1,721,959 research outputs found
Modeling and identification of endocrine-metabolic systems. Theoretical aspects and their importance in practice
No full textSome guidelines for modeling, identification, and validation in endocrinology and metabolism are presented. Fundamentals based on recent theoretical developments are given, and their essential role for solving physiological and clinical problems is shown. Concepts and issues discussed include a priori and a posteriori identifiability; optimal experiment design; assessment of model validity; simple and complex models; compartmental and noncompartmental models. Recent studies on the glucose-insulin system and on ketone body metabolism are used to illustrate the methodological line of thought discussed in the paper
Optimal input design for identification of compartmental models. Theory and application to a model of glucose kinetics.
No full textThe optimal input design problem for the identification of linear compartmental models is studied. The optimality criterion consists in maximizing the achievable precision of parameter estimates. The rationale, theory, and computational methods for solving the problem for the scalar case are presented first. An application to a two-compartment model of glucose kinetics is then shown. The effect on parameter precision of the measurement error structure and of various design factors, such as an equienergy or equidose class of admissible inputs and the time interval for input and measurement, is discussed. The performance of standard classical inputs, e.g. an impulse or an infusion, is also evaluated
Control of diabetes with artificial systems for insulin delivery - Algorithm independent limitations revealed by a modelling study.
No full textThe causes of the inability of insulin infusion systems to restore normal metabolic conditions in diabetic subjects have been investigated with the aid of modeling and computer simulation. It has been possible to compute, by the model, the so-called minimal insulin profile with peripheral insulin infusion, i. e., the time course of plasma insulin which should be observed in a diabetic subject after an oral glucose test, when insulin is infused in a peripheral vein, in order to have a normal blood glucose profile. This profile allows assessment of the performance of insulin infusion systems by evidencing the relative role of the route of infusion and of the control algorithm on the normalization of metabolic control. It is concluded that the route of infusion is of major importance, while the control algorithm plays a minor role. The importance of modeling and simulation in circumstances, which make in vivo experiments; unfeasible or unethical, is emphasized along with the clinical and physiological relevance of the results
Parameter estimation of biological stochastic compartmental models.
No full textIn this paper linear time invariant biological compartmental models are considered, in which the transfer rate constants are assumed to be stochastic variables
Accessible pool and system parameters: assumptions and models.
No full textQuantitative assessment of substrate metabolism from in vivo tracer kinetic data requires a model of the system, i.e., a hypothesis on the structure and functioning of the system. Some fundamentals of modeling important for studying intermediary metabolism in the steady state will be discussed. Accessible pool and system parameters are defined. Although the calculation of accessible pool parameters is structure-free, that of system parameters requires the use of non-compartmental or compartmental structures. Assumptions, bases for choice, and relative merits of these two modeling strategies are discussed. Glucose and leucine metabolism serve as prototypes to illustrate the theoretical points
Parameter estimation in a biological two compartment model. II: A computer experimental study of the influence of the initial estimate in the parameter space, of some sampling protocols and of weighting factors.
No full textA previous study [1] on conditions affecting parameterestimation in atwocompartmentmodel is extended. In this paper the following factors and their interaction have been examined: the initial guess in the parameterspace, sampling procedures at constant time intervals, data truncations and weightingfactors in the criterion function
Impulse Response Model in Reconstruction of Insulin Secretion by Deconvolution: Role of Input Design in the Identification Experiment
Full text linkInsulin secretion rate (ISR) in vivo can be reconstructed by deconvolution of plasma concentration of C-peptide (CP), a peptide co-secreted with insulin but not extracted by the liver and exhibiting linear kinetics. Deconvolution requires the knowledge of the CP impulse response. A two exponential model is usually chosen to describe the CP impulse response but three exponential and one exponential models have also been used. The purpose of this paper is to investigate the role of the CP impulse response model order in reconstructing ISR by deconvolution in three standard physiological/clinical situations: ultradian oscillations, rapid pulses, and biphasic response to a glucose stimulus. By resorting to simulation, we first show that, in each situation, the validity of impulse response models with different orders depends on the input chosen in the impulse response identification experiment. Real data are then used which support the simulation results
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