title: Correction of phase aberrations for sectored annular array ultrasound transducers.
abstract: Two methods for correction of unknown phase aberrations induced by inhomogeneous acoustic velocities in tissues are explored for the two dimensional geometry of a sectored annular array system. The methods employed are adaptations of a cross correlation technique and a speckle brightness maximization technique. The methods correct phase distortions via the introduction of phase shifts in the timing sequence at the beamformer stage of a sectored annular array transducer. The techniques are investigated employing software models and a computer controlled automated scanning system. A 65-element sectored annular array is modelled via a rotating 5 element transducer. Tissue equivalent materials were moulded into a double layer aberrating medium to simulate phase distortions encountered in the rectus abdominis muscle in vivo. A comparison of the effectiveness of the two correction methods is presented. Contrast of an anechoic region is increased from 0.34 +/- 0.08 to 0.48 +/- 0.06 for the cross correlation technique, and up to 0.62 +/- 0.05 for the speckle brightness maximization method. The performance of these correction techniques on target phantoms suggests that considerable improvements in image quality should be possible for clinical systems.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Gambetti
authors.forename: S F
authors.initials: SF
authors.lastname: Foster
mesh_terms: D008953:Models, Anatomic; D008962:Models, Theoretical; D012815:Signal Processing, Computer-Assisted; D012984:Software; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation