Figure 4

Examples of AIFs determined in human subjects with radiometric and LC–MS/MS methods for [¹¹C]PBR28. (a) AIFs for one subject injected with [¹¹C]PBR28 (10.1 MBq/kg; injected mass 92 pmol/kg, i.v.) with an A_m of 383.5 GBq/µmol. The AIF from radiometric method is without correction of γ-counter measured radioactivity for the systematic difference with LC–MS/MS. (b) Comparisons of AIFs from the same experiment after correction of γ-counter measured radioactivity. (c) AIFs from radiometric (corrected) and LC–MS/MS measurements in another human subject injected with [¹¹C]PBR28 (10.7 MBq/kg; injected mass 229 pmol/kg, i.v.) at a lower A_m of 141.8 GBq/µmol. (d) AIFs from the same methods in a subject injected with radiotracer (9.5 MBq/kg; injected mass 44 pmol/kg, i.v.) at a higher A_m of 631.1 GBq/µmol. Note all data are for unchanged radiotracer alone (i.e., radiometabolites are excluded).