3-Tissue Compartment Model, Sequential

This model has been developed by Bertoldo et al. [1] for the analysis of FDG uptake in skeletal muscle. In this context C₁, C₂ and C₃ correspond to extracellular, intracellular and phosphorylated intracellular FDG. K₁ [ml/ccm/min] and k₂ [1/min] are the exchange rate constants between plasma and the extracellular space, k₃ [1/min] and k₄ [1/min] describe the transport in and out of the cell, k₅ [1/min] and k₆ [1/min] phosphorylation and dephosphorylation.

Differential Equation of the Mass Balance

with input curve C_p(t).

Operational Model Curve

with the concentration C_B(t) of tracer in whole blood, and the blood volume fraction v_B.

Parameter Fitting

The model includes the 6 fitable parameters vB, K1, k2, k3, k4, k5, k6. Usually, vB is fixed at a physiologic value of 3-5%, and k₆ is fixed: k6=0. The influx Ki is given by

Reference

1. Bertoldo A, Peltoniemi P, Oikonen V, Knuuti J, Nuutila P, Cobelli C: Kinetic modeling of [18F]FDG in skeletal muscle by PET: a four-compartment five-rate-constant model. American journal of physiology Endocrinology and metabolism 2001;281(3):E524-536. PDF