The Rediscovery of Galligas

TO THE EDITOR: Recently, Borges et al. published an interesting study about ventilation distribution in piglets comparing Technegas (Vita Medical Ltd.) and ⁶⁸GaCl₃-labeled pseudogas (“Gallgas”) (1), on which we would like to comment.

The last big milestone in the development of aerosols that can be used routinely for lung ventilation scintigraphy was the introduction of Technegas by Bill Burch, produced simply in the now-widely-spread Technegas generator (2,3). After that, further labeling experiments with radionuclides other than ^99mTc, in particular positron emitters such as ⁶⁸Ga, were done in the 1990s to study their behavior in the Technegas generator (4).

The global shortage of molybdenum and consequently ^99mTc in 2009 forced a reevaluation of the use of the ⁶⁸Ga-labeled aerosol with the Technegas generator and PET/CT. We introduced it in human lung ventilation scintigraphy and called the aerosol Galligas (5). Subsequently, knowing that ⁶⁸Ga-labeled microspheres have been recognized for more than 30 y as a potential positron-emitting lung imaging agent (6), we combined the ⁶⁸Ga ventilation scan with a ⁶⁸Ga-based perfusion scan for patients in whom pulmonary embolism was suspected (7).

Regionally disturbed ventilation is well characterized in Technegas images by hilar and tracheal activity depots and a lower peripheral deposition of the ventilation agent. In our series of 15 patients suspected of having pulmonary embolism, 5 showed regionally disturbed ventilation.

The higher efficacy of the dedicated PET ring detector system than planar γ-camera imaging or SPECT allows the application of low-activity ⁶⁸Ga, resulting in an even lower radiation exposure than with ^99mTc-labeled compounds (7). Furthermore, the shorter physical half-life of ⁶⁸Ga (68 min) is sufficient for routine clinical use despite all the unexpected obstacles that can occur in the clinic, and both Galligas and ⁶⁸Ga-microspheres can be prepared from the same generator elution.

We do know that other research groups have had the idea of vaporizing various radionuclides (including ⁶⁸Ga) in the graphite boat of the Technegas generator (Ralf Bergmann, oral communication, February 2009; Hans-Jürgen Wester, oral communication, March 2011). However, to our knowledge, only our group has reported results (5).

• © 2011 by Society of Nuclear Medicine