title: Validation of a new T2* algorithm and its uncertainty value for cardiac and liver iron load determination from MRI magnitude images.
abstract: OBJECTIVE
  To validate an automatic algorithm for offline T2* measurements, providing robust, vendor-independent T2*, and uncertainty estimates for iron load quantification in the heart and liver using clinically available imaging sequences.
  
  
  METHODS
  A T2* region of interest (ROI)-based algorithm was developed for robustness in an offline setting. Phantom imaging was performed on a 1.5 Tesla system, with clinically available multiecho gradient-recalled-echo (GRE) sequences for cardiac and liver imaging. A T2* single-echo GRE sequence was used as reference. Simulations were performed to assess accuracy and precision from 2000 measurements. Inter- and intraobserver variability was obtained in a patient study (n = 23).
  
  
  RESULTS
  Simulations: Accuracy, in terms of the mean differences between the proposed method and true T2* ranged from 0-0.73 ms. Precision, in terms of confidence intervals of repeated measurements, was 0.06-4.74 ms showing agreement between the proposed uncertainty estimate and simulations. Phantom study: Bias and variability were 0.26 ± 4.23 ms (cardiac sequence) and -0.23 ± 1.69 ms (liver sequence). Patient study: Intraobserver variability was similar for experienced and inexperienced observers (0.03 ± 1.44 ms versus 0.16 ± 2.33 ms). Interobserver variability was 1.0 ± 3.77 ms for the heart and -0.52 ± 2.75 ms for the liver.
  
  
  CONCLUSIONS
  The proposed algorithm was shown to provide robust T2* measurements and uncertainty estimates over the range of clinically relevant T2* values. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.
authors.affiliation: Lund Cardiac MR Group, Department of Clinical Physiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.|Department of Biomedical Engineering, Faculty of Engineering, Lund University, Sweden.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bidhult
authors.affiliation: Lund Cardiac MR Group, Department of Clinical Physiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.|Department of Computer Science and Biomedical Informatics, University of Thessaly, Lamia, Greece.
authors.forename: Christos G
authors.initials: CG
authors.lastname: Xanthis
authors.affiliation: Lund Cardiac MR Group, Department of Clinical Physiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.
authors.forename: Love Lindau
authors.initials: LL
authors.lastname: Liljekvist
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom.|BHF Centre of Research Excellence and NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trusts and King's College London, London, United Kingdom.
authors.forename: Gerald
authors.initials: G
authors.lastname: Greil
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom.|BHF Centre of Research Excellence and NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trusts and King's College London, London, United Kingdom.
authors.forename: Eike
authors.initials: E
authors.lastname: Nagel
authors.affiliation: Lund Cardiac MR Group, Department of Clinical Physiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.|Laboratory of Medical Informatics, School of Medicine, Aristotle University of Thessaloniki, Greece.
authors.forename: Anthony H
authors.initials: AH
authors.lastname: Aletras
authors.affiliation: Lund Cardiac MR Group, Department of Clinical Physiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.|Department of Biomedical Engineering, Faculty of Engineering, Lund University, Sweden.
authors.forename: Einar
authors.initials: E
authors.lastname: Heiberg
authors.affiliation: Lund Cardiac MR Group, Department of Clinical Physiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.|Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom.|BHF Centre of Research Excellence and NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trusts and King's College London, London, United Kingdom.|Department of Diagnostic Radiology, Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Hedström
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007223:Infant; D007501:Iron / Q000032:analysis*; D008099:Liver / Q000737:chemistry / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000737:chemistry; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D007501:Iron
keywords: MRI relaxometry; iron-load; offline image processing; uncertainty estimation; validation