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At least 307 records · Page 17Linked to original sources
PubMed2004

Deconvolution of adaptive optics retinal images.

We quantitatively demonstrate the improvement to adaptively corrected retinal images by using deconvolution to remove the residual wave-front aberrations. Qualitatively, deconvolution improves the contrast of the adaptive optics images. In this work we demonstrate that quantitative information is also increased by investigation of the improvement to cone classification due to the reduction in confusion of adjacent cones because of the extended wings of the point-spread function. The results show that the error in classification between the L and M cones is reduced by a factor of 2, thereby reducing the number of images required by a factor of 4.

Algorithms↗
PubMed2005

Anisoplanatic deconvolution of adaptive optics images.

A modified method for maximum-likelihood deconvolution of astronomical adaptive optics images is presented. By parametrizing the anisoplanatic character of the point-spread function (PSF), a simultaneous optimization of the spatially variant PSF and the deconvolved image can be performed. In the ideal case of perfect information, it is shown that the algorithm is able to perfectly cancel the adverse effects of anisoplanatism down to the level of numerical precision. Exploring two different modes of deconvolution (using object bases of pixel values or stellar field parameters), we then quantify the performance of the algorithm in the presence of Poissonian noise for crowded and noncrowded stellar fields.

Journal Article↗
PubMed2006

Efficient deconvolution of noisy periodic interference signals.

The interference signal formed by combining two coherent light beams carries information on the path difference between the beams. When the path difference is a periodic function of time, as, for example, when one beam is reflected from a vibrating surface and the other from a fixed surface, the interference signal is periodic with the same period as the vibrating surface. Bessel functions provide an elegant and efficient means for deconvoluting such periodic interference signals, thus making it possible to obtain the displacement of the moving surface with nanometer resolution. Here we describe the mathematical basis for the signal deconvolution and employ this technique to obtain the amplitude of miniature capillary waves on water as a test case.

Journal Article↗
PubMed2003

Blind deconvolution under band limitation.

A blind deconvolution problem is newly stated with the following conditions: the point-spread function is band limited, both the object and the point-spread function are nonnegative, and the solution is to be a diffraction-limited object. A blind deconvolution method was developed that can easily be applied to problems in optics because of the conditions used. The performance of the method is investigated with computer simulations.

Journal Article↗
PubMed2005

Real data results with wavelength-diverse blind deconvolution.

Multiframe blind deconvolution is extended to incorporate simultaneous image acquisition at multiple wavelengths (wavelength diversity). The assumption of common path-length errors across the diversity channels allows for a parallel deconvolution procedure that exploits this coupling. No assumptions about variations in the object's intensity distribution at different wavelengths are required. The method is described and initial results for real images collected with a bench-scale imaging system are presented.

Journal Article↗
PubMed2005

Single-frame multichannel blind deconvolution by nonnegative matrix factorization with sparseness constraints.

Single-frame multichannel blind deconvolution is formulated by applying a bank of Gabor filters to a blurred image. The key observation is that spatially oriented Gabor filters produce sparse images and that a multichannel version of the observed image can be represented as a product of an unknown nonnegative sparse mixing vector and an unknown nonnegative source image. Therefore a blind-deconvolution problem is formulated as a nonnegative matrix factorization problem with a sparseness constraint. No a priori knowledge about the blurring kernel or the original image is required. The good experimental results demonstrate the viability of the proposed concept.

Journal Article↗
PubMed2006

Blind image deconvolution using the zero-lag slice of higher-order statistics.

A novel algorithm for blind image deconvolution using the zero-lag slice (ZLS) of higher-order statistics only is presented. This method first estimates the point-spread function (PSF) using the ZLS of its third-order moment (TOM) and then uses it with one of the known classical image deconvolution methods. The proposed method has simple computations for PSF estimation because it solves a nonlinear problem by using an iterative method with fast convergence. In each iteration, one need only calculate the ZLS of the TOM and estimate the PSF using simple two-dimensional operations. Furthermore, the method presented achieves good results, since the ZLS estimate obtained from the degraded image exhibits high reliability. The good performance of the proposed algorithm is demonstrated by applying it to synthetic and real data sets.

Journal Article↗
PubMed2006

Nonlinear dynamic range compression deconvolution.

We introduce a dynamic range image compression technique for nonlinear deconvolution; the impulse response of the distortion function and the noisy distorted image are jointly transformed to pump a clean reference beam in a two-beam coupling arrangement. The Fourier transform of the pumped reference beam contains the deconvolved image and its conjugate. In contrast to standard deconvolution approaches, for which noise can be a limiting factor in the performance, this approach allows the retrieval of distorted signals embedded in a very high-noise environment.

Journal Article↗
PubMed2004

Determination of uronic acids in isolated hemicelluloses from kenaf using diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method.

Hemicellulose samples were isolated from kenaf (Hibiscus cannabinus L.). Hemicellulosic fractions usually contain a variable percentage of uronic acids. The uronic acid content (expressed in polygalacturonic acid) of the isolated hemicelluloses was determined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method. A linear relationship between uronic acids content and the sum of the peak areas at 1745, 1715, and 1600 cm(-1) was established with a high correlation coefficient (0.98). The deconvolution analysis using the curve-fitting method allowed the elimination of spectral interferences from other cell wall components. The above method was compared with an established spectrophotometric method and was found equivalent for accuracy and repeatability (t-test, F-test). This method is applicable in analysis of natural or synthetic mixtures and/or crude substances. The proposed method is simple, rapid, and nondestructive for the samples.

Journal Article↗
PubMed2006

On-line concentration measurements in wastewater using nonlinear deconvolution and partial least squares of spectrophotometric data.

A procedure for the on-line measurement of concentrations of toxins in wastewater using spectrophotometric data is proposed. The complete absorbance spectrum of a wastewater sample is used to predict the concentrations of all possible substances within. Two techniques are examined. In nonlinear spectral deconvolution, the spectrum is decomposed as a linear combination of base spectra and the coefficients of this deconvolution are used to nonlinearly estimate the concentrations. Under partial least squares analysis, the concentrations are directly estimated as a linear combination of the measured spectrum data. Both techniques show good results for estimating the kinetics of samples taken during the reaction phase in a laboratory anaerobic/aerobic SBR used for p-nitrophenol biodegradation.

Aerobiosis↗
PubMed2004

Deconvolution analysis of dynamic contrast-enhanced data based on singular value decomposition optimized by generalized cross validation.

PURPOSE: To present an implementation of generalized cross validation (GCV) for automatically determining the regularization parameter--i.e., the threshold value in deconvolution analysis based on truncated singular value decomposition (TSVD) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data--and to investigate the usefulness of this approach in comparison with TSVD with a fixed threshold value (TSVD-F). METHODS: Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various cerebral blood flows (CBFs), cerebral blood volumes (CBVs), and signal-to-noise ratios (SNRs) for three different types of residue functions (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The TSVD with GCV (TSVD-G) and TSVD-F with a fixed threshold value of 0.2 were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIF, and the estimated values were compared with the assumed values. Additionally, the optimal threshold value was determined from the threshold value in TSVD-F giving the mean CBF value closest to the assumed value and was compared with the threshold value determined with TSVD-G. RESULTS: With TSVD-G, the CBF estimation was substantially improved over a wide range of CBFs for all types of residue functions at the cost of more noise than was seen with TSVD-F. The dependency of the threshold value determined with TSVD-G on the CBF, CBV, and SNR was similar to that of the optimal threshold value, with some discrepancy being observed for the box-shaped residue function, although they did not always agree in terms of absolute value. CONCLUSION: Given an improved SNR, TSVD-G is useful for quantification of CBF with deconvolution analysis of DCE-MRI data.

Algorithms↗
PubMed1999

A comparison of deconvolution and the Patlak-Rutland plot in renography analysis.

UNLABELLED: Deconvolution and the Patlak-Rutland plot are two of the most commonly used methods for analyzing dynamic radionuclide renography. Both methods allow estimation of absolute and relative renal uptake of radiopharmaceutical and of its rate of transit through the kidney. METHODS: A theoretical comparison of uptake assessment by both techniques is made and a mathematical derivation of the relationship between mean transit time (MTT) and renal outflow efficiency (ROE) is presented. The validity of these theoretical findings was tested in a series of 120 renograms obtained using 99mTc-mercaptoacetyltriglycine (MAG3). RESULTS: The estimates of renal uptake obtained are theoretically equivalent. The renogram measurements confirmed this, because there was no significant systematic difference in relative counts obtained by the two methods. Absolute counts were significantly higher for the deconvolution measurements, but only by 2.0%. The SDs of the differences between the two techniques, expressed as a percentage of the mean, were 1.7% and 5.4% for relative and absolute counts, respectively. There was an inverse monotonic relationship between MTT and ROE. ROE evaluated at a particular time was shown to depend on absolute renal function. Measured values of MTT and ROE were consistent with the theoretical prediction. CONCLUSION: The two approaches to renogram analysis provide consistent parameters for both uptake and transit evaluation.

Adolescent↗
PubMed1998

Deconvolution approaches in screening compound mixtures.

Combinatorial chemistry initiatives can be used to generate compound mixtures, and it has become a challenge to effectively screen these mixtures for activity against a specified target. Overall mixture activity can be readily measured, however it is not a straightforward matter to identify all those components giving rise to the total activity (a process referred to as deconvolution). This review discusses the attraction in preparing and screening mixtures, and also addresses the difficulties inherent in their screening. Attention is paid to the current approaches of achieving mixture deconvolution, including synthetic pooling, fractionation, affinity-based isolation, and techniques requiring no physical separation. Recent successes in mixture screening suggest a rekindled interest in this area.

Chemistry, Pharmaceutical↗
PubMed2000

Abnormal LH pulsatility in women with hyperprolactinaemic amenorrhoea normalizes after bromocriptine treatment: deconvolution-based assessment.

OBJECTIVE: The present study examines the LH secretory process in hyperprolactinaemic women before, during and after bromocriptine therapy, using restrictive clinical selection criteria as well as improved methodological tools. PATIENTS AND DESIGN: Six women (aged 20-40 years) with microprolactinomas (mean +/- SE prolactin, PRL: 2478 +/- 427 mU/l, range: 1370-3800 mU/l) and four age- and sex-matched healthy controls were admitted to the study. After an overnight fast, all patients and controls had blood samples withdrawn at 10 minute intervals for 6 h (during saline infusion) from 0800 h to 1400 h to determine serum LH and PRL concentrations. After baseline evaluation, patients were treated with bromocriptine, which was started at a daily dose of 1.25 mg for 7 days; the dose was then increased to 2.5 mg daily for the next 7 days and subsequently to 2.5 mg twice daily. PRL levels were evaluated at weekly intervals after the beginning of bromocriptine therapy for the duration of the study. The 6 h pulsatility study was repeated on four patients during treatment at a time when PRL levels were decreased, although not normalized (PRL range: 450-1350 mU/l) and, on four patients, with the attainment of normal serum PRL levels (PRL < 450 mU/l) in the early follicular phase of the menstrual cycle (days 2-5). The LH instantaneous secretion rate was reconstructed by a nonparametric deconvolution method. In addition to pulse analysis made using the program DETECT, the evaluation of the secretion rate yielded the pulse frequency as well as the pulse amplitude distribution. RESULTS: Each time series was submitted to deconvolution analysis using a nonparametric method in order to estimate the instantaneous secretion rate (ISR). Hyperprolactinaemic patients had very few high-amplitude LH pulses above 0.2 IU/(l minutes) before treatment (average frequency: 0.83 +/- 0.40 pulses/6 h) and at the intermediate evaluation (0.25 +/- 0.25 pulses/6 h). In both cases, the pulse frequency was significantly lower than in controls (P < 0.05 and P < 0.01, respectively). When PRL was normalized, the number of high-amplitude LH pulses (4.25 +/- 1.03 pulses/6 h), became statistically different from the pulse number before (P < 0.01) and during (P < 0.01) therapy; in particular the pulse frequency after therapy rose to a level not statistically different from that in controls. CONCLUSION: The present study shows the presence of reduced LH pulsatility in hyperprolactinaemic women that recovers completely to within the physiological distribution when PRL levels are normalized by bromocriptine therapy.

Adult↗
PubMed2001

Combining deconvolution and noise analysis for the estimation of transmitter release rates at the calyx of held.

The deconvolution method has been used in the past to estimate release rates of synaptic vesicles, but it cannot be applied to synapses where nonlinear interactions of quanta occur. We have extended this method to take into account a nonlinear current component resulting from the delayed clearance of glutamate from the synaptic cleft. We applied it to the calyx of Held and verified the important assumption of constant miniature EPSC (mEPSC) size by combining deconvolution with a variant of nonstationary fluctuation analysis. We found that amplitudes of mEPSCs decreased strongly after extended synaptic activity. Cyclothiazide (CTZ), an inhibitor of glutamate receptor desensitization, eliminated this reduction, suggesting that postsynaptic receptor desensitization occurs during strong synaptic activity at the calyx of Held. Constant mEPSC sizes could be obtained in the presence of CTZ and kynurenic acid (Kyn), a low-affinity blocker of AMPA-receptor channels. CTZ and Kyn prevented postsynaptic receptor desensitization and saturation and also minimized voltage-clamp errors. Therefore, we conclude that in the presence of these drugs, release rates at the calyx of Held can be reliably estimated over a wide range of conditions. Moreover, the method presented should provide a convenient way to study the kinetics of transmitter release at other synapses.

Animals↗
PubMedDate not supplied

[Recovery of medical ultrasound images based on an effective deconvolution of scanning data].

Described in the paper is a method of data deconvolution of ultrasound scanning (solution of the deconvolution equation in the linear metric) that ensures a higher precision of images being restored versus the traditional Wiener filtering. Simplex algorithm with an originally modified efficiency function was used to solve the task. The results of experiments testifying to the efficiency of algorithms in the ultrasound image processing of the mammary gland of a patient are presented.

Algorithms↗
PubMed2004

Combination of gas chromatography-mass spectrometry and mass spectral deconvolution for structural elucidation of an unusual C29-steroid detected in a complex sedimentary matrix.

A complex sedimentary sample from the Monterey Formation (CA, USA) has been submitted to GC-MS analysis followed by mass spectral deconvolution using Automated Mass Spectral Deconvolution and Identification System (AMDIS). Adjusting the parameters of the software allowed for the extraction of the spectrum of an unusual steroidal hydrocarbon coeluting with the major compound of the chromatogram. Following a careful interpretation of the "extracted" mass spectrum, the structure of the unknown has been postulated to be the 4,14-dimethylcholestane (DMC). Possible origins of this rare steroid are briefly discussed. Thus, application of AMDIS appears to be particularly suitable for the GC-MS analysis of natural complex mixtures characterized by a high number of analytes present in low amounts.

Cholestanes↗