PWH.
An observational cohort study.
Eighty-one older (≥50 years) PWH (83% men, 65% white) from the California NeuroAIDS Tissue Consortium completed the University of Pennsylvania Smell Identification Test (UPSIT; higher scores = better smell identification) and a comprehensive seven-domain neuropsychological test battery and neuromedical evaluation. HAND was classified via Frascati criteria. High aMCI risk was defined as impairment (>1.0 SD below normative mean) on two of four delayed recall or recognition outcomes (at least one recognition impairment required) from the Hopkins Verbal Learning Test-Revised and the Brief Visuospatial Memory Test-Revised. We examined UPSIT scores in relation to aMCI risk and HAND status, and continuous memory scores considering adjustments for demographics and relevant clinical or HIV disease characteristics.
Fifty-seven participants were classified with HAND (70%) and 35 participants were classified as high aMCI risk (43%). UPSIT scores were lower (worse) in the high versus low aMCI risk group F (1,76) = 10.04, P = 0.002, but did not differ by HAND status F (1,76) = 0.62, P = 0.43. UPSIT scores positively correlated with all memory outcomes (Ps < 0.05).
Olfactory assessments may help in detecting early aMCI/Alzheimer's disease among PWH and allow for appropriate and early disease intervention.
Evolution of intracranial aneurysmal disease is known to be related to hemodynamic forces acting on the vessel wall. Low wall shear stress (WSS) has been reported to have a negative effect on ...endothelial cells normal physiology and may be an important contributor to local remodeling of the arterial wall and to aneurysm growth and rupture.
Seven patient-specific models of intracranial aneurysms were constructed using MR angiography data acquired at two different time points (mean 16.4+/-7.4 months between the two time points). Numeric simulations of the flow in the baseline geometries were performed to compute WSS distributions. The lumenal geometries constructed from the two time points were manually coregistered, and the radial displacement of the wall was calculated on a pixel-by-pixel basis. This displacement, corresponding to the local growth of the aneurysm, was compared to the time-averaged wall shear stress (WSS TA) through the cardiac cycle at that location. For statistical analysis, radial displacement was considered to be significant if it was larger than half of the MR pixel resolution (0.3 mm).
Mean WSS TA values obtained for the areas with a displacement smaller and greater than 0.3 mm were 2.55+/-3.6 and 0.76+/-1.5 Pa, respectively (P<0.001). A linear correlation analysis demonstrated a significant relationship between WSS TA and surface displacement (P<0.001).
These results indicate that aneurysm growth is likely to occur in regions where the endothelial layer lining the vessel wall is exposed to abnormally low wall shear stress.
Purpose
Segmentation of cardiac medical images, an important step in measuring cardiac function, is usually performed either manually or semiautomatically. Fully automatic segmentation of the left ...ventricle (LV), the right ventricle (RV) as well as the myocardium of three‐dimensional (3D) magnetic resonance (MR) images throughout the entire cardiac cycle (four‐dimensional, 4D), remains challenging. This study proposes a deformable‐based segmentation methodology for efficiently segmenting 4D (3D + t) cardiac MR images.
Methods
The proposed methodology first used the Hough transform and the local Gaussian distribution method (LGD) to segment the LV endocardial contours from cardiac MR images. Following this, a novel level set‐based shape prior method was applied to generate the LV epicardial contours and the RV boundary.
Results
This automatic image segmentation approach has been applied to studies on 17 subjects. The results demonstrated that the proposed method was efficient compared to manual segmentation, achieving a segmentation accuracy with average Dice values of 88.62 ± 5.47%, 87.35 ± 7.26%, and 82.63 ± 6.22% for the LV endocardial, LV epicardial, and RV contours, respectively.
Conclusions
We have presented a method for accurate LV and RV segmentation. Compared to three existing methods, the proposed method can successfully segment the LV and yield the highest Dice value. This makes it an option for clinical assessment of the volume, size, and thickness of the ventricles.
Purpose: Late enhancement magnetic resonance imaging (MRI) was compared with thallium-201 rest-redistribution single photon emission computed tomography (SPECT) in patients with reduced left ...ventricular (LV) function and prior myocardial infarction (MI). Background: Hyperenhancement on contrast cardiac MRI using gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) has been reported to identify nonviable myocardium. Comparisons of MRI and thallium-201 SPECT have recently been reported. This study focuses on the comparison of these modalities specifically in patients with ischemic heart failure, where viability determination is most clinically relevant. Methods: Fifteen patients with LV dysfunction and prior MI mean ejection fraction (EF) 35 ± 11% underwent thallium-201 rest-redistribution scintigraphy and contrast MRI on separate days. Each short axis slice was divided into six 60-degree segments, and correlations between MRI and scintigraphy were made on viability detection for each segment. For SPECT, the mean uptake score was calculated from the average of all percent relative activity values throughout each segment. Areas with < 50% of maximal thallium uptake were considered nonviable. On MRI, regions with increased signal intensity after an injection of 0.1 mmol kg Gd-DPTA were considered nonviable. Results: A total of 558 segments were analyzed. Overall, there was a strong inverse relationship between the area of hyperenhancement on MRI and diminished thallium-201 uptake on SPECT (r = − 0.51, P < 0.001). There was a significant correlation between the imaging methods for each individual segment, except for the inferior-septal segment (r = − 0.38, P < 0.08). Conclusions: In patients with LV dysfunction and prior MI, our data suggest MRI hyperenhancement significantly correlates with myocardial nonviability by thallium-201 SPECT. Correlations were weaker in the inferior-septal region, which may be due to SPECT attenuation artifact.
Contemporary imaging methods provide detailed visualization of carotid athero-sclerotic plaque, enabling a major evolution of in vivo carotid plaque imaging evaluation. The degree of luminal stenosis ...in the carotid artery bifurcation, as assessed by ultrasound, has historically served as the primary imaging feature for determining ischemic stroke risk and the potential need for surgery. However, stroke risk may be more strongly driven by the presence of specific characteristics of vulnerable plaque, as visualized on CT and MRI, than by traditional ultrasound-based assessment of luminal narrowing. This review highlights six promising imaging-based plaque characteristics that harbor unique information regarding plaque vulnerability: maximum plaque thickness and volume, calcification, ulceration, intraplaque hemorrhage, lipid-rich necrotic core, and thin or ruptured fibrous cap. Increasing evidence supports the association of these plaque characteristics with risk of ischemic stroke, although these characteristics have varying suitability for clinical implementation. Key aspects of CT and MRI protocols for carotid plaque imaging are also considered. Practical next steps and hurdles are explored for implementing routine imaging assessment of these plaque characteristics in addition to, or even as replacement for, traditional assessment of the degree of vascular stenosis on ultrasound, in the identification of individuals at high risk of ischemic stroke.
Patients undergoing stent placement as treatment for severe stenosis of the internal carotid artery (ICA) were assessed with MR imaging in a combined MR-radiographic (XMR) angiography suite. MR ...imaging was performed before and immediately following conventional radiography-guided stent placement. Changes in MR imaging measurable properties, including flow and perfusion, resulting from stent placement were evaluated.
MR imaging analysis was performed for 12 patients with >70% stenosis of the ICA before and after conventional radiography-guided deployment of a carotid stent. MR imaging acquisitions included angiography, quantitative flow analysis, perfusion, diffusion, and turbo-fluid-attenuated inversion recovery (FLAIR). These acquisitions were all performed immediately before and following stent placement by using conventional techniques.
MR angiography proved sufficient for identifying the target lesion and permitting targeted flow analysis. MR flow analysis demonstrated a marked increase in flow in the treated carotid artery (+2.2 +/- 1.2 mL/s) and little change in other extracranial arteries. MR perfusion imaging showed no significant differences in relative cerebral blood volume between hemispheres before or after treatment, but there was a modest decrease in mean transit time and time to peak evident in the treated hemisphere after stent placement. Diffusion imaging did not demonstrate any ischemic foci resulting from carotid stent treatment. Hyperintensity of the CSF was noted on turbo-FLAIR acquisitions in the ipsilateral hemisphere following stent placement in 75% of patients.
MR imaging reliably reflects the state of the carotid artery and provides a means of monitoring and quantifying the effects of revascularization.
Abstract only Introduction: While some brain arteriovenous malformations (bAVM) demonstrate long-term stability, others demonstrate dynamic changes (new aneurysms or venous outflow stenosis) that ...confer higher rupture risk even after apparent cure. The objective of this study is to evaluate the feasibility and efficacy of 4D Flow MRI to quantitatively assess the hemodynamic changes in pediatric bAVMs following treatment and its use for early detection of high-risk changes. Methods: We have prospectively enrolled 20 children (mean age 11.8 ± 3.8 years) with bAVM into a single center cohort study. 4D Flow MRI was acquired in a transverse slab covering the circle of Willis using prospective gating, compressed sensing, and a resolution of 0.7 x 0.7 x 1.0 mm 3 on a 3T GE Discovery MR750 scanner. MRI at baseline and post-intervention (6-month and 1-year follow up) has been acquired for 5 patients thus far. 4D Flow data was post-processed by segmenting the main cerebral arteries and calculating cardiac-averaged flow rates in cross-sections orthogonal to the centerline of each vessel segment. Results: The flow rate accuracy was evaluated by calculating the flow conservation at the right/left internal carotid and basilar junctions, yielding average errors of 10.7% ± 12.7, 14.0% ± 9.5, and 19.3% ± 13.8 respectively. The hemisphere containing the bAVM received an average of 57.2% ± 2.8 of total brain flow at baseline, which decreased to an average of 51.2% ± 2.9 1-year follow-up. In 2 of 5 patients, the flow laterality between hemispheres flipped post-intervention with increased flow to the contralateral hemisphere. In all the post-intervention studies, we observed a decrease in flow and maximum velocities, as well as an increase in pulsatility index, in the primary feeding arteries to the bAVM (Figure). Conclusion: These preliminary results indicate that 4D Flow MRI may be a robust and useful tool for monitoring changes in intracranial flow patterns after bAVM treatment in children.
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