Abstract
Basic ultrasound physics and several clinical and experimental observations suggest that high-frequency Doppler ultrasound (HFD) operating in the frequency range 20–100 MHz holds the promise of detecting blood flow in the microcirculation. This article describes a directional, continuous-wave (CW), 1- to 200-MHz Doppler ultrasound system. The system electronics have a dynamic range of 100 dB, a noise floor of 10 nV and a directional isolation of 50 dB. The development of a 40-MHz Doppler transducer composed of two, 81-μm-thick, lithium niobate crystals that have been air-backed and transmission-line tuned for maximum sensitivity is described. This device is used to test the CW Doppler system using string and capillary phantoms and in vivo tissue. We show that HFD can detect and measure velocities on the order of the blood velocities found in the capillaries (1 mm/s) and arterioles (5 mm/s) with suitable velocity (50–500 μm/s) and temporal (20–250 ms) resolutions. In vivo measurements demonstrate that HFD is sensitive to the detection of blood flow in small vessels.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
