Neonatal brain and cardiac imaging would benefit from the increased signal-to-noise ratio levels at 7 T compared to lower field. Optimal performance might be achieved using purpose designed RF coil arrays. In this study, we introduce an 8-channel dipole array and investigate, using simulations, its RF performances for neonatal applications at 7 T.
Methods
The 8-channel dipole array was designed and evaluated for neonatal brain/cardiac configurations in terms of SAR efficiency (ratio between transmit-field and maximum specific-absorption-rate level) using adjusted dielectric properties for neonate. A birdcage coil operating in circularly polarized mode was simulated for comparison. Validation of the simulation model was performed on phantom for the coil array.
Results
The 8-channel dipole array demonstrated up to 46% higher SAR efficiency levels compared to the birdcage coil in neonatal configurations, as the specific-absorption-rate levels were alleviated. An averaged normalized root-mean-square-error of 6.7% was found between measured and simulated transmit field maps on phantom.
Conclusion
The 8-channel dipole array design integrated for neonatal brain and cardiac MR was successfully demonstrated, in simulation with coverage of the baby and increased SAR efficiency levels compared to the birdcage. We conclude that the 8Tx-dipole array promises safe operating procedures for MR imaging of neonatal brain and heart at 7 T.
Perfluorocarbons, saturated carbon chains in which all the hydrogen atoms are replaced with fluorine, form a separate phase from both organic and aqueous solutions. Though perfluorinated compounds are not found in living systems, they can be used to modify biomolecules to confer orthogonal behavior within natural systems, such as improved stability, engineered assembly, and cell-permeability. Perfluorinated groups also provide handles for purification, mass spectrometry, and 19F NMR studies in complex environments. Herein, we describe how the unique properties of perfluorocarbons have been employed to understand and manipulate biological systems. 相似文献
Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality. 相似文献
In the present study, human growth hormone-releasing factor (hGRF) and analogs were successfully pegylated at the carboxy-terminus using a novel solid- and solution-phase strategy. Following synthesis, these pegylated hGRF analogs were evaluated for in vitro and in vivo biological activity. Specifically, hGRF (1-29)-NH2, [Ala15]-hGRF (1-29)-NH2, [desNH2Tyr1, D-Ala2, Ala15]-hGRF(1-29)-NH2 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-OH were each C-terminally extended using a Gly-Gly-Cys-NH2 spacer (previously demonstrated not to alter intrinsic biological activity), and then monopegylated via coupling to an activated dithiopyridyl-PEG reagent. PEG moieties of 750, 2000, 5000 or 10,000 molecular weight (MW) were examined to determine the effect of polymer weight on activity. Initial biological evaluations in vitro revealed that all C-terminally pegylated hGRF analogs retained high growth hormone (GH)-releasing potencies, regardless of the MW of PEG polymer employed. Two of these pegylated hGRF analogs, [desNH2Tyr1, D-Ala2, Ala15]-hGRF (1-29)-Gly-Gly-Cys(NH2)-S-Nle-PEG5000 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-Gly-Cys(NH2)-S-Nle-PEG5000, were subsequently evaluated in both pig and mouse models and found to be highly potent (in vivo potency range = 12-55-fold that of native hGRF). Relative to their non-pegylated counterparts, these two pegylated hGRF analogs exhibited enhanced duration of activity. 相似文献