Given the sensitivity of hyperpolarized 3He MR imaging in depicting small ventilation defects in young asymptomatic cystic fibrosis patients, this technique could play a major role to study treatment at an early stage of the disease.
To assess the sensitivity of hyperpolarized helium 3 (3He) magnetic resonance (MR) imaging for the detection of peripheral airway obstruction in younger cystic fibrosis (CF) patients showing normal spirometric results (mean forced expiratory volume in 1 second [FEV1], 112% ± 14.5 [standard deviation]) and to observe the immediate effects of a single chest physical therapy (CPT) session, thereby comparing two image quantification techniques.
Materials and Methods
Ten pediatric CF patients (age range, 8–16 years) with normal spirometric results were included in this study after approval from the local research ethics committee. Spirometry followed by proton and hyperpolarized 3He three-dimensional lung imaging were performed with a 1.5-T MR unit before and after 20 minutes of CPT. The number of ventilation defects per image (VDI) and the ventilated lung fraction (VF), defined as the ratio of ventilated lung volume divided by total lung volume, were quantified.
Ventilation defects were found in all patients (mean VDI, 5.1 ± 1.9; mean global VF, 78.5% ± 12.3; and mean peripheral VF, 75.5% ± 17.1) despite normal spirometric results. After CPT, disparate changes in the distribution of ventilation defects were observed but the average VDI and VF did not change significantly (mean VDI, 5.1 ± 1.1; mean global VF, 83.5% ± 12.2; and mean peripheral VF, 80.3% ± 12.2). There was no correlation between FEV1 and VDI (ρ = −0.041, P = .863) or global VF (ρ = −0.196, P = .408) values but peripheral VF and VDI were correlated (ρ = −0.563, P = .011).
Although spirometric results indicate normal lung function, the mean VDI in patients (5.1) found in this study is well above the VDI in healthy subjects (1.6) reported in the literature. A single CPT session induces disparate changes in the distribution and extent of ventilation defects.
© RSNA, 2010
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Article HistoryReceived January 6, 2009; revision requested March 17; revision received September 8; accepted September 16; final version accepted October 26.
Published online: Mar 10 2010
Published in print: Apr 2010