title: Inter-study reproducibility of left ventricular torsion and torsion rate quantification using MR myocardial feature tracking.
abstract: BACKGROUND
  To determine the inter-study reproducibility of MR feature tracking (MR-FT) derived left ventricular (LV) torsion and torsion rates for a combined assessment of systolic and diastolic myocardial function.
  
  
  METHODS
  Steady-state free precession (SSFP) cine LV short-axis stacks were acquired at 9:00 (Exam A), 9:30 (Exam B), and 14:00 (Exam C) in 16 healthy volunteers at 3 Tesla. SSFP images were analyzed offline using MR-FT to assess rotational displacement in apical and basal slices. Global peak torsion, peak systolic and peak diastolic torsion rates were calculated using different definitions ("twist", "normalized twist" and "circumferential-longitudinal (CL) shear angle"). Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation.
  
  
  RESULTS
  The different methods showed good inter-study reproducibility for global peak torsion (intraclass correlation coefficient [ICC]: 0.90-0.92; coefficient of variation [CoV]: 19.0-20.3%) and global peak systolic torsion rate (ICC: 0.82-0.84; CoV: 25.9-29.0%). Conversely, global peak diastolic torsion rate showed little inter-study reproducibility (ICC: 0.34-0.47; CoV: 40.8-45.5%). Global peak torsion as determined by the CL shear angle showed the best inter-study reproducibility (ICC: 0.90;CoV: 19.0%). MR-FT results were not measurably affected by diurnal variation between morning and afternoon scans (CL shear angle: 4.8 ± 1.4°, 4.8 ± 1.5°, and 4.1 ± 1.6° for Exam A, B, and C, respectively; P = 0.21).
  
  
  CONCLUSIONS
  MR-FT based derivation of myocardial peak torsion and peak systolic torsion rate has high inter-study reproducibility as opposed to peak diastolic torsion rate. The CL shear angle was the most reproducible parameter independently of cardiac anatomy and may develop into a robust tool to quantify cardiac rotational mechanics in longitudinal MR-FT patient studies.
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, The Rayne Institute, St Thomas' Hospital, King's College London, London, United Kingdom.|Institute for Diagnostic and Interventional Radiology, Georg-August-University Göttingen, Göttingen, Germany.|DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Germany.
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Kowallick
authors.affiliation: Portsmouth Hospitals NHS Trust, Portsmouth, United Kingdom.
authors.forename: Geraint
authors.initials: G
authors.lastname: Morton
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, The Rayne Institute, St Thomas' Hospital, King's College London, London, United Kingdom.|Department of Computer Science, University of Oxford, Oxford, United Kingdom.
authors.forename: Pablo
authors.initials: P
authors.lastname: Lamata
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, The Rayne Institute, St Thomas' Hospital, King's College London, London, United Kingdom.
authors.forename: Roy
authors.initials: R
authors.lastname: Jogiya
authors.affiliation: Children's Hospital and Medical Center, University of Nebraska College of Medicine, Omaha, Nebraska, USA.
authors.forename: Shelby
authors.initials: S
authors.lastname: Kutty
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Georg-August-University Göttingen, Göttingen, Germany.|DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Lotz
authors.affiliation: DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Germany.|Department of Cardiology and Pneumology, Georg-August-University Göttingen, Göttingen, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Hasenfuß
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, The Rayne Institute, St Thomas' Hospital, King's College London, London, United Kingdom.
authors.forename: Eike
authors.initials: E
authors.lastname: Nagel
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, The Rayne Institute, St Thomas' Hospital, King's College London, London, United Kingdom.
authors.forename: Amedeo
authors.initials: A
authors.lastname: Chiribiri
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, The Rayne Institute, St Thomas' Hospital, King's College London, London, United Kingdom.|DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Germany.|Department of Cardiology and Pneumology, Georg-August-University Göttingen, Göttingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schuster
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015588:Observer Variation; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014102:Torsion Abnormality / Q000473:pathology*; D018487:Ventricular Dysfunction, Left / Q000473:pathology*
keywords: cardiovascular magnetic resonance; circumferential longitudinal shear angle; feature tracking; inter-study reproducibility; torsion; twist