title: Reproducibility of cine displacement encoding with stimulated echoes (DENSE) cardiovascular magnetic resonance for measuring left ventricular strains, torsion, and synchrony in mice.
abstract: BACKGROUND
  Advanced measures of cardiac function are increasingly important to clinical assessment due to their superior diagnostic and predictive capabilities. Cine DENSE cardiovascular magnetic resonance (CMR) is ideal for quantifying advanced measures of cardiac function based on its high spatial resolution and streamlined post-processing. While many studies have utilized cine DENSE in both humans and small-animal models, the inter-test and inter-observer reproducibility for quantification of advanced cardiac function in mice has not been evaluated. This represents a critical knowledge gap for both understanding the capabilities of this technique and for the design of future experiments. We hypothesized that cine DENSE CMR would show excellent inter-test and inter-observer reproducibility for advanced measures of left ventricular (LV) function in mice.
  
  
  METHODS
  Five normal mice (C57BL/6) and four mice with depressed cardiac function (diet-induced obesity) were imaged twice, two days apart, on a 7T ClinScan MR system. Images were acquired with 15-20 frames per cardiac cycle in three short-axis (basal, mid, apical) and two long-axis orientations (4-chamber and 2-chamber). LV strain, twist, torsion, and measures of synchrony were quantified. Images from both days were analyzed by one observer to quantify inter-test reproducibility, while inter-observer reproducibility was assessed by a second observer's analysis of day-1 images. The coefficient of variation (CoV) was used to quantify reproducibility.
  
  
  RESULTS
  LV strains and torsion were highly reproducible on both inter-observer and inter-test bases with CoVs ≤ 15%, and inter-observer reproducibility was generally better than inter-test reproducibility. However, end-systolic twist angles showed much higher variance, likely due to the sensitivity of slice location within the sharp longitudinal gradient in twist angle. Measures of synchrony including the circumferential (CURE) and radial (RURE) uniformity of strain indices, showed excellent reproducibility with CoVs of 1% and 3%, respectively. Finally, peak measures (e.g., strains) were generally more reproducible than the corresponding rates of change (e.g., strain rate).
  
  
  CONCLUSIONS
  Cine DENSE CMR is a highly reproducible technique for quantification of advanced measures of left ventricular cardiac function in mice including strains, torsion and measures of synchrony. However, myocardial twist angles are not reproducible and future studies should instead report torsion.
authors: Departments of Pediatrics, Physiology and Medicine, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.
authors: Christopher M
authors: CM
authors: Haggerty
authors: Sage P
authors: SP
authors: Kramer
authors: Cassi M
authors: CM
authors: Binkley
authors: David K
authors: DK
authors: Powell
authors: Andrea C
authors: AC
authors: Mattingly
authors: Richard
authors: R
authors: Charnigo
authors: Frederick H
authors: FH
authors: Epstein
authors: Brandon K
authors: BK
authors: Fornwalt
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D019028:Magnetic Resonance Imaging, Cine; D051379:Mice; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction; D009765:Obesity / Q000150:complications; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D054159:Torsion, Mechanical; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D016277:Ventricular Function, Left
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