A new system for 3D ultrasound-guided placement of cerebral ventricle catheters.

PURPOSE: We present a new system for 3D ultrasound-guided placement of cerebral ventricle catheters. The system has been developed with the aim to provide accurate ultrasound-based guidance with only minimal changes to the current surgical technique and workflow. METHODS: The system consists of a pre-calibrated navigation adapter for the catheter and a reference frame attached to a standard surgical retractor in addition to an ultrasound-based navigation system with a probe that fits on top of a standard burr hole. RESULTS: The accuracy of the pre-calibrated system has been evaluated, and our measurements indicate that the accuracy of the pre-calibrated system is better than 3 mm. We also present a clinical case. CONCLUSIONS: The navigation accuracy is considered sufficient for clinical use, and initial clinical tests are promising. Further testing will be necessary to fully evaluate the performance of the system in a clinical setting.

Integrated pre- and intraoperative imaging in a patient with an arteriovenous malformation located in eloquent cortex.

INTRODUCTION: The use of integrated pre- and intraoperative imaging may be useful when resecting brain lesions in close proximity to eloquent areas, such as the primary motor cortex and language cortices. CASE REPORT: A 32-year-old woman with an arteriovenous malformation (AVM) located in the primary motor cortex underwent surgery using functional neuronavigation. Blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) and diffusion tensor tractography (DTT) were used for preoperative mapping of primary motor areas and the corticospinal tracts, respectively. The BOLD fMRI activations and DTT tractograms were integrated into the neuronavigation system and visualized intraoperatively throughout the operation. Furthermore, stereoscopic visualizations of the angioarchitecture based on 3D MRI angiograms were used to rehearse the surgical approach to the feeder vessels. Finally, intraoperative ultrasound was used to locate and clip the feeding vessels. CONCLUSION: The AVM was carefully resected with the aid of the above-mentioned imaging techniques, and the intuitive usefulness of the techniques was further substantiated by the rewarding postoperative outcome.

Clinical validation of vessel-based registration for correction of brain-shift.

In this paper, we have tested and validated a vessel-based registration technique for correction of brain-shift using retrospective clinical data from five patients: three patients with brain tumors, one patient with an aneurysm and one patient with an arteriovenous malformation. The algorithm uses vessel centerlines extracted from segmented pre-operative MRA data and intra-operative power Doppler ultrasound images to compute first a linear fit and then a thin-plate spline transform in order to achieve non-linear registration. The method was validated using (i) homologous landmarks identified in the original data, (ii) selected vessels, excluded from the fitting procedure and (iii) manually segmented, non-vascular structures. The tracking of homologous landmarks show that we are able to correct the deformation to within 1.25 mm, and the validation using excluded vessels and anatomical structures show an accuracy of 1mm. Pre-processing of the data can be completed in 30 s per dataset, and registrations can be performed in less than 30s. This makes the technique well suited for intra-operative use.

Functional neuronavigation combined with intra-operative 3D ultrasound: initial experiences during surgical resections close to eloquent brain areas and future directions in automatic brain shift compensation of preoperative data.

OBJECTIVE: The aims of this study were: 1) To develop protocols for, integration and assessment of the usefulness of high quality fMRI (functional magnetic resonance imaging) and DTI (diffusion tensor imaging) data in an ultrasound-based neuronavigation system. 2) To develop and demonstrate a co-registration method for automatic brain-shift correction of pre-operative MR data using intra-operative 3D ultrasound. METHODS: Twelve patients undergoing brain surgery were scanned to obtain structural and fMRI data before the operation. In six of these patients, DTI data was also obtained. The preoperative data was imported into a commercial ultrasound-based navigation system and used for surgical planning and guidance. Intra-operative ultrasound volumes were acquired when needed during surgery and the multimodal data was used for guidance and resection control. The use of the available image information during planning and surgery was recorded. An automatic voxel-based registration method between preoperative MRA and intra-operative 3D ultrasound angiography (Power Doppler) was developed and tested postoperatively. RESULTS: The study showed that it is possible to implement robust, high-quality protocols for fMRI and DTI and that the acquired data could be seamlessly integrated in an ultrasound-based neuronavigation system. Navigation based on fMRI data was found to be important for pre-operative planning in all twelve procedures. In five out of eleven cases the data was also found useful during the resection. DTI data was found to be useful for planning in all five cases where these data were imported into the navigation system. In two out of four cases DTI data was also considered important during the resection (in one case DTI data were acquired but not imported and in another case fMRI and DTI data could only be used for planning). Information regarding the location of important functional areas (fMRI) was more beneficial during the planning phase while DTI data was more helpful during the resection. Furthermore, the surgeon found it more user-friendly and efficient to interpret fMRI and DTI information when shown in a navigation system as compared to the traditional display on a light board or monitor. Updating MRI data for brain-shift using automatic co-registration of preoperative MRI with intra-operative ultrasound was feasible. CONCLUSION: In the present study we have demonstrated how both fMRI and DTI data can be acquired and integrated into a neuronavigation system for improved surgical planning and guidance. The surgeons reported that the integration of fMRI and DTI data in the navigation system represented valuable additional information presented in a user-friendly way and functional neuronavigation is now in routine use at our hospital. Furthermore, the present study showed that automatic ultrasound-based updates of important pre-operative MRI data are feasible and hence can be used to compensate for brain shift.

Endoscopy guided by an intraoperative 3D ultrasound-based neuronavigation system.

OBJECTIVE: We have investigated the feasibility of using 3D ultrasound-based neuronavigation for guiding neuroendoscopy. METHODS: A neuronavigation system with an integrated ultrasound scanner was used for acquiring the 3D ultrasound image data. The endoscope with a tracking frame attached was calibrated to the navigation system. The endoscope was guided based on intraoperative 3D ultrasound data in 9 operations. In 5 of the operations, ultrasound angiography data were also obtained. Updated image data (e. g., more than one 3D ultrasound dataset) were obtained in 6 of the operations. RESULTS: We found that the image quality of 3D ultrasound was sufficient for image guidance of the endoscope. Planning of the entry point and trajectory as well as finding optimal sites for fenestration were successfully performed. Blood vessels were visualized by 3D ultrasound angiography. In one procedure of third ventriculostomy, the basilar artery was visualized. Updated image data were quickly obtained, and in two of the cases, a reduction of the size of cysts was demonstrated. CONCLUSIONS: 3D ultrasound gives accurate images of sufficiently high quality for image guidance of neuroendoscopy. Updated 3D ultrasound datasets can easily be acquired and may adjust for brain shift. Ultrasound angiography image data are also available with this technology and can visualize vessels of importance.

Intra-operative 3D ultrasound in neurosurgery.

In recent years there has been a considerable improvement in the quality of ultrasound (US) imaging. The integration of 3D US with neuronavigation technology has created an efficient and inexpensive tool for intra-operative imaging in neurosurgery. In this review we present the technological background and an overview of the wide range of different applications. The technology has so far mostly been applied to improve surgery of tumours in brain tissue, but it has also been found to be useful in other procedures such as operations for cavernous haemangiomas, skull base tumours, syringomyelia, medulla tumours, aneurysms, AVMs and endoscopy guidance.

Image-guided laparoscopic surgery. Review and current status.

The main drawback with laparoscopic surgery is that the surgeon is unable to palpate vessels, tumours and organs during surgery. Further-more, the laparoscope only provides a surface view of organs. There is a need for more advanced visualizations techniques that can enhance the display presented to the surgeon so that important information below the surface of the organs is included when planning the procedure as well as for guidance and control during treatment. In this paper, we present a review of the literature and the state of art within image-guided laparoscopic surgery. We describe our own experience using a prototype navigation system for advanced visualizations and guidance during laparoscopic procedures in the retroperitoneum. Furthermore, we show sample images from the Future Operating Room for laparoscopic surgery in Trondheim, where this technology is being further developed and tested in clinical studies. Our system is based on three-dimensional navigation technology, i.e. preoperatively acquired magnetic resonance or computed tomography data used in combination with tracked instruments, allowing the surgeon to interactively control the display of images prior to and during surgery with normal use of the instruments. In summary, we believe that abdominal image navigation using tracked instruments and advanced visualizations has a large potential for improving future laparoscopic surgery, especially in cases where vessels and anatomical relations beyond surfaces is difficult to identify using only a laparoscope. The technology helps the surgeon to better understand the anatomy and locate blood vessels. Accordingly, we believe that 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.

Stereoscopic navigation-controlled display of preoperative MRI and intraoperative 3D ultrasound in planning and guidance of neurosurgery: new technology for minimally invasive image-guided surgery approaches.

OBJECTIVE: This paper demonstrates a method that brings together three essential technologies for surgery planning and guidance: neuronavigation systems, 3D visualization techniques and intraoperative 3D imaging technologies. We demonstrate the practical use of an in-house interactive stereoscopic visualization module that is integrated with a 3D ultrasound based neuronavigation system. MATERIALS AND METHODS: A stereoscopy volume visualization module has been integrated with a 3D ultrasound based neuronavigation system, which also can read preoperative MR and CT data. The various stereoscopic display modalities, such as "cut plane visualization" and "interactive stereoscopic tool guidance" are controlled by a pointer, a surgical tool or an ultrasound probe. Interactive stereoscopy was tested in clinical feasibility case studies for planning and guidance of surgery procedures. RESULTS: By orientating the stereoscopic projections in accordance to the position of the patient on the operating table, it is easier to interpret complex 3D anatomy and to directly take advantage of this 3D information for planning and surgical guidance. In the clinical case studies, we experienced that the probe-controlled cut plane visualization was promising during tumor resection. By combining 2D and 3D display, interpretation of both detailed and geometric information may be achieved simultaneously. The possibilities of interactively guiding tools in a stereoscopic scene seemed to be a promising functionality for use during vascular surgery, due to specific location of certain vessels. CONCLUSION: Interactive stereoscopic visualization improves perception and enhances the ability to understand complex 3D anatomy. The practical benefit of 3D display is increased considerably when integrated with surgical navigation systems, since the orientation of the stereoscopic projection corresponds to the orientation of the patient on the operating table. Stereoscopic visualizations work well on MR and CT images, although volume rendering techniques are especially suitable for intraoperative 3D ultrasound image data.

SonoWand, an ultrasound-based neuronavigation system.

OBJECTIVE: We have integrated a neuronavigation system into an ultrasound scanner and developed a single-rack system that enables the surgeon to perform frameless and armless stereotactic neuronavigation using intraoperative three-dimensional ultrasound data as well as preoperative magnetic resonance or computed tomographic images. The purpose of this article is to describe our two-rack prototype and present the results of our work on image quality enhancement. DESCRIPTION OF INSTRUMENTATION: The system consists of a high-end ultrasound scanner, a modest-cost computer, and an optical positioning/digitizer system. Special technical and clinical efforts have been made to achieve high image quality. A special interface between the ultrasound instrument and the navigation computer ensures rapid transfer of digital three-dimensional data with no loss of image quality. OPERATIVE TECHNIQUE: The positioning system tracks the position and orientation of the patient, the ultrasound probe, the pointer, and various surgical instruments. This makes it possible to update the three-dimensional map during surgery and navigate by ultrasound data in a similar manner as with magnetic resonance data. METHODS: The two-rack prototype has been used for clinical testing since November 1997 at the University Hospital in Trondheim. EXPERIENCE AND RESULTS: The image quality improvements have enabled us, in most cases, to extract information from ultrasound with clinical value similar to that of preoperative magnetic resonance imaging. The overall clinical accuracy of the ultrasound-based navigation system is expected to be comparable to or better than that of a magnetic resonance imaging-based system. CONCLUSION: The SonoWand system enables neuronavigation through direct use of intraoperative three-dimensional ultrasound. Further research will be necessary to explore the potential clinical value and the limitations of this technology.