Robotically assisted ablative treatment guided by freehand 3D ultrasound

Robots can improve the accuracy of image-guided needle placement over traditional freehand techniques. While many research groups have demonstrated this, widespread clinical adoption of needle placement robots has not immediately followed, because (1) robots are generally expensive and (2) they are difficult to calibrate and register to the patient in a manner fast and user-friendly enough to be practical in the operating room. Our solution to these considerations is a novel, clinically applicable, low-cost system consisting of a robot (manipulating the needle through a surgeon-specified trajectory), guided by tracked freehand three-dimensional ultrasound (3DUS). We address cost by algorithmically enabling the robot to be unencoded, uncalibrated, and mechanically simple. We address ease of use by eliminating pre-operative registration, and nearly eliminating calibration. The surgical tool is tracked and thereby registered imager intra-operatively. A structured 3DUS volume, created using a tracked conventional 2DUS probe, provides the basis for accurate and reliable volumetric visualization, simulation, and planning. The system components are integrated using a 3D Slicer-based software package. Experiments have been conducted on both mechanical and calf liver phantoms (with embedded olives simulating tumors) with an overall accuracy of 2.54 mm and a targeting success rate of 100%.