title: Unit-delay focusing architecture and integrated-circuit implementation for high-frequency ultrasound.
abstract: High-frequency ultrasound (above 10 MHz) has been used successfully in many medical applications, including eye, skin, gastrointestinal, intravascular, and Doppler flow imaging. Most of these applications use single-element transducers, thereby imposing a tradeoff between resolution and depth of field. Fabrication difficulties and the need for high-speed electronic beamformers have prevented widespread use of arrays at high frequencies. In this paper, a unit-delay focusing architecture suitable for use with high-frequency ultrasound annular arrays is described. It uses a collection of identical, active delay cells that may be simultaneously varied to accomplish focusing. Results are presented for an analog integrated circuit intended for use with a five-element, 50-MHz planar annular array. Focusing is possible over an axial range for which the ratio of maximum to minimum f-number is 2.1. Unit-delay architectures also are described for curved annular arrays and linear arrays.
authors.affiliation: Cleveland Clinic Foundation, Biomedical Engineering, ND-20, Cleveland, OH, USA. talmanj@bme.ri.ccf.org
authors.forename: James R
authors.initials: JR
authors.lastname: Talman
authors.forename: Steven L
authors.initials: SL
authors.lastname: Garverick
authors.forename: Christine E
authors.initials: CE
authors.lastname: Morton
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Lockwood
mesh_terms: D004581:Electronics / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D008904:Miniaturization; D011846:Radio Waves; D012666:Semiconductors; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods*