Evaluation of the ratio method compared with graphical analyses for estimating nigrostriatal function in human 18F-dopa PET studies with or without carbidopa.
The striatal to cerebellar (S/C) activity ratio for estimating nigrostriatal function was compared with the Patlak analyses in 18F-dopa (FD) positron emission tomography (PET) with pretreatment with 100 mg carbidopa (CD). Two different time-activity curves of plasma FD or cerebellar 18F were used for the Patlak analyses. The S/C ratio increased linearly with time for 120 min and the ratio at 120 min correlated closely with the uptake constants by the two Patlak analyses (r = 0.94, 0.96) in six normal volunteers and six parkinsonism patients. The S/C ratio and the uptake constant by the cerebellar Patlak analysis without CD also showed a fairly good correlation (n = 30, r = 0.85). Then, the S/C ratios with and without CD were compared. Since CD increased both the striatal and the cerebellar radioactivities proportionally within each subject, CD did not change the S/C ratios. The S/C ratios both with and without CD were simple and comparable to the uptake constants in the FD PET studies.
Otsuka
M
M
Department of Radiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Ichiya
Y
Y
Kuwabara
Y
Y
Fukumura
T
T
Sasaki
M
M
Masuda
K
K
D000328:Adult; D002230:Carbidopa; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000502:physiology*; D004295:Dihydroxyphenylalanine; D005260:Female; D005462:Fluorine Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D012016:Reference Values; D013378:Substantia Nigra / Q000000981:diagnostic imaging / Q000502:physiology*; D014055:Tomography, Emission-Computed
D005462:Fluorine Radioisotopes; D004295:Dihydroxyphenylalanine; D002230:Carbidopa