Natural and synthetic hydrogel scaffolds exhibit distinct viscoelastic properties at various length scales and deformation rates. Laser Speckle Rheology (LSR) offers a novel, non-contact optical approach for evaluating the frequency-dependent viscoelastic properties of hydrogels. In LSR, a coherent laser beam illuminates the specimen and a high-speed camera acquires the time-varying speckle images. Cross-correlation analysis of frames returns the speckle intensity autocorrelation function, g2(t), from which the frequency-dependent viscoelastic modulus, G*(ω), is deduced. Here, we establish the capability of LSR for evaluating the viscoelastic properties of hydrogels over a large range of moduli, using conventional mechanical rheometry and atomic force microscopy (AFM)-based indentation as reference-standards. Results demonstrate a strong correlation between |G*(ω)| values measured by LSR and mechanical rheometry (r = 0.95, p < 10−9), and z-test analysis reports that moduli values measured by the two methods are identical (p > 0.08) over a large range (47 Pa – 36 kPa). In addition, |G*(ω)| values measured by LSR correlate well with indentation moduli, E, reported by AFM (r = 0.92, p < 10−7). Further, spatially-resolved moduli measurements in micro-patterned substrates demonstrate that LSR combines the strengths of conventional rheology and micro-indentation in assessing hydrogel viscoelastic properties at multiple frequencies and small length-scales.

Over the years, many computed optical interferometric techniques have been developed to perform high-resolution volumetric tomography. By utilizing the phase and amplitude information provided with interferometric detection, post-acquisition corrections for defocus and optical aberrations can be performed. The introduction of the phase, though, can dramatically increase the sensitivity to motion (most prominently along the optical axis). In this paper, we present two algorithms which, together, can correct for motion in all three dimensions with enough accuracy for defocus and aberration correction in computed optical interferometric tomography. The first algorithm utilizes phase differences within the acquired data to correct for motion along the optical axis. The second algorithm utilizes the addition of a speckle tracking system using temporally-and spatially-coherent illumination to measure motion orthogonal to the optical axis. The use of coherent illumination allows for high-contrast speckle patterns even when imaging apparently uniform samples or when highly aberrated beams cannot be avoided. ©2014 Optical Society of America

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Background: Mechanical circulatory support (MCS) with the Impella device (Abiomed, Danvers, MA) has been associated with higher in-hospital mortality than intra-aortic balloon pump (IABP) in the Premier Healthcare Database and National Cardiovascular Data Registry. Methods:The objective of this retrospective cohort study was to describe trends and outcomes of Impella usage in acute myocardial infarction complicated by cardiogenic shock (AMICS) treated with MCS (Impella or IABP) using real-world observational data from the National Inpatient Sample (NIS) including hospitalizations for AMICS managed with MCS between January 2012 to December 2017. The primary outcomes included in-hospital mortality, transfusion, acute kidney injury, stroke, total costs, and length of stay. Propensity score matching was performed with hierarchical models using risk factor and Elixhauser comorbidity variables. Results and Conclusion:We identified 54,480 hospitalizations for AMICS managed with MCS including 5750 (10.5%) utilizing Impella. Throughout the study period, Impella usage increased yearly to 19.9% of AMICS cases in 2017. After propensity score matching, Impella was associated with higher in-hospital mortality (odds ratio[OR] 1.74, 95% confidence interval [CI] 1.41-2.13) and transfusions (OR 1.97, 95% CI 1.40-2.78) than IABP, without association with acute kidney injury or stroke. Impella

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