TABLE 5.

Initial and Revised Algorithms for Interpreting MK-6240 PET

Scan assessment	Original algorithm	Refined algorithm	Reason for adjustment
Negative	No more than one region positive in cortex	All clusters negative	Allowing one region to be positive was to prevent interpretation of scans as positive when meningeal uptake near inferolateral temporal lobes could be misread as positive region; this was dropped with improved methods or instructions to identify this confounder
Positive, AD pattern	Evidence of increased uptake in two cortical regions with at least one region in temporal lobes	At least one cluster 1 region positive and no cluster 3 regions positive	Revision was made after observation of multiple cases with isolated cluster 1 abnormality in just one region
Positive, atypical AD pattern	Not assessed	Increased uptake in one or more regions in cluster 2 but not in clusters 1 or 3	This rare pattern was noted from review of other MK-6240 datasets and was expected pattern based on published literature on other tau PET tracers
Positive, non-AD pattern	Any positive scan not fitting AD criteria	Increased uptake in one or more regions in clusters 1–3, with at least one region in cluster 3	Adjustment was made after formalized uniform assessment for regions involved in non-AD tauopathies