MAPT and Alzheimer disease: It has been reported that 11C‐(R)‐PK11195 binding to microglia “burns out” as amyloidosis in early Alzheimer's disease advances30 but increases again as tau tangles form.31, 32 A biphasic trajectory could explain the lack of correlation between 18F‐dopa Ki and 11C‐(R)‐PK11195 BPND in our data set.