Assessment of Airway Distribution of Transnasal Solutions in Mice by PET/CT Imaging

Purpose Transnasal administration is one of the most common routes for allergen challenge in mouse models of airway diseases. Although this technique is widely used, neither the amount of allergen that reaches the lung nor its airway distribution has been well established. We used positron emission tomography (PET) and computed tomography (CT) to examine the anatomical distribution of a solution containing a tracer immediately after transnasal delivery and to determine the possible influence of age and administered volume. Procedures Forty-six female BALB/c mice were divided into three groups according to instillation volume and age: (A) 15 μl, 8–10 weeks old ( N = 10), (B) 30 μl, 8–10 weeks old ( N = 20), and (C) 30 μl, 32 weeks old ( N = 16). Anesthetized animals underwent a dynamic scan in a dedicated small-animal PET scanner immediately after transnasal administration of a solution containing 18 FDG. Regions of interest were used to obtain quantitative data. Animals were also imaged with a small-animal CT scanner to obtain complementary anatomical information. Results Mean ± SD (5.69 ± 4.51%) of the solution administered reached the lungs in group A, 41.84 ± 8.03% in group B, and 36.65 ± 16.15% in group C. A comparable percentage was delivered to the left and right lungs in all the groups. Analysis of variance revealed a significant difference between the groups in the proportion of the solution that reached the lungs depending on the injection volume ( P