¹⁸F-FDG Uptake Rate Is a Biomarker of Eosinophilic Inflammation and Airway Response in Asthma

Example images. First row: Axial CT slice through RML and RUL, where allergen and diluent, respectively, were administered. Green border shows approximate location of RML and RUL. Second row: Fused perfusion images from ¹³NN-saline PET scan during breath-hold and CT. Perfusion is reduced in allergen region but normal in diluent region. Third row: Fused end-washout image from ¹³NN ventilation scan and CT. Ventilation-defective area in region of allergen challenge manifests as tracer retention at end of washout. In contrast, no residual tracer was present in diluent region by end of washout. Fourth row: ¹⁸F-FDG scan showing increased uptake in allergen region, compared with diluent region.

Perfusion and ventilation. Mean-normalized perfusion and ventilation are substantially lower in allergen-challenged region than in diluent region (*P < 0.001 for each comparison).

Airway response. Aspect ratio was calculated as average airway wall area divided by average total airway area. Because we had no baseline CT scan for comparison, we chose other airways of similar size (within 25%) and calculated their aspect ratio. These were used as control airways for comparison. Baseline (lingula) and diluent airways are similar in aspect ratio to other airways of similar size (baseline-control and diluent-control, respectively). Allergen-challenged airway has larger aspect ratio (meaning either thicker wall or smaller inner lumen or both) than other airways of similar size (allergen compared with allergen-control, P < 0.05).

Functional variables vs. K_i. Clockwise from upper left: , , relative aspect ratio, and Fgas. Each symbol represents individual subject, with open symbols representing diluent and closed symbols allergen.