@inproceedings{098fd4960a534eb9a5988377d25ff26a,
title = "Coded ultrasound for blood flow estimation using subband processing",
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%. ",
keywords = "Temporal encoding, Medical ultrasound, Blood velocity estimation, Sub-band processing",
author = "Fredrik Gran and Jesper Udesen and Nielsen, {Michael bachmann} and Jensen, {J{\o}rgen Arendt}",
year = "2007",
doi = "10.1117/12.703345",
language = "English",
isbn = "978-0-8194-6631-0",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
publisher = "Society of Photo-Optical Instrumentation Engineers",
pages = "Article Number: 651309",
booktitle = "Medical Imaging 2007",
note = "SPIE Medical Imaging 2007 ; Conference date: 17-02-2007 Through 22-02-2007",
}