Imaging TSPO expression with F-18-DPA-714 PET/MRI in Patients with Suspected PACNS

Ziel/Aim:

Primary angiitis of the central nervous system (PACNS) represents a very rare inflammatory disease. Diagnosis and therapeutic management is challenging as current imaging strategies are insufficient to confirm diagnosis or to monitor disease dynamics. To investigate specific patterns of intracranial inflammation, we performed F-18-DPA-714 PET/MRI scans targeting the translocator protein 18 kDA (TSPO) in a small cohort of patients with suspected PACNS.

Methodik/Methods:

60-minute dynamic PET scans were performed after injection of 200 – 250 MBq F-18-DPA-714 using a Siemens Biograph mMR (3 T). A cerebral vasculitis MRI-protocol without contrast agent was applied simultaneously.

Ergebnisse/Results:

A total of seven patients were examined of which six received anti-inflammatory therapy at the time of initial PET scanning. One patient with suspected PACNS demonstrated focally elevated F-18-DPA-714 accumulation of the left-sided basal ganglia, diencephalon and brain stem. Relative uptake was reduced after initiation of immunosuppressive therapy. Biopsy in this patient revealed perivascular TSPO-expressing immune cells. In another patient with PACNS tracer accumulated dominantly in the right cerebral hemisphere greatly exceeding the spatial extent of MRI abnormalities. No pathologic tracer distribution was observed in three patients finally diagnosed with cerebral vasculitis. Two patients were finally diagnosed with stroke of unknown etiology and with moyamoya-disease, respectively. Both demonstrated elevated lesional uptake.

Schlussfolgerungen/Conclusions:

We report the principal feasibility of F-18-DPA-714 PET to reveal overexpression of TSPO in PACNS, to monitor therapy response and identified perivascular immune cells as a cellular source of uptake. The small size of our case study reflects the rareness of the disease and does not allow definite conclusions of specific TSPO patterns in PACNS. The need for undelayed onset of immunosuppressive therapy in suspected PACNS likely limits the sensitivity in our cohort.