Artifact quantification and tractography from 3T MRI after placement of aneurysm clips in subarachnoid hemorrhage patients

Abstract Background The application of advanced 3T MRI imaging techniques to study recovery after subarachnoid hemorrhage (SAH) is complicated by the presence of image artifacts produced by implanted aneurysm clips. To characterize the effect of these artifacts on image quality, we sought to: 1) quantify extent of image artifact in SAH patients with implanted aneurysm clips across a range of MR sequences typically used in studies of volumetry, blood oxygen level dependent signal change (BOLD-fMRI), and diffusion-weighted imaging (DW-MRI) and 2) to explore the ability to reconstruct white matter pathways in these patients. Methods T1- and T2-weighted structural, BOLD-fMRI, and DW-MRI scans were acquired at 3T in two patients with titanium alloy clips in ACOM and left ACA respectively. Intensity-based planimetric contouring was performed on aligned image volumes to define each artifact. Artifact volumes were quantified by artifact/clip length and artifact/brain volume ratios and analyzed by two-way (scan-by-rater) ANOVAs. Tractography pathways were reconstructed from DW-MRI at varying distances from the artifacts using deterministic methods. Results Artifact volume varied by MR sequence for length (p = 0.007) and volume (p < 0.001) ratios: it was smallest for structural images, larger for DW-MRI acquisitions, and largest on fMRI images. Inter-rater reliability was high (r = 0.9626, p < 0.0001), and reconstruction of white matter connectivity characteristics increased with distance from the artifact border. In both patients, reconstructed white matter pathways of the uncinate fasciculus and inferior fronto-occipital fasciculus were clearly visible within 2 mm of the artifact border. Conclusions Advanced 3T MR can successfully image brain tissue around implanted titanium aneurysm clips at different spatial ranges depending on sequence type. White matter pathways near clip artifacts can be reconstructed and visualized. These findings provide a reference for designing functional and structural neuroimaging studies of recovery in aSAH patients after clip placement

Carbon Dynamics on the Louisiana Continental Shelf and Cross-Shelf Feeding of Hypoxia

Large-scale hypoxia regularly develops during the summer on the Louisiana continental shelf. Traditionally, hypoxia has been linked to the vast winter and spring nutrient inputs from the Mississippi River and its distributary, the Atchafalaya River. However, recent studies indicate that much of the shelf ecosystem is heterotrophic. We used data from five late July shelfwide cruises from 2006 to 2010 to examine carbon and oxygen production and identify net autotrophic areas of phytoplankton growth on the Louisiana shelf. During these summer times of moderate river flows, shelfwide pH and particulate organic carbon (POC) consistently showed strong signals for net autotrophy in low salinity (<25) waters near the river mouths. There was substantial POC removal via grazing and sedimentation in near-river regions, with 66–85 % of POC lost from surface waters in the low and mid-salinity ranges without producing strong respiration signals in surface waters. This POC removal in nearshore environments indicates highly efficient algal retention by the shelf ecosystem. Updated carbon export calculations for local estuaries and a preliminary shelfwide carbon budget agree with older concepts that offshore hypoxia is linked strongly to nutrient loading from the Mississippi River, but a new emphasis on cross-shelf dynamics emerged in this research. Cross-shelf transects indicated that river-influenced nearshore waters <15 m deep are strong sources of net carbon production, with currents and wave-induced resuspension likely transporting this POC offshore to fuel hypoxia in adjacent mid-shelf bottom waters.Griffith Sciences, Griffith School of EnvironmentNo Full Tex

Violência contra a criança: indicadores dermatológicos e diagnósticos diferenciais Child abuse: skin markers and differential diagnosis

As denúncias de abuso contra a criança têm sido frequentes e configuram grave problema de saúde pública. O tema é desconfortável para muitos médicos, seja pelo treinamento insuficiente, seja pelo desconhecimento das dimensões do problema. Uma das formas mais comuns de violência contra a criança é o abuso físico. Como órgão mais exposto e extenso, a pele é o alvo mais sujeito aos maustratos. Equimoses e queimaduras são os sinais mais visíveis. Médicos (pediatras, clínicos-gerais e dermatologistas) costumam ser os primeiros profissionais a observar e reconhecer sinais de lesões não acidentais ou intencionais. Os dermatologistas podem auxiliar na distinção entre lesões traumáticas intencionais, acidentais e doenças cutâneas que mimetizam maus-tratos<br>Reports of child abuse have increased significantly. The matter makes most physicians uncomfortable for two reasons: a) Little guidance or no training in recognizing the problem; b - Not understanding its true dimension. The most common form of child violence is physical abuse. The skin is the largest and frequently the most traumatized organ. Bruises and burns are the most visible signs. Physicians (pediatricians, general practitioners and dermatologists) are the first professionals to observe and recognize the signs of intentional injury. Dermatologists particularly, can help distinguish intentional injury from accidental, or from skin diseases that mimic maltreatmen