Image-guided laparoscopic pelvic lymph node dissection using stereo visual tracking free-hand laparoscopic ultrasound.

Laparoscopic pelvic lymph node dissection is a delicate operation because pelvic arteries, which should be located first to guide the dissection, are often concealed by tissues and cannot be identified in the endoscopic view. Consequently, arteries can be damaged if they are not located accurately. To improve dissection safety and efficiency, we have developed an image-guided navigation system to provide pelvic artery position information by registering a 3D artery model extracted from CT images to a 3D model reconstructed from free-hand laparoscopic ultrasound images. The ultrasound probe is tracked using a proposed stereo vision-based tracking strategy that can simplify the system and reduce setup time. The artery is segmented from 2D ultrasound images using a local phase-based snakes framework. The accuracy of the proposed navigation system was estimated in a phantom experiment (the TRE error was 1.58 ± 0.70 mm), and the feasibility of the proposed navigation system was confirmed in an animal experiment.