An Acoustic Metamaterial Layer to Pass Through Calcified Plaques
Ashkan Ghanbarzadeh-Dagheyan (TNW-BMPI), Erqian Dong (Hong Kong University)
Abstract
Introduction
Recently, ultrasound velocimetry (echoPIV) has been used for arterial blood flow imaging. This involves injecting microbubbles into the bloodstream and monitoring their motion using high-frame-rate ultrasound (US) imaging. Yet, the presence of calcified plaques between the artery and the US probe can attenuate and disrupt the signal, leading to errors in velocity estimates. Various approaches have been explored to address this problem, such as increasing local the US pressure above the plaque. But such methods have limitations when dealing with strong reflections and aberrations.
Objective
This study aims to mitigate these effects by utilizing a broadband metamaterial matching layer (MML) in an in-vitro plaque model. This research applies the principles of acoustic metamaterials to a real-world medical challenge.
Methods
The in-vitro vascular model was created using resin-based 3D printing, with Flexible 80A for the artery wall and Clear V4 for the plaque. US imaging showed strong reflections and a signal attenuation of ~7 dB behind the plaque model, leading to a weakened and distorted velocity field. To address this, a similar model was numerically simulated for the design of the MML, which featured a triangular pattern with subwavelength features to facilitate the coupling of US waves into the reflective plaque model.
Results and Discussion
Our preliminary numerical findings indicate that the MML successfully reduces multiple reflections from the plaque model. Moreover, it amplifies pressure waves (approximately 5 dB at 3 MHz) behind the plaque, thereby enhancing transmission through the aberrating layer. Our next objectives involve refining the MML design and fabricating it for experimental validation.