title: Magnetic resonance imaging phantoms for quality-control of myocardial T1 and ECV mapping: specific formulation, long-term stability and variation with heart rate and temperature.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) phantoms are routinely used for quality assurance in MRI centres; however their long term stability for verification of myocardial T1/ extracellular volume fraction (ECV) mapping has never been investigated.
  
  
  METHODS
  Nickel-chloride agarose gel phantoms were formulated in a reproducible laboratory procedure to mimic blood and myocardial T1 and T2 values, native and late after Gadolinium administration as used in T1/ECV mapping. The phantoms were imaged weekly with an 11 heart beat MOLLI sequence for T1 and long TR spin-echo sequences for T2, in a carefully controlled reproducible manner for 12 months.
  
  
  RESULTS
  There were only small relative changes seen in all the native and post gadolinium T1 values (up to 9.0 % maximal relative change in T1 values) or phantom ECV (up to 8.3 % maximal relative change of ECV, up to 2.2 % maximal absolute change in ECV) during this period. All native and post gadolinium T2 values remained stable over time with <2 % change. Temperature sensitivity testing showed MOLLI T1 values in the long T1 phantoms increasing by 23.9 ms per degree increase and short T1 phantoms increasing by 0.3 ms per degree increase. There was a small absolute increase in ECV of 0.069 % (~0.22 % relative increase in ECV) per degree increase. Variation in heart rate testing showed a 0.13 % absolute increase in ECV (~0.45 % relative increase in ECV) per 10 heart rate increase.
  
  
  CONCLUSIONS
  These are the first phantoms reported in the literature modeling T1 and T2 values for blood and myocardium specifically for the T1mapping/ECV mapping application, with stability tested rigorously over a 12 month period. This work has significant implications for the utility of such phantoms in improving the accuracy of serial scans for myocardial tissue characterisation by T1 mapping methods and in multicentre work.
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK. V.Vassiliou@rbht.nhs.uk.|Imperial College, National Heart and Lung Institute, London, UK. V.Vassiliou@rbht.nhs.uk.
authors.forename: Vassilios S
authors.initials: VS
authors.lastname: Vassiliou
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Ee Ling
authors.initials: EL
authors.lastname: Heng
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Gatehouse
authors.affiliation: Department of Biochemistry, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Donovan
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Raphael
authors.affiliation: Siemens Medical Solutions USA, Inc, Chicago, USA.
authors.forename: Shivraman
authors.initials: S
authors.lastname: Giri
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Sonya V
authors.initials: SV
authors.lastname: Babu-Narayan
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gatzoulis
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Dudley J
authors.initials: DJ
authors.lastname: Pennell
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Prasad
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.|Imperial College, National Heart and Lung Institute, London, UK.
authors.forename: David N
authors.initials: DN
authors.lastname: Firmin
keywords: Agarose; Nickel; Phantoms; Stability; T1 mapping