Pixel Intensity (pixel + intensity)

Distribution by Scientific Domains


Selected Abstracts


REVERSIBLE JUMP MARKOV CHAIN MONTE CARLO METHODS AND SEGMENTATION ALGORITHMS IN HIDDEN MARKOV MODELS

AUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 2 2010
R. Paroli
Summary We consider hidden Markov models with an unknown number of regimes for the segmentation of the pixel intensities of digital images that consist of a small set of colours. New reversible jump Markov chain Monte Carlo algorithms to estimate both the dimension and the unknown parameters of the model are introduced. Parameters are updated by random walk Metropolis,Hastings moves, without updating the sequence of the hidden Markov chain. The segmentation (i.e. the estimation of the hidden regimes) is a further aim and is performed by means of a number of competing algorithms. We apply our Bayesian inference and segmentation tools to digital images, which are linearized through the Peano,Hilbert scan, and perform experiments and comparisons on both synthetic images and a real brain magnetic resonance image. [source]


Distribution and Quantity of Contractile Tissue in Postnatal Development of Rat Alveolar Interstitium

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2008
Renée Dickie
Abstract Alpha,smooth muscle actin (,-SMA) -expressing cells are important participants in lung remodeling, during both normal postnatal ontogeny and after injury. Developmental dysregulation of these contractile cells contributes to bronchopulmonary dysplasia in newborns, and aberrant recapitulation in adults of the normal ontogeny of these cells has been speculated to underlie disease and repair in mature lungs. The significance of airway smooth muscle has been widely investigated, but contractile elements within the pulmonary parenchyma, although also of structural and functional consequence in developing and mature lungs, are relatively unstudied and little quantitative information exists. Here, we quantify the areal density of ,-SMA expression in lung parenchyma and assess changes in its spatiotemporal distribution through postnatal ontogeny. Using an antibody against ,-SMA, we immunofluorescently labeled contractile elements in lung sections from a postnatal growth series of rats. Images were segmented using thresholded pixel intensity. Alpha-SMA areal density in the alveolar interstitium was calculated by dividing the area of ,-SMA,positive staining by the tissue area. The areal density of ,-SMA in 2-day neonates was 3.7%, almost doubled, to 7.2% by 21 days, and decreased to 3% in adults. Neonates had large, elongate concentrations of ,-SMA, and ,-SMA localized both at septal tips and within the interstitium. In adults, individual areas of ,-SMA expression were smaller and more round, and located predominately in alveolar ducts, at alveolar ends and bends. The results are consistent with increasing ,-SMA expression during the period of peak myofibroblast activity, corresponding to the phase of rapid alveolarization in the developing lung. Anat Rec, 291:83,93, 2007. © 2007 Wiley-Liss, Inc. [source]


Quantitative evaluation of corneal epithelial oedema by confocal microscopy

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 3 2009
Naoyuki Morishige MD PhD
Abstract Background:, To develop a novel quantitative index for evaluation of corneal epithelial oedema, the pixel intensity of confocal microscopic images was measured derived from the basal cell layer (BCL) of the corneal epithelium in normal eyes, eyes before and after cataract surgery, and eyes affected by bullous keratopathy. Methods:, Five eyes of five normal volunteers, 14 eyes of 11 cataract patients and 12 eyes of 12 bullous keratopathy patients were examined by confocal microscopy. The cataract patients underwent cataract surgery, and they were examined by confocal microscopy, corneal pachymetry, and anterior fluorometry both before and at various times after surgery. The pixel intensity of BCL images obtained by confocal microscopy was measured and expressed as the BCL index. Results:, The coefficient of variation for repeated (five times) measurement of the BCL index in each of the five normal eyes was 3.4%. The BCL index was 54.8 ± 5.3 (mean ± SD) before surgery, increased significantly to 65.2 ± 10.0 on the day after surgery, and gradually decreased thereafter in the cataract patients. The time-course of the BCL index coincided well with that of corneal thickness and anterior fluorometry value. The BCL index in eyes affected by bullous keratopathy was significantly increased at 95.0 ± 6.4. Conclusion:, The BCL index was increased after cataract surgery and in eyes affected by bullous keratopathy, conditions associated with corneal epithelial oedema. This quantitative measure obtained by confocal microscopy may prove useful in the clinical evaluation of corneal epithelial oedema. [source]


Lung fractional moving blood volume in normally grown and growth restricted foetuses

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2004
Edgar Hernandez-Andrade
Summary Objective:, To examine foetal lung blood perfusion using power Doppler ultrasound (PDU) and to compare fractional moving blood volume (FMBV) and mean pixel intensity (MPI) estimations in the lungs of normally grown (NG) foetuses and foetuses with intrauterine growth restriction (IUGR) and also to correlate foetal lung FMBV and MPI with respiratory complications after birth. Methods:, Lungs of 47 NG and 25 IUGR foetuses after 32 weeks of gestation were examined with PDU. FMBV and MPI were estimated in a defined region in the posterior part of the foetal lung closest to maternal abdominal wall. FMBV and MPI were correlated to foetal weight deviation and gestational age. Perinatal outcome and respiratory complications after birth were recorded in both groups. Results:, There were significantly lower FMBV and MPI values in IUGR than in NG foetuses. The overall variation was lower for FMBV than for MPI. There was a slightly higher correlation between FMBV and foetal weight deviation [r = 0·33, 95% confidence intervals (CI) 0·11,0·52] than between MPI and foetal weight deviation (r = 0·26, 95% CI 0·03,0·46). There was no significant correlation between FMBV or MPI and gestational age. No differences between the groups were found in the rate of respiratory complications, and they were not correlated either to the FMBV or MPI. Conclusion:, FMBV and MPI, estimated from the PDU signals of foetal lung circulation, showed lower values in third-trimester pregnancies complicated by IUGR. The frequency of neonatal respiratory complications was not increased in cases with low pulmonary FMBV and MPI values. [source]