scholarly journals Multiple Time Graphical Analysis

2020 ◽  
Author(s):  
Keyword(s):  
Graphical Analysis ◽  
Multiple Time

scholarly journals Graphical Evaluation of Blood-to-Brain Transfer Constants from Multiple-Time Uptake Data. Generalizations

1985 ◽  
Vol 5 (4) ◽  
pp. 584-590 ◽  
Author(s):  
Clifford S. Patlak ◽  
Ronald G. Blasberg
Keyword(s):  
Compartmental Analysis ◽  
Graphical Analysis ◽  
Test Substance ◽  
Multiple Time ◽  
Sequential Data ◽  
Compartmental System ◽  
Blood Concentrations ◽  
Reversible Binding ◽  
Uptake Data ◽  
Actual Configuration

The method of graphical analysis for the evaluation of sequential data (e.g., tissue and blood concentrations over time) in which the test substance is irreversibly trapped in the system has been expanded. A simpler derivation of the original analysis is presented. General equations are derived that can be used to analyze tissue uptake data when the blood–plasma concentration of the test substance cannot be easily measured. In addition, general equations are derived for situations when trapping of the test substance is incomplete and for a combination of these two conditions. These derivations are independent of the actual configuration of the compartmental system being analyzed and show what information can be obtained for the period when the reversible compartments are in effective steady state with the blood. This approach is also shown to result in equations with at least one less nonlinear term than those derived from direct compartmental analysis. Specific applications of these equations are illustrated for a compartmental system with one reversible region (with or without reversible binding) and one irreversible region.

scholarly journals A Strategy for Removing the Bias in the Graphical Analysis Method

2001 ◽  
Vol 21 (3) ◽  
pp. 307-320 ◽  
Author(s):  
Jean Logan ◽  
Joanna S. Fowler ◽  
Nora D. Volkow ◽  
Yu Shin Ding ◽  
Gene-Jack Wang ◽  
...  
Keyword(s):  
Least Squares ◽  
Graphical Method ◽  
Graphical Analysis ◽  
Distribution Volume ◽  
Noise Model ◽  
Data Sets ◽  
Multiple Time ◽  
Analysis Method ◽  
Reference Tissue ◽  
The One

The graphical analysis method, which transforms multiple time measurements of plasma and tissue uptake data into a linear plot, is a useful tool for rapidly obtaining information about the binding of radioligands used in PET studies. The strength of the method is that it does not require a particular model structure. However, a bias is introduced in the case of noisy data resulting in the underestimation of the distribution volume (DV), the slope obtained from the graphical method. To remove the bias, a modification of the method developed by Feng et al. (1993) , the generalized linear least squares (GLLS) method, which provides unbiased estimates for compartment models was used. The one compartment GLLS method has a relatively simple form, which was used to estimate the DV directly and as a smoothing technique for more general classes of model structures. In the latter case, the GLLS method was applied to the data in two parts, that is, one set of parameters was determined for times 0 to T1 and a second set from T1 to the end time. The curve generated from these two sets of parameters then was used as input to the graphical method. This has been tested using simulations of data similar to that of the PET ligand [11C]- d-threo-methylphenidate (MP, DV = 35 mL/mL) and 11C raclopride (RAC, DV = 1.92 mL/mL) and compared with two examples from image data with the same tracers. The noise model was based on counting statistics through the half-life of the isotope and the scanning time. Five hundred data sets at each noise level were analyzed. Results (DV) for the graphical analysis (DVg), the nonlinear least squares (NLS) method (DVnls), the one-tissue compartment GLLS method (DVf), and the two part GLLS followed by graphical analysis (DVfg) were compared. DVFG was found to increase somewhat with increasing noise and in some data sets at high noise levels no estimate could be obtained. However, at intermediate levels it provided a good estimation of the true DV. This method was extended to use a reference tissue in place of the input function to generate the distribution volume ratio (DVR) to the reference region. A linearized form of the simplified reference tissue method of Lammertsma and Hume (1996) was used. The DVR generated directly from the model (DVRfl) was compared with DVRfg (determined from a “smoothed” uptake curve as for DVfg) using the graphical method.

Mechanism of L-glucose, raffinose, and inulin transport across intact blood-brain barriers

1990 ◽  
Vol 258 (3) ◽  
pp. H695-H705 ◽  
Author(s):  
K. J. Lucchesi ◽  
R. E. Gosselin
Keyword(s):  
Molecular Size ◽  
Compartment Model ◽  
Graphical Analysis ◽  
Capillary Endothelium ◽  
Multiple Time ◽  
Brain Capillary ◽  
Molecular Weights ◽  
Blood Brain ◽  
Two Compartment Model ◽  
The Brain

Brain capillary permeability-surface area products (PS) of hydrophilic solutes were evaluated in terms of a conventional two-compartment model. In rats whose blood-brain barrier (BBB) was presumed to be intact, metabolically inert carbohydrates with different molecular weights were injected in pairs to elucidate whether their transfer into the brain proceeds by diffusion through water- or lipid-filled channels or by vesicular transport. The distribution volume of 70 kDa dextran 10 min after intravenous injection was used as a measure of the residual volume of plasma in brain tissue after death. The two-compartment model yielded larger PS values for inulin and raffinose than for L-glucose, and the PS values of inulin and L-glucose were found to decrease as the labeling time was lengthened (10, 30, and 60 min). These observations were interpreted to mean that a rapidly equilibrating compartment was present between blood and brain, rendering the two-compartment model inadequate for computing true transfer rate constants. When multiple-time uptake data were reanalyzed using the three-compartment graphical analysis of Patlak, Blasberg, and Fenstermacher (J. Cereb. Blood Flow Metab. 3: 1-7, 1983), solutes of differing molecular size were found to enter the brain at approximately equal rates. This observation suggested that the predominant transport mechanism across an intact BBB is vesicular. Specifically, unidirectional transport is likely to be initiated by solute binding to the glycocalyx on the luminal surface of brain capillary endothelium. Apparently more inulin than L-glucose is absorbed, which may account for its slightly faster transfer across the BBB. We suggest that this adsorptive surface is the location of the rapidly equilibrating compartment on the plasma side of the BBB.

Application of graphical analysis of taxonomical structure of diatom complexes in identification of critical conditions of the Neopleistocene lakes (on the example of Bibirevo section)

2019 ◽  
pp. 78-87
Author(s):  
Elena V. Bespalova
Keyword(s):  
Lake Sediments ◽  
Critical Points ◽  
Graphical Analysis ◽  
Volga Region ◽  
Critical Conditions ◽  
Ancient Lake ◽  
Diatom Complexes

Ancient lake sediments of Bibirevo section in the Yaroslavl and Kostroma Volga region are studied by means of graphical analysis of taxonomical structure of diatom complexes. This method allowed to record critical points (change of areas of stability) in the development of a Neopleistocene lake during the transition from stage to stage, as well as from phase to phase.

Causes of ecosystem transformations variability in lakes of the european part of Russia and Western Siberia (diatom analysis)

2019 ◽  
pp. 79-82
Author(s):  
Lev V. Razumovsky
Keyword(s):  
Western Siberia ◽  
Graphical Analysis ◽  
European Part ◽  
Analysis Method ◽  
Climatic Region ◽  
Diatom Analysis ◽  
Lake Ecosystems ◽  
Distinctive Features ◽  
European Part Of Russia

On the basis of author's graphical analysis method, the typification of lake ecosystems transformation scenarios depending on the size of lakes was carried out. It was confirmed that the type of transformation depends not only on size of the lake, but also on the landscape and climatic region in which it is located. The distinctive features of lake ecosystems transformation types in the European part of Russia and in Western Siberia were analyzed and compared.

Economic Growth and Defence Spending: An Efficiency Analysis of Romania’s Conscription Suspension

2020 ◽  
Vol 26 (2) ◽  
pp. 44-51
Author(s):  
Alin Teodor Huseraș ◽  
Andrei Ciprian Spînu
Keyword(s):  
Graphical Analysis ◽  
Defense Spending ◽  
National Defense ◽  
Effective Management ◽  
External Funding ◽  
The Public ◽  
Defence Spending ◽  
Key Sectors ◽  
The Military ◽  
Theoretical Issues

AbstractNational defense is one of the key sectors responsible for maintaining national security, being considered at the same time an element of great importance and strict necessity of the public sector. The performance of defense functions and missions are closely linked to the military capabilities of this sector, which in turn depend on the budget for defense spending. This paper deals with some theoretical issues in the economic field of defense, regarding the size of defense spending in GDP and their social effects. It is also trying to carry out an analysis on the efficiency versus inefficiency in the use of defense resources, to finance the two types of recruitment systems, namely: by conscription or voluntary will. In order to be able to achieve the above, graphical analysis methods and calculation dermination method were used. The efficiency of spending public funds depends on both objective factors such as: distribution of a certain share of GDP to a certain area; attracting internal and external funding, as well as subjective factors, like: allocating resources to certain categories of expenses; allocating resources to certain defense programs; effective management of these resources by the competent structures. Therefore, for a program to be considered effective, it must meet the requirements of the collective needs of society, be rationally implemented and be sustainable.

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