title: 2D cine DENSE with low encoding frequencies accurately quantifies cardiac mechanics with improved image characteristics.
abstract: BACKGROUND
  Displacement Encoding with Stimulated Echoes (DENSE) encodes displacement into the phase of the magnetic resonance signal. The encoding frequency (ke) maps the measured phase to tissue displacement while the strength of the encoding gradients affects image quality. 2D cine DENSE studies have used a ke of 0.10 cycles/mm, which is high enough to remove an artifact-generating echo from k-space, provide high sensitivity to tissue displacements, and dephase the blood pool. However, through-plane dephasing can remove the unwanted echo and dephase the blood pool without relying on high ke. Additionally, the high sensitivity comes with the costs of increased phase wrapping and intra-voxel dephasing. We hypothesized that ke below 0.10 cycles/mm can be used to improve image characteristics and provide accurate measures of cardiac mechanics.
  
  
  METHODS
  Spiral cine DENSE images were obtained for 10 healthy subjects and 10 patients with a history of heart disease on a 3 T Siemens Trio. A mid-ventricular short-axis image was acquired with different ke: 0.02, 0.04, 0.06, 0.08, and 0.10 cycles/mm. Peak twist, circumferential strain, and radial strain were compared between acquisitions employing different ke using Bland-Altman analyses and coefficients of variation. The percentage of wrapped pixels in the phase images at end-systole was calculated for each ke. The dephasing of the blood signal and signal to noise ratio (SNR) were also calculated and compared.
  
  
  RESULTS
  Negligible differences were seen in strains and twist for all ke between 0.04 and 0.10 cycles/mm. These differences were of the same magnitude as inter-test differences. Specifically, the acquisitions with 0.04 cycles/mm accurately quantified cardiac mechanics and had zero phase wrapping. Compared to 0.10 cycles/mm, the acquisitions with 0.04 cycles/mm had 9 % greater SNR and negligible differences in blood pool dephasing.
  
  
  CONCLUSIONS
  For 2D cine DENSE with through-plane dephasing, the encoding frequency can be lowered to 0.04 cycles/mm without compromising the quantification of twist or strain. The amount of wrapping can be reduced with this lower value to greatly simplify the input to unwrapping algorithms. The strain and twist results from studies using different encoding frequencies can be directly compared.
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA. gregory.wehner@uky.edu.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Wehner
authors.affiliation: Department of Pediatrics, University of Kentucky, Lexington, KY, USA. jonathan.grabau@uky.edu.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Grabau
authors.affiliation: Department of Pediatrics, University of Kentucky, Lexington, KY, USA. suever@gatech.edu.|Institute for Advanced Application, Geisinger Health System, Danville, PA, USA. suever@gatech.edu.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Suever
authors.affiliation: Department of Pediatrics, University of Kentucky, Lexington, KY, USA. chaggerty@uky.edu.|Institute for Advanced Application, Geisinger Health System, Danville, PA, USA. chaggerty@uky.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Haggerty
authors.affiliation: Department of Pediatrics, University of Kentucky, Lexington, KY, USA. lji222@uky.edu.|Institute for Advanced Application, Geisinger Health System, Danville, PA, USA. lji222@uky.edu.
authors.forename: Linyuan
authors.initials: L
authors.lastname: Jing
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA. dkpowe00@mri.uky.edu.
authors.forename: David K
authors.initials: DK
authors.lastname: Powell
authors.affiliation: Department of Electrical Engineering, University of Kentucky, Lexington, KY, USA. sean.hamlet@uky.edu.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Hamlet
authors.affiliation: Department of Physiology, University of Kentucky, Lexington, KY, USA. m.v@uky.edu.
authors.forename: Moriel H
authors.initials: MH
authors.lastname: Vandsburger
authors.affiliation: MR R&D Collaborations, Siemens Healthcare, Atlanta, GA, USA. xiaodong.zhong@siemens.com.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhong
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Department of Pediatrics, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Department of Physiology, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Department of Medicine, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Institute for Advanced Application, Geisinger Health System, Danville, PA, USA. bkf@gatech.edu.|Institute for Advanced Application, Geisinger Clinic, 100 North Academy Avenue, Danville, PA, 17822-4400, USA. bkf@gatech.edu.
authors.forename: Brandon K
authors.initials: BK
authors.lastname: Fornwalt
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006331:Heart Diseases / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D013314:Stress, Mechanical; D016276:Ventricular Function; D055815:Young Adult