title: Weighted Capon beamformer combined with coded excitation in ultrasound imaging.
abstract: BACKGROUND
  Capon-based beamformers are well-known methods to improve the SNR and quality of medical ultrasound images. Furthermore, they can improve the resolution of the images unexpectedly more than conventional DAS beamformers. Another method used in radar, sonar, and ultrasound imaging to increase the SNR is coded excitation with linear frequency-modulated signal (chirp).
  
  
  METHODS
  In this paper, we illustrate that the combination of coded excitation with a Capon beamformer provides better resolution and higher SNR. However, this combination suffers from high sidelobe levels. We propose a weighted Capon beamformer (WCB) with chirp excitation to suppress the sidelobes and obtain a higher contrast with approximately the same resolution as the standard Capon beamformer (SCB). The weights of the WCB are obtained using element-wise multiplication of the weights of the SCB and a desired window (Hanning) with the same dimension.
  
  
  RESULTS
  The results show a 20 dB reduction in the sidelobe levels in simulated point targets and a 6 dB increase in background contrast in simulated cyst phantoms.
authors.affiliation: Department of Biomedical Engineering, Tarbiat Modares University, Ale-Ahmad Avenue, P.o. Box 14115-194, Tehran, Islamic Republic of Iran. amin.izadi@modares.ac.ir.
authors.forename: Seyed Amin
authors.initials: SA
authors.lastname: Izadi
authors.affiliation: Department of Biomedical Engineering, Tarbiat Modares University, Ale-Ahmad Avenue, P.o. Box 14115-194, Tehran, Islamic Republic of Iran. mahlooji@modares.ac.ir.
authors.forename: Ali
authors.initials: A
authors.lastname: Mahloojifar
authors.affiliation: Department of Biomedical Engineering, Tarbiat Modares University, Ale-Ahmad Avenue, P.o. Box 14115-194, Tehran, Islamic Republic of Iran. babakmasl@modares.ac.ir.
authors.forename: Babak Mohammadzadeh
authors.initials: BM
authors.lastname: Asl
mesh_terms: D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio; D014463:Ultrasonography / Q000379:methods*
keywords: Adaptive beamformer; Capon; Chirp; Coded excitation; Minimum variance