[18F]FDG PET/MR to assess disease extension and inflammation in children and young adults with primary ciliary dyskinesia.

Background: Primary ciliary dyskinesia (PCD) is a rare condition characterized by ciliary dysfunction, impaired mucociliary clearance and mucus accumulation in the airways.

Purpose: Our aim was to evaluate the performance of [18F]FDG PET/MR in assessing structural and inflammatory pulmonary features in patients with PCD, using high-resolution CT (HRCT) as the gold-standard reference.

Materials and methods: We recruited patients with PCD (≥ 7 years) regularly followed at our Regional Center for PCD. They underwent chest HRCT and [18F]FDG PET/MR using sequences optimized for the morpho-functional study of the lung. Parametric PET images were obtained by dividing each voxel by the mean value in a reference area. The volume of interest (VOI in cm³), named Metabolic Inflammatory Volume (MIV), was calculated by thresholding the PET parametric image using a value twice the mean of the reference area. Standardized Uptake Value (SUV) Max, SUV mean, Total Lesion Glycolysis (TLG) and MIV were recorded. HRCT and MR were analyzed using the Eichinger score.

Results: Sixteen patients were enrolled. The Bland-Altman plot showed good agreement between HRCT and MR scores. Cumulative HRCT and MR scores correlated significantly with SUV mean score (HRCT: p = 0.02, r_s=0.6; MR: p = 0.006, r_s=0.66) and MIV (HRCT: p = 0.003, r_s =0.7; MR: p = 0.004, r_s =0.69). Total HRCT and MR scores and MIV score inversely correlated with spirometric parameters.

Conclusion: PET/MR proved to be accurate in evaluating disease extent in PCD. It enabled the simultaneous assessment of structural damage and lung inflammation, both of which resulted inversely related to lung function. PET/MR is a promising tool for PCD monitoring.