title: Quantitative assessment of regional myocardial function with MR-tagging in a multi-center study: interobserver and intraobserver agreement of fast strain analysis with Harmonic Phase (HARP) MRI.
abstract: OBJECTIVE
  To assess the reproducibility of Harmonic Phase (HARP) analysis of myocardial MR tagged images acquired in the Multi-Center Study of Atherosclerosis (MESA).
  
  
  METHODS
  Using the HARP method, three independent observers performed two separate quantitative strain analyses of myocardial cine MR-tagging images blindly in 24 participants. The images were obtained in four different centers and analyzed at a single core lab. Each study comprised 3 short-axis slices subdivided in 12 segments (24 x 3 x 12 = 864 segments), each with three layers. Normal strains (circumferential [Ecc] and radial [Err]), principal strains (Lambda1, Lambda2), and the angle alpha (between Ecc-Lambda2) were calculated. Intraclass correlation coefficient (R) for peak systolic strains, and all pooled systolic and diastolic strain data were used to determine inter- and intraobserver agreement. Two observers also visually graded study quality. R values were related to the image quality in different myocardial regions and layers.
  
  
  RESULTS
  Overall, HARP yielded an excellent inter- and intraobserver agreement for peak systolic strain data (for Ecc, R = 0.84 and 0.89, respectively) and all systolic pooled data (for Ecc, interobserver R = 0.82, intraobserver R = 0.69-0.76). Both inter and intraobserver agreement were lower for diastolic pooled data (R = 0.69 and 0.58-0.62, respectively). There was a direct relationship between image quality and performance of the HARP analysis, with increasing inter- and intraobserver R values in studies with longer tag persistence. Both inter- and intraobserver agreement were better in the anterior and septal myocardial regions, and in the midwall layer. The intraobserver agreement was similar among the three observers.
  
  
  CONCLUSIONS
  Employing the HARP method for quantitative strain analysis of myocardial MR tagged images provides a high inter- and intraobserver agreement. These good results are obtained in case of good to excellent MR image quality.
authors.affiliation: The Russell H. Morgan Department of Radiology and Radiological Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Castillo
authors.forename: Nael F
authors.initials: NF
authors.lastname: Osman
authors.forename: Boaz D
authors.initials: BD
authors.lastname: Rosen
authors.forename: Iman
authors.initials: I
authors.lastname: El-Shehaby
authors.forename: Li
authors.initials: L
authors.lastname: Pan
authors.forename: Michael
authors.initials: M
authors.lastname: Jerosch-Herold
authors.forename: Shenghan
authors.initials: S
authors.lastname: Lai
authors.forename: David A
authors.initials: DA
authors.lastname: Bluemke
authors.forename: João A C
authors.initials: JA
authors.lastname: Lima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D016037:Single-Blind Method