title: Fetal cystic lung lesions: evaluation with magnetic resonance imaging.
abstract: OBJECTIVE
  To investigate the contribution of magnetic resonance imaging (MRI) to the diagnosis of fetal cystic lung lesions found on routine prenatal ultrasound (US).
  
  
  METHODS
  Experienced radiologists retrospectively reviewed 34 fetal MRI studies performed in 20 fetuses (from 20 to 35 gestational weeks; including 14 repeat studies 10 weeks after the initial MRI), focusing on shape, signal characteristics, feeding artery, volume change, and location of the cystic lesions. Diagnoses were confirmed after birth by postnatal multidetector computed tomography (MDCT) and/or surgery.
  
  
  RESULTS
  Bronchopulmonary sequestration (BPS) in the second trimester appeared as a well-defined, homogeneous, hyperintense mass (pure BPS) in eight cases or as a lobulated, inhomogeneous hyperintense mass (BPS mixed with congenital cystic adenomatoid malformation (CCAM)) in three cases. The feeding artery was visible in all 11 cases in the initial MRI, and regression of the mass was seen in 7 cases. As the mass regressed in the third trimester, the signal intensity decreased, becoming inhomogeneous, and the margins became lobulated. The mean initial ratio of the volume of the BPS lesion to the ipsilateral lung in lesions with partial regression was 82%; the mean initial ratio in lesions with nearly complete regression was 61%. CCAM (6) cases also appeared as a hyperintense lobulated mass, and as the lesions regressed, they decreased in size and signal intensity. As with BPS, the larger the lesion on initial MRI, the less likely it was to regress completely. Congenital lobar fluid overload in three cases appeared as a hyperintense, homogeneous lobe with stretched hilar vessels.
  
  
  CONCLUSIONS
  Prenatal MRI is useful as a diagnostic tool complementary to US for evaluating fetal cystic lung lesions. Smaller lung lesions (<60%) may regress completely.
authors.affiliation: Department of Radiology, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Yu-Peng
authors.initials: YP
authors.lastname: Liu
authors.forename: Chih-Ping
authors.initials: CP
authors.lastname: Chen
authors.forename: Shin-Lin
authors.initials: SL
authors.lastname: Shih
authors.forename: Yi-Fang
authors.initials: YF
authors.lastname: Chen
authors.forename: Fei-Shih
authors.initials: FS
authors.lastname: Yang
authors.forename: Su-Chiu
authors.initials: SC
authors.lastname: Chen
mesh_terms: D001808:Blood Vessels / Q000002:abnormalities; D001998:Bronchopulmonary Sequestration / Q000175:diagnosis*; D015615:Cystic Adenomatoid Malformation of Lung, Congenital / Q000175:diagnosis*; D005260:Female; D005333:Fetus / Q000002:abnormalities*; D006801:Humans; D008168:Lung / Q000002:abnormalities* / Q000098:blood supply; D008279:Magnetic Resonance Imaging; D008297:Male; D011296:Prenatal Diagnosis / Q000379:methods*; D011656:Pulmonary Emphysema / Q000175:diagnosis; D012189:Retrospective Studies