title: Whole-heart four-dimensional flow can be acquired with preserved quality without respiratory gating, facilitating clinical use: a head-to-head comparison.
abstract: BACKGROUND
  Respiratory gating is often used in 4D-flow acquisition to reduce motion artifacts. However, gating increases scan time. The aim of this study was to investigate if respiratory gating can be excluded from 4D flow acquisitions without affecting quantitative intracardiac parameters.
  
  
  METHODS
  Eight volunteers underwent CMR at 1.5 T with a 5-channel coil (5ch). Imaging included 2D flow measurements and whole-heart 4D flow with and without respiratory gating (Resp(+), Resp(-)). Stroke volume (SV), particle-trace volumes, kinetic energy, and vortex-ring volume were obtained from 4D flow-data. These parameters were compared between 5ch Resp(+) and 5ch Resp(-). In addition, 20 patients with heart failure were scanned using a 32-channel coil (32ch), and particle-trace volumes were compared to planimetric SV. Paired comparisons were performed using Wilcoxon's test and correlation analysis using Pearson r. Agreement was assessed as bias±SD.
  
  
  RESULTS
  Stroke volume from 4D flow was lower compared to 2D flow both with and without respiratory gating (5ch Resp(+) 88±18 vs 97±24.0, p=0.001; 5ch Resp(-) 86±16 vs 97.1±22.7, p<0.01). There was a good correlation between Resp(+) and Resp(-) for particle-trace derived volumes (R2=0.82, 0.2±9.4 ml), mean kinetic energy (R2=0.86, 0.07±0.21 mJ), peak kinetic energy (R2=0.88, 0.14±0.77 mJ), and vortex-ring volume (R2=0.70, -2.5±9.4 ml). Furthermore, good correlation was found between particle-trace volume and planimetric SV in patients for 32ch Resp(-) (R2=0.62, -4.2±17.6 ml) and in healthy volunteers for 5ch Resp(+) (R2=0.89, -11±7 ml), and 5ch Resp(-) (R2=0.93, -7.5±5.4 ml), Average scan duration for Resp(-) was shorter compared to Resp(+) (27±9 min vs 61±19 min, p<0.05).
  
  
  CONCLUSIONS
  Whole-heart 4D flow can be acquired with preserved quantitative results without respiratory gating, facilitating clinical use.
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. mikael.kanski@med.lu.se.
authors.forename: Mikael
authors.initials: M
authors.lastname: Kanski
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. johannes.toger@med.lu.se.|Department of Numerical Analysis, Center of Mathematical Sciences, Lund University, Lund, Sweden. johannes.toger@med.lu.se.
authors.forename: Johannes
authors.initials: J
authors.lastname: Töger
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. katarina.ehrenborg@med.lu.se.
authors.forename: Katarina
authors.initials: K
authors.lastname: Steding-Ehrenborg
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. cxanthis@gmail.com.|Department of Computer Science and Biomedical informatics, University of Thessaly, Lamia, Greece. cxanthis@gmail.com.
authors.forename: Christos
authors.initials: C
authors.lastname: Xanthis
authors.affiliation: Philips Healthcare, Lund, Sweden. karin.markenroth@philips.se.
authors.forename: Karin Markenroth
authors.initials: KM
authors.lastname: Bloch
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. einar.heiberg@med.lu.se.|Department of Biomedical Engineering, Faculty of Engineering, Lund University, Lund, Sweden. einar.heiberg@med.lu.se.|Center for Mathematics, Faculty of Engineering, Lund University, Lund, Sweden. einar.heiberg@med.lu.se.
authors.forename: Einar
authors.initials: E
authors.lastname: Heiberg
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. marcus.carlsson@med.lu.se.
authors.forename: Marcus
authors.initials: M
authors.lastname: Carlsson
authors.affiliation: Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. hakan.arheden@med.lu.se.
authors.forename: Håkan
authors.initials: H
authors.lastname: Arheden
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001783:Blood Flow Velocity; D003326:Coronary Circulation; D005260:Female; D006333:Heart Failure / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D055425:Respiratory-Gated Imaging Techniques; D012680:Sensitivity and Specificity; D013382:Subtraction Technique