Xenon ventilation CT using dual-source and dual-energy technique in children with bronchiolitis obliterans: correlation of xenon and CT density values with pulmonary function test results.

Abstract

Xenon ventilation CT using dual-source and dual-energy technique is a recently introduced, promising functional lung imaging method. To expand its clinical applications evidence of additional diagnostic value of xenon ventilation CT over conventional chest CT is required.
To evaluate the usefulness of xenon ventilation CT using dual-source and dual-energy technique in children with bronchiolitis obliterans (BO).
Seventeen children (age 7-18 years; 11 boys) with BO underwent xenon ventilation CT using dual-source and dual-energy technique. Xenon and CT density values were measured in normal and hyperlucent lung regions on CT and were compared between the two regions. Volumes of hyperlucent regions and ventilation defects were calculated with thresholds determined by visual and histogram-based analysis. Indexed volumes of hyperlucent lung regions and ventilation defects were correlated with pulmonary function test results. Effective doses of xenon CT were calculated.
Xenon (14.6 +/- 6.4 HU vs 26.1 +/- 6.5 HU; P < 0.001) and CT density (-892.8 +/- 25.4 HU vs -812.3 +/- 38.7 HU; P < 0.001) values were significantly lower in hyperlucent regions than in normal lung regions. Xenon and CT density values showed significant positive correlation for the entire lung in 16 children (gamma = 0.55 +/- 0.17, P < 0.001 or =0.017) and for hyperlucent regions in 13 children (gamma = 0.44 +/- 0.16, P < 0.001 or =0.001-0.019). Indexed volumes and volume percentages of hyperlucent lung regions and ventilation defects showed strong negative correlations with forced expiratory volume [FEV1, (gamma = -0.64--0.85, P <or= 0.006)], FEV1/forced vital capacity [FVC, (gamma = -0.63--0.84, P <or= 0.008), and forced midexpiratory flow rate [FEF(25-75), (gamma = -0.68--0.88, P <or= 0.002). Volume percentages of xenon ventilation defects (35.0 +/- 16.4%) were not significantly different from those of hyperlucent lung regions (38.2 +/- 18.6%). However, mismatches between the volume percentages were variable up to 21.4-33.3%. Mean effective dose of xenon CT was 1.9 +/- 0.5 mSv.
In addition to high-resolution anatomic information, xenon ventilation CT using dual-source and dual-energy technique demonstrates impaired regional ventilation and its heterogeneity accurately in children with BO without additional radiation exposure.