Comparison of HRRT and HR plus Scanners for Quantitative (R)-[C-11]verapamil, [C-11]raclopride and [C-11]flumazenil Brain Studies

Purpose: This study was conducted to directly compare the high-resolution research tomograph (HRRT) (high-resolution brain) and HR+ (standard whole-body) positron emission tomography (PET) only scanners for quantitative brain studies using three tracers with vastly different tracer distributions.Procedures: Healthy volunteers underwent successive scans on HR+ and HRRT scanners (in random order) using either (R)-[¹¹C]verapamil (n = 6), [¹¹C]raclopride (n = 7) or [¹¹C]flumazenil (n = 7). For all tracers, metabolite-corrected plasma-input functions were generated.Results: After resolution matching, HRRT-derived kinetic parameter values correlated well with those of HR+ for all tracers (intraclass correlation coefficients ≥0.78), having a good absolute interscanner test-retest variability (≤15 %). However, systematic differences can be seen for HRRT-derived kinetic parameter values (range −13 to +15 %).Conclusion: Quantification of kinetic parameters based on plasma-input models leads to comparable results when spatial resolution between HRRT and HR+ data is matched. When using reference-tissue models, differences remain that are likely caused by differences in attenuation and scatter corrections and/or image reconstruction.