Visualising Neuroinflammation in Post-Stroke Patients: A Comparative PET Study with the TSPO Molecular Imaging Biomarkers [C-11]PK11195 and [C-11]vinpocetine

With the main objective of comparing the prospective diagnostic power of two 11C-labelled molecular imaging biomarkers with affinity for TSPO and used for the visualisation of activated microglia after a stroke, we measured with positron emission tomography (PET) in four post-stroke patients the regional brain uptake and binding potential of [C-11] vinpocetine and [C-11] PK11195. Percentage standard uptake values (%SUV) and binding potential (BPND) were used as outcome measures. The total peak brain uptake value and average global brain uptake value were higher for [C-11] vinpocetine than for [C-11] PK11195. The regional %SUV values were significantly higher for [C-11] vinpocetine than for [C-11] PK11195 in the hemispheres as well as in almost all standard brain regions. The %SUV values of [C-11] vinpocetine were higher in the peri-infarct zone than in the ischaemic core, however, the difference did not prove to be significant. There was basically no difference in %SUV values between the ischaemic core and the peri-infarct zone for [C-11] PK11195. The BPND values for [C-11] vinpocetine were higher in all standard regions than those for [C-11] PK11195, but the difference was not significant between them. The BPND values of [C-11] vinpocetine were higher in the peri-infarct zone than in the ischaemic core, however, the difference did not prove to be significant. A comparative analysis of the two ligands indicates that [C-11] vinpocetine shows a number of favourable characteristics over [C-11] PK11195, but to demonstrate that it may serve as a prospective molecular imaging biomarker of microglia activation in post-stroke patients, further studies are required.