Artifacts in brain magnetic resonance imaging due to metallic dental objects

Objective: Artifacts caused by metallic objects, such as dental crowns, dental implants and metallic orthodontic appliances, are a common problem in head and neck MRI. The aim of this retrospective study was to identify the main metal dental objects that produce artifacts on brain MRIs.Study design: Imaged metallic artifacts and their sources were identifi ed. Artifact image plane was rated on a score of 0 or 1 (0 - distinguishable for diagnosis and 1 - not distinguishable for diagnosis).Results: Seventy-eight percent of the artifacts appearing in images were caused by orthodontic appliances, followed by dental titanium implants (18%) and metallic crowns (4%). Orthodontic appliances obtained the highest scores in all planes.Conclusions: We concluded that is diffi cult to avoid the effect of metallic artifacts in the maxillofacial regions on brain scan. Removing metallic parts of the orthodontic appliance should ensure diagnostically useful quality scans

Coordinated And Circumlocutory Semantic Naming Errors Are Related To Anterolateral Temporal Lobes In Mild Ad, Amnestic Mild Cognitive Impairment, And Normal Aging.

Naming difficulties are characteristic of Alzheimer's disease (AD) and, to a lesser extent, of amnestic mild cognitive impairment (aMCI) patients. The association of naming impairment with anterior temporal lobe (ATL) atrophy in Semantic Dementia (SD) could be a tip of the iceberg effect, in which case the atrophy is a marker of more generalized temporal lobe pathology. Alternatively, it could reflect the existence of a functional gradient within the temporal lobes, wherein more anterior regions provide the basis for greater specificity of representation. We tested these two hypotheses in a study of 15 subjects with mild AD, 17 with aMCI, and 16 aged control subjects and showed that coordinate and circumlocutory semantic error production on the Boston Naming Test was weakly correlated with ATL gray matter density, as determined by voxel-based morphometry. Additionally, we investigated whether these errors were benefited by phonemic cues, and similarly to SD, our AD patients had small improvement. Because there is minimal gradient of temporal lobe atrophy in AD or MCI, and, therefore, no basis for a tip of the iceberg effect, these findings support the theory of a modest functional gradient in the temporal lobes, with the ATLs being involved in the naming of more specific objects.161099-10

White matter abnormalities associated with Alzheimer's disease and mild cognitive impairment: A critical review of MRI studies

In this article, the authors aim to present a critical review of recent MRI studies addressing white matter (WM) abnormalities in Alzheimer's disease (AD) and mild cognitive impairment (MCI), by searching PubMed and reviewing MRI studies evaluating subjects with AD or MCI using WM volumetric methods, diffusion tensor imaging and assessment of WM hyperintensities. Studies have found that, compared with healthy controls, AD and MCI samples display WM volumetric reductions and diffusion tensor imaging findings suggestive of reduced WM integrity. These changes affect complex networks relevant to episodic memory and other cognitive processes, including fiber connections that directly link medial temporal structures and the corpus callosum. Abnormalities in cortico-cortical and cortico-subcortical WM interconnections are associated with an increased risk of progression from MCI to dementia. It can be concluded that WM abnormalities are detectable in early stages of AD and MCI. Degeneration of WM networks causes disconnection among neural cells and the degree of such changes is related to cognitive decline. © 2013 2013 Expert Reviews Ltd

ATLANTIC ANTS: a data set of ants in Atlantic Forests of South America

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