title: Liver and heart MR relaxometry in iron loading: reproducibility of three methods.
abstract: OBJECTIVE
  To compare the derived T2* values and reproducibility of three methods used to assess iron-loading in heart and liver.
  
  
  METHODS
  In 23 pediatric patients, liver and cardiac gradient-echo imaging datasets (within-exam repeated sequence pairs) were evaluated. Data analyses compared derived relaxation values (average of pairs) and coefficient of variation (reproducibility of pairs).
  
  
  RESULTS
  T2* values showed differences across methods, with pixel-wise mean > average fit > pixel-wise median. Coefficient of variation was found to be lower (better) with pixel-wise median and average fit methods compared to the pixel-wise mean technique. Maximum coefficient of variation values were lowest for the pixel-wise median approach in both the heart and liver.
  
  
  CONCLUSIONS
  Differences in derived T2* values between methods must be considered when comparing values to established magnetic resonance imaging (MRI)-biopsy formulas. The pixel-wise median and average fit methods demonstrate substantial benefits in reproducibility compared to the pixel-wise mean method. Since minimal variation in measurement is critical for patient care, median processing of relaxometry data may be preferable in both tissue types.
authors.affiliation: Seattle Children's Hospital, Department of Radiology, Seattle, Washington, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Ferguson
authors.forename: Randolph K
authors.initials: RK
authors.lastname: Otto
authors.forename: Michael A
authors.initials: MA
authors.lastname: Bender
authors.forename: Orpheus
authors.initials: O
authors.lastname: Kolokythas
authors.forename: Seth D
authors.initials: SD
authors.lastname: Friedman
mesh_terms: D000293:Adolescent; D000741:Anemia, Aplastic / Q000473:pathology; D029503:Anemia, Diamond-Blackfan / Q000473:pathology; D000755:Anemia, Sickle Cell / Q000473:pathology; D002648:Child; D005260:Female; D006801:Humans; D007501:Iron / Q000737:chemistry*; D008099:Liver / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009206:Myocardium / Q000473:pathology*; D015203:Reproducibility of Results; D013789:Thalassemia / Q000473:pathology; D055815:Young Adult
chemical_list: D007501:Iron