Spatio-temporal encoding using narrow-band linear frequency modulated signals in synthetic aperture ultrasound imaging

Fredrik Gran, Jørgen Arendt Jensen

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

In this paper a method for spatio-temporal encoding is presented for synthetic transmit aperture ultrasound imaging (STA). The purpose is to excite several transmitters at the same time in order to transmit more acoustic energy in every single transmission. When increasing the transmitted acoustic energy, the signal to noise ratio will increase. However, to focus the data properly using the STA approach, the transmitters have to be separated from each other. This is done by dividing the available spectrum into several subbands with a small overlap. Separating different transmitters can be done by bandpass filtering. Therefore, the separation can be done instantaneously without the need for further transmissions, unlike spatial encoding relying on Hadamard or Golay coding schemes, where several transmissions have to be made before the decoding can be done. Motion artifacts from the decoding can, thus, be avoided. To further increase the transmitted energy, the excitation waveforms are designed as linear frequency modulated (FM) signals. This makes it possible to maintain the full excitation amplitude during most of the transmission. The design of the separation filters will also be discussed. The method was tested using the experimental ultrasound scanner RASMUS and evaluated using a reference setup with a linear FM excitation waveform and STA beamforming. The point spread function (PSF) was measured on a wire phantom in water. A wire phantom with an attenuating medium was also measured, where the proposed method achieved approximately 2 cm improvement in penetration depth. The signal to noise ratio was also measured, where the gain was ∼ 7 dB in comparison to the reference.
Original languageEnglish
Title of host publicationProceedings of SPIE Medical Imaging meeting : Ultrasonic Imaging and Signal Processing
Volume5750
PublisherSPIE - International Society for Optical Engineering
Publication date2005
Pages405-416
DOIs
Publication statusPublished - 2005
EventSPIE Medical Imaging Meeting: Ultrasonic Imaging and Signal Processing - San Diego, United States
Duration: 12 Feb 200517 Feb 2005
http://proceedings.spiedigitallibrary.org/volume.aspx?volumeid=2934

Conference

ConferenceSPIE Medical Imaging Meeting
CountryUnited States
CitySan Diego
Period12/02/200517/02/2005
Internet address

Keywords

  • Spatial and temporal encoding
  • Coded ultrasound imaging
  • Synthetic transmit aperture ultrasound

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