Robotic soft tissue tracking using an inexpensive bench-top robot and electromagnetics

40% of breast cancer patients require corrective surgery after tumour resection via breast-conserving surgery. Sweeping of the resection cavity by spectroscopy and ultrasound is emerging as a solution for identifying residual cancer. However, this is challenging as breast tissue moves frequently. We present an approach for tracking the motion of a resection cavity with a robotic arm. We use EM tracking and a 6-axis robotic arm to track a simulated resection cavity. We embed an EM sensor in a retractor that holds the cavity open. A 3D Slicer module is then used to detect motion from the sensor and command the arm to follow the movement. To assess this approach we move the retractor to 36 positions in the workspace and record the latency between when a command is published and when the robot moves. We attach a camera to the end-effector of the robot to determine when the robot has successfully tracked the cavity by checking if it is visible in the camera frame. The latency was recorded to be 832.1ms on average. We can also successfully track the motion of the cavity 92% of the time. These results suggest that tracking of the breast cavity using EM tracking and robotics is feasible.