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PubMed2004

Blind deconvolution of audio-frequency signals using the self-deconvolving data restoration algorithm.

A signal processing algorithm has been developed in which a filter function is extracted from degraded data through mathematical operations. The filter function can be used to restore much of the degraded content of the data through use of a deconvolution process. The operation can be performed without prior knowledge of the detection system, a technique known as blind deconvolution. The extraction process, designated self-deconvolving data reconstruction algorithm, is applied here to audio-frequency signals showing significant qualitative improvement. Degradation arising from the process of electronic recording and reproduction is significantly reduced.

Acoustics↗

PubMed1990

Measurement of hepatocellular function with deconvolutional analysis: application in the differential diagnosis of acute jaundice.

A direct, noninvasive technique was developed to quantitate hepatocyte function with computer assessment of scintiscans obtained after administration of technetium-99m disofenin in 53 patients with acute jaundice: 32 patients with normal livers, 10 patients with acute biliary obstruction, and 11 patients with acute hepatocellular dysfunction. In all patients a final clinical diagnosis was obtained with follow-up for a minimum of 4 months and, in most patients with obstruction or dysfunction, with surgery, intraoperative cholangiography, ultrasound, and/or computed tomography. Heart (blood pool) and liver time-activity curves were generated for 32 minutes after intravenous injection of 5-15 mCi (185-555 MBq) of Tc-99m disofenin and were subjected to deconvolutional analysis to determine the first-pass hepatocyte extraction fraction (HEF) of the tracer. The difference in HEF between patients with obstruction and those with dysfunction was highly significant (P = 3.3 X 10(-19)). Deconvolutional analysis eliminates the effects of tracer recirculation, thus permitting direct measurement of hepatic disofenin extraction, and appears to provide functional information useful in evaluation of the patient with acute jaundice.

Acute Disease↗

PubMed1993

Hepatic glucose production during the labeled IVGTT: estimation by deconvolution with a new minimal model.

A method for the estimation of hepatic glucose production during a labeled intravenous glucose tolerance test (IVGTT) is proposed. Stable-label IVGTT data in normal subjects have been considered. The method is based on deconvolution and uses a new two-compartment minimal model of glucose kinetics to describe the time-varying impulse response of the glucose system. A new model of glucose kinetics was needed because the available single-compartment minimal model, specifically developed to interpret labeled IVGTT data, provided a nonphysiological pattern of hepatic glucose production. The new minimal model has two novel features: glucose kinetics are described by a two-compartment structure, and insulin exerts its action on the irreversible loss of the slowly exchanging glucose pool. The deconvolution scheme used to reconstruct hepatic glucose production is described in detail both in terms of computational aspects and reliability. Confidence limits of the reconstructed hepatic glucose production in each individual are derived by taking into account both the measurement error of the data and the uncertainty associated with the description of the impulse response. Physiological plausibility of the time course of hepatic glucose production provided by this new method is discussed. The ability of the new model to reconstruct hepatic glucose production considerably enriches the kinetic portrait of glucose metabolism that can be obtained from the minimal-model analysis of labeled IVGTT data.

Blood Glucose↗

PubMed1993

Reanalysis of the rat proestrous LH surge by deconvolution analysis.

To evaluate the temporal mechanisms that give rise to the spontaneous proestrous surge of luteinizing hormone (LH) in the rat, we have applied deconvolution analysis to earlier immunoreactive LH concentration vs. time profiles obtained by sampling blood in proestrus at 2- to 3-min intervals in 10 animals over a span of 160-300 min. Six other animals were bled in 6-min intervals on day 1 of diestrus. Deconvolution analysis permitted us to calculate the number, duration, amplitude (maximal release rates), and mass of underlying LH secretory bursts and to simultaneously estimate basal secretion and the half-life of endogenous LH in each animal. Proestrus rats exhibited a significant increase in the number of computer-identified LH secretory bursts per hour (1.8 +/- 0.2 vs. 1.1 +/- 0.01 on diestrus, P < 0.01), with a corresponding reduction in the LH intersecretory burst interval from 61 +/- 6.4 min (diestrus) to 25 +/- 2.7 min (proestrus, P < 0.01). There was a remarkable 16-fold increase in the mass of LH secreted per burst, which rose from 72 +/- 5.2 to 1,230 +/- 200 ng/ml (P < 0.01). This resulted from a sixfold increase in LH secretory burst amplitude and a doubling of burst duration. The total amount of LH released in a burstlike fashion during the proestrous LH surge rose 20-fold, and calculated basal LH secretion increased to approximately 25% of this value. Of interest, the computed half-life of endogenous LH also increased from 10 +/- 1.1 to 19 +/- 3.7 min (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Thermal recovery after passage of the pulmonary circulation assessed by deconvolution.

For indicator-dilution studies, complete thermal recovery after passage of heat through the pulmonary circulation would be desirable. However, the results in the literature obtained by extrapolation techniques are inconsistent. To overcome problems of the extrapolation approach, transport functions of the pulmonary circulation (including the left heart) were computed by deconvolution of pulmonary arterial and aortic pairs of thermodilution curves after central venous indicator injection (10 ml of an ice-cold blood indocyanine green dye mixture). Thermal recovery was determined as the finite integral of the transport function. Thirteen mongrel dogs under piritramid-N2O anesthesia were examined under base-line conditions, in orthostasis to alter the distribution of pulmonary blood flow (9 dogs), and in oleic acid edema (8 dogs). Using the deconvolution approach, thermal recovery was 0.97 +/- 0.04 under base-line conditions, 0.96 +/- 0.03 in orthostasis, and 0.96 +/- 0.05 in pulmonary edema. Thermal recovery determined from extrapolated dilution curves was greater than 100% in all groups, a physically impossible finding. It is concluded that thermal recovery is incomplete but insensitive with respect to the distribution of blood flow and to the size of the extravascular compartment. Monoexponential extrapolation is unsuited for the determination of thermal recovery.

Animals↗

PubMed2001

Improvement of FISH mapping resolution on combed DNA molecules by iterative constrained deconvolution: a quantitative study.

Image restoration approaches, such as digital deconvolution, are becoming widely used for improving the quality of microscopic images. However, no quantification of the gain in resolution of fluorescence images is available. We show that, after iterative constrained deconvolution, fluorescent cosmid signals appear to be 25% smaller, and 1.2-kb fragment signals on combed molecules faithfully display the expected length.

Chromosomes, Artificial, Yeast↗

PubMed2000

Deconvolution analysis of cardiac natriuretic peptides during acute volume overload.

Cardiac natriuretic peptides, especially amino terminal pro-Brain Natriuretic Peptide (NT-proBNP), are emerging as powerful circulating markers of cardiac function. However, the in vivo secretion and elimination (t1/2) of these peptides during acute volume overload have not been studied. We present the first report of the secretion and elimination of cardiac natriuretic peptides, based on deconvolution analysis of endogenous ovine plasma levels measured by specific radioimmunoassay. Four normal, conscious sheep underwent rapid right ventricular pacing (225 bpm) for 1 hour to stimulate acute cardiac natriuretic peptide release. Plasma samples and right atrial pressure measurements were taken at regular intervals 30 minutes before, during, and 4 hours after pacing. Baseline right atrial pressure significantly increased (P:=0.02) during the 1 hour of pacing in association with a prompt increase in plasma BNP (P:=0.03), atrial natriuretic peptide (P:=0.01), and NT-proBNP (P:=0.02). Deconvolution analysis showed that the t1/2 of NT-proBNP (69.6+/-10.8 minutes) was 15-fold longer than BNP (4.8+/-1. 0 minutes). Despite sustained increases in atrial pressure, cardiac secretion of natriuretic peptides (particularly atrial natriuretic peptide) fell during the pacing period, suggesting a finite source of peptide for secretion. Size-exclusion high-performance liquid chromatography revealed NT-proBNP to be a single immunoreactive peak, whereas BNP comprised at least 2 immunoreactive forms. These findings, especially the prompt secretion of BNP and the prolonged t1/2 of NT-proBNP, clarify the metabolism of BNP forms and help to explain the diagnostic value of NT-proBNP measurement as a sensitive marker of ventricular function.

Algorithms↗

PubMed2001

Feasibility study of time-intensity-based blood flow measurements using deconvolution.

Ultrasonic contrast agents have been used to enhance the acoustic backscattered intensity of blood and to assist the assessment of blood flow parameters. One example is the time-intensity method based on the indicator-dilution theory. In this case, a mixing chamber model can be employed to describe the concentration of the contrast agent as a function of time. By measuring the time intensities at both the input and output of the blood mixing chamber, blood flow information can be obtained if proper deconvolution techniques are applied. Note that most deconvolution techniques assume a linear and time invariant (LTI) system for the mixing of the contrast agent with blood. In this paper, the hypothesis that a blood mixing chamber is an LTI system was tested. Several aspects were studied. One aspect was the linear relationship between the concentration of the contrast agent and the backscattered intensity. The other aspect was the dependence of the derived time constants on the concentration. The concept of an effective mixing volume was also introduced and evaluated. Finally, the input and the output time constants were measured and compared to theory under the LTI assumption. Extensive experiments were performed. Two in vitro flow models were constructed and two contrast agents were used. Results indicated that the LTI assumption does not hold and quantitative flow estimation is generally not possible. Nonetheless, the indicator-dilution theory can still be applied if only relative measurements of the flow rate are required.

Contrast Media↗

PubMed1987

The practical significance of two-dimensional deconvolution in echography.

This paper evaluates deconvolution (inverse filtering) as applied to ultrasonic imaging systems, and discusses the obstacles which are encountered employing the technique in practice. A minicomputer is used to generate artificial echo signals, simulating rf signals resulting from a set of point reflectors in a homogeneous medium, as recorded by an electronically focused group-steered linear array scanner. Two-dimensional deconvolution in combination with a Wiener noise reduction filter (i.e., a Wiener-Inverse filter) is applied to these simulated rf signals, which were contaminated with white noise. The efficacy of the Wiener-Inverse filter is defined in terms of its ability to resolve two point reflectors with a lateral spacing equal to the local -6 dB width of the ultrasonic beam. In favorable circumstances, the targets are resolved at signal-to-noise ratios (SNR) better than 20 dB, where SNR is defined as the maximum signal power divided by the average noise power level. Nonlinear effects due to quantization or signal clipping are investigated. In order to improve the resolution of an rf signal with a dynamic range of 40 dB, the input signal should be digitized at a minimum of 12 bits. The problem of signal clipping can be circumvented by oversampling. The two-dimensional Wiener-Inverse filter is defined in terms of both temporal and spatial properties of the insonification. Effects of wave diffraction give rise to a depth-dependent ultrasonic beam. As a result of a misfit of the Wiener-Inverse filter and the local properties of the ultrasonic beam, erroneous noisy texture arises in the image. Adaptation of the Wiener-Inverse filter with respect to the beam properties gives acceptable results, at the expense of a rather large computational effort.

Computer Simulation↗

PubMed1993

Deconvolution of in-vivo ultrasound B-mode images.

An algorithm for deconvolution of medical ultrasound images is presented. The procedure involves estimation of the basic one-dimensional ultrasound pulse, determining the ratio of the covariance of the noise to the covariance of the reflection signal, and finally deconvolution of the rf signal from the transducer. Using pulse and covariance estimators makes the approach self-calibrating, as all parameters for the procedure are estimated from the patient under investigation. An example of use on a clinical, in-vivo image is given. A 2 x 2 cm region of the portal vein in a liver is deconvolved. An increase in axial resolution by a factor of 2.4 is obtained. The procedure can also be applied to whole images, when it is ensured that the rf signal is properly measured. A method for doing that is outlined.

Adult↗

PubMed2006

Computational expression deconvolution in a complex mammalian organ.

BACKGROUND: Microarray expression profiling has been widely used to identify differentially expressed genes in complex cellular systems. However, while such methods can be used to directly infer intracellular regulation within homogeneous cell populations, interpretation of in vivo gene expression data derived from complex organs composed of multiple cell types is more problematic. Specifically, observed changes in gene expression may be due either to changes in gene regulation within a given cell type or to changes in the relative abundance of expressing cell types. Consequently, bona fide changes in intrinsic gene regulation may be either mimicked or masked by changes in the relative proportion of different cell types. To date, few analytical approaches have addressed this problem. RESULTS: We have chosen to apply a computational method for deconvoluting gene expression profiles derived from intact tissues by using reference expression data for purified populations of the constituent cell types of the mammary gland. These data were used to estimate changes in the relative proportions of different cell types during murine mammary gland development and Ras-induced mammary tumorigenesis. These computational estimates of changing compartment sizes were then used to enrich lists of differentially expressed genes for transcripts that change as a function of intrinsic intracellular regulation rather than shifts in the relative abundance of expressing cell types. Using this approach, we have demonstrated that adjusting mammary gene expression profiles for changes in three principal compartments--epithelium, white adipose tissue, and brown adipose tissue--is sufficient both to reduce false-positive changes in gene expression due solely to changes in compartment sizes and to reduce false-negative changes by unmasking genuine alterations in gene expression that were otherwise obscured by changes in compartment sizes. CONCLUSION: By adjusting gene expression values for changes in the sizes of cell type-specific compartments, this computational deconvolution method has the potential to increase both the sensitivity and specificity of differential gene expression experiments performed on complex tissues. Given the necessity for understanding complex biological processes such as development and carcinogenesis within the context of intact tissues, this approach offers substantial utility and should be broadly applicable to identifying gene expression changes in tissues composed of multiple cell types.

Adipose Tissue, Brown↗

PubMed1993

Estimation of daily cortisol production and clearance rates in normal pubertal males by deconvolution analysis.

To investigate daily cortisol production and clearance rates in a group (n = 18) of normal unstressed pubertal males, we applied deconvolution analysis to serum cortisol concentrations obtained every 20 min for 24 h. Subject-specific characterization of adrenocortical secretory episodes, cortisol production rate, and serum hormone half-life for nine early pubertal (Tanner I or II; early) and nine late pubertal (Tanner IV or V; late) subjects was undertaken to assess potential roles of sexual maturation and changing gonadal steroid hormone concentrations on glucocorticoid physiology. The estimated cortisol production rate for the early group [16.8 +/- 1.3 mumol/m2 x day (6.1 +/- 0.4 mg/m2 x day)] was indistinguishable from that of the late subjects [14.8 +/- 1.4 mumol/m2 x day (5.3 +/- 0.5 mg/m2 x day)]. No differences were observed between the two pubertal groups in the secretory burst frequency and half-duration, mass of cortisol released per secretory episode, average maximal rate of hormone secretion, and serum cortisol half-life. A significant diurnal pattern of cortisol secretion was observed for all subjects manifest by nyctohemeral variations in the frequency of adrenocortical secretory bursts, the amplitude (maximal rate of cortisol secretion) and the mass of cortisol released per secretory episode. Maximum serum hormone concentrations occurred between 0706 and 1114 h. We conclude that in normal pubertal males: 1) cortisol production rates as estimated by deconvolution analysis are in agreement with other recent independent isotopic estimates, but are lower than many previous estimates; 2) the rise in serum gonadal steroid hormone levels is unassociated with alterations in the production rate or metabolic clearance of cortisol; and 3) increased secretory burst frequency, increased amplitude (maximal rate of cortisol secretion attained within each secretory event), and increased mass of cortisol released per adrenocortical secretory episode give rise to the normal diurnal rhythm of circulating cortisol.

17-Hydroxycorticosteroids↗

PubMed1993

Characterization of pulsatile secretion and clearance of plasma cortisol in premature and term neonates using deconvolution analysis.

Pulsatile secretion of cortisol (F) has not been documented in the newborn infant. Using repeated blood sampling and deconvolution analysis, we investigated F secretion and elimination dynamics in a group of five premature (gestational age, 24-34 weeks) and five term neonates. These infants had required placement of an umbilical arterial cannula for monitoring respiratory status, but were otherwise clinically stable. Blood samples were obtained at 15-min intervals for a 6-h period. All plasma F determinations were 58 nmol/L (2.1 micrograms/dL) or more, and pulsatile F secretion was observed in all infants. No significant differences were noted between the two groups with regard to 6-h mean plasma F concentration [350 +/- 129 (premature) vs. 277 +/- 54 nmol/L (term)], plasma corticosteroid-binding globulin (14 +/- 0 vs. 13 +/- 1 mg/L), F secretory burst frequency (4 +/- 0 vs. 5 +/- 1 bursts/6 h), mass of F secreted per burst [760 +/- 480 vs. 310 +/- 100 nmol/Lv [Lv, liter of F distribution volume)], F production rate (FPR; 2.7 +/- 1.4 vs. 1.1 +/- 0.2 mumol/Lv.6 h), or plasma F half-life (45 +/- 6 vs. 56 +/- 4 min). However, the premature infants had a significantly longer F secretory burst half-duration (63 +/- 18 vs. 6.7 +/- 4.0 min; P < 0.01) and a significantly lower maximal F secretory rate (9.4 +/- 3.4 vs. 100 +/- 26 nmol/Lv.min; P < 0.02) than the term infants. Body surface area and body weight were inversely correlated with F secretory burst half-duration (r = -0.74 and -0.75, respectively); both were also positively correlated with the maximal F secretory rate (r = 0.66 and 0.72). The two most premature infants had significantly greater mean plasma F and FPR than the other three premature and all of the term infants. Extrapolating to 24 h and correcting for the distribution volume of F and body surface area, we estimate FPR to be approximately 17-24 mumol/m2.24 h (6.6-8.8 mg/m2.24 h) for newborn infants of 34 weeks or more gestational age. These values are consistent with newer estimates of FPR in older children and adults determined using either deconvolution analysis or stable isotope dilution methods.

Adrenal Cortex↗

PubMed1995

A deconvolution method for estimating the first-pass metabolism of orally administered drugs.

A deconvolution method for estimating the first-pass metabolism of orally administered drugs is proposed. This analysis can be carried out without assuming any pharmacokinetic models. The applicability of the deconvolution method was evaluated by application to the plasma concentration-time courses of aspirin and its metabolite, salicylic acid, reconstructed from pharmacokinetic parameters for orally administered drugs. The estimated absorption profiles for aspirin and salicylic acid were in fairly good agreement with the theoretical ones, although a series of numerical calculations is involved in the procedures. The potential of the present method was also confirmed by applying it to pharmacokinetic data with random errors.

Administration, Oral↗

PubMed1997

Optimization and deconvolution of lithium fluoride TLD-100 in diagnostic radiology.

Lithium fluoride (LiF) TLD-100 is one of the most commonly used thermoluminescent (TL) materials for the measurement of entrance surface dose (ESD) in diagnostic radiology. However, the minimum detectable dose (MDD) achieved, as derived from measurements of the random uncertainty present in the background signal, is usually quoted as being 50-100 microGy. A more appropriate definition of MDD for use in the clinical setting is the dose at which measurements exhibit a specified level of random uncertainty. This definition will give rise to a higher value for the MDD. An MDD of 50-100 microGy precludes accurate measurement of ESD in high tube potential (kVp) chest or neonatal radiography. Techniques described in the specialist literature for the reduction of the MDD of LiF were assessed both in the laboratory, and during a patient dose survey of high kVp chest radiography. Optimization of the pre-irradiation annealing and post-irradiation TL read heating cycles in terms of sensitivity and precision resulted in an MDD of 5/80 microGy (derived from background signal variation and 20% random uncertainty at 95% confidence limits, respectively). Deconvolution of the glowcurve was found to result in an MDD of approximately 10 microGy. Clinical measurements were contrasted with calculated values derived from ionization chamber measurements of tube output. The results support the hypothesis that glowcurve deconvolution permits the measurement of ESDs from low dose examinations using basic TL dosimetry equipment available to virtually all medical physics departments.

Fluorides↗

PubMed2005

Spatial deconvolution technique to improve the accuracy of reconstructed three-dimensional diffuse optical tomographic images.

A straightforward spatial deconvolution operation is presented that seeks to invert the information-blurring property of first-order perturbation algorithms for diffuse optical tomography (DOT) image reconstruction. The method that was developed to generate these deconvolving operators, or filters, was conceptually based on the frequency-encoding process used in magnetic resonance imaging. The computation of an image-correcting filter involves the solution of a large system of linear equations, in which known true distributions and the corresponding recovered distributions are compared. Conversely, application of a filter involves only a simple matrix multiplication. Simulation results show that application of this deconvolution operation to three-dimensional DOT images reconstructed by the solution of a first-order perturbation equation (Born approximation) can yield marked enhancement of image quality. In the examples considered, use of image-correcting filters produces obvious improvements in image quality, in terms of both location and mirco(a) of the inclusions. The displacements between the true and recovered locations of an inclusion's centroid location are as small as 1 mm, in an 8-cm-diameter medium with 1.5-cm-diameter inclusions, and the peak value of the recovered micro(a) for the inclusions deviates from the true value by as little as 5%.

Algorithms↗

PubMed2006

Initialization of iterative parametric algorithms for blind deconvolution of motion-blurred images.

Performances of iterative blind deconvolution methods for motion-blurred images are usually reduced depending on the accuracy of the required initial guess of the blur. We examine this dependency, and a two-stage restoration procedure is proposed: First we perform a direct technique with a single straight-forward process to produce a rough initial estimate of the blur, and then an iterative technique is employed to refine the blur estimate. Two common iterative techniques (the expectation-maximization and the Richardson-Lucy methods) are examined here and implemented in the combined direct-iterative modification for a variety of motion blur types. Results show that the combined method significantly improves the reliability of the deconvolution process.

Journal Article↗

PubMed1999

Parametric blind deconvolution: a robust method for the simultaneous estimation of image and blur.

Blind-deconvolution microscopy, the simultaneous estimation of the specimen function and the point-spread function (PSF) of the microscope, is an underdetermined problem with nonunique solutions that are usually avoided by enforcing constraints on the specimen function and the PSF. We derived a maximum-likelihood-based method for blind deconvolution in which we assume a mathematical model for the PSF that depends on a small number of parameters (e.g., less than 20). The algorithm then estimates the unknown parameters together with the specimen function. The mathematical model ensures that all the constraints of the PSF are satisfied, and the maximum-likelihood approach ensures that the specimen is nonnegative. The method successfully estimates the PSF and removes out-of-focus blur. The PSF estimation is robust to aberrations in the PSF and to noise in the image.

Algorithms↗