Image-guided liver surgery: intraoperative projection of computed tomography images utilizing tracked ultrasound

AbstractBackgroundUltrasound (US) is the most commonly used form of image guidance during liver surgery. However, the use of navigation systems that incorporate instrument tracking and three-dimensional visualization of preoperative tomography is increasing. This report describes an initial experience using an image-guidance system with navigated US.MethodsAn image-guidance system was used in a total of 50 open liver procedures to aid in localization and targeting of liver lesions. An optical tracking system was employed to localize surgical instruments. Customized hardware and calibration of the US transducer were required. The results of three procedures are highlighted in order to illustrate specific navigation techniques that proved useful in the broader patient cohort.ResultsOver a 7-month span, the navigation system assisted in completing 21 (42%) of the procedures, and tracked US alone provided additional information required to perform resection or ablation in six procedures (12%). Average registration time during the three illustrative procedures was <1min. Average set-up time was approximately 5min per procedure.ConclusionsThe Explorer™ Liver guidance system represents novel technology that continues to evolve. This initial experience indicates that image guidance is valuable in certain procedures, specifically in cases in which difficult anatomy or tumour location or echogenicity limit the usefulness of traditional guidance methods

Evaluation of a Minimally Invasive Image-Guided Surgery System for Hepatic Ablation Procedures

The Explorer Minimally Invasive Liver (MIL) system uses imaging to create a 3-dimensional model of the liver. Intraoperatively, the system displays the position of instruments relative to the virtual liver. A prospective clinical study compared it with intraoperative ultrasound (iUS) in laparoscopic liver ablations

Evaluation of a Minimally Invasive Image-Guided Surgery System for Hepatic Ablation Procedures

BACKGROUND: The Explorer Minimally Invasive Liver (MIL) system uses imaging to create a 3-dimensional model of the liver. Intraoperatively, the system displays the position of instruments relative to the virtual liver. A prospective clinical study compared it with intraoperative ultrasound (iUS) in laparoscopic liver ablations. METHODS: Patients undergoing ablations were accrued from 2 clinical sites. During the procedures, probes were positioned in the standard fashion using iUS. The position was synchronously recorded using the Explorer system. The distances from the probe tip to the tumor boundary and center were measured on the ultrasound image and in the corresponding virtual image captured by the Explorer system. RESULTS: Data were obtained on the placement of 47 ablation probes during 27 procedures. The absolute difference between iUS and the Explorer system for the probe tip to tumor boundary distance was 5.5 ± 5.6 mm, not a statistically significant difference. The absolute difference for probe tip to tumor center distance was 8.6 ± 7.0 mm, not statistically different from 5 mm. DISCUSSION: The initial clinical experience with the Explorer MIL system shows a strong correlation with iUS for the positioning of ablation probes. The Explorer MIL system is a promising tool to provide supplemental guidance information during laparoscopic liver ablation procedures

Biomedical Paper Surface Registration for Use in Interactive, Image- Guided Liver Surgery

ABSTRACT Objective: Liver surgery is difficult because of limited external landmarks, significant vascularity, and inexact definition of intra-hepatic anatomy. Intra-operative ultrasound (IOUS) has been widely used in an attempt to overcome these difficulties, but is limited by its two-dimensional nature, inter-user variability, and image obliteration with ablative or resectional techniques. Because the anatomy of the liver and intra-operative removal of hepatic ligaments make intrinsic or extrinsic point-based registration impractical, we have implemented a surface registration technique to map physical space into CT image space, and have tested the accuracy of this method on an anatomical liver phantom with embedded tumor targets. Materials and Methods: Liver phantoms were created from anatomically correct molds with “tumors ” embedded within the substance of the liver. Helical CT scans were performed with 3-mm slices. Using an optically active position sensor, the surface of the liver was digitized according to anatomical segments. A surface registration was performed and RMS errors of the locations of internal tumors are presented as verification. An initial point-based marker registration was performed and considered the “gold standard ” for error measurement. Results: Errors for surface registration were 2.9 mm for the entire surface and 2.8 mm for embedded targets. Conclusion: This is an initial study considering the use of surface registration for the purpose of physical-to-image registration in the area of liver surgery. Comp Aid Surg 5:11–17 (2000). ©2000 Wiley-Liss, Inc. Key words: image-guided surgery, liver surgery, registratio