Introduction Hyperpolarised ³He MRI provides high resolution images of lung ventilation and is more sensitive than spirometry to early changes in lung ventilation in cystic fibrosis (CF). Lung clearance index (LCI) is a global measure of ventilation heterogeneity which is also sensitive to early changes in the lungs in CF before spirometry. The aim of this study was to investigate the capability of hyperpolarised ³He MRI and LCI to detect ventilation changes in children with mild CF.

Methods 4 CF patients (FEV₁ 78 110% predicted) and 4 healthy volunteers have been assessed so far. ³He ventilation images were acquired at breath-hold following inhalation of hyperpolarised ³He, with 2.7x2.7x10mm resolution and full lung coverage using a 1.5T MRI system. The percentage of lung ventilated (VV%) was calculated as ³He ventilated volume divided by total lung volume segmented from ¹H MR images. LCI was measured using 0.2% SF6 and a modified Innocor gas analyser. LCI was performed sitting and repeated supine to mimic the position adopted for MRI scanning. Spirometry and plethysmography were also performed. Gas trapping was calculated as% difference in plethysmographic versus washout FRC.

Results Healthy volunteers had a mean (standard deviation) age of 8.8(1.5) years, FEV₁% predicted = 97(10) and gas trapping = 4.4(9.1)%. LCI sitting was 6.9,7.3,6.6 and 6.9, LCI supine was 7.3,7.5,6.8 and 6.4. Healthy volunteers had homogeneous ventilation in ³He ventilation images e.g. Fig1(a), and VV% = 94.5(2.8). CF patients had an age of 11.8(2.9) years, FEV₁% predicted = 95(13), and gas trapping = 8.7(11.0). LCI sitting was 7.7,6.6,6.6 and 9.1, LCI supine was 7.8,7.3,7.1 and 11.8. Ventilation abnormalities were observed using ³He MRI in all four CF patients scanned (Fig 1(b-e), with order corresponding to the LCI values given), and VV% = 89.2(2.6). 2 of the 4 CF patients had normal sitting and supine LCI and 2 of 3 had no evidence of gas trapping, but ³He MRI showed clear focal ventilation defects in all patients (b-d).

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Abstract S8 Figure 1.

Ventilation images from (a) a healthy volunteer and (b-e) patients with mild CF.

Conclusions High quality ³He MRI images can be produced in young children. Preliminary results suggest that hyperpolarised ³He ventilation MRI may be more sensitive to early ventilation changes in CF than LCI or conventional lung function tests.

Acknowledgements CF Trust funding