title: Coded excitation with spectrum inversion (CEXSI) for ultrasound array imaging.
abstract: In this paper, a scheme called coded excitation with spectrum inversion (CEXSI) is presented. An established optimal binary code whose spectrum has no nulls and possesses the least variation is encoded as a burst for transmission. Using this optimal code, the decoding filter can be derived directly from its inverse spectrum. Various transmission techniques can be used to improve energy coupling within the system pass-band. We demonstrate its potential to achieve excellent decoding with very low (< 80 dB) side-lobes. For a 2.6 micros code, an array element with a center frequency of 10 MHz and fractional bandwidth of 38%, range side-lobes of about 40 dB have been achieved experimentally with little compromise in range resolution. The signal-to-noise ratio (SNR) improvement also has been characterized at about 14 dB. Along with simulations and experimental data, we present a formulation of the scheme, according to which CEXSI can be extended to improve SNR in sparse array imaging in general.
authors.affiliation: Biomedical Engineering Department, University of Michigan, Ann Arbor, MI 48109, USA. ywangz@eecs.umich.edu
authors.forename: Yao
authors.initials: Y
authors.lastname: Wang
authors.forename: Kurt
authors.initials: K
authors.lastname: Metzger
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Stephens
authors.forename: Gregory
authors.initials: G
authors.lastname: Williams
authors.forename: Scott
authors.initials: S
authors.lastname: Brownlie
authors.forename: Matthew
authors.initials: M
authors.lastname: O'Donnell
mesh_terms: D000465:Algorithms; D007089:Image Enhancement / Q000379:methods*; D019047:Phantoms, Imaging; D011786:Quality Control; D012542:Scattering, Radiation; D012815:Signal Processing, Computer-Assisted; D013269:Stochastic Processes; D014159:Transducers; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*