High resolution focused-ultrasound-induced thermoacoustic imaging

Abstract

We report a new imaging modality, focused-ultrasound-induced thermoacoustic imaging (FUTAI). FUTAI provides high imaging resolution and unique contrast of acoustic absorption and thermodynamic properties of tissue. When a short pulse of the focused ultrasound beam is applied to biological tissue, the tissue will absorb the energy of the incident ultrasound causing a rapid change in local temperature, which leads to thermoelastic expansion and generates acoustic waves. In this work, we investigated this focused-ultrasound-induced thermoacoustic effect through theoretical simulation and experimental validation. A novel imaging modality FUTAI is proposed and demonstrated for the first time. By scanning the focus of the incident ultrasound beam, a 2D or 3D image of tissue properties can be formed. FUTAI provides better resolution compared to traditional B-mode ultrasound imaging, and deeper imaging depth compared to photoacoustic imaging. Additionally, since FUTAI is sensitive to acoustic absorption, it has unique advantages in guiding therapies like high intensity focused ultrasound (HIFU) in which treatment efficiency is determined by the acoustic absorption property. In this work, we also proposed a new method to localize the focus of HIFU with high accuracy using FUTAI. The results indicate that FUTAI has great potential in applications such as noninvasive imaging and therapy guidance.