title: Accuracy and reproducibility of semi-automated late gadolinium enhancement quantification techniques in patients with hypertrophic cardiomyopathy.
abstract: BACKGROUND
  The presence and extent of late gadolinium enhancement (LGE) has been associated with adverse events in patients with hypertrophic cardiomyopathy (HCM). Signal intensity (SI) threshold techniques are routinely employed for quantification; Full-Width at Half-Maximum (FWHM) techniques are suggested to provide greater reproducibility than Signal Threshold versus Reference Mean (STRM) techniques, however the accuracy of these approaches versus the manual assignment of optimal SI thresholds has not been studied. In this study, we compared all known semi-automated LGE quantification techniques for accuracy and reproducibility among patients with HCM.
  
  
  METHODS
  Seventy-six HCM patients (51 male, age 54 ± 13 years) were studied. Total LGE volume was quantified using 7 semi-automated techniques and compared to expert manual adjustment of the SI threshold to achieve optimal segmentation. Techniques tested included STRM based thresholds of >2, 3, 4, 5 and 6 SD above mean SI of reference myocardium, the FWHM technique, and the Otsu-auto-threshold (OAT) technique. The SI threshold chosen by each technique was recorded for all slices. Bland-Altman analysis and intra-class correlation coefficients (ICC) were reported for each semi-automated technique versus expert, manually adjusted LGE segmentation. Intra- and inter-observer reproducibility assessments were also performed.
  
  
  RESULTS
  Fifty-two of 76 (68%) patients showed LGE on a total of 202 slices. For accuracy, the STRM >3SD technique showed the greatest agreement with manual segmentation (ICC = 0.97, mean difference and 95% limits of agreement = 1.6 ± 10.7 g) while STRM >6SD, >5SD, 4SD and FWHM techniques systematically underestimated total LGE volume. Slice based analysis of selected SI thresholds similarly showed the STRM >3SD threshold to most closely approximate manually adjusted SI thresholds (ICC = 0.88). For reproducibility, the intra- and inter-observer reproducibility of the >3SD threshold demonstrated an acceptable mean difference and 95% limits of agreement of -0.5 ± 6.8 g and -0.9 ± 5.6 g, respectively.
  
  
  CONCLUSIONS
  FWHM segmentation provides superior reproducibility, however systematically underestimates total LGE volume compared to manual segmentation in patients with HCM. The STRM >3SD technique provides the greatest accuracy while retaining acceptable reproducibility and may therefore be a preferred approach for LGE quantification in this population.
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. ymikami@ucalgary.ca.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mikami
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. loukolman@gmail.com.
authors.forename: Louis
authors.initials: L
authors.lastname: Kolman
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. sebastien.joncas@usherbrooke.ca.
authors.forename: Sebastien X
authors.initials: SX
authors.lastname: Joncas
authors.affiliation: Imaging Research Laboratory - Robarts Research Institute, Western University, London, ON, Canada. jstirrat2015@meds.uwo.ca.
authors.forename: John
authors.initials: J
authors.lastname: Stirrat
authors.affiliation: Imaging Research Laboratory - Robarts Research Institute, Western University, London, ON, Canada. david.scholl@mail.utoronto.ca.
authors.forename: David
authors.initials: D
authors.lastname: Scholl
authors.affiliation: Imaging Research Laboratory - Robarts Research Institute, Western University, London, ON, Canada. mrajchl@robarts.ca.
authors.forename: Martin
authors.initials: M
authors.lastname: Rajchl
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. carmen.lydell@gmail.com.|Diagnostic Imaging, University of Calgary, Calgary, AB, Canada. carmen.lydell@gmail.com.
authors.forename: Carmen P
authors.initials: CP
authors.lastname: Lydell
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. sgweeks@ucalgary.ca.|Cardiac Sciences, University of Calgary, Calgary, AB, Canada. sgweeks@ucalgary.ca.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Weeks
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. ahowarth@ucalgary.ca.|Cardiac Sciences, University of Calgary, Calgary, AB, Canada. ahowarth@ucalgary.ca.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Howarth
authors.affiliation: Stephenson Cardiac Imaging Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. jawhit@ucalgary.ca.|Cardiac Sciences, University of Calgary, Calgary, AB, Canada. jawhit@ucalgary.ca.
authors.forename: James A
authors.initials: JA
authors.lastname: White
mesh_terms: D000328:Adult; D000368:Aged; D001331:Automation; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D003287:Contrast Media; D005355:Fibrosis; D019786:Gadolinium DTPA; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology*; D009942:Organometallic Compounds; D011237:Predictive Value of Tests; D012042:Registries; D015203:Reproducibility of Results; D013318:Stroke Volume; D016277:Ventricular Function, Left
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol; D019786:Gadolinium DTPA