title: Influence of phase correction of late gadolinium enhancement images on scar signal quantification in patients with ischemic and non-ischemic cardiomyopathy.
abstract: BACKGROUND
  Myocardial fibrosis imaging using late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) has been validated as a quantitative predictive marker for response to medical, surgical, and device therapy. To date, all such studies have examined conventional, non-phase corrected magnitude images.  However, contemporary practice has rapdily adopted phase-corrected image reconstruction. We sought to investigate the existence of any systematic bias between threshold-based scar quantification performed on conventional magnitude inversion recovery (MIR) and matched phase sensitive inversion recovery (PSIR) images.
  
  
  METHODS
  In 80 patients with confirmed ischemic (N = 40), or non-ischemic (n = 40) myocardial fibrosis, and also in a healthy control cohort (N = 40) without fibrosis, myocardial late enhancement was quantified using a Signal Threshold Versus Reference Myocardium technique (STRM) at ≥2, ≥3, and ≥5 SD threshold, and also using the Full Width at Half Maximal (FWHM) technique. This was performed on both MIR and PSIR images and values compared using linear regression and Bland-Altman analyses.
  
  
  RESULTS
  Linear regression analysis demonstrated excellent correlation for scar volumes between MIR and PSIR images at all three STRM signal thresholds for the ischemic (N = 40, r = 0.96, 0.95, 0.88 at 2, 3, and 5 SD, p < 0.0001 for all regressions), and non ischemic (N = 40, r = 0.86, 0.89, 0.90 at 2, 3, and 5 SD, p < 0.0001 for all regressions) cohorts. FWHM analysis demonstrated good correlation in the ischemic population (N = 40, r = 0.83, p < 0.0001). Bland-Altman analysis demonstrated a systematic bias with MIR images showing higher values than PSIR for ischemic (3.3 %, 3.9 % and 4.9 % at 2, 3, and 5 SD, respectively), and non-ischemic (9.7 %, 7.4 % and 4.1 % at ≥2, ≥3, and ≥5 SD thresholds, respectively) cohorts. Background myocardial signal measured in the control population demonstrated a similar bias of 4.4 %, 2.6 % and 0.7 % of the LV volume at 2, 3 and 5 SD thresholds, respectively. The bias observed using FWHM analysis was -6.9 %.
  
  
  CONCLUSIONS
  Scar quantification using phase corrected (PSIR) images achieves values highly correlated to those obtained on non-corrected (MIR) images. However, a systematic bias exists that appears exaggerated in non-ischemic cohorts. Such bias should be considered when comparing or translating knowledge between MIR- and PSIR-based imaging.
authors.affiliation: Robarts Research Institute, University of Western Ontario, London, Ontario, Canada. jstirrat@imaging.robarts.ca.
authors.forename: John
authors.initials: J
authors.lastname: Stirrat
authors.affiliation: Division of Cardiology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada. Sebastien.Joncas@USherbrooke.ca.|Stephenson Cardiac Imaging Centre, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada. Sebastien.Joncas@USherbrooke.ca.
authors.forename: Sebastien Xavier
authors.initials: SX
authors.lastname: Joncas
authors.affiliation: Departments of Medicine, Radiology, and Biomedical Engineering, University of Virginia, Charlottesville, VA, USA. MS5PC@hscmail.mcc.virginia.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Salerno
authors.affiliation: Robarts Research Institute, University of Western Ontario, London, Ontario, Canada. mdrangov@imaging.robarts.ca.|Stephenson Cardiac Imaging Centre, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada. mdrangov@imaging.robarts.ca.
authors.forename: Maria
authors.initials: M
authors.lastname: Drangova
authors.affiliation: Division of Cardiology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada. jawhit@ucalgary.ca.|Stephenson Cardiac Imaging Centre, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada. jawhit@ucalgary.ca.
authors.forename: James
authors.initials: J
authors.lastname: White
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D009202:Cardiomyopathies / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D016022:Case-Control Studies; D002921:Cicatrix / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D003287:Contrast Media; D005260:Female; D005355:Fibrosis; D019786:Gadolinium DTPA; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016014:Linear Models; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D009942:Organometallic Compounds; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013318:Stroke Volume; D016277:Ventricular Function, Left
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol; D019786:Gadolinium DTPA