Time-warping for robust automated arterial wall-recognition and tracking from single-scan-line ultrasound signals

• Published in: Ultrasonics Vol. 126; p. 106828
• Main Authors: Raj, Kiran V., Nabeel, P.M., Sivaprakasam, Mohanasankar, Joseph, Jayaraj
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2022
• Subjects: A-mode; Radio-frequency; Single-channel; Wall-motion-tracking; Wall-recognition; Radio-frequency; Wall-recognition; Single-channel; A-mode; Wall-motion-tracking
• ISSN: 0041-624X; 1874-9968; 1874-9968
• DOI: 10.1016/j.ultras.2022.106828

•Automated image-free ultrasound signal-processing technique for arterial wall recognition and motion tracking.•The method discerns presence and absence of arterial wall echoes in one-dimensional A-scans.•Recognition and tracking are robust to noise, any hyper-echoic regions or slow-moving structures adjacent to arterial walls.•The method supports development of inexpensive A-mode ultrasound systems.•It operates in real-time and is promising for large-scale field studies and resource-constrains settings. Current ultrasound methods for recognition and motion-tracking of arterial walls are suited for image-based B-mode or M−mode scans but not adequately robust for single-line image-free scans. We introduce a time-warping-based technique to address this need. Its performance was validated through simulations and in-vivo trials on 21 subjects. The method recognized wall locations with 100 % precision for simulated frames (SNR > 10 dB). Clustering detections for multiple frames achieved sensitivity >98 %, while it was ∼90 % without clustering. The absence of arterial walls was predicted with 100 % specificity. In-vivo results corroborated the performance outcomes yielding a sensitivity ≥94 %, precision ≥98 %, and specificity ≥98 % using the clustering scheme. Further, excellent frame-to-frame tracking accuracy (absolute error <3 %, RMSE <2 μm) was demonstrated. Image-free measurements of peak arterial distension agreed with the image-based ones, within an error of 1.08 ± 3.65 % and RMSE of 38 μm. The method discerned the presence of arterial walls in A-mode frames, robustly localized, and tracked them even when they were proximal to hyperechoic regions or slow-moving tissue structures. Unification of delineation techniques with the proposed methods facilitates a complete image-free framework for measuring arterial dynamics and the development of reliable A-mode devices.