{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T05:19:01Z","timestamp":1787635141636,"version":"build-2736575974"},"reference-count":33,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,8,23]],"date-time":"2026-08-23T00:00:00Z","timestamp":1787443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key R&D Program of China","doi-asserted-by":"crossref","award":["2022YFF0706500"],"award-info":[{"award-number":["2022YFF0706500"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Sichuan Natural Science Foundation Project","award":["2024NSFSC0043671"],"award-info":[{"award-number":["2024NSFSC0043671"]}]},{"name":"Tianfu Jincheng Laboratory, City of Future Medicine","award":["TFJC-2024-JB002"],"award-info":[{"award-number":["TFJC-2024-JB002"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Shear-wave time-of-flight (TOF) measurement enables controlled assessment of frequency-dependent wave propagation, but its feasibility in biological tissues remains insufficiently established. This study evaluated whether a custom shear-wave TOF device could detect frequency- and direction-dependent responses in ex vivo tissues. Three porcine liver samples and three chicken breast samples were examined. Chicken breast was measured with propagation parallel and perpendicular to visible muscle fibers. One-cycle sinusoidal excitations were applied at 40\u2013160 Hz, with 50 acquisitions ensemble-averaged per sample\u2013frequency measurement. TOF was estimated using Tx threshold detection and cumulative-energy-based Rx onset detection, and TOF-derived apparent shear-wave propagation speed was calculated from the Tx\u2013Rx distance and the measured TOF. Frequency-dependent data were fitted using the Kelvin\u2013Voigt fractional derivative model to obtain model-dependent KVFD fit parameters. Signal quality was assessed, and a preliminary descriptive comparison with HISKY EQTouch UD3000 (Wuxi Hisky Medical Technologies Co., Ltd., Wuxi, China) SWE was performed. All 63 averaged sample\u2013frequency measurements satisfied the predefined primary-detection criteria. Mean apparent shear-wave speed was 3.145 m\/s in porcine liver, 6.133 m\/s in chicken breast measured parallel to the fibers, and 5.914 m\/s in chicken breast measured perpendicular to the fibers, giving a parallel-to-perpendicular speed ratio of 1.037. Mean post-averaging, post-processing SNR ranged from 24.47 to 31.52 dB. The UD3000 comparison showed the same tissue ranking. The device detected frequency- and direction-dependent responses in averaged ex vivo signals, supporting its feasibility as a controlled research platform. Claims of absolute stiffness accuracy and intrinsic muscle anisotropy require independent calibration and validation.<\/jats:p>","DOI":"10.3390\/bioengineering13090959","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T14:49:34Z","timestamp":1787582974000},"page":"959","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Frequency and Direction-Dependent Shear-Wave Responses in Ex Vivo Tissues Measured by a Time-of-Flight Device"],"prefix":"10.3390","volume":"13","author":[{"given":"Jotham Josephat","family":"Kimondo","sequence":"first","affiliation":[{"name":"School of Life Sciences and Technology, University of Electronic Science and Technology of China, Chengdu 610054, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ziang","family":"Feng","sequence":"additional","affiliation":[{"name":"School of Life Sciences and Technology, University of Electronic Science and Technology of China, Chengdu 610054, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jie","family":"Yang","sequence":"additional","affiliation":[{"name":"Department of Medical Ultrasound, West China Hospital of Sichuan University, Chengdu 610041, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qiang","family":"Lu","sequence":"additional","affiliation":[{"name":"Department of Medical Ultrasound, West China Hospital of Sichuan University, Chengdu 610041, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5413-0965","authenticated-orcid":false,"given":"Sandra","family":"P\u00e9rez-Buitrago","sequence":"additional","affiliation":[{"name":"Department of Engineering, Medical Device Research Group, Pontifical Catholic University of Peru, San Miguel 15088, Lima, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhe","family":"Wu","sequence":"additional","affiliation":[{"name":"School of Life Sciences and Technology, University of Electronic Science and Technology of China, Chengdu 610054, China"},{"name":"Tianfu Jincheng Laboratory, City of Future Medicine, Chengdu 641400, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Faris, I.H., Melchor, J., Callejas, A., Torres, J., and Rus, G. 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