Revolutionizing Liver Surgery: The Rise of Real-Time Navigation
"Discover how a novel automatic registration system is making liver resections safer, faster, and more accurate, benefiting both surgeons and patients."
Liver resection, a standard treatment for primary and secondary liver malignancies, has seen remarkable advancements. Three-dimensional (3D) simulation software now enables more precise preoperative planning, often referred to as virtual hepatectomy. However, the challenge remains in seamlessly transferring this pre-operative plan to the actual intraoperative setting.
Surgeons must not only understand the preoperative plan but also intuitively identify the optimal liver transection line and locate critical vessels buried within the liver. To address this, intraoperative ultrasonography (IOUS) has been utilized since the 1980s, yet it requires extensive knowledge of liver anatomy and considerable experience to interpret the images effectively.
Real-time virtual sonography (RVS) has emerged as a valuable tool, aiding in the interpretation of ultrasound images by providing synchronized two-dimensional (2D) computed tomography (CT) images alongside ultrasound views. This technology allows surgeons to visualize target vessels and planned transection lines marked with colors using 3D simulation software. A recent breakthrough involves a novel automatic registration system that simplifies and accelerates the alignment of CT and IOUS images, potentially enhancing the precision and accessibility of liver surgery.
Image-Guided Navigation and Its Limits
Image-guided navigation systems are being developed to display liver anatomy during laparoscopic surgery, often by spatially correlating 3D models created from cross-sectional imaging with the operative site. Conventional systems rely on preoperative imaging, but pneumoperitoneum can deform the liver and reduce the accuracy of correspondence between the images and intraoperative reality. A 2025 review summarizes both established and emerging intraoperative imaging technologies, including their advantages and limitations.
From Intraoperative Ultrasound to Navigation
Intraoperative navigated liver surgery is defined as presenting perioperatively acquired imaging or computer-modeled data in relation to the patient's anatomy and surgical instruments. The development of surgical navigation followed a broader evolution described across operating-room applications, including neurosurgery, spinal surgery, and orthopedics. In liver surgery, the introduction of intraoperative ultrasound had an impact comparable to intraoperative cholangiography in biliary surgery, helping surgeons identify liver division lines, tumors, portal structures, and hepatic veins.
How Does the New RVS System Work?
The enhanced RVS navigation system integrates intraoperative ultrasonography with electromagnetic tracking technology. It features an ultrasound scanner with a specialized intraoperative ultrasound probe, an electromagnetic tracking device, and a workstation for real-time analysis. During surgery, an electromagnetic transmitter is positioned near the patient, and a sterilized sensor is attached to the ultrasound probe, enabling precise tracking of the probe's location and orientation.
- Initial Point Definition: The RVS workstation begins by defining an 'initial point,' which roughly aligns the spatial position and direction of the IOUS probe. This point, located on the left liver surface, is identified in both the 2D CT images and the IOUS view.
- Diagonal Scanning: Surgeons perform a 'diagonal scan' by moving the IOUS probe across the liver surface, capturing a volume of ultrasound data around the bifurcation of the left and right portal veins. This scan typically covers about 15 cm of the liver surface and takes only a few seconds.
- Automatic Registration: The acquired ultrasound volume images are reconstructed into 3D images and compared with the preoperatively obtained 3D CT images at the workstation. The system automatically matches these two sets of 3D images, adjusting the position and orientation of the CT images to achieve accurate multiplanar reconstruction.
Real-Time Fusion and Adaptive Navigation
A feasibility study of anatomical liver resection using real-time virtual sonography combined with indocyanine green fluorescent imaging reported a 100.0% one-year overall survival rate among 41 patients. The study reported tumor recurrence in 3 patients, or 7.3%, and a one-year tumor-free survival rate of 92.7%, representing 38 of 41 patients. These findings come from a feasibility study rather than a definitive comparison with conventional navigation.
Deformation Remains a Core Challenge
Liver navigation is difficult because the organ is soft and can deform during intraoperative manipulation, changing anatomical distances represented in a 3D model. In laparoscopic surgery, pneumoperitoneum can also deform the liver and create inaccuracies between preoperative images and intraoperative anatomy. One study indicates that intraoperative imaging can compensate for some of these deformations, but the need for such compensation underscores a limitation of navigation based only on preoperative representations.
The Future of Liver Surgery
The RVS system with automatic registration represents a significant step forward in liver surgery. By providing quick, easy, and accurate image registration, this technology enhances the precision and efficiency of liver resections. While challenges remain, such as compensating for liver deformation and minimizing positional errors, the RVS system has the potential to improve surgical outcomes and expand the use of IOUS in liver surgery, ultimately benefiting patients and surgeons alike.