Mapping of central dopamine synthesis in man, using positron emission tomography with L-[beta-11C]DOPA.
OBJECTIVE
To estimate the presynaptic function of the central dopaminergic system, positron emission tomography measurement of the endogenous dopamine synthesis rate was performed with L-[beta-11C]DOPA. In the present study, we developed a simple method for calculating an indicator of the dopamine synthesis rate with L-[beta-11C]DOPA on a voxel-by-voxel basis for parametric mapping.


METHODS
After intravenous injection of L-[beta-11C]DOPA, dynamic scanning was performed on ten healthy men for 89 min. The dopamine synthesis ratio was calculated on a voxel-by-voxel basis as the ratio of the area under the time-activity curves of brain regions to the reference brain region, that is, occipital cortex. The overall uptake rate constant as an indicator of dopamine synthesis was also calculated by kinetic and graphical analyses.


RESULTS
The dopamine synthesis ratio calculated by the present method was in good agreement with the indicators of dopamine synthesis calculated by kinetic and graphical analyses, although a systemic underestimation was observed, especially when the integration interval was set in the early phase of the scan duration. In particular, underestimations were prominent in brain regions with relatively lower influx rate constant K1.


CONCLUSIONS
By this method, regional dopamine synthesis could be estimated on a voxel-by-voxel basis. This method does not need an arterial input function and should prove to be useful for clinical research.
Ito
Hiroshi
H
Clinical Neuroimaging Team, Molecular Neuroimaging Group, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Chiba 263-8555, Japan. hito@nirs.go.jp
Shidahara
Miho
M
Takano
Harumasa
H
Takahashi
Hidehiko
H
Nozaki
Shoko
S
Suhara
Tetsuya
T
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002250:Carbon Radioisotopes; D004298:Dopamine / Q000378:metabolism*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007980:Levodopa / Q000493:pharmacokinetics*; D008297:Male; D008657:Metabolic Clearance Rate; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution
D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D007980:Levodopa; D004298:Dopamine