Tectonic Implications of Postcontractional Magmatism of the Alisitos Arc Segment of the Peninsular Ranges, Baja California, Mexico

The Alisitos arc segment is the southernmost and only part of the western Peninsular Ranges batholith accreted during the Cretaceous. Collision-related deformation is concentrated along the northern and eastern margins of the arc segment. While shortening within the Alisitos arc produced similar amounts of crustal thickening throughout the arc, suppression of parts of the lower crust of the Alisitos arc due to throw across the terrane-bounding faults varies substantially. Geobarometric change across the Main Mártir thrust suggests that ~15 km of additional crust was thrust onto the central Alisitos arc. Geochemical and geochronologic data from intrusive rocks of the Alisitos arc indicate arc magmatism was active before, during, and after collision. The data suggest that all Peninsular Ranges batholith intrusive rocks within the Alisitos arc were derived from a broadly similar primitive source, lacking interaction with evolved continental lithologies. Postcollisional intrusions from the central Alisitos arc adjacent to the Main Mártir thrust yield trace elemental signatures suggesting melt derivation at depths where garnet would be a stable residual phase. The spatial and temporal coincidence of these intrusions with the Main Mártir thrust suggests that the increased pressure of anatexis inferred for the depth of generation of these melts was generated by displacement on this fault. Further, close temporal and spatial characteristics, and similar geochemical characteristics between the central Alisitos arc intrusions and La Posta intrusions east of the Main Mártir thrust suggest that the Alisitos arc intrusions represent precursors to the much larger flare-up event. This observation supports models suggesting collision as a cause of magmatic flare-ups in arcs

COSMOS-based susceptibility estimations: Accuracy assessment and comparisons of QSM and multiple-angle acquisitions

Calculation Of Susceptibility through Multiple Orientation Sampling (COSMOS) is assessed comparing the optimal, a clinically feasible and multiple-orientation schemes. The optimal COSMOS estimation is used as a gold standard and is compared to the other schemes using the similarity index (SSIM), mean absolute error (MAE) and Pearson’s coefficient (PC). Further comparisons include Thresholded K-space Division (TKD) quantitative susceptibility mapping. For selected white-matter regions, linear regression is used to assess the similarities between the different estimations

Beyond diffusion-based analysis of fiber architecture: Estimation of orientation distributions from high angular resolution susceptibility imaging

We present a novel approach to estimate fiber Orientation Distribution Functions (ODFs) by applying the generalized Constant Solid Angle (CSA) method to High Angular Resolution Susceptibility Imaging (HARSI) data from post-mortem chimpanzee brain. The acquisition details and analytical pipelines are presented and derived susceptibility tensor metrics and ODFs are compared to metrics derived from traditional High Angular Resolution Diffusion Imaging (HARDI). The ODFs estimated from susceptibility data indicate comparable efficiency in resolving intersecting fiber orientations compared to HARDI-ODFs and increased sensitivity to secondary direction. This suggests a potential to obtain complementary information on brain white matter microstructural properties

Atypical presentation of myoepithelial hamartoma in the antrum of the stomach, mimicking a gastrointestinal stromal tumor: a case report

<p>Abstract</p> <p>Introduction</p> <p>A myoepithelial hamartoma is a very uncommon submucosal tumor of the stomach. In an atypical presentation in our case, it mimicked the clinical presentation of a gastrointestinal stromal tumor. To the best of our knowledge, it is the first case of a hamartoma of the stomach reported from Bangladesh and one of few cases described in the literature.</p> <p>Case presentation</p> <p>We describe the case of a 35-year-old Bengali man with recurrent epigastric pain and occasional vomiting with radiographic findings of a gut mass. An upper gastrointestinal endoscopy revealed a healed duodenal ulcer, deformed ‘D’ bulb and a submucosal swelling in his antrum. Ultrasonography and a contrast-enhanced computed tomography scan confirmed the presence of a well-defined, oval gut mass in his upper abdomen, compressing his duodenum. The mass had a mixed density and was considered to probably be a gastrointestinal stromal tumor. Ultrasonography-guided fine needle aspiration cytology was inconclusive. After resection at laparotomy, a histopathological examination revealed a myoepithelial hamartoma. These tumors are characterized by hypertrophic smooth muscle bands surrounding varied epithelial elements, which may be arranged in diverse patterns such as simple glandular structure, Brunner’s gland, pancreatic ducts and sometimes pancreatic acini. This case report is complemented by a literature review relating to the atypical presentation.</p> <p>Conclusion</p> <p>Gut masses need to be investigated thoroughly and the possibility of rare tumors should not be excluded. Although the recommended treatment for such lesions is limited resection, radical procedures such as a pancreaticoduodenectomy are often performed when the lesion occurs in the periampullary area because of preoperative misdiagnosis as a carcinoma. Therefore, it is essential for clinicians to maintain current knowledge of the lesion to avoid inaccurate diagnosis and prevent unnecessary surgery.</p