title: An iterative approach to respiratory self-navigated whole-heart coronary MRA significantly improves image quality in a preliminary patient study.
abstract: OBJECTIVE
  In respiratory self-navigated coronary MRA, the selection of a reference position may have a direct effect on image quality. While end-expiration is commonly used as reference, it may be ill defined in cases of irregular breathing. Here, an iterative self-navigation approach that operates without a reference position was implemented and tested in healthy volunteers and patients.
  
  
  METHODS
  Data were acquired in 15 healthy volunteers and in 23 patients. Images obtained with end-expiratory self-navigation were compared with those obtained with the iterative approach that incorporates cross-correlation to iteratively minimize a global measure of respiratory displacement. Vessel sharpness, length, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were evaluated while differences in breathing patterns between the two sub-groups were assessed, too.
  
  
  RESULTS
  Vessel sharpness and length were similar for both methods in healthy volunteers. In patients, a significant improvement in vessel sharpness and length was obtained using the iterative approach. SNR and CNR remained constant. While end-expiration was the most frequent respiratory phase in healthy volunteers (57.6 ± 16.2%), intermediate respiratory phases (43.4 ± 30.1%) were predominantly found in patients.
  
  
  CONCLUSIONS
  An iterative approach to respiratory motion correction in self-navigation may lead to significant improvements in coronary MRA image quality in patients with a less consistent end-expiratory respiratory phase.
authors.affiliation: Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.|Center for Biomedical Imaging (CIBM), Lausanne, Switzerland.
authors.forename: Giulia
authors.initials: G
authors.lastname: Ginami
authors.affiliation: Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.|Center for Biomedical Imaging (CIBM), Lausanne, Switzerland.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Bonanno
authors.affiliation: Division of Cardiology and Cardiac MR Center, University Hospital (CHUV), Lausanne, Switzerland.
authors.forename: Juerg
authors.initials: J
authors.lastname: Schwitter
authors.affiliation: Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.|Center for Biomedical Imaging (CIBM), Lausanne, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Stuber
authors.affiliation: Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland.|Center for Biomedical Imaging (CIBM), Lausanne, Switzerland.|Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland.
authors.forename: Davide
authors.initials: D
authors.lastname: Piccini
mesh_terms: D000328:Adult; D000465:Algorithms; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D012119:Respiration; D059629:Signal-To-Noise Ratio
keywords: coronary MRI; free-breathing; iterative self-navigation