title: Real-time 3D magnetic resonance imaging of the pharyngeal airway in sleep apnea.
abstract: OBJECTIVE
  To investigate the feasibility of real-time 3D magnetic resonance imaging (MRI) with simultaneous recording of physiological signals for identifying sites of airway obstruction during natural sleep in pediatric patients with sleep-disordered breathing.
  
  
  METHODS
  Experiments were performed using a three-dimensional Fourier transformation (3DFT) gradient echo sequence with prospective undersampling based on golden-angle radial spokes, and L1-norm regularized iterative self-consistent parallel imaging (L1-SPIRiT) reconstruction. This technique was demonstrated in three healthy adult volunteers and five pediatric patients with sleep-disordered breathing. External airway occlusion was used to induce partial collapse of the upper airway on inspiration and test the effectiveness of the proposed imaging method. Apneic events were identified using information available from synchronized recording of mask pressure and respiratory effort.
  
  
  RESULTS
  Acceptable image quality was obtained in seven of eight subjects. Temporary airway collapse induced via inspiratory loading was successfully imaged in all three volunteers, with average airway volume reductions of 63.3%, 52.5%, and 33.7%. Central apneic events and associated airway narrowing/closure were identified in two pediatric patients. During central apneic events, airway obstruction was observed in the retropalatal region in one pediatric patient.
  
  
  CONCLUSIONS
  Real-time 3D MRI of the pharyngeal airway with synchronized recording of physiological signals is feasible and may provide valuable information about the sites and nature of airway narrowing/collapse during natural sleep.
authors.affiliation: Ming Hsieh Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Yoon-Chul
authors.initials: YC
authors.lastname: Kim
authors.forename: R Marc
authors.initials: RM
authors.lastname: Lebel
authors.forename: Ziyue
authors.initials: Z
authors.lastname: Wu
authors.forename: Sally L Davidson
authors.initials: SL
authors.lastname: Ward
authors.forename: Michael C K
authors.initials: MC
authors.lastname: Khoo
authors.forename: Krishna S
authors.initials: KS
authors.lastname: Nayak
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D003199:Computer Systems; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D010614:Pharynx / Q000473:pathology* / Q000503:physiopathology; D017286:Polysomnography / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D055815:Young Adult
keywords: MRI; airway obstruction; constrained reconstruction; parallel imaging; sleep apnea; upper airway