Compressed SENSE in Pediatric Brain Tumor MR Imaging : Assessment of Image Quality, Examination Time and Energy Release.

PURPOSE: To compare the image quality, examination time, and total energy release of a standardized pediatric brain tumor magnetic resonance imaging (MRI) protocol performed with and without compressed sensitivity encoding (C-SENSE). Recently introduced as an acceleration technique in MRI, we hypothesized that C­SENSE would improve image quality, reduce the examination time and radiofrequency-induced energy release compared with conventional examination in a pediatric brain tumor protocol. METHODS: This retrospective study included 22 patients aged 2.33-18.83 years with different brain tumor types who had previously undergone conventional MRI examination and underwent follow-up C­SENSE examination. Both examinations were conducted with a 3.0-Tesla device and included pre-contrast and post-contrast T1-weighted turbo-field-echo, T2-weighted turbo-spin-echo, and fluid-attenuated inversion recovery sequences. Image quality was assessed in four anatomical regions of interest (tumor area, cerebral cortex, basal ganglia, and posterior fossa) using a 5-point scale. Reader preference between the standard and C­SENSE images was evaluated. The total examination duration and energy deposit were compared based on scanner log file analysis. RESULTS: Relative to standard examinations, C­SENSE examinations were characterized by shorter total examination times (26.1 ± 3.93 vs. 22.18 ± 2.31 min; P = 0.001), reduced total energy deposit (206.0 ± 19.7 vs. 92.3 ± 18.2 J/kg; P < 0.001), and higher image quality (overall P < 0.001). CONCLUSION: C­SENSE contributes to the improvement of image quality, reduction of scan times and radiofrequency-induced energy release relative to the standard protocol in pediatric brain tumor MRI.

Reindeer control over subarctic treeline alters soil fungal communities with potential consequences for soil carbon storage.

The climate-driven encroachment of shrubs into the Arctic is accompanied by shifts in soil fungal communities that could contribute to a net release of carbon from tundra soils. At the same time, arctic grazers are known to prevent the establishment of deciduous shrubs and, under certain conditions, promote the dominance of evergreen shrubs. As these different vegetation types associate with contrasting fungal communities, the belowground consequences of climate change could vary among grazing regimes. Yet, at present, the impact of grazing on soil fungal communities and their links to soil carbon have remained speculative. Here we tested how soil fungal community composition, diversity and function depend on tree vicinity and long-term reindeer grazing regime and assessed how the fungal communities relate to organic soil carbon stocks in an alpine treeline ecotone in Northern Scandinavia. We determined soil carbon stocks and characterized soil fungal communities directly underneath and >3 m away from mountain birches (Betula pubescens ssp. czerepanovii) in two adjacent 55-year-old grazing regimes with or without summer grazing by reindeer (Rangifer tarandus). We show that the area exposed to year-round grazing dominated by evergreen dwarf shrubs had higher soil C:N ratio, higher fungal abundance and lower fungal diversity compared with the area with only winter grazing and higher abundance of mountain birch. Although soil carbon stocks did not differ between the grazing regimes, stocks were positively associated with root-associated ascomycetes, typical to the year-round grazing regime, and negatively associated with free-living saprotrophs, typical to the winter grazing regime. These findings suggest that when grazers promote dominance of evergreen dwarf shrubs, they induce shifts in soil fungal communities that increase soil carbon sequestration in the long term. Thus, to predict climate-driven changes in soil carbon, grazer-induced shifts in vegetation and soil fungal communities need to be accounted for.

CT of the medial clavicular epiphysis for forensic age estimation: hands up?

PURPOSE: The aim of this study was to assess the impact of arm position in computed tomography (CT) of the clavicle performed for forensic age estimation on clavicular position, image noise, and radiation dose. METHODS AND MATERIALS: Forty-seven CT scans of the medial clavicular epiphysis performed for forensic age estimation were conducted with either hands and arms held upwards (CTHU, 28 persons) or positioned at the body (CTHD, 19 persons). Presets were identical for both positions (70 mAs/140 kVp; Brilliance iCT, Philips). Each CT scan was reconstructed with an iterative algorithm (i-Dose 4) and evaluated at the middle of the sternoclavicular joint. Clavicular angle was measured on a.p. topograms in relation to a horizontal line. Quantitative image noise was measured in air at the level of medial clavicular epiphysis. Effective dose and scan length were recorded. RESULTS: Hands-up position compared with hands-down position resulted in a lower lateral body diameter (CTHU 41.1 ± 3.6 cm vs. CTHD 44.6 ± 3.1 cm; P = 0.03), a reduced quantitative image noise (CTHU: 39.5 ± 9.2; CTHD: 46.2 ± 8.3; P = 0.02), and lower CTDIvol (5.1 ± 1.4 mGy vs. 6.7 ± 1.8 mGy; P = 0.001). Scan length was longer in patients examined with hands up (HU: 8.5 ± 3.4 cm; HD: 6.2 ± 2.1 cm; P = 0.006). Mean effective dose for CTHU was 0.79 ± 0.32 mSv compared with 0.95 ± 0.38 mSv in CTHD (P = 0.12). Clavicular angle was 17° ± 6° in patients with hands down and 32° ± 7° in patients with hands up (P < 0.001). CONCLUSION: By elevated arm positioning, the image quality of clavicular CT scans can be improved while maintaining radiation dose compared with hands down. Clavicular position differs according to the hand position. Thus, positioning patients with elevated hands is advisable for forensic clavicular CT examinations, but multiplanar CT reconstructions should be adjusted to clavicular position and scan length should be reduced to a minimum.

Cellular localization of endothelial alkaline phosphatase reaction product and enzyme protein in the myocardium.

Myocardial capillary endothelial cells, arteriolar endothelial cells, and the arterial adventitia show positive alkaline phosphatase (AP) enzyme reaction and immunoreactivity in both rat and human hearts. In guinea pigs, however, capillary endothelial staining is discontinuous and arterial adventitia is negative. The ultrastructural correlate of discontinuous capillary staining is a pronounced labeling of pericytes in guinea pig heart and relatively weak endothelial staining. In rat and human heart, enzyme reaction products are localized mainly on plasma membranes and cytotic vesicles of endothelial cells. Comparison of two strains of rat reveals a more dense deposition of enzyme reaction product along the luminal and particularly along the abluminal plasma membrane of Sprague-Dawley rats than of Wistar rats. Quantitative analysis of immunogold labeled anti-AP antibody density confirms the pronounced polarity of capillary endothelial cell labeling in Sprague-Dawley rats. More than 80% of total endothelial AP protein in Sprague-Dawley rats is localized over the abluminal plasma membrane and basal lamina, as compared with less than 30% in Wistar rats. Moreover, the total endothelial cell labeling is almost sixfold higher in Sprague-Dawley than in Wistar rats. Total endothelial labeling and proportion of labeling on the abluminal endothelial plasma membrane in human hearts is intermediate between the two strains of rat. The strain and species differences in enzyme distribution could provide important information concerning enzyme function.

Postembedding ultrastructural in situ hybridization on ultrathin cryosections and LR white resin sections.

A method was developed for nonisotopic postembedding in situ hybridization (ISH) on ultrathin sections of frozen and of LR White resin-embedded material at the electron microscopic level. The method was successfully applied to detect Epstein-Barr virus (EBV) DNA in the P3HR1 human Burkitt's lymphoma cell line. Each of the steps in the procedure had to be optimized for successful ISH on the frozen and LR White sections. The most important conditions are described. Predigestion with proteinase K was only necessary with the resin sections. Sections were treated with sodium hydroxide to denature target DNA and were hybridized with a biotinylated probe. The probe was best detected with a primary antibody to biotin followed by a gold-conjugated secondary antibody. EBV DNA was detected in the nucleus and/or cytoplasm in 10% to 20% of P3HR1 cells. A similar percentage of cells in thin L-sectioned material prepared by routine methods showed virus particles at different stages of maturation.

Retrovirus-induced osteopetrosis in mice. Ultrastructural evidence of early virus production in osteoblasts and osteocytes.

Newborn female strain NMRI mice were given injections of a mouse retrovirus (OA MuLV) known to induce osteopetrosis, osteoma, and lymphoma. Femur metaphyses and lumbar vertebrae were investigated ultrastructurally 3 d, 7 d and 28 d after infection. Budding, immature and mature virus was observed associated with osteoblasts and osteocytes, but not with osteoclasts or chondrocytes, 28 d after infection with the virus. No production of virus particles was observed in bone-tissue in mock-treated controls. Thus, the primary target cell for OA virus in bone appears to belong to the osteoblastic/osteocytic cell lineage.

Application of monoclonal antibodies and genetically-engineered hybrid B-subunit proteins to the analysis of the cholera/coli enterotoxin family.

Single amino acid substitutions, introduced by genetic engineering, significantly modify the behavior of the B-subunits of the cholera/coli enterotoxin family in SDS-PAGE and also markedly affect the reactivity of the proteins with mouse hybridoma-derived monoclonal antibodies raised against H-LT. The results indicate that single amino acids play an important role in defining epitopes in these proteins.

Preparation of procoligenoids from Escherichia coli heat-labile enterotoxins.

Heat-labile enterotoxins from Escherichia coli strains of porcine and human origin polymerize on heating to form high-molecular-weight aggregates, "procoligenoids," analogous to procholeragenoid derived from the cholera enterotoxin. This aggregation is accompanied by loss of biological activity (toxicity). Further heating results in the release of B-subunit oligomers, coligenoids, analogous to choleragenoid. Further studies are needed to determine whether, like procholeragenoid, the procoligenoids are superior antigens in stimulating gut immunity after parenteral administration.