Macroscopic Veins Research Articles

Imaging Features with Histopathologic Correlation of CNS High-Grade Neuroepithelial Tumors with a BCOR Internal Tandem Duplication.

A new brain tumor entity occurring in early childhood characterized by a somatic BCL6 corepressor gene internal tandem duplication was recently described. The aim of this study was to describe the radiologic pattern of these tumors and correlate this pattern with histopathologic findings. This retrospective, noninterventional study included 10 children diagnosed with a CNS tumor, either by ribonucleic acid-sequencing analysis or deoxyribonucleic acid methylation analysis. Clinical, radiologic, and histopathologic data were collected. A neuropathologist reviewed 9 tumor samples. Preoperative images were analyzed in consensus by 7 pediatric radiologists. All tumors were relatively large (range, 4.7-9.2 cm) intra-axial peripheral masses with well-defined borders and no peritumoral edema. All tumors showed mild and heterogeneous enhancement and marked restriction on DWI of the solid portions. Perfusion imaging showed a relatively lower CBF in the tumor than in the adjacent normal parenchyma. Nine of 10 tumors showed areas of necrosis, with the presence of hemorrhage in 8/10 and calcifications in 4/7. Large intratumoral macroscopic veins were observed in 9/10 patients. No intracranial or spinal leptomeningeal dissemination was noted at diagnosis. CNS tumors with a BCL6 corepressor gene internal tandem duplication present as large intra-axial peripheral masses with well-defined borders, no edema, restricted diffusion, weak contrast enhancement, frequent central necrosis, hemorrhage and calcifications, intratumoral veins, and no leptomeningeal dissemination at the time of diagnosis. Knowledge of these imaging characteristics may aid in histologic, genomic, and molecular profiling of brain tumors in young children.

Hydrothermally enhanced magnetization at the center of the Haughton impact structure?

AbstractHaughton is a ~24 Myr old midsize (apparent diameter 23 km) complex impact structure located on Devon Island in Nunavut, Canada. The center of the structure shows a negative gravity anomaly of −12 mGal coupled to a localized positive magnetic field anomaly of ~900 nT. A field expedition in 2013 led to the acquisition of new ground magnetic field mapping and electrical resistivity data sets, as well as the first subsurface drill cores down to 13 m depth at the top of the magnetic field anomaly. Petrography, rock magnetic, and petrophysical measurements were performed on the cores and revealed two different types of clast‐rich polymict impactites: (1) a white hydrothermally altered impact melt rock, not previously observed at Haughton, and (2) a gray impact melt rock with no macroscopic sign of alteration. In the altered core, gypsum is present in macroscopic veins and in the form of intergranular selenite associated with colored and zoned carbonate clasts. This altered core has a natural remanent magnetization (NRM) four to five times higher than materials from the other core but the same magnetic susceptibility. Their magnetization is still higher than the surrounding crater‐fill impact melt rocks. X‐ray fluorescence data indicate a similar proportion of iron‐rich phases in both cores and an enrichment in silicates within the altered core. In addition, alternating‐field demagnetization results show that one main process remagnetized the rocks. These results support the hypothesis that intense and possibly localized post‐impact hydrothermal alteration enhanced the magnetization of the clast‐rich impact melt rocks by crystallization of magnetite within the center of the Haughton impact structure. Subsequent erosion was followed by in situ concentration in the subsurface leading to large magnetic gradient on surface.

Developmental morphology and phylogeny of Paraglossum amsleri sp. nov. (Delesseriaceae, Rhodophyta), a species from Antarctica previously known as Delesseria lancifolia

:Paraglossum amsleri S.-M. Lin & Hommersand sp. nov. (Delesseriaceae, Rhodophyta), a species previously reported as Delesseria lancifolia from the Antarctic Peninsula and associated Antarctic Islands, was investigated based on rbcL sequence analysis and morphological evidence. The genetic distance between the type species, Paraglossum lancifolium and ‘D. lancifolia’ from Antarctica was 3.8% (52 pairwise differences); whereas, the interspecific genetic divergence within the genus Paraglossum ranged from 0.95% to 6.96% (13–95 pairwise base differences). Procarps and cystocarps were formed in bladelets with broad bases borne along the margins of the midrib and macroscopic veins or scattered over the thallus surface in P. lancifolium; whereas, they were formed in bladelets with short stalks borne along the midrib and macroscopic veins in P. amsleri. Tetrasporangia were formed in bladelets initiated from surface cells in P. lancifolium but were produced in cells in linear files alongside the margins and from the surfaces of the midrib and macroscopic veins in P. amsleri. Intercalary cell divisions were absent in primary cell rows that formed the midrib in all species of Paraglossum but occurred frequently in second and higher orders of cell rows. Fourth-order cell rows were produced both abaxially and adaxially in P. lancifolium but were formed only adaxially in rapidly growing tips of P. amsleri. Paraglossum salicifolium, the only other species of this genus known from Antarctica, exhibited a pattern of vegetative growth similar to that seen in P. amsleri. The formation of uniseriate filaments from the pericarps of P. salicifolium was a character that that clearly distinguished this species from P. amsleri, in which the pericarps were smooth. New species combinations were proposed as Paraglossum for Delesseria crozetii Levring, Delesseria macloviana Skottsberg in Kylin & Skottsberg and Delesseria minor Baardseth.

Phase based venous suppression in resting-state BOLD GE-fMRI

Resting-state functional MRI (RS-fMRI) is a widely used method for inferring connectivity between brain regions or nodes. As with task-based fMRI, the spatial specificity of the connectivity maps can be distorted by the strong biasing effect of the BOLD signal in macroscopic veins. In RS-fMRI this effect is exacerbated by the temporal coherences of physiological origin between large veins that are widely distributed in the brain. In gradient echo based EPI, used for the vast majority of RS-fMRI, macroscopic veins that carry BOLD-related changes exhibit a strong phase response. This allows for post-processing identification and removal of venous signals using a phase regressor technique. Here, we employ this approach to suppress macrovascular venous contributions in high-field whole-brain RS-fMRI data sets, resulting in significant changes to both the spatial localization of the networks and the correlations between the network nodes. These effects were observed at both the individual and group analysis level, suggesting that venous contamination is a confounding factor for RS-fMRI studies even at relatively low image resolutions. Suppression of the macrovascular signal using the phase regression approach may therefore help to better identify, delineate, and interpret the true structure of large-scale brain networks.

Loss of venous integrity in cerebral small vessel disease: a 7-T MRI study in cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

Previous pathological studies in humans or in animal models have shown alterations of small arteries and veins within white matter lesions in cerebral small vessel disease. We aimed to evaluate in vivo, the integrity of the cerebral venous network using high-resolution MRI both within and outside white matter hyperintensities in cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). High-resolution T2*-weighted images were obtained at 7-T in 13 CADASIL patients with no or only mild symptoms and 13 age- and sex-matched controls. Macroscopic veins were automatically counted in the centrum semiovale and compared between patients and controls. In addition, T2* was compared between groups in the normal-appearing white matter. Vein density was found lower in CADASIL patients compared with that in controls (-14.6% in patients, P<0.001). This was detected both within and outside white matter hyperintensities. Mean T2*, that is presumably inversely related to the venous density, was also found increased in normal-appearing white matter of patients (+7.2%, P=0.006). All results were independent from the extent of white matter hyperintensities. A significant reduction in the number of visible veins was observed in the centrum semiovale of CADASIL patients both within and outside white matter hyperintensities, together with an increase of T2* in the normal-appearing white matter. Additional studies are needed to decipher the exact implication of such vasculature changes in the appearance of white matter lesions.

Systematic revision of the genus Phycodrys (Delesseriaceae, Rhodophyta) from New Zealand, with the descriptions of three new species, P. novae-zelandiae sp. nov., P. franiae sp. nov. and P. adamsiae sp. nov.

Two species of Phycodrys, Phycodrys quercifolia (Bory) Skottsberg and Phycodrys profunda E.Y.Dawson were previously recorded from New Zealand. However, an examination of Phycodrys collections from the New Zealand region showed that all were morphologically different from P. quercifolia (Type locality: the Falkland Islands) and P. profunda (Type locality: CA, USA). RbcL sequence analyses established that the New Zealand Phycodrys species formed a natural assemblage within the genus, consisting of three new species: P. novae-zelandiae sp. nov., P. franiae sp. nov. and P. adamsiae sp. nov. Phycodrys novae-zelandiae is the largest of the three, up to 20 cm in height, with a distinct midrib and multicellular, opposite to subopposite lateral macroscopic veins. It has entirely monostromatic blades except near the midrib and veins, and its procarp contains a three-celled sterile group one (st1) and a one-celled sterile group two (st2). Phycodrys franiae was previously treated as a cryptic species among herbarium collections of P. ‘quercifolia’. It is smaller (4–11 cm high) with weakly developed midribs and veins, the blade is tristromatic throughout, except at the growing margins, and the procarp consists of a four-celled st1 and a two–three-celled st2. Phycodrys adamsiae, previously reported as P. profunda, is a small decumbent or prostrate plant, 1–8 cm long, with a midrib and inconspicuous lateral veins. The blades are tristromatic with serrated margins, two–four-celled surface spines and multicellular marginal holdfasts that differ from those of Californian specimens. The tetrasporangia are borne on marginal bladelets. Phylogenetic analyses place the New Zealand species in a separate group that is distantly removed from most other Phycodrys species.

Transfer of melt between microscopic pores and macroscopic veins in migmatites

A new model is proposed to numerically simulate transfer of melt between microscopic pores and macroscopic veins in a deforming porous matrix. Matrix rheology is assumed to be visco-elastic. Darcy flow of porous melt through the matrix is calculated in accord with the theory of poroelasticity. Veins of melt are described separately. The model is realized using a code for a 2-D rectangle that is deformed at a constant strain rate. We reproduce in 2-D the main analytical results derived by Sleep (1988) but add calculations concerning the flow and local compaction processes around veins with different inclinations to the maximum (compressive) deviatoric stress. Inclusions perpendicular to σ1 tend to close while those parallel to σ1 tend to grow. Surrounding regions either compact or dilate and inclined veins propagate parallel to σ1. The incremental porosity decreases exponentially with distance from the vein walls by a factor equal to the compaction length. Local redistribution of melt from microscopic pores to macroscopic veins strongly enhances melt segregation into the vein networks which can lead to bodies sufficiently massive to become buoyant.

Suppression of Vascular Artifacts in Functional Magnetic Resonance Images Using MR Angiograms

This paper describes a method for processing functional magnetic resonance images that suppresses signal changes originating from macroscopic veins visible in acquired magnetic resonance angiograms. Finger tapping experiments were performed on a 1.5-T scanner and the response was evaluated with voxel-by-voxel cross-correlation of the time course with a sinusoid at the paradigm frequency. After applying a vascular mask to suppress signal changes under macroscopic vessels, the vascular and nonvascular subpopulations of the data were compared. By visual inspection, the method was found to remove extracortical activation while preserving activation in the parenchyma. The observed higher signal amplitudes and temporal phase lags of the vascular population agree with theoretical models and previous studies. A significant portion of negatively correlated voxels occurs adjacent to through-plane vessels. Finally, comparing the centers of mass of the activated area before and after vascular suppression showed significant shifts in some subjects.

Fractal clustering of metamorphic veins

Metamorphic veins record the fracture-controlled flow of fluids throughout the oceanic and continental crust. I show that the spatial distributions of veins from three diverse metamorphic settings are fractal and self-similar. Vein densities were measured by counting the number of macroscopic veins intersected along linear transects. The localities included wol-lastonite-quartz veins in marbles, for which the fractal dimension D is 0.46, actinolite-chlorite veins in hydrothermally altered oceanic diabases ( D = 0.81), and epidote-quartz veins in contact-metamorphosed basalts ( D = 0.25-0.63). The fractal clustering of veins provides a geometric framework for understanding spatial and temporal patterns of fluid flow and mineral reaction during metamorphism.

Fracture and permeability analysis in magma‐hydrothermal transition zones in the Samail ophiolite (Oman)

Many numerical models have stressed the key importance of processes operative within magma‐hydrothermal transition zones of spreading centers, but few studies have attempted a geologic characterization of the key physical parameters of this zone. With this in mind, fracture‐related data have been collected in the Samail ophiolite (Oman) within gabbro/dike transition zones and major plagiogranite plutons, and at each site the nature, abundance, orientation, filling, and attitude of the fractures were determined. Two main hydrothermal vein groups can be distinguished: an amphibole vein system and a quartz‐epidote‐sulfide vein system. Amphibole veins are restricted to the gabbro, whereas quartz‐epidote‐sulfide veins mainly appear in the sheeted‐dike complex and plagiogranite. The amphibole vein system is strongly anisotropic (perpendicular to the layering and subparallel to the sheeted dikes) and heterogeneous. The quartz‐epidote‐sulfide veins, too, are subparallel to the sheeted dikes. They are characterized by a sharp density decrease of macroscopic veins: from an average 0.5 m−1 (sheeted dikes) to 0.2 m−1 (transition zone) to less than 0.0l m−1 (gabbro). In plagiogranite, where no concentric or radiating vein systems were seen, they are 0.1 to 0.3 m−1. The ubiquitous presence of ridge parallel hydrothermal veins implies a major contribution of regional tectonic stresses associated with spreading in addition to other mechanisms involved in fracture generation: thermal cracking, volatile‐rich magma expansion, differential expansion of pore fluids.

Serpentine minerals from veins in serpentinite rocks

SummaryCrystal-chemical analyses of the serpentine polymorphs, sampled from macroscopic veins in the serpentinite rocks from Sasso della Mantesca and Sasso di S. Zanobi, are reported. The samples were examined by X-ray diffraction, thermal analysis (TG and DTG), scanning and transmission electron microscopy, IR absorption spectroscopy, microprobe, and chemical tests.The results show: chrysotile 2Orc1 in tubular fibrils placed perpendicularly to walls of iso-oriented ‘lenticular veins’; and polygonal serpentine formed by flat layers of lizardite 2H and/or 1T, arranged as an outer shell of a central core of chrysotile 2Mc1 fibres; this type of serpentine with high crystallinity and unusual morphological development is included in ‘green veins’, which show variable Al, Fe, and Mg contents.A genetic mechanism correlating the petrographic observations with the mineralogical results is discussed.