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-methy-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-methy-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 speparated 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 30min 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 NaH₂PO₄ as the HPLC mobile phase.