title: 40 MHz high-frequency ultrafast ultrasound imaging.
abstract: OBJECTIVE
  Ultrafast high-frame-rate ultrasound imaging based on coherent-plane-wave compounding has been developed for many biomedical applications. Most coherent-plane-wave compounding systems typically operate at 3-15 MHz, and the image resolution for this frequency range is not sufficient for visualizing microstructure tissues. Therefore, the purpose of this study was to implement a high-frequency ultrafast ultrasound imaging operating at 40 MHz.
  
  
  METHODS
  The plane-wave compounding imaging and conventional multifocus B-mode imaging were performed using the Field II toolbox of MATLAB in simulation study. In experiments, plane-wave compounding images were obtained from a 256 channel ultrasound research platform with a 40 MHz array transducer. All images were produced by point-spread functions and cyst phantoms. The in vivo experiment was performed from zebrafish. Since high-frequency ultrasound exhibits a lower penetration, chirp excitation was applied to increase the imaging depth in simulation.
  
  
  RESULTS
  The simulation results showed that a lateral resolution of up to 66.93 μm and a contrast of up to 56.41 dB were achieved when using 75-angles plane waves in compounding imaging. The experimental results showed that a lateral resolution of up to 74.83 μm and a contrast of up to 44.62 dB were achieved when using 75-angles plane waves in compounding imaging. The dead zone and compounding noise are about 1.2 mm and 2.0 mm in depth for experimental compounding imaging, respectively. The structure of zebrafish heart was observed clearly using plane-wave compounding imaging.
  
  
  CONCLUSIONS
  The use of fewer than 23 angles for compounding allowed a frame rate higher than 1000 frames per second. However, the compounding imaging exhibits a similar lateral resolution of about 72 μm as the angle of plane wave is higher than 10 angles. This study shows the highest operational frequency for ultrafast high-frame-rate ultrasound imaging.
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, 701, No.1, University Rd, Tainan City, 70101, Taiwan.
authors.forename: Chih-Chung
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, 701, No.1, University Rd, Tainan City, 70101, Taiwan.
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Chen
authors.affiliation: Department of Electrical Engineering, Fu Jen Catholic University, New Taipei City, Taiwan.
authors.forename: Po-Hsun
authors.initials: PH
authors.lastname: Peng
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, 701, No.1, University Rd, Tainan City, 70101, Taiwan.
authors.forename: Po-Yang
authors.initials: PY
authors.lastname: Lee
mesh_terms: D006801:Humans; D019047:Phantoms, Imaging; D014463:Ultrasonography
keywords: high-frequency ultrasound; plane wave imaging; ultrafast imaging