Autonomous Ultrasound Scanning to Localize Needle Tip in Breast Brachytherapy

The functionality of ultrasound (US) imaging for cancer diagnosis and providing visual assistance for percutaneous therapies has been proven. Clinicians show limited accuracy in performing US imaging, especially for percutaneous therapies, where a needle tip needs to be placed accurately under image guidance. US imaging in the transverse plane is more commonly used in comparison to US imaging in the sagittal plane as what matters more is the position of the needle tip rather than the shape of the entire needle in procedures such as brachytherapy or biopsy. Using a robotic system to perform transverse US image acquisition can enhance the accuracy and repeatability of the imaging and, therefore, help with needle steering. In this paper, an autonomous system for US scanning to help the clinician with localizing and tracking the needle tip is presented. Two strategies to manipulate the probe in synchrony with the needle tip motion are proposed and implemented. As the needle is inserted by the human user, in order to depict the needle tip's deviation from its ideal path for the human user, the ideal needle tip position, which is coincident with one of the guide template's grid points, is dynamically projected on the US image in a real-time fashion. The conducted feasibility study proves the ability of the proposed robotic system to track the needle tip accurately and the helpfulness of the image overlay scheme for guiding the user about the needle tip motion.