F-Dopa as an amino acid tracer to detect brain tumors

A 57-yr-old woman suffering from light movement disorder of the left arm and hand was referred for 18F-Dopa PET. The PET study not only proved asymmetrically reduced dopamine uptake in the putamen (influx constant Ki right 0.0064/min, left 0.0086) but also revealed pathologically increased 18F-Dopa accumulation in the right frontal lobe. Further PET examinations demonstrated increased 11C-methionine uptake and low glucose metabolism in this right frontal region. MRI and 1H-MRSI showed a heterogeneous lesion with reduced N-acetyl-aspartate and increased choline and lactate, suggesting a mixed, low-grade glioma. In 15O-water studies, during intentional movements of one hand the respective motor areas were identified, indicating asymmetries due to the mass occupying lesion. The tumor could be removed in open surgery, thus sparing the motor areas; a mild postoperative motor deficit resolved to the presurgical state. Histology confirmed the diagnosis of a grade 2 oligo-astrocytoma. This case impressively demonstrates that 18F-Dopa can be used as an amino acid tracer for brain tumor detection in addition to its established application to assess aromatic acid decarboxylase activity.