Novel Acousto-Optic Sensor for Needle Tip Tracking and Internal Ultrasound Imaging from the Tip for Biopsy and Thermal Ablation.

PURPOSE: To evaluate a novel acousto-optic sensor integrated into a needle stylet for real-time tracking, internal imaging, and thermal ablation monitoring under ultrasound (US) guidance. MATERIALS AND METHODS: A 125-micron acousto-optic sensor was embedded in a 24-gauge needle stylet to enable 3-dimensional needle tip localization relative to the US imaging plane. Bench testing assessed in-plane accuracy N = 10 and detection range thresholds N = 20 in a phantom using an abdominal US probe with computed tomography (CT) validation. Ex vivo experiments in bovine liver evaluated ablation monitoring, including detection of ablation margins and relative temperature estimation after water bath calibration. In vivo feasibility was tested in 1 swine for organ targeting (liver and kidney) and internal imaging from the view of the needle tip. Descriptive statistics were performed. RESULTS: Bench testing showed a mean in-plane localization accuracy of 1.4 mm (SD ± 1.7) and a median out-of-plane detection threshold of 2.1 cm (interquartile range, 1.7-3.0 cm) away from the US plane. Ex vivo, the system was able to track needle tip location through the ablation zone and to measure relative temperature at ablation margins with stable signal performance up to 65 °C. In vivo, internal intratissue imaging from the needle tip provided sufficient resolution to differentiate tissue structures, including vessel lumen and cystic versus solid regions. CONCLUSIONS: This acousto-optic sensor enabled accurate needle tip tracking for US guidance and real-time internal intratissue imaging capability, as well as relative temperature monitoring, in this preclinical study. Further studies will determine the extent to which this technology could enhance US-guided interventions in a clinical setting.