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Catheter Correction ( UNFINSHED )

When evaluating indicator dilution experiments, one has to take into account the influence of the experimental setup on the measurements. Ideally, a tracer would be instantaneously introduced at a predetermined location within the circulation, and its concentration measured at another predetermined location. In practice, however, application of the tracer and collection of samples is achieved through catheters introduced into the circulation that distort to a certain degree the time course of the measured tracer concentration. Tracer kinetics obeys the principles of linear time-invariant system theory (put in reference). The injection catheter, the investigated organ, and the collection catheter can therefore be regarded as linear systems connected in series, such that the overall impulse response is the convolution of the individual impulse responses. Because convolution is commutative, the injection and collection catheter can be lumped together by considering the convolution of their impulse responses. The impulse response of the organ can then be obtained by deconvolution of the catheter responses from the overall impulse response. Monoexponential catheter distortion Experiments by Goresky and Silverman (1964) have shown that the impulse-response of a single catheter equipped with a peristaltic pump can be approximated by a delay followed by a single exponential decay. In these pilot experiments (without any biological material), the inflow to the catheter was switched between unlabeled and labeled blood, thus providing a step input. The data, normalized to the inflow tracer concentration, are shown in the following applet. These data are described by the following expressions:

c0(t) = 1 − e−α(t − τ), t > τ

c0(t) = 0, t ≤ τ

The impulse response of the catheter, h(t), is obtained as the first derivative of the response to a step input. It is described by the equation

h(t) = α e −α(t − τ), t > τ

h(t) = 0, t ≤ τ

where τ is the time delay and α is the exponential rate (decay) constant. The impulse response of the organ can then obtained from that of the total system by deconvolution according to the following equation: (unfinished)

Please cite in any publication for which this software is used and send an email with the citation and, if possible, a PDF file of the paper to:
Or send a copy to:
The National Simulation Resource, Director J. B. Bassingthwaighte, Department of Bioengineering, University of Washington, Seattle WA 98195-5061.

[This page was last modified 30Jul13, 11:06 am.]

Model development and archiving support at provided by the following grants: NIH U01HL122199 Analyzing the Cardiac Power Grid, 09/15/2015 - 05/31/2020, NIH/NIBIB BE08407 Software Integration, JSim and SBW 6/1/09-5/31/13; NIH/NHLBI T15 HL88516-01 Modeling for Heart, Lung and Blood: From Cell to Organ, 4/1/07-3/31/11; NSF BES-0506477 Adaptive Multi-Scale Model Simulation, 8/15/05-7/31/08; NIH/NHLBI R01 HL073598 Core 3: 3D Imaging and Computer Modeling of the Respiratory Tract, 9/1/04-8/31/09; as well as prior support from NIH/NCRR P41 RR01243 Simulation Resource in Circulatory Mass Transport and Exchange, 12/1/1980-11/30/01 and NIH/NIBIB R01 EB001973 JSim: A Simulation Analysis Platform, 3/1/02-2/28/07.