Semi-autonomous needle-positioning device for percutaneous nephrolithotomy procedures
At present, manual needle-positioning techniques known as "triangulation" and "keyhole surgery" are implemented during percutaneous nephrolithotomy (PCNL) to gain initial kidney access. These techniques do not ensure correct needle placement inside the kidney, resulting in multiple needle punctures, unnecessary hemorrhage, excessive radiation exposure to all involved and increased surgery time. A cost-effective fluoroscopy-guided needle-positioning system is proposed for aiding urologists in gaining accurate and repeatable kidney calyx access. Guidance is realized by modeling a C-arm fluoroscopic system as an adapted pinhole camera model and utilizing stereovision principles on an image pair. Targeting is realized with the aid of a graphical user interface operated by the surgeon. An average target registration error of 2.5 mm (SD = 0.8 mm) was achieved in a simulated environment. Similar results were achieved in the operating room environment with successful needle access in two in-vitro porcine kidneys. © 2011 World Scientific Publishing Company.