Biomechanical characteristics in the carotid artery: Noninvasive assessment using subharmonic emissions from microbubbles

Background Stroke is closely related to carotid atherosclerotic plaques, which tend to occur in specific parts of the arteries, especially at the bifurcations, and are considered to be caused by biomechanical factors. Quantitative analysis of hemodynamic stress characteristics of the carotid sinus in vivo provides a mechanical basis for the development of atherosclerotic plaque in the carotid sinus. Previous studies found that ultrasound (US) contrast agent microbubbles would vibrate nonlinearly under the excitation of sound pressure, generating subharmonics (transmission fundamental frequency, i.e., f 0 and subharmonic frequency at f 0 /2), which have the highest sensitivity to pressure changes and exhibit an inverse linear relationship with environmental pressure. Purpose This study employed subharmonic aided pressure estimation (SHAPE) technology to reflect carotid artery hydrodynamic characteristics in the carotid lumen. Methods From May 2021 to December 2021, this prospective study reviewed a total of 26 normal carotid arteries of 13 participants, all of whom received bilateral carotid artery routine US and SHAPE US examinations. During this study, the lumen of the bilateral distal segment of the common carotid artery (Distal‐CCA), carotid artery bifurcation (CAB), and carotid bulb (CB) were scanned section by section from bottom to top in longitudinal and transverse sections. Subsequently, the subharmonic amplitudes in the lumen of normal carotid arteries were collected and analyzed. Results This study found that the amplitude of subharmonic amplitude in the carotid was distributed unevenly, with the amplitudes of subharmonic at the CAB being higher. Specifically, the subharmonic gradient of the carotid artery bifurcation apex plane was maximum (9.72 ± 4.31 dB), while the average subharmonic amplitude of the outer lateral layer of the carotid artery was higher (‐56.40 ± 6.31 dB) ( p < 0.001). Conclusion The SHAPE technique is capable of indirectly reflecting the pressure changes of vascular system tissues, which may provide a new monitoring method for evaluating mechanical characteristics obviating invasion.