title: Inter-examination precision of magnitude-based MRI for estimation of segmental hepatic proton density fat fraction in obese subjects.
abstract: OBJECTIVE
  To prospectively describe magnitude-based multi-echo gradient-echo hepatic proton density fat fraction (PDFF) inter-examination precision at 3 Tesla (T).
  
  
  METHODS
  In this prospective, Institutional Review Board-approved, Health Insurance Portability and Accountability Act (HIPAA) compliant study, written informed consent was obtained from 29 subjects (body mass indexes > 30 kg/m2). Three 3T MRI examinations were obtained over 75-90 min. Segmental, lobar, and whole liver PDFF were estimated (using three, four, five, or six echoes) by magnitude-based multi-echo MRI in colocalized regions of interest. For estimate (using three, four, five, or six echoes), at each anatomic level (segmental, lobar, whole liver), three inter-examination precision metrics were computed: intra-class correlation coefficient (ICC), standard deviation (SD), and range.
  
  
  RESULTS
  Magnitude-based PDFF estimates using each reconstruction method showed excellent inter-examination precision for each segment (ICC ≥ 0.992; SD ≤ 0.66%; range ≤ 1.24%), lobe (ICC ≥ 0.998; SD ≤ 0.34%; range ≤ 0.64%), and the whole liver (ICC = 0.999; SD ≤ 0.24%; range ≤ 0.45%). Inter-examination precision was unaffected by whether PDFF was estimated using three, four, five, or six echoes.
  
  
  CONCLUSIONS
  Magnitude-based PDFF estimation shows high inter-examination precision at segmental, lobar, and whole liver anatomic levels, supporting its use in clinical care or clinical trials. The results of this study suggest that longitudinal hepatic PDFF change greater than 1.6% is likely to represent signal rather than noise.
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California at San Diego, San Diego, California, USA; Alpert Medical School of Brown University, Providence, Rhode Island, USA.
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Negrete
authors.forename: Michael S
authors.initials: MS
authors.lastname: Middleton
authors.forename: Lisa
authors.initials: L
authors.lastname: Clark
authors.forename: Tanya
authors.initials: T
authors.lastname: Wolfson
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Gamst
authors.forename: Jessica
authors.initials: J
authors.lastname: Lam
authors.forename: Chris
authors.initials: C
authors.lastname: Changchien
authors.forename: Ivan M
authors.initials: IM
authors.lastname: Deyoung-Dominguez
authors.forename: Gavin
authors.initials: G
authors.lastname: Hamilton
authors.forename: Rohit
authors.initials: R
authors.lastname: Loomba
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Schwimmer
authors.forename: Claude B
authors.initials: CB
authors.lastname: Sirlin
mesh_terms: D050154:Adiposity; D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis* / Q000503:physiopathology*; D015588:Observer Variation; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: PDFF; inter-examination precision; magnitude-based MRI; proton density fat fraction; steatosis