نتایج جستجو برای: scatter
تعداد نتایج: 12375 فیلتر نتایج به سال:
We examine coding strategies for coded aperture scatter imagers. Scatter imaging enables tomography of compact regions from snapshot measurements. We present coded aperture designs for pencil and fan beam geometries, and compare their singular value spectra with that of the Radon transform and selected volume tomography. We show that under dose constraints scatter imaging improves conditioning ...
In multivariate analysis we often deal with situations involving several populations, such as discriminant analysis, where the assumption of equality of scatter matrices is usually assumed. Yet sometimes, this assumption is not adequate but problems related to an excessive number of parameters will arise if we estimate the scatter matrices separately for each population. In many practical situa...
OBJECTIVE Positron emission tomography (PET) enables quantitative measurements of various biological functions. Accuracy in data acquisition and processing schemes is a prerequisite for this. The correction of scatter is especially important when a 3D PET scanner is used. The aim of this study was to validate the use of a simplified calculation-based scatter correction method for 15O studies in...
Well-known radar scattering mechanisms are Rayleigh scattering (incoherent particle scattering), and clear-air scattering (coherent air scattering). This article discusses the importance in clouds of these two mechanisms compared to a third scattering mechanism: coherent particle scattering, which is caused by spatial variations in the liquid water content of the clouds. We will argue that for ...
Planar g-scintigraphy is often used to quantify pulmonary deposition patterns from aerosol inhalers. The results are quite different from those obtained using 3-dimensional PET and SPECT. The purpose of this study was to characterize the effects of scatter and tissue attenuation on the distribution of radiolabeled aerosol as measured by planar scintigraphy using Monte Carlo simulations. This st...
Biological specimens are intrinsically three dimensional; however, because of the obscuring effects of light scatter, imaging deep into a tissue volume is problematic. Although efforts to eliminate the scatter by "clearing" the tissue have been ongoing for over a century, there have been a large number of recent innovations. This Review introduces the physical basis for light scatter in tissue,...
Epithelia and mesenchyme interact during various physiologic and pathologic processes. Scatter factor is a mesenchyme-derived cytokine that stimulates motility, proliferation, and morphogenesis of epithelia. Recent studies suggest that scatter factor and its receptor (c-met) mediate mesenchyme/epithelia signalling and even interconversion. In this mini-review, we will discuss how scatter factor...
This paper reports on a further development of an image simulation chain, and in particular, the inclusion of contrast degradation across an image using scatter to primary ratios calculated using Monte Carlo simulation. The Monte Carlo technique, using the Geant4 toolkit, has been implemented to model the scatter conditions when imaging the CDMAM phantom with commercial digital mammography. Obs...
Time-Segmented Scatter Plots: A View On Time-Dependent State Relations In Discrete-Event Time Series
Pairs of discrete event time series are characterised by their asynchronous nature, often hampering direct application of otherwise common analysis methods. For correct application of scatter plots, pairs of discrete event time series first have to be pre-processed and merged into a new synthetic time series of so-called coobservations. While standard scatter plots suggest analysis of global st...
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