Real-time 3D Ultrasonic Needle Tracking with a Photoacoustic Beacon

Abstract: We present an interventional ultrasound system capable of simultaneous 3D tracking and B-mode guidance of a novel, trackable needle core biopsy tool. Interventional radiology procedures such as core needle biopsy of focal liver lesions are ideally performed under ultrasound guidance, during which having a clear understanding of the location of the needle tip is essential to avoid adverse events and the need for repeat procedures. However, the 3D nature of the procedure and poor image contrast of the needle in heterogeneous tissue or at steep insertion angles often leads to confusion over the true location of the tip relative to the ultrasound imaging plane. This leads services to rely ionising, slow and expensive X-ray computed tomography guidance and/or senior clinicians for risky or otherwise challenging procedures. Existing methods to enhance needle visibility largely remain limited to 2D, and do not offer real-time volumetric guidance. Our proposed system provides the clinician with a real-time, quantitative visualisation of the 3D location of the needle tip superimposed onto B-mode ultrasound images. The tip location is determined from the time-of-flight of ultrasound generated by a photoacoustic beacon embedded in the needle bevel and received by a sparse receiver array distributed around the imaging system's curvilinear ultrasound probe. The performance of the system was assessed both in water and in an ex vivo tissue phantom, with referenced positions derived from X-ray computed tomography. The usability of the system was assessed by 12 clinicians performing simulated biopsies on a second ex vivo tissue phantom.