title: Validation of endoscopic ultrasound measured flow rate in the azygos vein using a flow phantom.
abstract: Increase in flow rate within the azygos vein may be used as an indicator of the degree of liver cirrhosis. The aim of this study was to evaluate the error in measurement of flow rate using a commercial endoscopic ultrasound system, using a flow phantom that mimicked azygos vein depth, diameter and flow rate. Diameter was underestimated in all cases, with an average underestimation of 0.09 cm. Maximum velocity was overestimated, by 4 ± 4% at 50°, 11 ± 3% at 60° and 23 ± 7% at 70°. The increase in error with beam-vessel angle is consistent with the error as arising from geometric spectral broadening. Flow was underestimated by amounts up to 33%, and it is noted that the overestimation caused by geometric spectral broadening is in part compensated by underestimation of diameter. It was concluded that measurement of flow rate using a commercially available endoscopic ultrasound system is dependent on the beam-vessel angle, with errors up to 33% for typical vessel depths, diameter and beam-vessel angle.
authors.affiliation: Medical Physics Department, University of Edinburgh, Edinburgh, United Kingdom. P.Hoskins@ed.ac.uk
authors.forename: Peter R
authors.initials: PR
authors.lastname: Hoskins
authors.forename: Monica
authors.initials: M
authors.lastname: Soldan
authors.forename: Steven
authors.initials: S
authors.lastname: Fortune
authors.forename: Scott
authors.initials: S
authors.lastname: Inglis
authors.forename: Tom
authors.initials: T
authors.lastname: Anderson
authors.forename: John
authors.initials: J
authors.lastname: Plevris
mesh_terms: D001401:Azygos Vein / Q000000981:diagnostic imaging*; D001783:Blood Flow Velocity; D019160:Endosonography / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D019047:Phantoms, Imaging