Chet W Hammill, MD, Maria A Cassera, Logan W Clements, PhD, Prashanth Dumpuri, PhD, James D Stefansic, PhD
Liver and Pancreas Surgery Program, Providence Medical Center, Portland, OR and Pathfinder Technologies, Inc., Nashville, TN
The Explorer™ Minimally Invasive Liver (MIL) device is a 3-D image guidance system that is intended to be used as a navigation aid during laparoscopic liver ablation procedures and to be used in conjunction with other standard of care intraoperative imaging modalities.
Laparoscopic hepatic ablation procedures are currently performed under the guidance of intraoperative ultrasound, which is 2-D and requires considerable expertise. The Explorer™ MIL device is an experimental 3-D image-guidance system intended to be used in conjunction with ultrasound during laparoscopic liver ablation procedures. The Explorer™ MIL device allows for intraoperative surgical instrument tracking and the display of the location of tracked instrumentation on preoperative tomographic imaging and 3-D models of anatomical structures of interest. Additionally, the Explorer™ MIL device has the ability to track rigid laparoscopic ultrasound transducers and integrate the images into the 3-D model.
Determining the accuracy of tumor targeting using an ablation device during clinical procedures is a difficult problem. To overcome this problem, a human cadaver model re-perfused with a contrast agent solution was utilized. Seven to eight biopsy clips (UltraClip® Dual Trigger Breast Tissue Marker, Bard Biopsy Systems, Tempe, AZ) visible on both ultrasound and CT were distributed throughout the liver in five cadavers. After the biopsy clips were placed, a “preoperative” CT was acquired of the cadaveric specimen for use in the Explorer™ MIL device. After randomization the clips were targeted using either laparoscopic ultrasound alone or laparoscopic ultrasound in conjunction with the Explorer™ MIL device. Two different percutaneous ablation instruments, the Covidien Evident™ MWA antenna or the Angiodynamics StarBurst® Xli-enhanced RFA probe, were used for targeting. Once the tip of the probe was placed as close as possible to the specified target it was fixed in place and a “postoperative” CT was acquired. Over all of the ablation probe placements (N = 37), the mean distance between instrument tip and target marker was found to be 8.7±7.5mm for probe placements performed with laparoscopic ultrasound guidance and 6.8±3.8mm for probe placements using the Explorer™ MIL device in concert with laparoscopic ultrasound.
Conclusions & Future Directions
The results from the human cadaver evaluation of the Explorer™ MIL device indicate that there is a potential for the 3-D navigation system to provide some incremental benefit in laparoscopic ablation procedures. Future directions of the Explorer™ MIL device include more extensive evaluation of the benefit provided by tracked laparoscopic ultrasound and the interactive 3-D display of the ultrasound information. Additionally, ongoing research and development efforts are being made to transition to a electromagnetic tracking system which will allow for more accurate tracking of non-rigid surgical instrumentation.
Session: Podium Presentation
Program Number: ET007