Dual-Phase C-11 PiB PET Images for Detecting Tau Pathology in Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a major cause of lobar intracerebral hemorrhage and cognitive dysfunction in the elderly, and frequently coexists with Alzheimer's disease and tau pathology. Dual-phase ¹¹C-PiB PET detects amyloid deposition and cerebral perfusion changes and may have diagnostic value for identifying tau in CAA.

We prospectively enrolled patients with probable CAA for dynamic PiB and AV1451 scans. We compared early-phase (0-6 min after tracer injection) and late-phase (40-70 min) PiB PET between the tau(+) and tau(-) groups (based on AV1451 PET) and investigated their diagnostic values for detecting tau.

CAA/tau(+) had lower early-phase temporal PiB uptake than CAA/tau(-) (p = 0.014) and higher late-phase uptake in the whole cortex and temporal and parietal lobes (all p < 0.05). Early-phase temporal PiB SUVR correlated with tau burden (r = -0.34, p = 0.038). Using Youden's cut-off, early-phase and late-phase PET had sensitivities of 55% and 80% and specificities of 85% and 65% for detecting tau, respectively. Combining early- and late-phase scans provided a rule-out sensitivity of 90% and rule-in specificity of 100% for tau pathology in CAA.

Dual-phase ¹¹C-PiB PET represents a reliable approach for assessing tau and could potentially identify CAA patients for tau biomarker testing.