Navigation Improves Tumor Ablation Performance: Results From a Novel Liver Tumor Simulator Study.

BACKGROUND: The efficacy of microwave ablation in treating hepatic tumors requires advanced ultrasound skills. Failure of proper technique has the potential for either under- or over-treatment and possible harm to the patient. Emprint SX™ navigation provides surgeons with intra-operative, real-time navigation through augmented reality localization of the ablation antenna and the expected ablation zone. We hypothesize that incorporating this technology leads to improved targeting and optimizes ablation coverage. This study utilizes a simulated model to evaluate ablation outcomes using Emprint SX™ navigation vs standard ultrasound. METHODS: Surgical residents and faculty were recruited from a single institution. Using a novel tumor ablation simulator, participants performed ablations via 2 modes: standard ultrasound guidance (STD) and Emprint SX™ navigation (NAV). Primary outcome was the percentage of under-ablation. Secondary outcomes included percentage of over-ablation, time to complete trial, and number of attempts to position antenna. RESULTS: 281 trials were performed by fifteen participants, with 47% female and 60% novice ablationists. Under-ablation volume decreased by a mean of 16.3% (SEM ±12.9, P < .001) with NAV compared to STD. Over-ablation volume decreased by a mean of 14.0% (±8.2, P < .001). NAV time was faster by a mean of 32 seconds (±24.9, P < .001) and involved fewer antenna placement attempts by a mean of 1.3 (±1.0, P < .001). For novice ablationists, all outcomes were improved with NAV and novices saw larger improvements compared to experienced ablationists (P = .018). DISCUSSION: In a simulated model, NAV improves ablation efficacy and efficiency, with novices gaining the greatest benefit over standard ultrasound.

Laparoscopic microwave ablation of human liver tumours using a novel three-dimensional magnetic guidance system.

BACKGROUND: Accurate antenna placement is essential for effective microwave ablation (MWA) of lesions. Laparoscopic targeting is made particularly challenging in liver tumours by the needle's trajectory as it passes through the abdominal wall into the liver. Previous optical three-dimensional guidance systems employing infrared technology have been limited by interference with the line of sight during procedures. OBJECTIVE: The aim of this study was to evaluate a newly developed magnetic guidance system for laparoscopic MWA of liver tumours in a pilot study. METHODS: Thirteen patients undergoing laparoscopic MWA of liver tumours gave consent to their participation in the study and were enrolled. Lesion targeting was performed using the InnerOptic AIM™ 3-D guidance system to track the real-time position and orientation of the antenna and ultrasound probe. RESULTS: A total of 45 ablations were performed on 34 lesions. The median number of lesions per patient was two. The mean ± standard deviation lesion diameter was 18.0 ± 9.2 mm and the mean time to target acquisition was 3.5 min. The first-attempt success rate was 93%. There were no intraoperative or immediate postoperative complications. Over an average follow-up of 7.8 months, one patient was noted to have had an incomplete ablation, seven suffered regional recurrences, and five patients remained disease-free. CONCLUSIONS: The AIM™ guidance system is an effective adjunct for laparoscopic ablation. It facilitates a high degree of accuracy and a good first-attempt success rate, and avoids the line of site interference associated with infrared systems.

Recognition in ultrasound videos: where am I?

A novel approach to the problem of locating and recognizing anatomical structures of interest in ultrasound (US) video is proposed. While addressing this challenge may be beneficial to US examinations in general, it is particularly useful in situations where portable US probes are used by less experienced personnel. The proposed solution is based on the hypothesis that, rather than their appearance in a single image, anatomical structures are most distinctively characterized by the variation of their appearance as the transducer moves. By drawing on recent advances in the non-linear modeling of video appearance and motion, using an extension of dynamic textures, successful location and recognition is demonstrated on two phantoms. We further analyze computational demands and preliminarily explore insensitivity to anatomic variations.

Review of four studies on the use of physiological reaction as a measure of presence in stressful virtual environments.

A common measure of effectiveness of a virtual environment (VE) is the amount of presence it evokes in users. Presence is commonly defined as the sense of being there in a VE. There has been much debate about the best way to measure presence, and presence researchers need and have sought a measure that is reliable, valid, sensitive, and objective. We hypothesized that to the degree that a VE seems real, it would evoke physiological responses similar to those evoked by the corresponding real environment, and that greater presence would evoke a greater response. To examine this, we conducted four experiments, each of which built upon findings that physiological measures in general, and heart rate in particular, are reliable, valid, sensitive, and objective presence measures. The experiments compare participants' physiological reactions to a nonthreatening virtual room and their reactions to a stressful virtual height situation. We found that change in heart rate satisfied our requirements for a measure of presence, change in skin conductance did to a lesser extent, and that change in skin temperature did not. Moreover, the results showed that significant increases in heart rate measures of presence appeared with the inclusion of a passive haptic element in the VE, with increasing frame rate (30 FPS > 20 FPS > 15 FPS) and when end-to-end latency was reduced (50 ms > 90 ms).