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Results for “IODOHIPPURIC ACID”

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PubMed1987

Effects of statistical noise and digital filtering on the parameters calculated from the impulse response function.

Radiotracers are widely used for the investigation of organ perfusion and function. One of the quantitative approaches to analyze radiotracer data is the calculation of the impulse response function, which is obtained by deconvolution analysis of the time-activity curves measured over the organ. Since exactness of the calculated impulse response function depends both on the counting statistics and on the deconvolution algorithm applied, computer simulated time-activity curves were used to test the least squares deconvolution program based on the matrix regularization algorithm. Criteria of clinical importance (error in the calculated organ function parameters) and criteria of mathematical importance (deconvolution and reconvolution error) were investigated. For three typical impulse response functions f(t), it was found that: 1. In cases of noncompartmental vascular-capillary f(t)'s, a high degree of smoothing is preferable during deconvolution, in this way the error becomes systematic but controllable. 2. Noncompartmental vascular-tubular f(t)'s are noise sensitive, but fortunately, noise in the data can be held to a minimum. 3. Compartmenta f(t)'s need only a minimal degree of smoothing; their components can be identified in a second step using a multiexponential least squares fit.

Algorithms↗
PubMed1982

Induced hyperosmolality effects on extracellular fluid volume, lymph flow and osmolar equilibrium: studies in the rat.

The effects of experimentally induced hyperosmolality has been studied in rats. Renal vascular pedicle ligation was performed on all animals to prevent renal clearance of the infused solute, xylose, and allow accurate ECF space determinations with 51Cr EDTA. Small volume hyperosmolar xylose infusions caused parallel elevation of the osmolality of thoracic duct lymph and arterial plasma. A positive correlation was obtained between lymph osmolality and flow alterations. The maximal osmolality elevation of 22 mosm X kg-1 H2O was associated with an intracellular fluid mobilisation which was equal to 7.1% of the ECF space. The infused and mobilised fluid volumes were distributed unequally between the intra and extra vascular compartments of the ECF.

Animals↗