Laparoscopic navigation pointer for three-dimensional image-guided surgery.

BACKGROUND: The main drawback with the laparoscopic approach is that the surgeon is unable to palpate vessels, tumors, and organs during surgery. Furthermore, the laparoscope provides only surface view of organs. There is a need for more advanced visualizations that can enhance the view to include information below the surface of the organs for planning of the procedure and for control and guidance during treatment. METHODS: We propose three-dimensional (3D) navigation technology based on preoperatively acquired magnetic resonance or computed tomography data used in combination with a laparoscopic navigation pointer (LNP). The LNP has an attached position tracker that allows the surgeon to control the display of images interactively before and during surgery. This study evaluated the patient registration accuracy, the feasibility of image-based navigation and, qualitatively, the navigation precision in the retroperitoneum during laparoscopic surgery. RESULTS: This technology was used during the treatment of six patients (involving adrenalectomies and a neuroma protruding into the pelvis). An average patient registration accuracy of 6.90 mm was achieved. The precision during navigation in the retroperitoneum was, in some cases, better than the patient registration accuracy suggested. The technology helped the surgeons to understand better the anatomy and to locate blood vessels. CONCLUSIONS: In the reported cases, the LNP was a useful tool for image guidance in laparoscopic surgery, both for planning the surgical approach in detail and for guidance. The authors believe that adominal 3D image guidance using an LNP has a large potential for improving laparoscopic surgery, especially when vessels and anatomic relations may be difficult to identify using only a laparoscope. Accordingly, they believe this new technology could increase safety and make it easier for the surgeon to perform successful laparoscopic surgery.

Three-dimensional ultrasound-based navigation combined with preoperative CT during abdominal interventions: a feasibility study.

PURPOSE: Three-dimensional (3D) intraoperative ultrasound may be easier to interpret when used in combination with less noisy preoperative image data such as CT. The purpose of this study was to evaluate the use of preoperative image data in a 3D ultrasound-based navigation system specially designed for minimally invasive abdominal surgery. A prototype system has been tested in patients with aortic aneurysms undergoing clinical assessment before and after abdominal aortic stent-graft implantation. METHODS: All patients were first imaged by spiral CT followed by 3D ultrasound scanning. The CT volume was registered to the patient using fiducial markers. This enabled us to compare corresponding slices from 3D ultrasound and CT volumes. The accuracy of the patient registration was evaluated both using the external fiducial markers (artificial landmarks glued on the patient's skin) and using intraoperative 3D ultrasound as a measure of the true positioning of anatomic landmarks inside the body. RESULTS: The mean registration accuracy on the surface was found to be 7.1 mm, but increased to 13.0 mm for specific landmarks inside the body. CT and ultrasound gave supplementary information of surrounding structures and position of the patient's anatomy. Fine-tuning the initial patient registration of the CT data with a multimodal CT to intraoperative 3D ultrasound registration (e.g., mutual information), as well as ensuring no movements between this registration and image guidance, may improve the registration accuracy. CONCLUSION: Preoperative CT in combination with 3D ultrasound might be helpful for guiding minimal invasive abdominal interventions.

3D ultrasound-based navigation for radiofrequency thermal ablation in the treatment of liver malignancies.

BACKGROUND: The aim of the study was to compare three methods for ultrasound-based guidance of a radiofrequency probe into liver tumors in a model setup. METHODS: The liver model tumors were placed inside excised calf livers, and the radiofrequency probe was guided into the center using either a new 3D navigation method or two conventional 2D methods-freehand scanning and a method based on a biopsy guide. We performed 54 experiments, measuring the physical distance (all methods) and image distance (3D method only) from the tip of the probe to the center of the tumors. RESULTS: Based on the physical measurements alone, the biopsy-based guiding performed better than both the 2D freehand and the 3D navigation method. However, the 3D image measurements showed that the tip of the probe was better positioned in the center of the model tumors for the 3D navigation method as compared to the physical measurement results for the 2D methods. CONCLUSION: Although it was easier to position the radiofrequency probe accurately using the 3D image display technique, movement of the model tumor during 3D navigation is a challenge.