wide-necked bifurcation aneurysms (wNBAs) make up 26-36% of all brain aneurysms. Treatments for wNBAs pose unique challenges due to the need to preserve major bifurcation vessels while achieving a durable occlusion of the aneurysm. intrasaccular flow disruption is an innovative technique for the treatment of wNBAs. The woven endoBridge (weB) device is the only United States Food and Drug Administration approved intrasaccular flow disruption device. in this review article we discuss various aspects of treating wNBAs with the weB device, including indications for use, aneurysm/device selection strategies, antiplatelet therapy requirement, procedural technique, potential complications and bailouts, and management strategies for residual/recurrent aneurysms after initial weB treatment.
Aneurysm height axis-parent artery angleBoth the dome size and the angle between the long axis of the aneurysm and the parent artery play on June 9, 2020 by guest. Protected by copyright.
Circular dichroism (CD), defined as the difference in absorption between left and right circularly polarized light, is used to spectroscopically study the structures of chiral materials. In this article, various methodologies are presented for characterizing the performance of CD spectrometers to determine (1) experimental conditions for optimal data collection, (2) noise characteristics dependent on machine parameters, (3) the relative significance of spectral data as a function of detector gain, and (4) stray light and dark current as a function of wavelength. The results of case studies of two commercial CD spectrometers (specifically, Jasco J810 and J815) are described. The analyses show that the variation of CD signal is Poisson distributed and hence can be considered shot noise. Also, optimum scan parameters are established and a weighting function of CD data significance is produced so that wavelength-dependent gain (as determined by the high tension, HT, voltage applied to the photomultiplier tube, PMT, detector) can be accommodated. Lastly, the amount of stray light and dark current for the photomultiplier tube is determined. Though specific to the Jasco CD spectrometers characterized in this study, it is expected that all CD spectrometers exhibit similar behavior and the methodology described here can be usefully applied to characterize CD spectrometers independent of manufacturer.
Both the voltage-induced and the inherent (static) birefringence of a photoelastic modulator (PEM) affect the phase difference between orthogonal components of light passing through the PEM. This phase difference determines the polarization state of the light and is essential for determining true circular and linear dichroism (CD and LD, respectively) spectroscopy. Presented here are a more complete theoretical model of CD and LD and a new technique to determine the phase difference and static birefringence of a PEM in CD and LD. The intensity of the light for various configurations of the analyzer is interpreted (by using Mueller matrices and Stokes parameters) to calibrate the voltage-induced phase difference and to characterize the static birefringence in the photoelastic modulator. The effects of the static birefringence as well as intermediate polarization states (between left- and right-circularly polarized light) on LD and CD are characterized. Appropriate adjustments to the voltage applied to the PEM in order to mitigate these effects are discussed. It is expected that the techniques presented here will have a broad impact on the calibration of CD and LD spectrometers.
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