Assessment by airway ellipticity on cine-MRI to differentiate severe obstructive sleep apnea

Introduction: The severity of obstructive sleep apnea (OSA) is assessed by the apnea–hypopnea index (AHI) determined from polysomnography (PSG). However, PSG requires a specialized facility with well-trained specialists and takes overnight. Therefore, simple tools, which could distinguish severe OSA, have been needed before performing PSG. Objectives: We propose the new index using cine-MRI as a screening test to differentiate severe OSA patients, who would need PSG and proper treatment. Methods: Thirty-six patients with suspected OSA (mean age 54.6 y, mean AHI 52.6 events/h, 33 males) underwent airway cine-MRI at the fourth cervical vertebra level during 30 s of free breathing and PSG. The minimum airway ellipticity (AE) in 30 s duration was measured, and was defined as the severity of OSA. Patients were divided into severe OSA, not-severe OSA, and normal groups, according to PSG results. The comparison of AE between any two of the three groups was performed by Wilcoxon rank-sum test. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off of AE for identifying severe OSA patients. Results: The minimum AE for severe OSA was significantly lower than that for not-severe OSA and normal (severe, 0.17 ± 0.16; not severe, 0.31 ± 0.17; normal, 0.38 ± 0.19, P <.05). ROC analysis revealed that the optimal cutoff of the minimum AE 0.21 identified severe OSA patients, with an area under the curve of 0.75, 68% sensitivity, and 83% specificity. Conclusion: AE is a feasible quantitative index, and a promising screening test for detecting severe OSA patients.