Ultrasonic multipath and beamforming clutter reduction: a chirp model approach

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 61; no. 3; pp. 428 - 440
• Main Authors: Byram, Brett, Jakovljevic, Marko
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.03.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Array signal processing; Beamforming; Clutter; Computer Simulation; Degradation; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; In vivo; Models, Theoretical; Noise levels; Nonhomogeneous media; Patients; Phantoms, Imaging; Reproducibility of Results; Scattering; Sensitivity and Specificity; Surgical implants; Transducers; Ultrasonography - methods
• ISSN: 0885-3010; 1525-8955; 1525-8955
• DOI: 10.1109/TUFFC.2014.2928

In vivo ultrasonic imaging with transducer arrays suffers from image degradation resulting from beamforming limitations, including diffraction-limited beamforming and beamforming degradation caused by tissue inhomogeneity. Additionally, based on recent studies, multipath scattering also causes significant image degradation. To reduce degradation from both sources, we propose a model-based signal decomposition scheme. The proposed algorithm identifies spatial frequency signatures to decompose received wavefronts into their most significant scattering sources. Scattering sources originating from a region of interest are used to reconstruct decluttered wavefronts, which are beamformed into decluttered RF scan lines or A-lines. To test the algorithm, ultrasound system channel data were acquired during liver scans from 8 patients. Multiple data sets were acquired from each patient, with 55 total data sets, 43 of which had identifiable hypoechoic regions on normal B-mode images. The data sets with identifiable hypoechoic regions were analyzed. The results show the decluttered B-mode images have an average improvement in contrast over normal images of 7.3 ± 4.6 dB. The contrast-to-noise ratio (CNR) changed little on average between normal and decluttered Bmode, -0.4 ± 5.9 dB. The in vivo speckle SNR decreased; the change was -0.65 ± 0.28. Phantom speckle SNR also decreased, but only by -0.40 ± 0.03.