Abstract
241269
Introduction: Dynamic positron emission tomography (PET) enables a comprehensive analysis of the tracer kinetics, allowing for an accurate quantification of the in vivo distribution of PET tracers. The graphical analysis is a powerful tool for quantifying the radiotracer’s kinetics in vivo. As for the reversible radiotracers, the Logan plot and its noise-resistant variant, and the reversible equilibrium (RE) graphical plot, are widely used for the analysis of the distribution volume of the radiotracer in different tissues. However, such methods require long acquisition time. In this work, we proposed a simplified RE model for dynamic PET graphical analysis to address the scan duration issue.
Methods: The proposed simplified RE model is based on the principles of the RE plot (also the Logan plot), but with a significantly reduced scan time. The differences between these plot equations are shown in Table 1. Compared with the RE models, the data of tissue tracer concentration Ct and plasma input function Cp before the reversible equilibrium time t* are not needed, which could significantly reduce the required acquisition time for dynamic PET scanning. Theoretical proof is conducted to validate the relation between the estimated coefficients (DVT' and DVT) in the proposed simplified RE model and the conventional RE model. (Fig. 1). Moreover, the proposed model is validated with computer simulations and real patient with JR11 radiotracer.
Results: The theoretical derivation shows that the estimated coefficients in the simplified and the conventional RE model show a nearly proportional relation when the following two conditions are satisfied: (1) the linearity between the two normalized time integral terms of the blood input function, and (2) the negligibility of the scaled ratio between the early time integral of the tissue concentration and that of the blood input function when compared to the scaled estimated slope of the RE model (Fig. 1).
In our experiments, we demonstrate that the above-mentioned conditions are mostly satisfied (Fig. 2), and the estimated coefficients of the simplified and the conventional RE models show fair proportional relations in all the experiments (Fig. 3). The results show the model's ability to maintain strong linear relationships and produce parametric images comparable to those of the RE plot, but with the considerable advantage of shorter scan durations. The clinical data analysis is shown in Fig. 4, indicating that the difference is quite trivial between the parametric images of the estimated slopes by the proposed simplified RE and the RE methods.
Conclusions: In summary, the simplified RE model offers a promising alternative for reversible radiotracers in dynamic PET imaging, which successfully balances the need for precision with reduced scan durations.
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