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PubMed1988

Extravascular background subtraction using deconvolution analysis of the renogram.

The effect of the intravascular background in the renogram on the calculated renal retention function is known and can be removed. However, the effect of the extravascular background (EVB) has not been thoroughly investigated using patient data. By varying the size of the region of interest containing a single kidney and by deconvolving the 131I-hippuran and 99Tcm-DTPA renograms so generated, the following has been found: (a) the effect of EVB on the mean transit time (MTT) is negligible and EVB subtraction is not necessary, (b) the EVB overestimates the lower relative kidney function (RKF) and underestimates the higher RKF, so that EVB subtraction should be performed if the RKFs are asymmetric. A new method is described in which the correction for EVB is performed following deconvolution. If the RKFs are greater than about 30%, the correction can be performed using a regression equation between the RKFs corrected for EVB and those that are not corrected. When the RKFs are asymmetric to a greater extent, the correction should be performed for each study separately. The proposed method includes a small systematic error due to the inherent limitations of nuclear medicine equipment.

Adult↗

PubMed1991

Perfect-mixer retention function by analytical deconvolution of tracer histograms: application to evaluation of left-ventricular contractility and competence.

The analytical solution for the perfect-mixer retention function, r(t), was developed from tracer histograms sampled at the system input, i(t), and its output, y(t), linked by the convolution integral y = i * r. Theories were developed for both continuous-output mixer and pulsatile, discrete mixer. The latter method was applied in first-pass radioangiography (FPRA) to calculate the forward ejection fraction of the left ventricle (LVFEF). Curves generated over the lungs and the ventricle provided system input and output respectively. LVFEF correlated strongly with the reference values obtained with simultaneously acquired gated FPRA(LVGEF) in 32 non-regurgitant patients: LVGEF = 0.90LVFEF + 5.93, r = 0.96, SEE = 3.98, p less than 0.001. In 14 patients with left-side valvular incompetence LVFEF values (0.41 +/- 0.13) were consistently lower than the corresponding LVGEF values (0.63 +/- 0.11). The method is free from instability inherent in numerical deconvolution. Applied in FPRA it yielded accurate estimates of LV contractility and competence. The continuous-mixer theory may apply to arbitrary compartmental models studied via tracer kinetics.

Adolescent↗

PubMed2001

Accuracy of deconvolution analysis based on singular value decomposition for quantification of cerebral blood flow using dynamic susceptibility contrast-enhanced magnetic resonance imaging.

Deconvolution analysis (DA) based on singular value decomposition (SVD) has been widely accepted for quantification of cerebral blood flow (CBF) using dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI). When using this method, the elements in the diagonal matrix obtained by SVD are set to zero when they are smaller than the threshold value given beforehand. In the present study, we investigated the effect of the threshold value on the accuracy of the CBF values obtained by this method using computer simulations. We also investigated the threshold value giving the CBF closest to the assumed value (optimal threshold value) under various conditions. The CBF values obtained by this method largely depended on the threshold value. Both the mean and the standard deviation of the estimated CBF values decreased with increasing threshold value. The optimal threshold value decreased with increasing signal-to-noise ratio and CBF, and increased with increasing cerebral blood volume. Although delay and dispersion in the arterial input function also affected the relationship between the estimated CBF and threshold values, the optimal threshold value tended to be nearly constant. In conclusion, our results suggest that the threshold value should be carefully considered when quantifying CBF in terms of absolute values using DSC-MRI for DA based on SVD. We believe that this study will be helpful in selecting the threshold value in SVD.

Algorithms↗

PubMed2001

Extension of HRTEM resolution by semi-blind deconvolution method and Gerchberg-Saxton algorithm: application to grain boundary and interface.

A generalized maximum entropy method coupled with Gerchberg-Saxton algorithm has been developed to extend the resolution from high-resolution TEM image(s) for weak objects. The Gerchberg-Saxton algorithm restores spatial resolution by operating real space and reciprocal space projections cyclically. In our methodology, a generalized maximum entropy method (Kullback-Leibler cross entropy) dealing with weak objects is used as a real space (P1) projection. After P1 projection, not only are the phases within the input spatial frequencies improved, but also the phases in the next higher frequencies are extrapolated. An example of semi-blind deconvolution (P1 project only) to improve the resolution in SiC twin boundary is shown. The nature of the bonding in this twin boundary is Si-C but it was rotated 180 degrees along the boundary normal. The optimum solution from P1 projection can be further improved by a P2 projection. The square roots of diffraction intensities from a diffraction pattern are then substituted to complete a cycle operation of the Gerchberg-Saxton algorithm. Application examples of Gerchberg-Saxton algorithm to solve the atomic structure of defects (2 x 1 interfacial reconstruction and dislocation) in NiSi2/Si interfaces will be shown also.

Journal Article↗

PubMed2002

Computerised glow curve deconvolution using general and mixed order kinetics.

Some accurate glow curve fitting functions for general and mixed order kinetics glow peaks are proposed and discussed. These mathematical expressions are used together with peak search and non-linear minimisation algorithms in order to provide a fast glow curve deconvolution for those materials which cannot be well fitted using first order kinetics. To test the accuracy of the proposed method. the result of the fitting of synthetic glow curves is compared with the original data giving negligible errors for values of parameters currently found in TL materials.

Computer Simulation↗

PubMed2002

Glow curve analysis of composite peak 5 in LiF:Mg,Ti (TLD-100) using optical bleaching, thermal annealing and computerised glow curve deconvolution.

The relative intensity of glow peak 5a in the composite glow peak 5 of LiF:Mg,Ti (TLD-100) is very weak following gamma irradiation, and has been estimated at approximately 0.1 of the intensity of peak 5. Typical glow curve analysis using computerised glow curve deconvolution with unconstrained variation of the peak shape parameters, yields values of the relative intensity of glow peak 5a varying from 0 to 15%. Due to the potential of peak 5a to fulfil the criteria of a quasi-tissue-equivalent nanodosemeter which estimates quality factor, considerable efforts have been invested in ancilliary techniques to improve the reliability of the estimation of the intensity of peak 5a. Optical bleaching and thermal annealing techniques were used to obtain single-peak glow curves consisting of peak 4 only and peak 5 only. A multi-stage CGCD protocol was then constructed using these peak shape parameters for peaks 4 and 5, which allows more accurate estimation of the relative intensity of peak 5a. Following 60Co irradiation of ten chips to a dose level of 1 Gy, the technique yields a relative intensity of 0.08 +/- 0.008 (1 SD).

Equipment Design↗

PubMed2002

On the possibility of using commercial software packages for thermoluminescence glow curve deconvolution analysis.

This paper explores the possibility of using commercial software for thermoluminescence glow curve deconvolution (GCD) analysis. The program PEAKFIT has been used to perform GCD analysis of complex glow curves of quartz and dosimetric materials. First-order TL peaks were represented successfully using the Weibull distribution function. Second-order and general-order TL peaks were represented accurately by using the Logistic asymmetric functions with varying symmetry parameters. Analytical expressions were derived for determining the energy E from the parameters of the Logistic asymmetric functions. The accuracy of these analytical expressions for E was tested for a wide variety of kinetic parameters and was found to be comparable to the commonly used expressions in the TL literature. The effectiveness of fit of the analytical functions used here was tested using the figure of merit (FOM) and was found to be comparable to the accuracy of recently published GCD expressions for first- and general-order kinetics.

Kinetics↗

PubMed1998

Characterization of attenuated proestrous luteinizing hormone surges in middle-aged rats by deconvolution analysis.

Reproductive aging in female rats is associated with attenuated preovulatory LH surges. In this study, detailed analyses of the episodic characteristics of the proestrous LH surge were conducted in young and middle-aged regularly cyclic rats. On proestrus, blood samples were withdrawn at 3-min intervals for 6 h and analyzed for LH concentrations by RIA in triplicate. Deconvolution analysis of immunoreactive LH concentrations revealed that there was no difference in the detectable LH secretory burst frequency between young and middle-aged rats. However, in middle-aged rats with an attenuated LH surge on proestrus, the mass of LH secreted per burst and the maximal rate of LH secretion per burst were only one fourth (p < 0.01) of those in young and middle-aged rats with normal LH surges. Furthermore, middle-aged rats with attenuated LH surges had a 4-fold decrease (p < 0.01) in the maximal rate of LH secretion per burst compared to young and middle-aged females with normal LH surges. The apparent half-life of endogenous LH was similar among the 3 groups. The attenuated LH surges of middle-aged rats were related specifically to a decrease in LH burst amplitude with no change in pulse frequency. The orderliness of moment-to-moment LH release as quantified by the regularity statistic, approximate entropy, was comparable in the 3 groups. Our findings of a markedly decreased amount of LH released per burst and preserved orderliness of the LH release process strongly suggest that a deficient GnRH drive and/or reduced responsivity to the GnRH signal, rather than altered timing of the signal, accounts for the age-related decline in reproductive function in female rats as presaged by an attenuated proestrous LH surge in middle age.

Aging↗

PubMed1989

Scatter compensation in digital chest radiography using Fourier deconvolution.

The authors present a numerical deconvolution technique to compensate for image degrading effects caused by scattered photons in radiographic chest images. Fourier transform techniques are used to deconvolve a shift invariant model of the two dimensional point spread response functions of the scattered radiation. This approach uses a digitized radiograph acquired with a standard chest imaging protocol, so no specialized imaging equipment is required. While the shift variant shape of the scatter model is optimized for the lung field, effective compensation is provided when this model shape is applied to other chest regions. Preliminary evaluation suggests that this technique can provide improved image contrast over the entire chest region.

Computer Simulation↗

PubMed1984

99Tcm-TDG renography with deconvolution analysis: a comparative study with 99Tcm-DTPA and 123I-hippuran.

TDG has been compared with hippuran and DTPA in normal subjects and the derived gamma camera renograms of both the whole kidney and parenchymal regions subjected to deconvolution analysis using the matrix algorithm. The transit time of TDG was found to be longer than both hippuran and DTPA. The parenchymal mean transit time of TDG was 3.0 +/- 0.6 min (mean +/- S.D.). That of hippuran was 2.2 +/- 0.7 min and DTPA, 2.6 +/- 0.5 min. It is thought that a small fraction of the TDG is bound to the renal parenchyma thus prolonging both the mean and maximum transit times.

Adult↗

PubMed1985

The reduction of renogram deconvolution to a direct method of transit time determination.

It is known that the intrarenal mean transit time (MTT) can be determined using renography by first deconvoluing the kidney retention function from the obtained time-activity curve and then integrating the retention function. A direct and approximate calculational method, based on an integral mathematical model, has also been employed to estimate the MTT. In this work it is shown that the direct approximate method is equivalent to the standard deconvolution method applied with the assumption of a time independent retention function. Potential errors incurred using the direct method are thus quantified and assessed over a range of representative decay parameters.

Humans↗

PubMed1994

99Tcm-MAG3 renogram deconvolution in normal subjects and in normal functioning kidney grafts.

This study provides values of transit times obtained by 99Tcm- mercaptoacetyl triglycine (99Tcm-MAG3) renogram deconvolution for both normal subjects and kidney graft recipients. The analysis included 50 healthy kidney units from 25 volunteers and 28 normal functioning kidney grafts. The parameters calculated for the whole kidney (WK) and for the renal parenchyma (P) were: mean transit time (MTT) and times at 20% (T20) and 80% (T80) of renal retention function initial height. For healthy kidneys the WK MTT was 174 +/- 27 s and P MTT 148 +/- 22 s. The WK T20 values were 230 +/- 33 s and P T20 231 +/- 34 s. The WK T80 was 108 +/- 19 s and P T80 106 +/- 12 s. Whole kidney and parenchymal values of transit times for normal functioning kidney grafts do not present significant differences with respect to healthy kidneys.

Adolescent↗

PubMed1997

Renogram deconvolution in the management of diabetic nephropathy: utility of the measurement of initial tracer uptake.

Our objective was to assess mean transit time (MTT) and initial uptake, both parameters derived from the renal retention function (RRF), in the study of renal function in patients with diabetic nephropathy. We studied 25 patients, 7 with type I diabetes mellitus and 18 with type II diabetes mellitus, all of whom fulfilled the criteria for diabetic nephropathy with proteinuria and/or retinopathy. We found a statistically significant correlation between initial uptake and the other biochemical and renographic parameters studied except proteinuria: serum creatinine (r = 0.66, P < 0.002), creatinine clearance (r = 0.61, P < 0.003), glomerular filtration rate (r = 0.74, P < 0.003) and effective renal plasma flow (r = 0.66, P < 0.003). The other renographic parameters studied (maximal activity of the conventional renogram and MTT of the deconvoluted renogram) did not show any correlation. Initial uptake is a semi-quantitative renographic parameter that can provide complementary information to biochemical data and it may be useful in the management of diabetic nephropathy, especially in patients with high serum creatinine or creatinine clearance.

Adult↗

PubMed2001

Atomic spectral line free parameter deconvolution procedure.

We report an advanced numerical procedure for deconvolution of theoretical asymmetric convolution integral of a Gaussian and a plasma broadened spectral line profile j(A,R)(lambda) for spectal lines. Our method determines all broadening parameters, self-consistently and directly from the line profile with minimal assumptions or prior knowledge. This method is useful for obtaining complete information on all plasma parameters directly from the recorded shape of a single line, which is very important in case no other diagnostic methods are available. The method is also convenient for determination of plasma parameters in the case of a symmetrical profile such as Voigt one.

Journal Article↗

PubMed1990

[Delimiting the molecular envelope of a protein by deconvolution of the Patterson function for native proteins].

A process, based on the superposition method, is described to delimit the molecular envelope of a protein by deconvolution of the Patterson function. The object is to obtain a preliminary set of phases from native structure-factor amplitudes with only native intensity data. The method has been tested with data from two immunoglobulin Fab fragments, Fab NEW and Fab R19.9. Several zones of resolution were explored.

Immunoglobulin Fragments↗

PubMed1991

Deconvolution of tracer and dilution data using the Wiener filter.

In the study of living systems it is often necessary to inject or infuse a substance into the peripheral circulation and monitor its subsequent concentration in the plasma with time. Examples abound in the pharmacokinetic study of drugs and in the use of the indicator dilution technique for measuring blood flow. Furthermore, it is often necessary to deconvolve one such measured, and hence noisy, data set with another. One of the standard methods for deconvolving noisy signals is the Wiener filter, which is generally derived as a real window in the frequency domain such that the mean squared error between the estimated deconvolved function and the truth, on average, is minimized. Application of the Wiener filter requires some (often crude) model of the noise-to-signal power ratio as a function of frequency. In the pharmacokinetic and indicator dilution situations, however, one invariably has a good model of the actual function to be deconvolved in the form of a sum of decaying exponential functions. Such a model may be employed to calculate the signal-to-noise power ratio for use in the Wiener filter, or alternatively may be directly deconvolved itself. It is shown that better results are achieved with the Wiener filter if the model of the signal is not particularly accurate, whereas with a very accurate model it is better to deconvolve the model itself. The point at which the two deconvolution approaches perform comparably occurs when the error in the model is of a similar magnitude to the noise.

Mathematical Computing↗

PubMed1993

Linear and nonlinear techniques for the deconvolution of hormone time-series.

Pulsatile hormone secretion is usually investigated by measuring hormone concentration in samples of peripheral plasma. In this paper, the deconvolution of hormone time-series to reconstruct the instantaneous secretion rate of glands is considered. Various techniques are discussed and compared in order to overcome the ill-conditioning of the problem and reduce the computational burden. In particular, linear techniques based on least squares, maximum a posteriori (MAP) estimation, and Wiener filtering are compared. A new nonlinear MAP estimator that keeps into account the non-Gaussian distribution of the unknown signal is worked out and shown to yield the best results. The performances of the algorithms are tested on simulated time-series as well as on series of Luteinizing Hormone (LH).

Algorithms↗

PubMed1994

An automated film reader for DNA sequencing based on homomorphic deconvolution.

An automated reader for electrophoresis based DNA sequencing methods is described that provides fast and accurate sequence determination. Digitized sequencing lanes are processed with homomorphic blind deconvolution in preparation for peak detection, interlane alignment, peak refinement and base calling. Initial reads from direct blot sequencing films have error rates of about 1% at the rate of 5 nucleotides/s. Typical read lengths are 500-600 nucleotides. The described reader is a significant improvement over existing readers and could be an essential component in the sequencing efforts of the Human Genome Project.

Base Sequence↗