title: Comparison of T1 mapping techniques for ECV quantification. Histological validation and reproducibility of ShMOLLI versus multibreath-hold T1 quantification equilibrium contrast CMR.
abstract: BACKGROUND
  Myocardial extracellular volume (ECV) is elevated in fibrosis or infiltration and can be quantified by measuring the haematocrit with pre and post contrast T1 at sufficient contrast equilibrium. Equilibrium CMR (EQ-CMR), using a bolus-infusion protocol, has been shown to provide robust measurements of ECV using a multibreath-hold T1 pulse sequence. Newer, faster sequences for T1 mapping promise whole heart coverage and improved clinical utility, but have not been validated.
  
  
  METHODS
  Multibreathhold T1 quantification with heart rate correction and single breath-hold T1 mapping using Shortened Modified Look-Locker Inversion recovery (ShMOLLI) were used in equilibrium contrast CMR to generate ECV values and compared in 3 ways.Firstly, both techniques were compared in a spectrum of disease with variable ECV expansion (n=100, 50 healthy volunteers, 12 patients with hypertrophic cardiomyopathy, 18 with severe aortic stenosis, 20 with amyloid). Secondly, both techniques were correlated to human histological collagen volume fraction (CVF%, n=18, severe aortic stenosis biopsies). Thirdly, an assessment of test:retest reproducibility of the 2 CMR techniques was performed 1 week apart in individuals with widely different ECVs (n=10 healthy volunteers, n=7 amyloid patients).
  
  
  RESULTS
  More patients were able to perform ShMOLLI than the multibreath-hold technique (6% unable to breath-hold). ECV calculated by multibreath-hold T1 and ShMOLLI showed strong correlation (r(2)=0.892), little bias (bias -2.2%, 95%CI -8.9% to 4.6%) and good agreement (ICC 0.922, range 0.802 to 0.961, p<0.0001). ECV correlated with histological CVF% by multibreath-hold ECV (r(2)= 0.589) but better by ShMOLLI ECV (r(2)= 0.685). Inter-study reproducibility demonstrated that ShMOLLI ECV trended towards greater reproducibility than the multibreath-hold ECV, although this did not reach statistical significance (95%CI -4.9% to 5.4% versus 95%CI -6.4% to 7.3% respectively, p=0.21).
  
  
  CONCLUSIONS
  ECV quantification by single breath-hold ShMOLLI T1 mapping can measure ECV by EQ-CMR across the spectrum of interstitial expansion. It is procedurally better tolerated, slightly more reproducible and better correlates with histology compared to the older multibreath-hold FLASH techniques.
authors.affiliation: The Heart Hospital, 16-18 Westmoreland Street, London, W1G 8PH, United Kingdom. james.moon@uclh.nhs.uk
authors.forename: Marianna
authors.initials: M
authors.lastname: Fontana
authors.forename: Steve K
authors.initials: SK
authors.lastname: White
authors.forename: Sanjay M
authors.initials: SM
authors.lastname: Banypersad
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sado
authors.forename: Viviana
authors.initials: V
authors.lastname: Maestrini
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Flett
authors.forename: Stefan K
authors.initials: SK
authors.lastname: Piechnik
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
authors.forename: Neil
authors.initials: N
authors.lastname: Roberts
authors.forename: James C
authors.initials: JC
authors.lastname: Moon
mesh_terms: D000328:Adult; D000368:Aged; D000686:Amyloidosis / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D001024:Aortic Valve Stenosis / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D001706:Biopsy; D062485:Breath Holding; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D003094:Collagen / Q000032:analysis; D003287:Contrast Media; D005260:Female; D005355:Fibrosis; D006571:Heterocyclic Compounds; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000737:chemistry / Q000473:pathology*; D009942:Organometallic Compounds; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012720:Severity of Illness Index
chemical_list: D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D003094:Collagen; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate