Real-Time Speed-of-Sound Estimation In Vivo via Steered Plane Wave Ultrasound

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 71; no. 6; pp. 673 - 686
• Main Authors: Xiao, Di, Torre, Pat De la, Yu, Alfred C. H.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.06.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustics; Algorithms; Array signal processing; Biomarkers; Biomedical imaging; Estimates; Estimation; Human tissues; Humans; Image Processing, Computer-Assisted - methods; In vivo; Innovations; Medical imaging; Muscle, Skeletal - diagnostic imaging; Phantoms, Imaging; Plane wave imaging; Plane waves; Real time; real-time measurements; Real-time systems; speed-of-sound (SoS); Time measurement; tissue biomarker; Ultrasonic imaging; Ultrasonic scanners; Ultrasonography - methods
• ISSN: 0885-3010; 1525-8955; 2373-7840; 1525-8955
• DOI: 10.1109/TUFFC.2024.3395490

Speed-of-sound (SoS) is an intrinsic acoustic property of human tissues and has been regarded as a potential biomarker of tissue health. To foster the clinical use of this emerging biomarker in medical diagnostics, it is important for SoS estimates to be derived and displayed in real time. Here, we demonstrate that concurrent global SoS estimation and B-mode imaging can be achieved live on a portable ultrasound scanner. Our innovation is hinged upon the design of a novel pulse-echo SoS estimation framework that is based on steered plane wave imaging. It has accounted for the effects of refraction and imaging depth when the medium SoS differs from the nominal value of 1540 m/s that is conventionally used in medical imaging. The accuracy of our SoS estimation framework was comparatively analyzed with through-transmit time-of-flight measurements in vitro on 15 custom agar phantoms with different SoS values (1508-1682 m/s) and in vivo on human calf muscles (<inline-formula> <tex-math notation="LaTeX">{N} =9 </tex-math></inline-formula>; SoS range: 1560-1586 m/s). Our SoS estimation framework has a mean signed difference (MSD) of <inline-formula> <tex-math notation="LaTeX">- 0.6 \, \pm \, 2.3 </tex-math></inline-formula> m/s in vitro and <inline-formula> <tex-math notation="LaTeX">- 2.2 \, \pm \, 11.2 </tex-math></inline-formula> m/s in vivo relative to the reference measurements. In addition, our real-time system prototype has yielded simultaneous SoS estimates and B-mode imaging at an average frame rate of 18.1 fps. Overall, by realizing real-time tissue SoS estimation with B-mode imaging, our innovation can foster the use of tissue SoS as a biomarker in medical ultrasound diagnostics.