This study presents an upgraded electrospray differential mobility analysis (ES-DMA) setup for the absolute quantification of bionanoparticle concentrations in biological samples, with a special focus on non-high-density-lipoprotein particle concentrations (non-HDL-P). Metrological characterization of the system's analytical performances for concentration measurements shows that the mean intermediate precision relative standard deviation is 14% for biological samples, 6% for silica nanoparticles, and less than 1% for diameter measurements. This study also demonstrates that the most accurate method for non-HDL-P quantification in native serum samples implies daily calculation of the electrospray transmission efficiency (E) of the system with the WHO SP3-08 reference material. The establishment of the uncertainty budget reveals that the main contribution to particle concentration measurement uncertainties is the electrospray transmission efficiency. This data additionally shows that E is not only low (approximately 15-20%) but also highly variable over time and strongly affected by sample composition. This work suggests that absolute enumeration of bionanoparticles is achievable with ES-DMA but provided that a special care is taken to quantifying E with a calibrator of nature and matrix highly similar to the samples ones.
The size characterization of particles present in the form of agglomerates in images measured by scanning electron microscopy (SEM) requires a powerful image segmentation tool in order to properly define the boundaries of each particle. In this work, we propose to use an algorithm from the deep statistical learning community, the Mask-RCNN, coupled with transfer learning to overcome the problem of generalization of the commonly used image processing methods such as watershed or active contour. Indeed, the adjustment of the parameters of these algorithms is almost systematically necessary and slows down the automation of the processing chain. The Mask-RCNN is adapted here to the case study and we present results obtained on titanium dioxide samples (non-spherical particles) with a level of performance evaluated by different metrics such as the DICE coefficient, which reaches an average value of 0.95 on the test images.
Quantification of myocardial perfusion by contrast-enhanced cardiovascular magnetic resonance imaging (CMR) aims for an observer independent and reproducible risk assessment of cardiovascular disease. Currently, the data used for the pixel-wise analysis of cardiac perfusion are either filtered prior to a fitting procedure, which inherently reduces the spatial resolution of data; or all pixels are considered without any regularization or prior filtering, which yields an unstable fit in the presence of low signal-to-noise ratio. Here, we propose a new pixel-wise analysis based on spatial Tikhonov regularization which exploits the spatial smoothness of the data and ensures accurate quantification even for images with low signal-to-noise ratio. The regularization parameter is determined automatically by an L-curve criterion. We study the performance of our method on a numerical phantom and demonstrate that the method reduces significantly the root-mean square error in the perfusion estimate compared to a non-regularized fit. In patient data our method allows us to recover the myocardial perfusion and to distinguish between healthy and ischemic regions.
Scanning Mobility Particle Sizer (SMPS) is a high resolution nanoparticle sizing system that is widely used as the standard method to measure airborne particle size distributions in the size range 1 nm -1 µm. This paper addresses the problem to assess the uncertainty associated with the particle size distribution (PSD) when the Differential Mobility Analyzer (DMA) operates under scanning mode. The sources of uncertainty are described and then modeled either through experiments or knowledge extracted from the literature. Special care is brought to model the physics and to account for competing theories. Indeed, it appears that the modeling errors resulting from approximations of the physics can largely affect the final estimate of this indirect measurement especially for quantities that are not measured during the day-to-day experiments. Monte-Carlo method is used to compute the uncertainty associated with the PSD. The method is finally tested against real data sets that are monosize Polystyrene Latex Spheres (PSL) with nominal diameters of 100 nm, 200 nm and 450 nm. The median diameters and associated standard uncertainty of the aerosol particles are estimated as 101.22 nm ± 0.18 nm, 204.39 nm ± 1.71 nm and 443.87 nm ± 1.52 nm with the new approach. Other statistical parameters such as the mean diameter, the mode and the geometric mean and associated standard uncertainty are also computed. These results are finally compared with the results obtained by SMPS embedded software.
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