Image guidance helps enhance robotic surgery

October 15, 2008

Incorporating image guidance into robotic surgery significantly enhanced tumor resection in a series of mock procedures involving surgical phantoms

Compared with standard robotic surgery, image-guided procedures were associated with a threefold reduction in the mean resection ratio, said first author S. Duke Herrell, MD, associate professor of urologic surgery at Vanderbilt University in Nashville, TN. Surgical task time was reduced by more than one-third with image-guided surgery.

"This was a preliminary study, building on our collaboration with biomedical engineering and image guidance to minimally invasive surgery in urology," Dr. Herrell told Urology Times. "As it turns out, even in early experience, augmenting robotic surgery with image guidance is beneficial."

"We have previously shown that the daVinci-S has a localization error of 1.05 mm, and we have designed a robotic image-guided surgical [RIGS] system using the daVinci-S," Dr. Herrell said. "We validated this novel platform through a series of mock surgical experiments requiring extraction of phantom subsurface tumors."

The RIGS system consists of the daVinci-S (Intuitive Surgical, Sunnyvale, CA) with intraoperative hybrid image guidance.

Dr. Herrell reported findings from a study of 13 cylindrical polyvinyl alcohol gel phantoms, which were injected with diluted iodinated contrast medium visible to a laparoscopic camera. The phantoms were divided into image-guided and nonimage-guided groups.

Enhanced resection and task time

For the nonimage control group, the surgeon was given a preoperative CT scan of the phantom and was asked to resect the contrast-enhanced tumor using the daVinci-S.

During image-guided surgery, the preoperative CT scan was co-registered with the daVinci RIGS system and displayed on the surgeon's console. Operators used a Polaris optical tracker (Northern Digital Instruments, Waterloo, Ontario) to track robotic arms and ORION software (Pathfinder Therapeutics, Nashville, TN) to perform image registration and integration with the daVinci-S. Instrument tips could be tracked in real time and correlated with the preoperative CT.

Investigators used a postoperative CT scan to examine resection cavity size and tumor remnant, and computer resection ratios were plotted against tumor radii.

The mean tumor radius was 0.48 cm, with a mean ideal resection volume of 1.75 cm3 . The mean resection ratio was 9.01 for the control group and 3.26 for image-guided surgery (p<.05). Mean surgical task time was reduced from 13 minutes in the control group to 8 minutes with image-guided surgery (p<.05).

The results of the study suggest that the image-guided platform may have potential application in urology and in other surgical fields, Dr. Herrell and colleagues concluded.