Chirality of isomers of aldosterone formed in dilute alkali

In the presence of dilute alkali at room temperature aldosterone undergoes rearrangement to form 11 beta,18:18,21-diepoxy-20,21-dihydroxy-4-pregnen-3-one (V). X-Ray crystallographic analysis demonstrates that isomers of both 18R, 20S, 21S and 18R, 20S, 21R configuration are formed rather than the 18R, 20R, 21R isomer postulated on the basis of examination of 1H-NMR spectra. The spectra appears to be consistent with the major component of the mixture. The 20S configuration observed is in agreement with the chirality assigned to the degradation product obtained when the same alkaline solution of aldosterone is subjected to reflux. The crystals of (V) are monoclinic P2(1), Z = 4 with a = 20.891(2), b = 6.3848(5), c = 16.067(2)A, beta = 122.09 degrees(1) with two molecules in the asymmetric unit. Molecule A has the 20S,21S configuration and the molecules in the second site are a mixture of the 20S, 21S and 20S, 21R configuration in the ratio of 3:2.     

Movement correction method for laser speckle contrast imaging of cerebral blood flow in cranial windows in rodents

Laser speckle contrast imaging (LSCI) is used in clinical research to dynamically image blood flow. One drawback is its susceptibility to movement artifacts. We demonstrate a new, simple method to correct motion artifacts in LSCI signals measured in awake mice with cranial windows during sensory stimulation. The principle is to identify a region in the image in which speckle contrast (SC) is independent of blood flow and only varies with animal movement, then to regress out this signal from the data. We show that (1) the regressed signal correlates well with mouse head movement, (2) the corrected signal correlates better with independently measured blood volume and (3) it has a (59 ± 6)% higher signal-to-noise ratio. Compared to three alternative correction methods, ours has the best performance. Regressing out flow-independent global variations in SC is a simple and accessible way to improve the quality of LSCI measurements.     

Cross‐scanning optical coherence tomography angiography for eye motion correction

We propose a cross‐scanning optical coherence tomography (CS‐OCT) system to correct eye motion artifacts in OCT angiography images. This system employs a dual‐illumination configuration with two orthogonally polarized beams, each of which simultaneously perform raster scanning in perpendicular direction with each other over the same area. In the reference arm, a polarization delay unit is used to acquire the two orthogonally polarized interferograms with a single photo detector by introducing different optical delay lines. The two cross‐scanned volume data are affected by the same eye motion but in two orthogonal directions. We developed a motion correction algorithm, which removes artifacts in the slow axis of each angiogram using the other and merges them through a nonrigid registration algorithm. In this manner, we obtained a motion‐corrected angiogram within a single volume scanning time without additional eye‐tracking devices.     

Predictive Configural Frequency Analysis Evaluated by Simultaneous Berchtold-Corrected Fourfold X2-Tests

For testing against outlying cells in r × c contingency tables in predictive configural frequency analysis, it is suggested not to replace the usual PEARSON fourfold X²-test by YATES ' discontinuity corrected test but by BERCHTOLD'S test correcting for skewed hypergeometric distributions. In general, the BERCHTOLD correction is most efficient for tables involving three small and one large fourfold frequency. The correction is illustrated by configural frequency analysis of data from psychotherapy research.     

Gafchromic film dosimetry: Four years experience using FilmQA Pro software and Epson flatbed scanners

Purposes: To assess performance of FilmQA Pro software for pre-treatment patient-specific quality assurance (QA), using radiochromic films and two commercial flatbed scanners. To evaluate a novel multichannel approach compared to the classical red channel evaluation.Material and methodsPatient films (mostly EBT2 films, one box of EBT3) were digitalized using successively two flatbed scanners: the A4-size Epson V750 and the A3-size Epson 10000XL. Prior to patient dose verification, basic characteristics of films and scanners were investigated. Patient films were analyzed using FilmQA Pro software, which enables to use the signal from all three colour channels (Red, Green, Blue).ResultsCompared to the red channel evaluation, multichannel evaluation presents better passing rates with regard to local gamma index. As expected, we obtained better results using A3-size scanner compared to A4-size scanner, especially when considering large region of interest. An observation of great interest was made for both scanners: after intensive use, a tilting in the blue transmittance profiles appeared in the lamp direction, making multichannel analysis unsuitable for accurate dose evaluation.     

Deep-learning-based motion correction in optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) is a widely applied tool to image microvascular networks with high spatial resolution and sensitivity. Due to limited imaging speed, the artifacts caused by tissue motion can severely compromise visualization of the microvascular networks and quantification of OCTA images. In this article, we propose a deep-learning-based framework to effectively correct motion artifacts and retrieve microvascular architectures. This method comprised two deep neural networks in which the first subnet was applied to distinguish motion corrupted B-scan images from a volumetric dataset. Based on the classification results, the artifacts could be removed from the en face maximum-intensity-projection (MIP) OCTA image. To restore the disturbed vasculature induced by artifact removal, the second subnet, an inpainting neural network, was utilized to reconnect the broken vascular networks. We applied the method to postprocess OCTA images of the microvascular networks in mouse cortex in vivo. Both image comparison and quantitative analysis show that the proposed method can significantly improve OCTA image by efficiently recovering microvasculature from the overwhelming motion artifacts.     

Evaluation of three scatter correction methods based on estimation of photopeak scatter spectrum in SPECT imaging: A simulation study

Three practical methods for scatter correction of Tc-99m SPECT images are evaluated. Among these, two methods, three-energy window (TEW) methods using the trapezoidal and triangular approximations, have been described previously by investigators, and a new approximation is offered in this work. The SIMIND (SIMulation of Imaging Nuclear Detectors) Monte Carlo program is used to simulate a line source placed at on-axis and 5 cm off-axis locations, a cold-sphere/hot-background phantom, a hot-sphere/cold-background phantom, and a more clinically realistic NCAT (Nonuniform Rational B-spline-based CArdiac-Torso) phantom. For evaluation of these methods, the scatter line-spread functions and scatter fractions for the on- and off-axis line source, image contrast, signal-to-noise ratio and relative noise for the cold spheres, and recovery coefficient for the hot spheres of different diameters are compared. For the NCAT phantom, a line profile through a slice of the reconstructed image is considered before and after scatter correction, and also image contrast defined by this profile is used to compare the correction methods. The results of this study indicate that for the line source simulation the scatter fractions obtained from the proposed method are a better estimation of true scatter fractions. Also, for both the sphere simulation and NCAT simulation, the proposed method improves the image contrast as compared to the two other methods.