Image-derived input function for [11C]flumazenil kinetic analysis in human brain.
OBJECTIVE
We describe a method for analysis of [11C]flumazenil data using an input curve directly derived from the positron emission tomography (PET) images.


METHODS
The shape of the tracer plasma curve was obtained from the product of the intact flumazenil fraction in plasma in six arterial samples and the internal carotid artery time-activity curve (TAC). The resulting curve was calibrated using the [11C]flumazenil concentration in three of the six samples. The curve peak was recovered by adding an exponential function to the scaled curve whose parameters were estimated from simultaneous fittings of several tissue TACs assuming that all regions share the same input.


RESULTS
Good agreement was found between the image-derived and the experimental plasma curves in six subjects. Distribution volumes were highly correlated with linear regression slope and intercept values between [0.94, 1.03] and [-0.10, 0.16], respectively.


CONCLUSIONS
The proposed method is suitable for benzodiazepine receptor quantification requiring only a few blood samples.
D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000378:metabolism; D005442:Flumazenil / Q000097:blood / Q000493:pharmacokinetics*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007700:Kinetics; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012702:Serotonin Antagonists / Q000097:blood / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed / Q000379:methods*
D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D012702:Serotonin Antagonists; D005442:Flumazenil