PET imaging of brain tumor with [methyl-11C]choline

Abstract

This article describes a new method of [11C]choline synthesis for intravenous injection. We aimed at the utilization of this compound for brain tumor imaging with PET.

Methods: After [11C]carbon dioxide production in a cyclotron and the subsequent [11C]methyl iodide synthesis, [methyl-11C]choline was synthesized by the reaction of [11C]methyl iodide with "neat" dimethylaminoethanol at 120 degrees C for 5 min. Purification was achieved by evaporation of the reactants followed by passage of the aqueous solution of the product through a cation-exchange resin cartridge. The time required for overall chemical processing, excluding the cyclotron operation, was 15 min. Radiochemical yield was > 98%. Radiochemical purity was > 98%. Chemical purity was > 90% (dimethylaminoethanol was the only possible impurity). Specific radioactivity of the product was > 133 GBq/mumol. The whole body distribution was examined in rabbits with PET. Clinical studies were performed in patients with brain tumor using PET after intravenous injection of 370 MBq of [11C]choline.

Results: In rabbits,[11C]choline was taken up from blood by various tissues very rapidly, and the radioactivity remaining in blood became almost negligible 5 min after intravenous injection. Taking advantage of this characteristic, we obtained stable tissue distribution images of human brain using PET. In patients with brain tumor, PET produced clearly delineated positive images of the tumors.

Conclusion: Carbon-11-choline can be used for obtaining clear images of brain tumor in PET.