Cynomolgus and rhesus monkeys have been studied via PET with [18F]-L-6 
fluorodopa tracer. Striatal fluorodopa uptake rate constants have been derived 
by graphical analysis of transaxial slice images centered on the striata. The 
differences between pairs of values of the rate constant, obtained from two 
scans on the same monkey separated by two weeks or more, exhibited a relative 
standard deviation of 34.4%. If the two scans were conducted one immediately 
after the other, with the position of the monkey undisturbed, the standard 
deviation was reduced to 14.0%. The utility of this technique was demonstrated 
by comparing the effects on the scans of halothane and pentobarbital anesthesia 
and by the administration of NSD 1015, a peripheral and central inhibitor of 
L-aromatic amino-acid decarboxylase, between back-to-back scans. With NSD 1015, 
the fluorodopa uptake constant was reduced by an average of 76.0%.