The early plasma concentration of 51Cr-EDTA in patients with cirrhosis and ascites: a comparison of three models.

Objectives: The aim of the study was to determine which of three two-parameter fitting functions (exponential, linear-log, and negative-power function of time) most accurately models early chromium-51-EDTA (51Cr-EDTA) plasma concentration data prior to 120 min in patients with cirrhosis and ascites and understand how these fitting functions affect the calculation of the area under the plasma concentration curve (AUC).

Methods: A bolus, antecubital intravenous injection of 2.6 MBq of 51Cr-EDTA was given to 13 patients with cirrhosis and ascites.

Validation of Tikhonov adaptively regularized gamma variate fitting with 24-h plasma clearance in cirrhotic patients with ascites.

Purpose: The aim was to compare late-time extrapolation of plasma clearance (CL) from Tikhonov adaptively regularized gamma variate fitting (Tk-GV) and from mono-exponential (E1) fitting.

Methods: Ten (51)Cr-ethylenediaminetetraacetic acid bolus IV studies in adults--8 with ascites--assessed for liver transplantation, with 12-16 plasma samples drawn from 5-min to 24-h, were fit with Tk-GV and E1 models and CL results were compared using Passing-Bablok fitting.

Results: The 24-h CL(Tk-GV) values ranged from 11.

Tikhonov adaptively regularized gamma variate fitting to assess plasma clearance of inert renal markers.

The Tk-GV model fits Gamma Variates (GV) to data by Tikhonov regularization (Tk) with shrinkage constant, λ, chosen to minimize the relative error in plasma clearance, CL (ml/min). Using (169)Yb-DTPA and (99m)Tc-DTPA (n = 46, 8-9 samples, 5-240 min) bolus-dilution curves, results were obtained for fit methods: (1) Ordinary Least Squares (OLS) one and two exponential term (E₁ and E₂), (2) OLS-GV and (3) Tk-GV. Four tests examined the fit results for: (1) physicality of ranges of model parameters, (2) effects on parameter values when different data subsets are fit, (3) characterization of residuals, and (4) extrapolative error and agreement with published correction factors.

Spectral restoration and energy resolution improvement of electron energy-loss spectra by Pixon reconstruction: II. Application to practical ELNES analysis of low SNR.

We applied Pixon deconvolution as introduced in Part I to several practical, examples of low signal-to-noise ratio (SNR), electron energy-loss spectra with a goal toward restoring their fine spectral features and/or improving the energy resolution. We demonstrate that by directly fitting the two-dimensional spectral data recorded on the CCD; the method enables us to reveal fine spectral structures. Consequently, Pixon reconstruction extends the ability to probe electronic states in very spatially localized areas, a capability currently unique to our method.

Spectral restoration and energy resolution improvement of electron energy-loss spectra by Pixon reconstruction: I. Principle and test examples.

We explore the use of the Pixon method, one of the highest performance image reconstruction methods available today, for the analysis of electron energy loss spectra (EELS). The method takes particular advantage of two-dimensional (2-D) CCD data, in which the data are blurred by a PRF (point-response-function as measured by the low-loss spectrum) both in the direction of energy dispersion and in the cross-dispersion direction. The Pixon method is used to simultaneously (i) deconvolve the PRF, increasing the spectral resolution, and (ii) fit the data in the cross-dispersion direction which efficiently combines the signal into a single parent spectrum.

An improved method for determining renal sufficiency using volume of distribution and weight from bolus 99mTc-DTPA, two blood sample, paediatric data.

Objectives: To find an improved method of determining renal sufficiency by exploring power functions for estimating normal value, E(arg), single compartment glomerular filtration rate (G1), rate constant (gamma) and renal sufficiency index, RSI = gamma/E(gamma) = G1/E(G1), using compartment volume (V), patient mass ( W), patient age (A), patient height (H), and sex (S). To present the best estimator of normal, E(G1) = f(V, W).

Methods: One hundred and thirty 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) combined imaging and G1 studies in 97 children were screened by findings and history to obtain 44 normal studies of patients 1.

Improved lesion detection from spatially adaptive, minimally complex, Pixon reconstruction of planar scintigraphic images.

Pixon noise reduction was applied to 18 planar images, six each from 99mTc-methylene diphosphonate (99mTc-MDP), 67Ga citrate (67Ga), and (123)I-metaiodobenzylguanidine ((123)I-MIBG) studies. Pixon processing increased patient signal-to-noise ratio, 6.8-11.