Coded ultrasound for blood flow estimation using subband processing

Fredrik Gran, Jesper Udesen, Michael bachmann Nielsen, Jørgen Arendt Jensen

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

    Abstract

    This paper further investigates the use of coded excitation for blood flow estimation in medical ultrasound. Traditional autocorrelation estimators use narrow-band excitation signals to provide sufficient signal-to-noise-ratio (SNR) and velocity estimation performance. In this paper, broadband coded signals are used to increase SNR, followed by sub-band processing. The received broadband signal, is filtered using a set of narrow-band filters. Estimating the velocity in each of the bands and averaging the results yields better performance compared to what would be possible when transmitting a narrow-band pulse directly. Also, the spatial resolution of the narrow-band pulse would be too poor for brightness-mode (B-mode) imaging and additional transmissions would be required to update the B-mode image. In the described approach, there is no need for additional transmissions, because the excitation signal is broadband and has good spatial resolution after pulse compression. Two different codin-schemes are used in this paper, Barker codes and Golay codes. The performance of the codes for velocity estimation is compared to a conventional approach transmitting a narrow-band pulse. The study was carried out using an experimental ultrasound scanner and a commercial linear array 7 MHz transducer. A circulating flow rig was scanned with a beam-to-flow angle of 60 degrees. The flow in the rig was laminar and had a parabolic flow-profile with a peak velocity of 0.09 m/s. The mean relative standard deviation of the reference method using an eight cycle excitation pulse at 7 MHz was 0.544% compared to the peak velocity in the rig. Two Barker codes were tested with a length of 5 and 13 bits, respectively. The corresponding mean relative standard deviations were 0.367% and 0.310%, respectively. For the Golay coded experiment, two 8 bit codes were used, and the mean relative standard deviation was 0.335%.
    Original languageEnglish
    Title of host publicationMedical Imaging 2007 : Ultrasonic Imaging and Signal Processing
    Number of pages10
    Publication date2007
    PagesArticle Number: 651309
    ISBN (Print)978-0-8194-6631-0
    DOIs
    Publication statusPublished - 2007
    EventSPIE Medical Imaging 2007 - Town & Country Hotel, San Diego, United States
    Duration: 17 Feb 200722 Feb 2007

    Conference

    ConferenceSPIE Medical Imaging 2007
    LocationTown & Country Hotel
    Country/TerritoryUnited States
    CitySan Diego
    Period17/02/200722/02/2007
    SeriesProceedings of SPIE - The International Society for Optical Engineering
    ISSN0277-786X

    Keywords

    • Temporal encoding
    • Medical ultrasound
    • Blood velocity estimation
    • Sub-band processing

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