M. J. Schueller

FluoroDOPA PET shows the nondopaminergic as well as dopaminergic destinations of levodopa

Objective: To evaluate the visible and quantitative anatomic distribution of fluorine-18–labeled l-DOPA in the healthy human brain, to thereby expand the understanding of extrastriatal sites of levodopa function, and to provide a broader foundation for clinical and research studies of fluoroDOPA accumulation in patients. Methods: The authors performed dynamic three-dimensional fluoroDOPA PET imaging in 10 healthy volunteers and analyzed the images visually and quantitatively. Twenty-eight regions of interest were applied to parametric images of the uptake rate constant (using the multiple-time graphic plot method with cortical input function) and also were used to quantitate regional radioactivity at 80 to 90 minutes. The authors correlated the uptake constants with published human regional neurotransmitter and decarboxylation data. Results: PET imaging with fluoroDOPA demonstrates trapping of labeled dopamine or its metabolites in substantial quantities in many areas of the brain other than the mesostriatal pathways, including considerable uptake in the serotonergic and noradrenergic areas of the hypothalamus and brainstem as well as in extrastriatal cerebral sites. Total fluoroDOPA uptake correlates best with the sum of catecholamine and indolamine concentrations in the brain and moderately well with regional activity of aromatic l-amino acid decarboxylase, but correlates poorly with extrastriatal dopamine concentration. Conclusion: Neither l-DOPA nor its radiolabeled analog fluoroDOPA is metabolized or accumulates specifically in dopaminergic or even catecholaminergic neurons. Substantial dopamine production within serotonin and norepinephrine neurons may play a role in either therapeutic effects or adverse effects of therapy with l-DOPA.

Production and Extraction of [10C]-CO2 from Proton Bombardment of Molten 10B2O3

This work describes the production of 10C (t12 = 19 s) from an enriched 10B2O3 target using a CTI RDS‐112 11 MeV proton cyclotron. Proton beam heating is used to raise the target to a molten state (∼ 1300 °C), enabling the activity to diffuse to the surface of the melt. An infrared thermocouple monitors the melt temperature. Helium sweep gas then transports the activity to flow‐through chemistry processing for human inhalation of 10CO2 for blood flow imaging with Positron Emission Tomography. The temperature‐related diffusion of activity out of the white‐hot molten glass target is discussed.