Noninvasive vascular ultrasound An asset in vascular medicine

### 1.1 Introduction There are always moments in life, inviting to look back on the past. Entering the next millennium is certainly such an occasion, because it happens generally only once in a life-time. Therefore, we very much liked the idea of the Editors to publish a special issue of Cardiovascular Research on the occasion of this event and to explore the impact of the articles in the journal most frequently cited over the years on further developments in the field. We gladly accepted their invitation to evaluate in this respect the article by Levenson et al. published in Cardiovascular Research in 1981 [1]. ### 1.2 Content of the article In this article the authors described an ultrasound system to assess diameter, blood flow velocity and volume flow in the brachial artery in man. The apparatus consisted of an adjustable range-gated pulsed Doppler system, emitter frequency 8 MHz, combined with a double transducer system to accurately determine the angle between ultrasound beam and vessel axis. The latter is a prerequisite for accurate determination of both the velocity in and the diameter of the artery and, hence, for proper calculation of volume flow. The length of the sample volume could be adjusted by varying the length of the reception duration. A small sample volume was used to measure velocity locally in the artery and to determine the diameter of the vessel accurately and a large one to estimate the average velocity over the cross-sectional area of the vessel. A static high-pass filter with a lower cut-off frequency of 250 Hz was used to reduce interference of high amplitude low frequency signals reflected by the arterial walls. The validity of the system was tested in an in vitro set-up and the results showed that the diameter as assessed with the system compared favorably with the diameter of the tubing in …