Preparation and assessment of F-18 fluorogas for lung scintigraphy

Objectives In addition to radioactive gases (Xe-133/127, Kr-81m), Tc-99m-labeled aerosols of carbon particles have been utilized for scintigraphic imaging of lung ventilation. Recently, a Ga-68 labeled pseudogas was described. We herein describe our investigations in the production of a F-18-pseudogas (Fluorogas) via the established method for the production of Tc-99-pseudogas.

Methods A carbon crucible was filled with approx. 0.1 ml F-18-fluoride solution (~5 mCi) eluted from a standard anion-exchange cartridge with aqueous K2CO3, preconditioned with 96% EtOH, and inserted in a commercially available Technegas generator (Tetley, Australia). Subsequently, the standard program for generation of particles was initiated, consisting of a warming-phase while blowing pure argon gas over the top of the crucible for 6 min, followed by heating to a temperature of 2500°C. To demonstrate the general applicability of this method to nonvolatile F-18 radiopharmaceuticals, further experiments with FDG under identical conditions were performed. Male healthy volunteers (n = 3) inhaled Fluorogas from the apparatus. PET/CT scans of the lungs were taken from 5 min after inhalation (3 bed-positions, 3 min/frame).

Results Non-optimized productions allowed for the preparation of > 1 mCi Fluorogas from a 5 mCi fluoride or FDG loaded into the crucible. Fluorogas-PET demonstrated similar activity pattern in the lungs as that obtained with Technegas, i.e. homogenous distribution of activity over the entire lung parenchyma, including the peripheral areas, with only minor activity in the bronchi.

Conclusions The results from this proof of concept study indicate that commercially available Technegas generators can be exploited for Fluorogas production using fluoride or FDG, and presumably other non-volatile F-18 labeled pharmaceuticals. Fluorogas-PET showed the typical activity pattern in the lungs obtained with Technegas and is a promising approach for differential diagnosis e.g. acute lung embolism