Raman V Chirakal

Learn More
In recent years, 6-l-18F-fluorodihydroxyphenylalanine (18F-DOPA) PET has emerged as a new diagnostic tool for the imaging of neuroendocrine tumors. This application is based on the unique property of neuroendocrine tumors to produce and secrete various substances, a process that requires the uptake of metabolic precursors, which leads to the uptake of(More)
The tracers 6-[18F]fluoro-L-3,4-dihydroxyphenylalanine (6-[18F]fluoro-L-DOPA) and L-[14C]DOPA were injected simultaneously into rhesus monkeys, and the time course of their metabolites was measured in the striatum and in the occipital and frontal cortices. In the striatum, 6-[18F]fluoro-L-DOPA was metabolized to 6-[18F]fluorodopamine,(More)
OBJECTIVES To determine whether an increase in cardiac sympathetic activity produced by exercise or sublingual glyceryl trinitrate causes an increased rate of loss of fluorine-18 from the myocardium after intravenous [18F]6-fluorodopamine ([18F]F-DA) in normal volunteers. In addition, to determine the contribution of non-specific uptake of [18F]F-DA in the(More)
Positron tomography, using [18F]6-fluoro-L-dopa as a tracer, has been used for the study of Parkinson's disease. Unfortunately, the analysis of data obtained with this agent is bedeviled because it readily forms labeled methylated metabolites that enter the brain. We have evaluated [18F]6-fluoro-L-m-tyrosine (FmT) as an alternative tracer to study(More)
Positron emission tomography, using the dopa analogue [18F]6-fluoro-L-dopa, has been used to depict the neostriatum in living monkeys. The amount of 18F that accumulated preferentially in the striatum could be augmented by a peripheral decarboxylase inhibitor. Striatal 18F could also be discharged with reserpine. This is the first time that the regional(More)
BACKGROUND The implication of an arrhythmogenic role for infarction-induced disruption of regional myocardial sympathetic nerve activity has led to a search for noninvasive methods to study regional sympathetic nerve activity in patients after infarction. METHODS AND RESULTS By using positron emission tomography, we measured the time course of myocardial(More)
The analysis of positron tomographic studies of 3,4-dihydroxyphenylethylamine (dopamine) metabolism in which [18F]6-fluoro-L-3,4-dihydroxyphenylalanine (F-dopa) is used as a tracer is confounded by the presence of [18F]6-fluoro-3-O-methyl-L-3,4-dihydroxyphenylalanine (OMFD). This labeled molecule, formed by the action of peripheral(More)
A new synthesis is described for the routine production of 3,4-dihydroxy-6-[18F]fluoro-phenyl-L-alanine (6-[18F]fluoro-L-dopa). The reaction between [18F]fluorine gas and 3,4-dihydroxyphenyl-L-alanine (L-dopa) in liquid hydrogen fluoride gave 2-, 5-, and 6-[18F]fluoro-L-dopa. 6-[18F]Fluoro-L-dopa was isolated by reverse-phase high-pressure liquid(More)
Fluorine-18 labeled fluorodopamine (FDA) was synthesized by the direct fluorination with [18F]F2 [produced by the nuclear reaction 18O(p,n)18F] of dopamine in anhydrous hydrogen fluoride containing boron trifluoride at -65 degrees C. Reverse-phase high-performance liquid chromatography (HPLC) was used to separate [18F]6-FDA from the reaction mixture(More)
6-[18F]Fluoro-L-dopa was designed to trace the dopamine metabolism in the brain with positron tomography. 6-[18F]Fluoro-L-dopa resembles natural L-dopa biochemically, it crosses the blood-brain barrier with the similar kinetics, it is decarboxylated by dopa decarboxylase and is stored intraneuronally in vesicles. In addition the rate of O-methylation of(More)