Determination of an Optimal Pharmacokinetic Model of ¹⁸F-FET for Quantitative Applications in Rat Brain Tumors.

Abstract

<i>O</i>-(2-¹⁸F-fluoroethyl)-l-tyrosine (¹⁸F-FET) is a radiolabeled artificial amino acid used in PET for tumor delineation and grading. The present study compares different kinetic models to determine which are more appropriate for ¹⁸F-FET in rats. <b>Methods:</b> Rats were implanted with F98 glioblastoma cells in the right hemisphere and scanned 9-15 d later. PET data were acquired during 50 min after a 1-min bolus of ¹⁸F-FET. Arterial blood samples were drawn for arterial input function determination. Two compartmental pharmacokinetic models were tested: the 2-tissue model and the 1-tissue model. Their performance at fitting concentration curves from regions of interest was evaluated using the Akaike information criterion, <i>F</i> test, and residual plots. Graphical models were assessed qualitatively. <b>Results:</b> Metrics indicated that the 2-tissue model was superior to the 1-tissue model for the current dataset. The 2-tissue model allowed adequate decoupling of ¹⁸F-FET perfusion and internalization by cells in the different regions of interest. Of the 2 graphical models tested, the Patlak plot provided adequate results for the tumor and brain, whereas the Logan plot was appropriate for muscles. <b>Conclusion:</b> The 2-tissue-compartment model is appropriate to quantify the perfusion and internalization of ¹⁸F-FET by cells in various tissues of the rat, whereas graphical models provide a global measure of uptake.