Lung W Lau, MD1, Xinyang Liu, PhD1, William Plishker, PhD1, David A Geller, MD2, Timothy D Kane1, MD, Raj Shekhar, PhD1. 1Children’s National Health System, 2University of Pittsburgh Medical Center
Objective: Ablation needle placement is the critical step in laparoscopic ablation of unresectable liver tumors. Even to skilled surgeons, it can be difficult to correspond the three dimensional surgical field of view with the two dimensional laparoscopic ultrasound image. This leads to prolonged operative time as well as increased needle punctures into the liver due to off-target trajectory. A way to improve needle placement would be through augmented reality (AR) by overlaying the ultrasound image onto the live laparoscopic video while also providing a needle trajectory in the video. In this study, we developed and tested an AR guidance system for needle placement that could be used during laparoscopic liver ablations.
Methods: The AR guidance system overlays real-time laparoscopic ultrasound image (LUS) onto live laparoscopic video while providing a trajectory for needle guidance all on a single screen. This system utilizes an electromagnetic (EM) tabletop field generator for 3D location tracking of the LUS transducer and the laparoscope. Tracking of the radiofrequency ablation needle (2-mm diameter, 25-cm cannula length) is achieved by a mechanical mount with an embedded EM sensor that is attached to the needle handle. With an off-field computer, the system compiles the location and orientation of the LUS, laparoscope, and needle tip and builds the overlay for AR . A live laparoscopic video is then presented with augmented reality, showing the ultrasound image with a needle trajectory projected from the axis of the needle tip. The guidance overlay targets the point of intersection between the ultrasound plane and the needle axis, allowing the surgeon to aim for a lesion visualized under the ultrasound probe (Figure 1). The application of this system was evaluated with a gel-phantom containing targetable lesions under ultrasound. Targeting was performed with and without AR guidance. The accuracy or registration of the needle placement (distance between needle tip and lesion) and time needed for placement were measured.
Results: The AR guidance system was tested by the first author (L.L.), a third-year surgical resident. Needle targeting was performed on six targets, three with AR and three without (i.e., the conventional approach), with lesion locations blinded to the user. On average, difference in needle tip position and actual target location was 4.9 mm for the conventional approach, whereas for the AR approach was 5.0 mm. The averaged time needed for needle placement was 59 s by the conventional method, while, with AR guidance, the timing was 24 s.
Conclusion: This AR system could be beneficial to guide needle placement during laparoscopic liver ablations. Our early experience shows the applicability of this system to reduce time needed for needle placement in lesion targeting. The targeting accuracy was similar with either technique but AR decreased targeting time by over 50%. While more testing is needed and planned, compared to the conventional approach, we anticipate the AR system will improve the efficiency of liver lesion ablation while achieving similar therapeutic outcomes.
Figure 1. A snapshot of laparoscopic video showing the AR overlay with LUS image and the radiofrequency ablation needle trajectory.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 98920
Program Number: ETP771
Presentation Session: Emerging Technology Poster Session (Non CME)
Presentation Type: Poster