title: Pulse wave velocity with 4D flow MRI: systematic differences and age-related regional vascular stiffness.
abstract: OBJECTIVE
  The objective of this study was to compare multiple methods for estimation of PWV from 4D flow MRI velocity data and to investigate if 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time is sufficient to discern age-related regional differences in PWV.
  
  
  METHODS
  4D flow MRI velocity data were acquired in 8 young and 8 older (age: 23±2 vs. 58±2 years old) normal volunteers. Travel-time and travel-distance were measured throughout the aorta and piecewise linear regression was used to measure global PWV in the descending aorta and regional PWV in three equally sized segments between the top of the aortic arch and the renal arteries. Six different methods for extracting travel-time were compared.
  
  
  RESULTS
  Methods for estimation of travel-time that use information about the whole flow waveform systematically overestimate PWV when compared to methods restricted to the upslope-portion of the waveforms (p<0.05). In terms of regional PWV, a significant interaction was found between age and location (p<0.05). The age-related differences in regional PWV were greater in the proximal compared to distal descending aorta.
  
  
  CONCLUSIONS
  Care must be taken as different classes of methods for the estimation of travel-time produce different results. 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time can discern age-related differences in regional PWV well in line with previously reported data.
authors.affiliation: Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden. Electronic address: petter.dyverfeldt@liu.se.
authors.forename: Petter
authors.initials: P
authors.lastname: Dyverfeldt
authors.affiliation: Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Division of Media and Information Technology, Department of Science and Technology/Swedish e-Science Research Centre (SeRC), Linköping University, Linköping, Sweden.
authors.forename: Tino
authors.initials: T
authors.lastname: Ebbers
authors.affiliation: Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Department of Cardiovascular Surgery, Linköping University Hospital, County Council of Östergötland, Linköping, Sweden.
authors.forename: Toste
authors.initials: T
authors.lastname: Länne
mesh_terms: D000328:Adult; D000367:Age Factors; D000465:Algorithms; D001011:Aorta / Q000473:pathology*; D001783:Blood Flow Velocity; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008858:Microscopy, Phase-Contrast; D008875:Middle Aged; D010363:Pattern Recognition, Automated; D011673:Pulsatile Flow; D063177:Pulse Wave Analysis; D015203:Reproducibility of Results; D012984:Software; D059289:Vascular Stiffness; D055815:Young Adult
keywords: 4D flow MRI; Aging; MR flow imaging; Phase-contrast MRI; Pulse wave velocity; Vascular stiffness