title: Surveillance for hemodialysis access stenosis: usefulness of ultrasound vector volume flow.
abstract: OBJECTIVE
  To investigate if ultrasound vector-flow imaging (VFI) is equal to the reference method ultrasound dilution technique (UDT) in estimating volume flow and changes over time in arteriovenous fistulas (AVFs) for hemodialysis.
  
  
  METHODS
  From January 2014 to January 2015, patients with end-stage renal disease and matured functional AVFs were consecutively solicited to participate in this prospective study. All patients were included after written informed consent and approval by the National Committee on Biomedical Research Ethics and the local Ethics Committee (journal no. H-4-2014-FSP). VFI and UDT measurements were performed monthly over a six-month period. Nineteen patients were included in the study. VFI measurements were performed before dialysis, and UDT measurements after. Statistical analyses were performed with Bland-Altman plot, Student's t-test, four-quadrant plot, and regression analysis. Repeated measurements and precision analysis were used for reproducibility determination.
  
  
  RESULTS
  Precision measurements for UDT and VFI were 32% and 20%, respectively (p = 0.33). Average volume flow measured with UDT and VFI were 1161 mL/min (±778 mL/min) and 1213 mL/min (±980 mL/(min), respectively (p = 0.3). The mean difference was -51 mL/min (CI: -150 mL/min to 46 mL/min) with limits of agreement from -35% to 54%, with a strong correlation (r2 = 0.87). A large change in volume flow between dialysis sessions detected by UDT was confirmed by VFI (p = 0.0001), but the concordance rate was poor (0.72).
  
  
  CONCLUSIONS
  VFI is an acceptable method for volume flow estimation and volume flow changes over time in AVFs.
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Copenhagen - Denmark.
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Brandt
authors.affiliation: Center for Fast Ultrasound Imaging, Technical University of Denmark, Lyngby - Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Jensen
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Copenhagen - Denmark.
authors.forename: Kristoffer L
authors.initials: KL
authors.lastname: Hansen
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Copenhagen - Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Hansen
authors.affiliation: Department of Biostatistics, University of Copenhagen, Copenhagen - Denmark.
authors.forename: Theis
authors.initials: T
authors.lastname: Lange
authors.affiliation: Department of Nephrology, Copenhagen University Hospital, Copenhagen - Denmark.
authors.forename: Marianne
authors.initials: M
authors.lastname: Rix
authors.affiliation: Center for Fast Ultrasound Imaging, Technical University of Denmark, Lyngby - Denmark.
authors.forename: Jørgen A
authors.initials: JA
authors.lastname: Jensen
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Copenhagen - Denmark.|Department of Vascular Surgery, Copenhagen University Hospital, Copenhagen - Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Lönn
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Copenhagen - Denmark.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Nielsen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001166:Arteriovenous Shunt, Surgical; D001783:Blood Flow Velocity; D003718:Denmark; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007676:Kidney Failure, Chronic / Q000175:diagnosis / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012039:Regional Blood Flow; D006435:Renal Dialysis; D015203:Reproducibility of Results; D013997:Time Factors; D016896:Treatment Outcome; D014463:Ultrasonography / Q000379:methods*; D014654:Vascular Patency