MTL index: A simple new method for measuring atrophy of the medial temporal lobe using clinically available neuroimaging

accumulation was comparable across groups. Interaction effects were observed when comparing PiB groups among NL (P<0.03), as PiB+ subjects showed higher rates of PiB accumulation compared to PiB(annual PiB increases: PiB+ 1⁄4 0.09 SUVR (6%) vs PiB1⁄4 0.006 SUVR (.05%) using WCer). Average rates of amyloid accumulation in PiB+ MCI and AD groups were approximately 1-2% per year, depending upon reference region. Consistency was found across reference regions, and systematic examination of effect size, variance and change over time identified optimal reference regions for each comparison. Conclusions: These results provide a benchmark for measuring therapeutic impact upon amyloid progression, support robustness of findings across multiple reference regions, and demonstrate the benefit of applying optimized procedures for data sampling.