A Stochastic Approach to Tracer Kinetics^[*]

Summary

The single compartment well-mixed model (SCWMM) which has been used in almost all dynamic studies in nuclear medicine is, in fact, strictly accurate only in the case of a steady state obtained by means of constant administration of long-lived isotopes. That is the reason why SCWMM is not a good predictor of the behaviour of short-lived isotopes and why the distribution and transport of short- and long-lived isotopes in various situations has not yet been discussed in general terms. The aim of this paper is to do that by means of a more general stochastic approach. This more general approach takes into account the distribution and transport of tracer in the system, not requiring a hypothesis of good mixing and providing a possibility of making corrections due to decay in the case of short-lived isotopes studies.

Zusammenfassung

Das Modell eines gut durchmischten Einzelkompartments, das bisher in fast allen dynamischen Studien in der Nuklearmedizin verwendet wurde, ist nur im Falle eines Steady-state-Zustands, der durch konstante Verabreichung eines langlebigen Isotops erzielt wurde, völlig genau. Dies ist der Grund, warum dieses Modell das Verhalten kurzlebiger Isotope nicht gut Voraussagen kann und warum die Verteilung und der Transport kurz- und langlebiger Isotope in verschiedenen Situationen bis jetzt nicht in allgemeinen Begriffen diskutiert worden ist. Der Zweck dieser Arbeit ist es, dies mittels einer generelleren stochastischen Annäherung zu tun. Diese mehr generelle Annäherung nimmt auf die Verteilung und den Transport des Tracers im System Rücksicht, verlangt keine Hypothese einer guten Mischung und ergibt die Möglichkeit der Anbringung von Korrekturen für den Zerfall bei Untersuchungen mit kurzlebigen Isotopen.

^* 3rd International Symposium on Radiopharmacology, Freiburg i. Br. September 1983.

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