[68Ga]-DOTA-E-[c(RGDfK)]2 is a radioligand for PET imaging of αvβ3 integrin. It was synthesized and evaluated preclinically by Janssen et al (2002) and Dijkgraaf et al (2011), and the tracer is reviewed in MICAD by Leung. Tracer was seen to accumulate in tumour, and the binding was confirmed to be specific by co-injection of cold ligand.
Currently, there are no reports on modelling or data analysis beyond SUV calculation for [68Ga]-DOTA-E-[c(RGDfK)]2, but several studies regarding other αvβ3 integrin tracers.
Two-tissue compartment model with five parameters (K1, k2, k3, k4, and VB) and plasma input has been found to best represent the measured tissue concentration curves (Ferl et al., 2009; Guo et al., 2012a; Kim et al., 2013), although reliability of model parameters may need to be improved by constraining some of the parameters, like setting k4 to a constant value (Ferl et al., 2009). Variability in model rate constants may not necessary be a major problem since the final outcome, representing receptor density, is the macroparameter VT (total volume of distribution), also marked with Vd.
The VT has also been calculated using MTGA for reversible uptake (Logan plot); the result correlated well with the VT from compartmental model analysis (Guo et al., 2012a; Kim et al., 2013; Kiugel et al., 2014). Logan plot analysis is a robust and fast method, and it has therefore been applied to compute parametric images with labeled RGD peptides (Guo et al., 2012a; Kim et al., 2013; Kiugel et al., 2014).
Rate of internalization was assumed to be zero (Ferl et al., 2009).