NDLI: Real time vector Doppler for tissue motion

Content Provider	IEEE Xplore Digital Library
Author	Criton, A. Steel, R. Hoskins, P.R. McDicken, W.N. Routh, H.F.
Copyright Year	2002
Description	Author affiliation: Philips Ultrasound, Washington, DC, USA (Criton, A.)
Abstract	Tissue Doppler Imaging (TDI) can assess tissue motion in vascular and cardiac imaging. However, a major drawback of these measurements is that the motion estimation is limited to the component along the ultrasound beam axis. Cardiac and vessel wall motion studies have shown that complex three-dimensional motions can be observed, and that there is a clinical need to fully assess the three components of the vector motion. This work describes how TDI can be extended by acquiring a real time two-component velocity vector via a dual beam vector Doppler technique. A vector Doppler velocity estimator using a small interbeam angle can suffer from both bias and large variance. This estimator is also strongly dependent on the settings of the echographic system. To reduce the large bias and variance, most vector velocity techniques use a very large ensemble length (EL) (>20), which does not allow real time implementation. We propose a new processing technique, which reduces the bias and the standard deviation of the vector velocity estimate. The new method assumes that the vector velocity angle varies slowly over the cardiac cycle. The angle can then be estimated using a large time window. The performance of this new technique has been tested experimentally using a tissue mimicking rotating phantom. It is shown that the factors influencing the results are the EL, the precision of the TDI estimates and the time window. The results indicate that the variance and bias of velocity magnitude and orientation estimates decrease with increasing EL, increasing precision of the TDI estimates and increasing time window. Using an EL of 9, 8 bits for the velocity estimate, and an observation time of one second, a 5-degree bias of the angle estimate is observed, with a variance below 7 degree averaged over all angles. A 10% bias of the velocity magnitude is observed, with a variance of 1%. In conclusion, TDI can be improved with vector Doppler providing two-dimensional tissue motion estimation, enabling more accurate biomechanical tissue property assessment.
Sponsorship	Ultransonics Ferroelectr., & Frequency Control Soc
Starting Page	1529
Ending Page	1534
File Size	372151
Page Count	6
File Format	PDF
ISBN	0780375823
ISSN	10510117
DOI	10.1109/ULTSYM.2002.1192587
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2002-10-08
Publisher Place	Germany
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Ultrasonic imaging Acoustic beams Ultrasonic transducers Ultrasonic transducer arrays Ultrasonic variables measurement Motion estimation Imaging phantoms Frequency Phase estimation Blood
Content Type	Text
Resource Type	Article

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