radiosynthesis of 11C-meta-(-) hydroxyephedrine and micro PET imaging

11C-meta-(-) Hydroxyephedrine (11C-(-) HED, 11C-HED) is a radiotracer suitable for mapping human sympathetic nervous system for heart failure, heart transplantation, arrhythmia and diabetic autonomic neuropathy and imaging tumors of the adrenal marrow. 11C-HED was synthesized by direct N-methylation of metaraminol with the 11C-methyl-iodine and purified by semi-preparative reversed-phase HPLC(Semi-HPLC). The uptake of myocardium was studied by co-injection of 11C-(-) HED with metaraminol in mice. The results showed that the by-products can be reduced with 11C-methyl-iodine as the N-methylation agents. HPLC purification was started with 3% EthOH in 0.24 moL/L NaH2PO4, and then switched to 10% EthOH in 0.24 moL/L NaH2PO4 after 10 min, through this process the precursor was separated from 11C-HED. Results of biodistribution showed that the uptake of 11C-HED in heard was blocked by co-injection of the metaraminol at 2 mg/kg, but the ID%/g of adrenals was increased. Micro PET imaging showed that the heart can be visualized at 10 and 30 min postinjection, but the uptake of myocardium was decreased and the washout was speeded after co-injection of the precursor. The chemical and radiochemical purity of 11C-(-) HED can be improved by using 3% EthOH in 0.24 moL/L NaH2PO4 and then switching to 10% EthOH in 0.24 moL/L NaH3PO4 as the HPLC mobile phase. (authors)