ObjectiveTo evaluate measurement confounders on 2D shear wave elastography (2D-SWE) elastography of muscle.Materials and Methods
Ex vivo
, porcine muscle was examined with a GE LOGIQ E9 ultrasound machine with a 9 L linear (9 MHz) and C1-6 convex probe (operating at 2.5 or 6 MHz). The influence of different confounders on mean shear wave velocity (SWVmean) was analyzed: probes, pressure applied by probe, muscle orientation, together with the impact of different machine settings such as frequency, placement depth and size of region of interest (ROI). The mean of twelve repeated SWVmean measurements (m/s) and coefficient of variation (CV; standard deviation/mean in %) were assessed for each test configuration.
ResultsReproducibility (CV) and maximum possible tissue depth of the linear probe were inferior to the convex probe. With the linear probe, there was a linear decrease of SWVmean with placement depth from 4.56 m/s to 1.81 m/s. A significant increase of SWVmean (p<0.001) was observed for larger ROI widths (range 3.96 m/s to 6.8 m/s). A change in the machine operation mode ('penetration' instead of 'general') led to a significant increase of SWVmean (p=0.04). SWVmean in the longitudinal direction of muscle was significantly higher than in cross section (p<0.001) (e. g. 4.56 m/s versus 3.42 m/s). An increase of linear probe pressure significantly increased muscle SWVmean from 5.29 m/s to 7.21 m/s (p<0.001).Conclusions2D-SWE of muscle is influenced by a wealth of parameters. Therefore, standardization of measurement is advisable before application in clinical research studies and routine patient assessment.
Cystic fibrosis (CF) is associated with impaired ion transport across epithelial membranes and an increased transepithelial potential difference (PD) that can be measured in airway epithelium. The aim of this study was to investigate the diagnostic value of nasal PD in CF, and to test a modified approach to the measurement of this PD. The reproducibility and diagnostic sensitivity and specificity of nasal PD measurements were tested with the perfusion technique and with a simplified modification of the technique done with a novel, solid-state exploring electrode. With the perfusion method, basal PD values were different in CF patients (mean +/- SEM: -51.6 +/- 0.9 mV, n = 104) than in normal (-15.5 +/- 0.9 mV, n = 58, p < 0.01) subjects. CF patients with acute rhinitis or other nasal pathology had mean PD values that were intermediate between those of the patients and normal and disease-control groups (-28.3 +/- 1.2 mV, n = 40, p < 0.01, different from normal). The diagnostic sensitivity of the perfusion method for CF was 91.3%, and the specificity was 96.4%. PD measurements with the modified technique correlated highly with the results achieved with the perfusion method (r = 0.94, n +/- 158). The measurement of nasal PD effectively distinguishes CF from control subjects. Care must be taken in the interpretation of measurements made on acutely inflamed epithelium. The modified method was simpler than the conventional perfusion technique, and equally effective.
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