Eigen-based clutter filter design for ultrasound color flow imaging: a review

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 57; no. 5; pp. 1096 - 1111
• Main Authors: Yu, Alfred, Lovstakken, Lasse
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic signal processing; Acoustics; Adaptive filters; Algorithm design and analysis; Algorithms; Biological and medical sciences; Blood flow; Cardiovascular system; Carotid Arteries - diagnostic imaging; Design; Echocardiography; Exact sciences and technology; Frequency; Fundamental areas of phenomenology (including applications); Humans; Image analysis; Image motion analysis; In vivo; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Motion analysis; Physics; Signal Processing, Computer-Assisted; Studies; Thyroid Gland - diagnostic imaging; Ultrasonic imaging; Ultrasonic investigative techniques; Ultrasonography, Doppler, Color - methods; Visualization; Human; Ultrasound imaging; Noise reduction; Eigenvalue; Thyroid gland; Doppler effect; Clutter; Modeling; Color image; Blood; Blood flow; Tissue; Energy gap; Filter; Medical imagery; Eigenvalue problem; Circulatory system; Hemodynamics; Frequency filtering; Acoustic image; Image contrast
• ISSN: 0885-3010; 1525-8955; 1525-8955
• DOI: 10.1109/TUFFC.2010.1521

Proper suppression of tissue clutter is a prerequisite for visualizing flow accurately in ultrasound color flow imaging. Among various clutter suppression methods, the eigen- based filter has shown potential because it can theoretically adapt its stopband to the actual clutter characteristics even when tissue motion is present. This paper presents a formative review on how eigen-based filters should be designed to improve their practical efficacy in adaptively suppressing clutter without affecting the blood flow echoes. Our review is centered around a comparative assessment of two eigen-filter design considerations: 1) eigen-component estimation approach (single-ensemble vs. multi-ensemble formulations), and 2) filter order selection mechanism (eigenvalue-based vs. frequencybased algorithms). To evaluate the practical efficacy of existing eigen-filter designs, we analyzed their clutter suppression level in two in vivo scenarios with substantial tissue motion (intra-operative coronary imaging and thyroid imaging). Our analysis shows that, as compared with polynomial regression filters (with or without instantaneous clutter downmixing), eigen-filters that use a frequency-based algorithm for filter order selection generally give Doppler power images with better contrast between blood and tissue regions. Results also suggest that both multi-ensemble and single-ensemble eigen-estimation approaches have their own advantages and weaknesses in different imaging scenarios. It may be beneficial to develop an algorithmic way of defining the eigen-filter formulation so that its performance advantages can be better realized.