AIM: We compared 68Gallium (68Ga)- and fluorescence-labeled microspheres for measurement of pulmonary perfusion distribution in anesthetized pigs without lung injury.

METHODS: In two mechanically ventilated pigs, the distribution of pulmonary perfusion was marked in vivo with 68Ga- and fluorescence-labeled microspheres in supine and prone position. After each injection, the distribution of 68Ga-labeled microspheres was measured in vivo with positron emission tomography/ computed tomography (PET/CT) in the position in which microspheres were injected and vice versa. The distribution of fluorescence-labeled microspheres was measured ex vivo. Perfusion distributions were compared between methods and postures within four lung regions and along the ventro-dorsal gradient. After each injection of 68Ga-labeled microspheres, changes in ventro-dorsal perfusion gradients induced by repositioning were compared for volume- and mass-normalized PET/CT measurements.

RESULTS: Regional and gradient analyses of in vivo and ex vivo measurements, respectively, consistently revealed higher pulmonary perfusion in dorsal than ventral regions in supine positioned animals. Both methods showed more pronounced perfusion gradients in supine compared to prone position. Changes in animal position were associated with alterations in the ventro-dorsal perfusion gradient when volume-, but not mass-normalization was conducted for PET/CT data.

CONCLUSIONS: Ex vivo fluorescence- and in vivo68Ga-labeled microspheres measurements revealed similar perfusion distributions. Mass-normalized perfusion measurements by 68Ga-labeled microspheres and PET/CT were not affected by positioning artifacts.