[F-18]Sodium fluoride "on-demand": An answer to reliance on technetium diphosphonates

Abstract

1303

Objectives: To have [F-18]NaF available "as needed". The raw F-18 fluoride (18F-) will be from unreacted 18F- used in earlier FDG production that is trapped on Al2O3. Utilize well established recycling alumina technology practiced in rural defluorination projects.

Methods: Remove the Al2O3 SPE unit from the FDG purification unit at a suitable time after completion of FDG synthesis. Flush the SPE unit with 10 mL H2O using a motorized syringe to remove any residual FDG activity. Follow this with 200 mM NaOH @ 1 mL/min. The accessible 18F- was typically eluted with the first 8 mL. The resultant eluant was neutralized with HCl, which could be adjusted to give an isotonic solution if desired. During the neutralization insoluble Al salts were generated that were removed by filtration prior to final sterile filtration. TLC, HPLC, and IC analysis and gamma spectrometry were conducted to determine the presence of 18F- and absence of other radiochemical and radionuclidic impurities.

Results: [F-18]Fluoride that was trapped on Al2O3 during FDG synthesis could be readily recovered in reasonable yield by elution of the activity from the SPE unit with NaOH followed by neutralization, filtration of Al species, and final sterile filtration. TLC, HPLC and ion chromatography showed the only radiochemical present was 18F-. Gamma spectroscopy showed no significant contamination from any other radionuclide - especially those associated with the target chamber and foil.

Conclusions: We have demonstrated that we can recover unreacted [F-18]Fluoride trapped during FDG synthesis on Al2O3. At the end of a multi-Ci FDG run typically many hundreds of mCi of 18F- have not been incorporated into FDG. This represents a valuable source of material that is otherwise disposed of as radioactive waste. The material that we recover is suitable for bone scans using PET.