title: Dual-/tri-apodization techniques for high frequency ultrasound imaging: a simulation study.
abstract: BACKGROUND
  In the ultrasound B-mode (Brightness-mode) imaging, high side-lobe level reduces contrast to noise ratio (CNR). A linear apodization scheme by using the window function can suppress the side-lobe level while the main-lobe width is increased resulting in degraded lateral resolution. In order to reduce the side-lobe level without sacrificing the main-lobe width, a non-linear apodization method has been suggested.
  
  
  METHODS
  In this paper, we computationally evaluated the performance of the non-linear apodization method such as dual-/tri-apodization focusing on the high frequency ultrasound image. The rectangular, Dolph-Chebyshev, and Kaiser window functions were employed to implement dual-/tri-apodization algorithms. The point and cyst target simulations were conducted by using a dedicated ultrasound simulation tool called Field-II. The center frequency of the simulated linear array transducer was 40 MHz and the total number of elements was 128. The performance of dual-/tri-apodization was compared with that of the rectangular window function focusing on the side-lobe level and the main-lobe widths (at -6 dB and -35 dB).
  
  
  RESULTS
  In the point target simulation, the main-lobe widths of the dual-/tri-apodization were very similar to that of the rectangular window, and the side-lobe levels of the dual-/tri-apodization were more suppressed by 9~10 dB. In the cyst target simulation, CNR values of the dual-/tri-apodization were improved by 41% and 51%, respectively.
  
  
  CONCLUSIONS
  The performance of the non-linear apodization was numerically investigated. In comparison with the rectangular window function, the non-linear apodization method such as dual- and tri-apodization had low side-lobe level without sacrificing the main-lobe width. Thus, it can be a potential way to increase CNR maintaining the main-lobe width in the high frequency ultrasound imaging.
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Sung
authors.affiliation: Department of Medical Biotechnology, Dongguk University, Seoul 100-715, Republic of Korea. jjsspace@dongguk.edu.
authors.forename: Jong Seob
authors.initials: JS
authors.lastname: Jeong
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D003287:Contrast Media / Q000737:chemistry; D003952:Diagnostic Imaging / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D015398:Signal Transduction; D012984:Software; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media