title: A medical device-grade T1 and ECV phantom for global T1 mapping quality assurance-the T1Mapping and ECV Standardization in cardiovascular magnetic resonance (T1MES) program.
abstract: BACKGROUND
  T1mapping and extracellular volume (ECV) have the potential to guide patient care and serve as surrogate end-points in clinical trials, but measurements differ between cardiovascular magnetic resonance (CMR) scanners and pulse sequences. To help deliver T1mapping to global clinical care, we developed a phantom-based quality assurance (QA) system for verification of measurement stability over time at individual sites, with further aims of generalization of results across sites, vendor systems, software versions and imaging sequences. We thus created T1MES: The T1 Mapping and ECV Standardization Program.
  
  
  METHODS
  A design collaboration consisting of a specialist MRI small-medium enterprise, clinicians, physicists and national metrology institutes was formed. A phantom was designed covering clinically relevant ranges of T1and T2in blood and myocardium, pre and post-contrast, for 1.5 T and 3 T. Reproducible mass manufacture was established. The device received regulatory clearance by the Food and Drug Administration (FDA) and Conformité Européene (CE) marking.
  
  
  RESULTS
  The T1MES phantom is an agarose gel-based phantom using nickel chloride as the paramagnetic relaxation modifier. It was reproducibly specified and mass-produced with a rigorously repeatable process. Each phantom contains nine differently-doped agarose gel tubes embedded in a gel/beads matrix. Phantoms were free of air bubbles and susceptibility artifacts at both field strengths and T1maps were free from off-resonance artifacts. The incorporation of high-density polyethylene beads in the main gel fill was effective at flattening the B1field. T1and T2values measured in T1MES showed coefficients of variation of 1 % or less between repeat scans indicating good short-term reproducibility. Temperature dependency experiments confirmed that over the range 15-30 °C the short-T1tubes were more stable with temperature than the long-T1tubes. A batch of 69 phantoms was mass-produced with random sampling of ten of these showing coefficients of variations for T1of 0.64 ± 0.45 % and 0.49 ± 0.34 % at 1.5 T and 3 T respectively.
  
  
  CONCLUSIONS
  The T1MES program has developed a T1mapping phantom to CE/FDA manufacturing standards. An initial 69 phantoms with a multi-vendor user manual are now being scanned fortnightly in centers worldwide. Future results will explore T1mapping sequences, platform performance, stability and the potential for standardization.
authors.affiliation: UCL Biological Mass Spectrometry Laboratory, Institute of Child Health and Great Ormond Street Hospital, 30 Guilford Street, London, UK.|NIHR University College London Hospitals Biomedical Research Center, Maple House Suite, Tottenham Court Road, London, W1T 7DN, UK.|Barts Heart Center, St Bartholomew's Hospital, West Smithfield, London, EC1A 7BE, UK.|UCL Institute of Cardiovascular Science, University College London, Gower Street, London, WC1E 6BT, UK.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Captur
authors.affiliation: CMR Department, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Gatehouse
authors.affiliation: National Institutes of Standards and Technology (NIST), Boulder, MS 818.03, 325 Broadway, Boulder, CO, 80305-3337, USA.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Keenan
authors.affiliation: Biomagnetics Group, School of Physics, University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.|NeuroImaging group, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, P.O. Box 217, 7500 AE, Enschede, Netherlands.
authors.forename: Friso G
authors.initials: FG
authors.lastname: Heslinga
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2 - 12, D-10587, Berlin, Germany.
authors.forename: Ruediger
authors.initials: R
authors.lastname: Bruehl
authors.affiliation: Cardiology, Charité, Medical Faculty of Humboldt-University Berlin ECRC and HELIOS Clinics, Berlin, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Prothmann
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Graves
authors.affiliation: Department of Physics, Imperial College London, Prince Consort Rd, London, SW7 2BB, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Eames
authors.affiliation: University of Milan-Bicocca, Piazza dell'Ateneo Nuovo 1, 20100, Milan, Italy.
authors.forename: Camilla
authors.initials: C
authors.lastname: Torlasco
authors.affiliation: San Raffaele Hospital, Via Olgettina 60, 20132, Milan, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Benedetti
authors.affiliation: Department of Clinical Biochemistry, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Donovan
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2 - 12, D-10587, Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Ittermann
authors.affiliation: Cardiovascular Biomedical Research Unit, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
authors.forename: Redha
authors.initials: R
authors.lastname: Boubertakh
authors.affiliation: Resonance Health, 278 Stirling Highway, Claremont, WA, 6010, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Bathgate
authors.affiliation: Resonance Health, 278 Stirling Highway, Claremont, WA, 6010, Australia.
authors.forename: Celine
authors.initials: C
authors.lastname: Royet
authors.affiliation: Resonance Health, 278 Stirling Highway, Claremont, WA, 6010, Australia.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Pang
authors.affiliation: Department of Medicine (Cardiovascular Division) Beth Israel Deaconess Medical Center, Harvard Medical School, Cardiology East Campus, Room E/SH455, 330 Brookline Ave, Boston, MA, 02215, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Nezafat
authors.affiliation: University of Virginia Health System, 1215 Lee St, PO Box 800158, Charlottesville, VA, 22908, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Salerno
authors.affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, 10 Center Drive, Building 10, Room B1D416, MSC1061, Bethesda, MD, 20892-1061, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Kellman
authors.affiliation: NIHR University College London Hospitals Biomedical Research Center, Maple House Suite, Tottenham Court Road, London, W1T 7DN, UK. j.moon@ucl.ac.uk.|Barts Heart Center, St Bartholomew's Hospital, West Smithfield, London, EC1A 7BE, UK. j.moon@ucl.ac.uk.|UCL Institute of Cardiovascular Science, University College London, Gower Street, London, WC1E 6BT, UK. j.moon@ucl.ac.uk.
authors.forename: James C
authors.initials: JC
authors.lastname: Moon
keywords: Phantom; Standardization; T1 mapping