Authors: Pardeep Kumar¹, Raman Kumar Joshi¹, Chandana Nagaraj¹, N. Sridhar Goud¹, Naren P Rao²  

Department of Neuroimaging and Interventional Radiology¹,

Psychiatry²

Background

Fluorine-18 [¹⁸F]flumazenil (FMZ) has been used for the assessment of the gamma amino butyric acid (GABA) receptors by positron emission tomography (PET). [¹¹C] or [¹⁸F]flumazenil have been used for PET imaging of various types of neurodisorders.  

Aims

To standardize and synthesize [¹⁸F]flumazenil using various combinations of the solid phase cartridges in order to minimize the loss of radiochemical yield during purification.

Methods

The precursor nitormazenil was procured from Syncom BV, Netherlands. The radio-fluorination was standardized for various parameters like temperature (130-160°C), precursor concentration (3-5 mg), various combination of SPE cartridges (HLB, tC18, C18 and alumina) and final product eluted by using 2.0 mL of 20% ethanol/ phosphate buffer (pH-4.0). The radiochemical purity was calculated by using Radio-HPLC.

Results and Conclusion

The combination of C18 and alumina cartridges gave the highest yield (15 ± 2 %) as compare to 1-2% by other two combination. The radiochemical purity was 95 ± 3 % with retention time at 15.4 ± 0.3 min (n = 10). [¹⁸F]flumazenil was synthesized with higher radiochemical purity and a simple automated method has been developed for the clinical use.