Fitting of late dynamic [¹⁸F]MK6240 PET scans for in vivo tau quantification

Dear Sir,

We read with great interest the comparison by Guehl et al. of different strategies for in vivo quantification of tau aggregates with [¹⁸F]MK6240 in patients with Alzheimer’s disease (AD) or mild cognitive impairment (MCI) and in control subjects (CTRL)[1]. This comparison involved compartment modeling analysis including arterial blood sampling, as well as graphical and simplified methods. For all subjects, the preferred compartmental model was a reversible two-tissue model with the blood contribution included as a model parameter (2T4k1v). This model allowed the authors to fit the [¹⁸F]MK6240 uptake of MCI/AD patients, revealing a wide dynamic range as compared with CTRL subjects uptake (Fig. 2 by Guehl et al.). It also showed that the corresponding binding patterns were consistent with neurofibrillary tau deposition patterns [1]. In particular, the 2T4k1v model provided distribution volume ratios (DVR) where cerebellar gray matter (CGM) was used as the reference tissue,...