title: Quantitative ultrashort echo time imaging for assessment of massive iron overload at 1.5 and 3 Tesla.
abstract: Hepatic iron content (HIC) quantification via transverse relaxation rate (R2*)-MRI using multi-gradient echo (mGRE) imaging is compromised toward high HIC or at higher fields due to the rapid signal decay. Our study aims at presenting an optimized 2D ultrashort echo time (UTE) sequence for R2* quantification to overcome these limitations.
  
  
  
  Two-dimensional UTE imaging was realized via half-pulse excitation and radial center-out sampling. The sequence includes chemically selective saturation pulses to reduce streaking artifacts from subcutaneous fat, and spatial saturation (sSAT) bands to suppress out-of-slice signals. The sequence employs interleaved multi-echo readout trains to achieve dense temporal sampling of rapid signal decays. Evaluation was done at 1.5 Tesla (T) and 3T in phantoms, and clinical applicability was demonstrated in five patients with biopsy-confirmed massively high HIC levels (>25 mg Fe/g dry weight liver tissue).
  
  
  
  In phantoms, the sSAT pulses were found to remove out-of-slice contamination, and R2* results were in excellent agreement to reference mGRE R2* results (slope of linear regression: 1.02/1.00 for 1.5/3T). UTE-based R2* quantification in patients with massive iron overload proved successful at both field strengths and was consistent with biopsy HIC values.
  
  
  
  The UTE sequence provides a means to measure R2* in patients with massive iron overload, both at 1.5T and 3T. Magn Reson Med 78:1839-1851, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.|Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
authors.forename: Axel J
authors.initials: AJ
authors.lastname: Krafft
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Ralf B
authors.initials: RB
authors.lastname: Loeffler
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Ruitian
authors.initials: R
authors.lastname: Song
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Aaryani
authors.initials: A
authors.lastname: Tipirneni-Sajja
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: M Beth
authors.initials: MB
authors.lastname: McCarville
authors.affiliation: OCMR, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Robson
authors.affiliation: Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Jane S
authors.initials: JS
authors.lastname: Hankins
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Hillenbrand
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019190:Iron Overload / Q000000981:diagnostic imaging*; D008099:Liver / Q000737:chemistry / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D013997:Time Factors
keywords: T2* quantification; UTE; half-pulse excitation; liver MRI; transfusional iron overload; ultrashort echo time imaging