Ultrasound Tomography with a Ring array Ultrasound Transducer for Image-Guided Activation of Phase-Change Nanodroplets

Acoustic-responsive drug carriers, such as phase-change nanodroplets, hold significant potential for targeted drug delivery (TDD). However, their activation through deep, heterogeneous tissues presents challenges for conventional ultrasound (US)-assisted systems. Some of these challenges stem from limitations in precise acoustic focusing and inadequate imaging guidance to correct for acoustic aberrations. In addition, the need for a secondary imaging device to monitor the activation of nanodroplets adds complexity to the system. This study introduces a ring array ultrasound tomography (UST)-guided TDD system that addresses these limitations by enabling precise, image-guided acoustic field generation in complex tissue environments. The system utilizes a 256-element ring array transducer in combination with a novel waveform optimization method that accounts for tissue properties, such as sound speed (SS) and acoustic attenuation (AA), to generate accurate, arbitrary acoustic field patterns deep within heterogeneous tissues. We demonstrate the system’s capability to generate acoustic fields ranging from small, point-like (D = 1 mm) to larger, tumor-shaped focal regions (D = 1 cm). Additionally, we show its effectiveness in activating and monitoring nanodroplets’ activation within deep tissue-mimicking phantoms. The proposed UST-guided TDD system has the potential to serve as a quantitative image-guided therapeutic platform for accurate TDD using a single ring array transducer.