3′-Deoxy-3′-18F-fluorothymidine (18F-FLT) is a radiotracer which accumulates in proliferating cells and is used for positron emission tomography (PET) imaging. This study investigates the heterogeneous transport and uptake of FLT in tumors, aiming to understand the links between FLT dynamics described by a mechanistic spatial-temporal model and by a simplified 3-compartment model, and to study the validity of the compartment model.

In the proposed multi-scale spatial-temporal model, the tumor consists of vasculature, interstitium and tumor cells. The heterogeneous spatial-temporal distribution of FLT is determined by a convection-diffusion-reaction equation, numerically solved using the finite difference method (FDM). Physiological parameters were collated from the literature and used as model coefficients, and vascular maps were created based on histological micro-vascular density (MVD). Results show that the multi-scale model can generate FLT time activity curves (TACs) similar to TACs derived from clinical PET images. And so long as the region of interest (ROI) is a near-closed system, a 3-compartment model can recover reasonable estimates of averaged FLT dynamics.

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