Achieving coaxial photoacoustic/ultrasound dual-modality imaging by high-performance Sm: 0.72PMN-0.28PT transparent piezoelectric ceramic

Abstract

As a promising new medical imaging method, photoacoustic imaging (PAI) has the advantages of optical resolution and acoustic depth of penetration. The transparent ultrasound transducer (TUT), as a novel device applied to PAI, can combine the laser and acoustic beam coaxially to improve the imaging quality. Transparent piezoelectric materials are the key to developing piezoelectric TUTs. However, due to the birefringence and light scattering caused by ferroelectric domains, it is very hard to prepare transparent piezoelectric materials with both high optical transmittance and excellent piezoelectricity. In this study, 2.5 mol% Sm-doped 0.72Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ (PMN-PT) ceramic with a piezoelectric coefficient d₃₃ of 1460 pC N^-1 and an optical transmission of 69% at Near-Infrared (NIR) is successfully prepared, and its optical, microstructure, ferroelectric and dielectric properties are fully studied. Subsequently, a 3 mm-diameter photoacoustic coaxial probe is fabricated, involving a transparent ultrasound transducer based on the prepared ceramic. The TUT has a center frequency (f_c) of 18.5 MHz, a −6 dB bandwidth of 20%, and a high effective electromechanical factor ($k_{\mathit{eff}})$$k_{\mathit{eff}})$ of 0.62. In addition, the imaging capability of the miniature probe is firstly confirmed through PA/US dual-modality imaging of in-vivo animals and phantoms, which indicates that the proposed transparent piezoelectric ceramic has great potential for photoacoustic/ultrasound imaging.