Clinical Report: Ultrasound-Guided Navigated Resection of Hepatic Tumors

Overview

This study evaluates a novel electromagnetic image guidance system that generates 3D liver models directly from intraoperative ultrasound to assist hepatic tumor resections. The approach aims to improve surgical accuracy by eliminating reliance on preoperative imaging registration, addressing limitations of conventional navigation systems.

Background

Complete tumor resection with preservation of liver parenchyma and critical structures is the primary goal in liver surgery. Conventional intraoperative 2D ultrasound is limited by interpretation complexity, operator dependency, and signal disruption during electrocautery, contributing to a 14–22% incidence of R1 resections. Image-guided surgical navigation offers 3D visualization but often depends on preoperative imaging registration, which is unreliable due to liver deformation and tumor changes. Ultrasound-only navigation systems may provide more accurate guidance by relying solely on intraoperative imaging.

Data Highlights

A prospective single-center feasibility study was conducted including 25 patients with hepatic tumors > 2 cm visible on intraoperative ultrasound. The first five patients were used to optimize workflow and excluded from accuracy analysis. Electromagnetic tracking was applied to the ultrasound transducer, vessel sealer, and surgical pointer. The navigation system integrated real-time tracking and 3D modeling using 3D Slicer and PLUS toolkit software. A rigid single landmark registration aligned preoperative imaging with intraoperative anatomy for spatial context.

Key Findings

• The electromagnetic navigation system successfully generated 3D liver models directly from intraoperative ultrasound data.
• Tracking of surgical instruments including ultrasound probe and vessel sealer was feasible using electromagnetic sensors with custom adapters.
• Navigation eliminated the need for continuous registration to preoperative 3D models, potentially improving accuracy by accounting for liver deformation.
• The system provided real-time visualization of tumor location and spatial relationships during resection.
• Initial clinical feasibility was demonstrated in 20 patients after workflow optimization.

Clinical Implications

This ultrasound-based navigation approach may enhance intraoperative tumor localization and margin assessment by providing continuous, real-time 3D visualization without reliance on preoperative imaging registration. It could reduce the incidence of incomplete resections and improve preservation of critical liver structures. Adoption of electromagnetic tracking for surgical instruments facilitates integration into existing workflows.

Conclusion

Ultrasound-guided electromagnetic navigation for hepatic tumor resection is clinically feasible and may overcome limitations of conventional navigation systems by providing accurate, real-time 3D guidance. Further studies are warranted to confirm its impact on surgical outcomes.

References

1. Pérez de Frutos et al. 2022 -- Rigid image-to-patient registration using tracked tool orientation
2. Netherlands Cancer Institute Study 2022-2025 -- Ultrasound-based navigated surgical resection feasibility
3. 3D Slicer and PLUS toolkit -- Open-source surgical navigation software