tracer kinetics in biomedical research

[...]... with them can arise By definition, the tracer has its own kinetics The goal of a tracer kinetic study is to infer from the tracer kinetics information on the tracee kinetics If the three requirements are met, this goal can be attained 2.2 2.2.1 THE TRACER- TRACEE SYSTEM Concepts and Definitions A convenient scheme to illustrate the kinetics of a substance is shown in Figure 2.2.1 In this figure, the circles... accessible pool, set the stage for using a tracer to characterize these 14 TRACER KINETICS IN BIOMEDICAL RESEARCH kinetics By appealing to the definition of an ideal tracer, one can assume that the system described in Figure 2.2.2 for the tracee is the same as that for the tracer Therefore, superimposing the tracer system on that shown in Figure 2.2.2, one has the system shown in Figure 2.2.3 These two figures... can be written by again appealing to the mass balance principal, i.e the rate of change of tracer mass is the difference between the rate of tracer input u(t) and tracer disposal f(t): 18 TRACER KINETICS IN BIOMEDICAL RESEARCH In (2.2.4), means that when the experiment starts at there is no tracer mass in the system (In mathematical terms, m (0) is called the initial condition) In this situation, unlike... will be on characterizing the kinetics of substances already present in the body by using isotopic tracers as probes 11 TRACER KINETICS IN BIOMEDICAL RESEARCH 12 A naturally occurring substance is called a tracee The tracers will be assumed to be ideal where an ideal tracer is a substance with the following characteristics: a it is detectable by an observer, b its introduction into a system does not... be pointed to specific texts or the appendices With this in mind, who should read this book? The book is intended for those individuals who are using or planning to use tracer kinetic techniques to probe different metabolic systems In addition, it can be used as an introductory text in tracer kinetic analysis and mathematical modeling of biological systems Finally, it can be used by researchers in pharmacokinetics... parameter, k, (and thus of the tracee parameters since and the known tracer input u(t) For instance, if the tracer 20 TRACER KINETICS IN BIOMEDICAL RESEARCH experiment consists of injecting the tracer as a bolus of dose d at time zero, then the solution of (2.2.11) is Hence the tracer measurement can be related to the model parameters In particular, if a radioactive tracer is used and its concentration c(t)... Briefly, the conservation of mass principal applied to the tracer (i.e., the amount of tracer introduced into the system equals the amount leaving the system), can be written Fundamentals of Tracer Kinetics 21 since d, the total amount of tracer introduced into the system, is equal to Substituting the expression for f ( t ) given in (2.2.10) into this equation, one obtains which, when solved for F, gives... Medicine WileyLiss, New York, NY, 1992 This page intentionally left blank Chapter 2 FUNDAMENTALS OF TRACER KINETICS 2.1 INTRODUCTION As defined in Chapter 1, the kinetics of a substance in a biological system are its spatial and temporal distribution in that system The kinetics are the result of several complex events including circulatory dynamics, transport into cells, and utilization Utilization usually... tracee and tracer are structurally identical, and demonstrate the need for an accessible pool into which tracer can be introduced and from which measurements of tracer and tracee can be made The main difference between the two is in the inputs In the tracee system shown in Figure 2.2.2, the input is endogenous into a nonaccessible component of the system In the tracer system shown above, the input is... often require, in addition, programming skills This level of usage is beyond the scope of the present text so these packages will not be listed 1.5 ORGANIZATION OF THE BOOK This book provides a description of the processes involved in designing and analyzing tracer kinetic studies starting from the steps involved in choosing an isotope, or isotopes, for a tracer, or tracers, through formulating models .