title: R2* imaging of transfusional iron burden at 3T and comparison with 1.5T.
abstract: OBJECTIVE
  To determine normative R2* values in the liver and heart at 3T, and establish the relationship between R2* at 3T and 1.5T over a range of tissue iron concentrations.
  
  
  METHODS
  A total of 20 healthy control subjects and 14 transfusion-dependent patients were scanned at 1.5T and 3T. At each field strength R2* imaging was performed in the liver and heart.
  
  
  RESULTS
  Normative R2* values in the liver were estimated from the control group to be 39.2 +/- 9.0 second(-1) at 1.5T and 69.1 +/- 21.9 second(-1) at 3T. Normative cardiac values were estimated as 23.4 +/- 2.2 second(-1) at 1.5T and 30.0 +/- 3.7 second(-1) at 3T. The combined R2* data from patients and control subjects exhibited a linear relationship between 3T and 1.5T. In the liver, the line of best fit to the 3T vs. 1.5T data had a slope of 2.00 +/- 0.06 and an intercept of -11 +/- 4 second(-1). In the heart, it had a slope of 1.88 +/- 0.14 and an intercept of -15 +/- 4 second(-1).
  
  
  CONCLUSIONS
  These preliminary data suggest that the iron-dependent component of R2* scales linearly with field strength over a wide range of tissue iron concentrations. The incidence of susceptibility artifacts may, however, also increase with field strength.
authors.affiliation: Radiology Department, Evanston Northwestern Healthcare, Evanston, Illinois 60201, USA. p-storey@northwestern.edu
authors.forename: Pippa
authors.initials: P
authors.lastname: Storey
authors.forename: Alexis A
authors.initials: AA
authors.lastname: Thompson
authors.forename: Christine L
authors.initials: CL
authors.lastname: Carqueville
authors.forename: John C
authors.initials: JC
authors.lastname: Wood
authors.forename: R Andrew
authors.initials: RA
authors.lastname: de Freitas
authors.forename: Cynthia K
authors.initials: CK
authors.lastname: Rigsby
mesh_terms: D000293:Adolescent; D000328:Adult; D000742:Anemia, Dyserythropoietic, Congenital / Q000378:metabolism*; D016477:Artifacts; D002138:Calibration; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007501:Iron / Q000378:metabolism*; D019190:Iron Overload / Q000175:diagnosis* / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008297:Male; D009206:Myocardium / Q000378:metabolism; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D017086:beta-Thalassemia / Q000378:metabolism*
chemical_list: D007501:Iron