Robotically assisted intraoperative ultrasound with application to ablative therapy of liver cancer

Management of primary and metastatic tumors of the liver remains a significant challenge to the health care community worldwide. There has been an increasing interest in minimally invasive ablative approaches that typically require precise placement of the tissue ablator within the volumetric center of the tumor, in order to achieve adequate destruction. Standard clinical technique involves free hand transcutaneous ultrasonography (TCUS) in conjunction with manual positioning of the tissue ablator. Unfortunately, existing TCUS systems suffer from many limitations. TCUS fails to identify nearly half of all treatable liver lesions, whereas intraoperative or laparoscopic US provides excellent tissue differentiation. Furthermore, freehand manipulation of the US probe critically lacks the level of control, accuracy, and stability required for guiding liver ablation. Volumetric reconstruction from sparse and irregular 2D image data is suboptimal. Variable pressure from the sonographer's hand also causes anatomic deformation. Finally, maintaining optimal scanning position with respect to the target lesion is crucial, but virtually impossible to achieve with freehand guidance. In response to these limitations, we propose the use of a fully encoded dexterous robotic arm to manipulate the US probe during surgery.