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

摘要

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 manual free hand ultrasonography (US) in conjunction with free hand positioning of the tissue ablator. Several investigational systems exist that simultaneously track a transcutaneous ultrasound (TCUS) probe and an ablator and provide visual overlay of the two on a computer screen, and some of those systems also register the TCUS images with pre-operative CT and/or MRI. 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 critical, 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.