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

Background: 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.

Methods: 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.

Results: 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.

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