Vascular wall shear rate measurement using coded excitation techniques

Jean K. Tsou, Jie Liu, Michael F. Insana

Research output: Contribution to journalConference articlepeer-review


Wall shear rate (WSR) is the derivative of blood velocity with respect to vessel radius at the endothelial surface. The product of WSR and blood viscosity is the wall shear stress (WSS) that must remain relatively high to maintain normal endothelial cell function, arterial health and prevent plaque formation. Accurate WSR estimation requires the lowest possible variance and bias for blood velocity estimates near the wall. This situation is achieved for conditions where the echo signal-to-noise ratio (eSNR) and spatial resolution for velocity are high. We transmitted coded pulses, i.e., those with time-bandwidth product greater than 1, to increase eSNR from weak blood scatter without increasing instantaneous power or reducing spatial resolution. This paper is a summary of WSR measurements from a flow phantom where a variety of acoustic pulses were transmitted: frequencymodulated (FM) codes and phase-modulated (PM) codes were compared with uncoded broadband and narrow band pulse transmissions. Both simulation and experimental results show that coded-pulse excitation increases accuracy and precision in WSR estimation when compared to standard pulsing techniques. Additionally, PM codes can reduce WSR errors more than FM codes for equal pulse energy. This reduction in WSR error could greatly extend the application of ultrasound in the study of cardiovascular disease.

Original languageEnglish (US)
Article number30
Pages (from-to)269-280
Number of pages12
JournalProgress in Biomedical Optics and Imaging - Proceedings of SPIE
StatePublished - 2005
Externally publishedYes
EventMedical Imaging 2005 - Ultrasonic Imaging and Signal Processing - San Diego, CA, United States
Duration: Feb 15 2005Feb 17 2005


  • Bias and variance
  • Blood velocity estimation
  • Coded excitation
  • Wall shear rate

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


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