Feasibility and reference values of left atrial longitudinal strain imaging by two-dimensional speckle tracking

<p>Abstract</p> <p>Background</p> <p>The role of speckle tracking in the assessment of left atrial (LA) deformation dynamics is not established. We sought to determine the feasibility and reference ranges of LA longitudinal strain indices measured by speckle tracking in a population of normal subjects.</p> <p>Methods</p> <p>In 60 healthy individuals, peak atrial longitudinal strain (PALS) and time to peak longitudinal strain (TPLS) were measured using a 12-segment model for the left atrium. Values were obtained by averaging all segments (global PALS and TPLS) and by separately averaging segments measured in the two apical views (4- and 2-chamber average PALS and TPLS).</p> <p>Results</p> <p>Adequate tracking quality was achieved in 97% of segments analyzed. Inter and intra-observer variability coefficients of measurements ranged between 2.9% and 5.4%. Global PALS was 42.2 ± 6.1% (5–95° percentile range 32.2–53.2%), and global TPLS was 368 ± 30 ms (5–95° percentile range 323–430 ms). The 2-chamber average PALS was slightly higher than the 4-chamber average PALS (44.3 ± 6.0% vs 40.1 ± 7.9%, p < 0.0001), whereas no differences in TPLS were found (p = 0.93).</p> <p>Conclusion</p> <p>Speckle tracking is a feasible technique for the assessment of longitudinal myocardial LA deformation. Reference ranges of strain indices were reported.</p

Surface modification of polystyrene films. depth profiling and mapping by raman microscopy

The chemical modification of polymer films was studied using Raman microscopy. The nitration of polystyrene films (PS) in a non-swelling reaction medium was compared with the nucleophilic substitution of chlorine atoms by cyano groups in poly(p-chloromethylstyrene) (PSC) films in mixtures of a good and a non-solvent for the polymer. Using Raman microscopy in the confocal mode, depth profiles of films modified in different conditions were recorded. In both reactions, conditions could be found which allowed the polymer films to be preferentially modified at the surface. The gradient of the degree of modification and the surface selectivity are functions of reaction time, temperature and solvent quality. The homogeneity of the modification reactions was compared by mapping of surface areas using Raman spectroscopy in the conventional mode.</p