Journal of neuroimaging : official journal of the American Society of Neuroimaging
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Granulomatous amebic encephalitis (GAE) is a rare and oftentimes fatal disease in immune compromised patients caused by free living amebae Acanthamoeba and Balamuthia. We report a patient in whom GAE secondary to Acanthamoeba was the initial presentation of acquired immunodeficiency syndrome in a 41-year-old male, and discuss the FDG positron emission tomography (PET) and magnetic resonance imaging findings that preceded the pathological diagnosis. The PET results provided complementary information when coupled with the MR brain findings. Improved understanding of the clinical and imaging findings of this deadly disease is the best hope for early diagnosis and treatment of this uncommon but deadly disease.
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Meta Analysis
A Meta-Analysis of fMRI Activation Differences during Episodic Memory in Alzheimer's Disease and Mild Cognitive Impairment.
Functional MRI (fMRI) has the potential to be used as a tool to detect biomarkers related to classifying Alzheimer's disease (AD) and its prodromal stage, mild cognitive impairment (MCI). Previous meta-analyses suggest that during episodic memory tasks, MCI patients exhibit hyperactivation in the medial temporal lobe (MTL) while AD patients exhibit hypoactivation, compared to healthy older adults (HOAs). However, these previous studies have methodological weaknesses that limit the generalizability of the results. ⋯ Additionally, the HOA sample showed more activation in the right hippocampus compared to the AD sample. The MCI studies showed greater activation in the cerebellum compared to the HOA sample, potentially indicating a compensatory mechanism for verbal encoding. MTL hypoactivation in the AD sample is consistent with previous studies, but more evidence of MCI hyperactivation is needed before considering MTL activation as an early biomarker for the AD disease process.
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Comparative Study
Relative FLAIR Signal Intensities over Time in Acute Ischemic Stroke: Comparison of Two Methods.
Visibility of lesions on fluid attenuated inversion recovery (FLAIR) images appears indicative of the time window in acute ischemic stroke. We compared two published methods for calculation of relative FLAIR signal intensities (rSI) regarding their association with time from symptom onset in a longitudinal fashion. ⋯ Both methods show a similar performance, and might be a suitable help for the visual assessment of FLAIR lesion visibility.
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Randomized Controlled Trial
The Effect of Three Times a Week Glatiramer Acetate on Cerebral T1 Hypointense Lesions in Relapsing-Remitting Multiple Sclerosis.
Two definitions of T1 hypointense (T1H) lesions can be derived from pre-contrast images: those that may or may not have a corresponding gadolinium-enhancing correlate on post-contrast images (T1H total), and those that are simultaneously non-gadolinium-enhancing on post-contrast scans (T1H non-enhancing). To determine the differences in lesion evolution between these two T1H definitions, we examined the effect of glatiramer acetate 40 mg/mL three times weekly subcutaneous injection (GA40) on the number of new or enlarging T1H total and T1H non-enhancing lesions in patients with relapsing-remitting multiple sclerosis (RRMS). ⋯ GA40 significantly reduced the number of new or enlarging T1H total lesions and T1H non-enhancing lesions compared with placebo. Although the treatment effect magnitude was comparable with both definitions, the use of T1H non-enhancing lesions may be more relevant for more uniform standardization in future clinical trials.
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Voxel-based DTI analysis is an important approach in the comparison of subject groups by detecting and localizing gray and white matter changes in the brain. One of the principal problems for intersubject comparison is the absence of a "gold standard" processing pipeline. As a result, contradictory results may be obtained from identical data using different data processing pipelines, for example, in the data normalization or smoothing procedures. ⋯ As a result, we recommend repeating TBSS analysis using different fitting algorithms, in particular, using on iteratively-assessed robust estimators, as accurate and more reliable approach in voxel-based analysis, particularly, for TBSS. Repeating TBSS analysis allows one to detect and localize suspicious regions in white matter which were estimated as the regions with significant difference. Finally, we did not find a favorite fitting algorithm (or class of them) which can be marked as more reliable for group comparison.