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

Computed tomography-guided stereotactic surgery in the management of brain lesions: A single-center experience

Background

The present study presents our experience with computed tomography (CT)-guided stereotactic surgery in managing deep-seated brain lesions and provides a background in the expanding fields of morphological stereotactic neurosurgery.

Methods

We conducted this retrospective cohort study on 80 patients managed at the Department of Neurosurgery, Zagazig University Hospitals, Zagazig, Egypt, between January 2019 to January 2021. We targeted patients with morphological stereotactic surgeries performed as the primary management modality of their treatment.

Results

A total of 80 patients, with a mean age of 44.3 years, were included in the study. The stereotactic targets were supratentorial in 71 patients (88.75%), infratentorial in seven patients (8.75%), and both supraand infratentorial in two patients (2.5%). The lesions showed enhancements with IV contrast in 55 patients (68.75%). Stereotactic procedures were performed under local anesthesia in 64 patients and general anesthesia in 16 patients. Of the 80 stereotactic procedures, 52 were biopsies (65%). We observed a significant improvement in the postoperative Karnofsky performance score compared to the postoperative score (63.4 ± 19.8 vs. 56.7 ± 15.4, P = 0.001). The level of agreement between clinical, radiological, and final pathological diagnosis was assessed; it was complete in 47.5% of the patients. The postprocedural CT scan demonstrated intracranial hemorrhage in five patients (6.25%); four (5%) were silent with no neurological complications.

Conclusion

This study provided evidence that the stereotactic procedure is easy to perform, accurate in targeting the lesion, and spares patients from undergoing major surgical procedures. Stereotactic applications of spontaneous intracerebral hemorrhage, deep-seated abscesses, encysted tumors, or medically refractory benign intracranial hypertension can improve the outcome even in medically high-risk patients.

A comparison of thin-plate spline deformation and finite element modeling to compensate for brain shift during tumor resection

PURPOSE

Brain shift during tumor resection can progressively invalidate the accuracy of neuronavigation systems and affect neurosurgeons' ability to achieve optimal resections. This paper compares two methods that have been presented in the literature to compensate for brain shift: a thin-plate spline deformation model and a finite element method (FEM). For this comparison, both methods are driven by identical sparse data. Specifically, both methods are driven by displacements between automatically detected and matched feature points from intraoperative 3D ultrasound (iUS). Both methods have been shown to be fast enough for intraoperative brain shift correction (Machado et al. in Int J Comput Assist Radiol Surg 13(10):1525-1538, 2018; Luo et al. in J Med Imaging (Bellingham) 4(3):035003, 2017). However, the spline method requires no preprocessing and ignores physical properties of the brain while the FEM method requires significant preprocessing and incorporates patient-specific physical and geometric constraints. The goal of this work was to explore the relative merits of these methods on recent clinical data.

METHODS

Data acquired during 19 sequential tumor resections in Brigham and Women's Hospital's Advanced Multi-modal Image-Guided Operating Suite between December 2017 and October 2018 were considered for this retrospective study. Of these, 15 cases and a total of 24 iUS to iUS image pairs met inclusion requirements. Automatic feature detection (Machado et al. in Int J Comput Assist Radiol Surg 13(10):1525-1538, 2018) was used to detect and match features in each pair of iUS images. Displacements between matched features were then used to drive both the spline model and the FEM method to compensate for brain shift between image acquisitions. The accuracies of the resultant deformation models were measured by comparing the displacements of manually identified landmarks before and after deformation.

RESULTS

The mean initial subcortical registration error between preoperative MRI and the first iUS image averaged 5.3 ± 0.75 mm. The mean subcortical brain shift, measured using displacements between manually identified landmarks in pairs of iUS images, was 2.5 ± 1.3 mm. Our results showed that FEM was able to reduce subcortical registration error by a small but statistically significant amount (from 2.46 to 2.02 mm). A large variability in the results of the spline method prevented us from demonstrating either a statistically significant reduction in subcortical registration error after applying the spline method or a statistically significant difference between the results of the two methods.

CONCLUSIONS

In this study, we observed less subcortical brain shift than has previously been reported in the literature (Frisken et al., in: Miller (ed) Biomechanics of the brain, Springer, Cham, 2019). This may be due to the fact that we separated out the initial misregistration between preoperative MRI and the first iUS image from our brain shift measurements or it may be due to modern neurosurgical practices designed to reduce brain shift, including reduced craniotomy sizes and better control of intracranial pressure with the use of mannitol and other medications. It appears that the FEM method and its use of geometric and biomechanical constraints provided more consistent brain shift correction and better correction farther from the driving feature displacements than the simple spline model. The spline-based method was simpler and tended to give better results for small deformations. However, large variability in the spline results and relatively small brain shift prevented this study from demonstrating a statistically significant difference between the results of the two methods.

Preliminary Results Comparing Thin Plate Splines with Finite Element Methods for Modeling Brain Deformation during Neurosurgery using Intraoperative Ultrasound

Brain shift compensation attempts to model the deformation of the brain which occurs during the surgical removal of brain tumors to enable mapping of presurgical image data into patient coordinates during surgery and thus improve the accuracy and utility of neuro-navigation. We present preliminary results from clinical tumor resections that compare two methods for modeling brain deformation, a simple thin plate spline method that interpolates displacements and a more complex finite element method (FEM) that models physical and geometric constraints of the brain and its material properties. Both methods are driven by the same set of displacements at locations surrounding the tumor. These displacements were derived from sets of corresponding matched features that were automatically detected using the SIFT-Rank algorithm. The deformation accuracy was tested using a set of manually identified landmarks. The FEM method requires significantly more preprocessing than the spline method but both methods can be used to model deformations in the operating room in reasonable time frames. Our preliminary results indicate that the FEM deformation model significantly out-performs the spline-based approach for predicting the deformation of manual landmarks. While both methods compensate for brain shift, this work suggests that models that incorporate biophysics and geometric constraints may be more accurate.

Guided Punctures with Ultrasound Volume Navigation in Percutaneous Transforaminal Endoscopic Discectomy: A Technical Note

OBJECTIVE

Ultrasound volume navigation (UVN) has been widely used for accurate guidance and decreased radiation exposure. However, few studies have focused on the clinical significance of UVN in guiding percutaneous puncture in percutaneous transforaminal endoscopic discectomy (PTED). We evaluated UVN to guide percutaneous puncture in PTED.

METHODS

We retrospectively reviewed the medical records of 12 patients (8 men and 4 women), who had undergone PTED with the help of UVN or fluoroscopic guidance for lumbar disc herniation from November 2017 to December 2017.

RESULTS

The age of these 12 patients range was 26-71 years, and the body mass index range was 18.19-26.91 kg/m². Of the 12 patients, 6 were in UVN group and 6 were in fluoroscopy group. The mean number of punctures was 1.00 in UVN group and 3.83 in fluoroscopy group. The mean exposure time was 3.60 and 13.80 seconds in UVN and fluoroscopy groups, respectively. The mean operation time was 48.17 minutes and 61.33 minutes in UVN and fluoroscopy groups, respectively. A positive relationship was found between operation time and exposure time (P < 0.05). All patients achieved excellent or good clinical outcomes. The Oswestry Disability Index and visual analog scales for leg pain and back pain all showed significant improvement after the procedure (P < 0.05). None of patients experienced a complication.

CONCLUSIONS

UVN decreased the number of puncture attempts, radiation exposure, and operation time compared with fluoroscopic guidance in PTED. Therefore, UVN is a feasible and efficient method for guiding percutaneous puncture in PTED.

Neck tumor dissection improved with 3-dimensional ultrasound image guidance: technical case report

BACKGROUND AND IMPORTANCE

Three-dimensional ultrasound navigation has been performed to assist in resection of cranial and spinal tumors, but to the best of our knowledge, no one has described the use of real-time 3-dimensional ultrasound navigation in the resection of neck tumors beyond biopsy.

CLINICAL PRESENTATION

This case report describes the use of 3-dimensional ultrasonic navigation in assisting with resection of a large neck paraganglioma. The 3-dimensional ultrasonic navigation improved real-time visualization of the carotid arteries, the trachea, and other vital structures.

CONCLUSION

The use of 3-dimensional ultrasound navigation should be considered in aiding resection of large neck tumors because it can allow more efficient and safer tumor resection.

Two eyes see more than one: double echo stereoscopic MRA for rapid 3D visualization of vascular structures

OBJECT

A three-dimensional (3D) visualization of the target region during intravascular interventions in real-time is challenging since the acquisition of a time-consuming 3D dataset is required. In this work, a novel stereoscopic double echo sequence for achieving 3D depth perception by sampling only two oblique projection images is presented.

MATERIALS AND METHODS

A double echo (DE) FLASH pulse sequence was developed to acquire continuously stereoscopic image pairs of the vascular target anatomy. Stereo image data were displayed on a stereoscopic 3D LCD monitor in real time after image reconstruction. Phantom experiments followed by a depth perception test were performed to assess the usability of the stereo image pairs for 3D visualization. In an animal experiment the sequence was tested in vivo and was compared with a slower interleaved (IL) sequence variant.

RESULTS

In the phantom experiments an SNR difference of 6 % between left and right image was found which did not influence the depth perception. The DE acquisition was superior to the IL sequence (SNR(DE) = 10.3, 2.3 images/s over SNR(IL) = 7.1, 1.7 images/s), and during contrast enhancement the abdominal arterial vasculature was clearly perceived as a 3D structure.

CONCLUSION

A novel stereoscopic DE pulse sequence can be utilized for the fast 3D stereoscopic visualization of vascular structures in real-time.

A guide to stereoscopic 3D displays in medicine

Stereoscopic displays can potentially improve many aspects of medicine. However, weighing the advantages and disadvantages of such displays remains difficult, and more insight is needed to evaluate whether stereoscopic displays are worth adopting. In this article, we begin with a review of monocular and binocular depth cues. We then apply this knowledge to examine how stereoscopic displays can potentially benefit diagnostic imaging, medical training, and surgery. It is apparent that the binocular depth information afforded by stereo displays 1) aid the detection of diagnostically relevant shapes, orientations, and positions of anatomical features, especially when monocular cues are absent or unreliable; 2) help novice surgeons orient themselves in the surgical landscape and perform complicated tasks; and 3) improve the three-dimensional anatomical understanding of students with low visual-spatial skills. The drawbacks of stereo displays are also discussed, including extra eyewear, potential three-dimensional misperceptions, and the hurdle of overcoming familiarity with existing techniques. Finally, we list suggested guidelines for the optimal use of stereo displays. We provide a concise guide for medical practitioners who want to assess the potential benefits of stereo displays before adopting them.

Virtual reality augmentation in skull base surgery

OBJECTIVE

Skull base anatomy is complex and subject to individual variation. Understanding the complexity of surgical anatomy is faster and easier with virtual models created from primary imaging data of the patient. This study was designed to investigate the usefulness of virtual reality in image guidance for skull base procedures.

DESIGN

Primary volumetric image data from 110 patients was acquired using magnetic resonance, computed tomography (CT), and CT angiography. Pathologies included lesions in the anterior, middle, and posterior skull base. The data were transferred to an infrared-based image-guidance system for creation of a virtual operating field (VOF) with translucent surface modulation and optional "fly-through" video mode. During surgery, the target registration error for anatomical landmarks was assessed and the VOF was compared with the patient's anatomy in the operative field.

RESULTS

Complex structures like the course of the sigmoid sinus, the carotid artery, and the outline of the paranasal sinuses were well visualized in the VOF and were recognized by the surgeon instantly. Perception was greatly facilitated as compared with routine mental reconstruction of triaxial images. Accurate assessment of the depth of field and very small objects was not possible in VOF images.

CONCLUSION

Supported by sound anatomical knowledge, creation of a virtual operating field for a surgical approach in an individual patient offers a déjà vu experience that can enhance the capabilities of a surgical team in skull base approaches. In addition, application of this technique in image-guided procedures assists in targeting or avoiding hidden anatomical structures.

Standardized 3D Documentation for Neurosurgery

OBJECTIVE

Although direct volume visualization is now a standard tool for diagnosis and therapy planning for medical conditions in the brain, its application is normally restricted to radiological workstations. We propose the use of standardized digital video sequences which can be easily ported to mobile computing platforms and thereby to diverse clinical environments. The effectiveness of this approach is demonstrated in the operating room.

MATERIALS AND METHODS

Segmented MR data corresponding to neurovascular compression syndrome pathologies was examined with 3D visualization based on tagged volumes. CT-angiography data containing aneurysms close to the skull base was analyzed with volume visualization based on bidimensional transfer functions. Furthermore, automatic adjustment of bidimensional transfer function templates was implemented. An extension of the applied volume visualization tool made it possible to standardize the creation of pathology-specific digital video sequences.

RESULTS

Five cases of neurovascular compression syndromes and 4 cases of aneurysms close to the skull base were examined. One-dimensional transfer function templates were successfully applied for the visualization of neurovascular compression syndromes. Automatic adjustment of transfer function templates made it possible to achieve good-quality results for visualization of aneurysms without external adjustment. The resulting digital video sequences were successfully used in the operating room.

CONCLUSION

The portability of the 3D video sequences broadens their application spectrum, making them adequate not only for database purposes, but also for surgical support and cooperative environments. Furthermore, the required technical knowledge is encapsulated, making this approach more suitable for clinical applications.

[Navigation-assisted sonography for soft tissues in the head and neck region]

BACKGROUND

In soft tissue surgery of the head and neck region tissue shifts limit the usefulness of conventional CT/MRI-based navigation procedures. Furthermore, changes caused by invasive measures cannot be visualized.

METHODS

A novel navigation device for sonography of soft tissues was developed. This consists of a navigated ultrasound scanner, a navigated surgical instrument, and a personal computer with custom-made software. Its use makes an additional visualization by means of CT or MRI dispensable.

RESULTS

The system deviation (three-dimensional error) of this newly developed prototype was less than 1 mm. The practical application in a model setup showed good handling properties of the system. Orientation and approach of the surgical instrument to the sonographically visualized target structure were rapid and accurate.

CONCLUSION

This new navigation system does not require additional CT or MRI images. The navigated ultrasound probe shows tissue changes in real time. This navigation system is especially suitable for invasive procedures in soft tissues.

[Sonography aided computer assisted surgery (SACAS) in orbital surgery]

BACKGROUND

The application of computer assisted procedures in orbital surgery is made more difficult by the intraoperative tissue shift in intraorbital structures, since this intraoperative dislocation cannot be imaged in preoperative CT/MR datasets.

METHODS

After preoperative recording of CT and/or MR datasets in five patients with orbita affected by frontobasal tumors, we used intraoperative sonography by coupling the ultrasound unit to the navigation system.

RESULTS

Registration, referencing and calibration of the ultrasound system proceeded without any difficulties. Intraoperatively, the structures of the anterior and middle thirds of the orbita and their tissue shift could be particularly well evaluated sonographically.

CONCLUSION

The use of navigated sonography enables repeated intraoperative re-evaluation of preoperative CT/MR datasets. The fusion of intraoperative sonography with preoperative imaging visualizes the tissue shift and facilitates the identification of anatomical structures and the spatial orientation of the surgeon. This appears to allow both increased operative radicality and greater tissue protection. In our opinion, the intraoperative parallel application of a non-calibrated ultrasound system and an only CT/MRT based navigation system cannot fulfill these requirements because of anatomical complexity.

Intraoperative navigated 3-dimensional ultrasound angiography in tumor surgery

BACKGROUND

Avoiding damage to blood vessels is often the concern of the neurosurgeon during tumor surgery. Using angiographic image data in neuronavigation may be useful in cases where vascular anatomy is of special interest. Since 2003, we have routinely used 3D ultrasound angiography in tumor surgery, and between January 2003 and May 2005, 62 patients with different tumors have been operated using intraoperative 3D ultrasound angiography in neuronavigation.

METHODS

An ultrasound-based neuronavigation system was used. In addition to 3D ultrasound tissue image data, 3D ultrasound angiography (power Doppler) image data were acquired at different stages of the operation. The value and role of navigated 3D ultrasound angiography as judged by the surgeon were recorded.

RESULTS

We found that intraoperative ultrasound angiography was easy to acquire and interpret, and that image quality was sufficient for neuronavigation. In 26 of 62 cases, ultrasound angiography was found to be helpful by visualizing hidden vessels adjacent to and inside the tumor, facilitating tailored approaches and safe biopsy sampling.

CONCLUSIONS

Intraoperative 3D ultrasound angiography is straightforward to use, image quality is sufficient for image guidance, and it adds valuable information about hidden vessels, increasing safety and facilitating tailored approaches. Furthermore, with updated 3D ultrasound angiography imaging, accuracy of neuronavigation may be maintained in cases of brain shift.

Image-guidance for surgical procedures

Contemporary imaging modalities can now provide the surgeon with high quality three- and four-dimensional images depicting not only normal anatomy and pathology, but also vascularity and function. A key component of image-guided surgery (IGS) is the ability to register multi-modal pre-operative images to each other and to the patient. The other important component of IGS is the ability to track instruments in real time during the procedure and to display them as part of a realistic model of the operative volume. Stereoscopic, virtual- and augmented-reality techniques have been implemented to enhance the visualization and guidance process. For the most part, IGS relies on the assumption that the pre-operatively acquired images used to guide the surgery accurately represent the morphology of the tissue during the procedure. This assumption may not necessarily be valid, and so intra-operative real-time imaging using interventional MRI, ultrasound, video and electrophysiological recordings are often employed to ameliorate this situation. Although IGS is now in extensive routine clinical use in neurosurgery and is gaining ground in other surgical disciplines, there remain many drawbacks that must be overcome before it can be employed in more general minimally-invasive procedures. This review overviews the roots of IGS in neurosurgery, provides examples of its use outside the brain, discusses the infrastructure required for successful implementation of IGS approaches and outlines the challenges that must be overcome for IGS to advance further.

Technology and Perception in the 21st-Century Reading Room

Radiology reading rooms have changed dramatically over the past 15 years, moving from analog-light-box-based environments to digital-display-based environments. Most of the focus in the early stages of this transition was on the technology, but it soon became obvious that it was not possible or even prudent to consider the technology without considering radiologists. The information being presented to radiologists in digital reading rooms is in many ways very different from that presented on traditional film. On one hand, the digital workstation display medium itself is very different from traditional film images hung on light boxes. On the other hand, without large-area light boxes, images such as those from computed tomography (CT) can no longer be displayed all at once in a series of film sheets. The digital world also introduces the possibility of manipulating image data in ways that were never possible with analog film. Not only can radiologists manipulate image data with various image-processing tools, but also, computers can analyze images and provide even more information to incorporate into the interpretation process. As a consequence of these differences, it has been necessary to focus attention on radiologists to discover ways to optimize the digital reading environment with respect to the human visual system and the way the eye-brain system processes information. This article reviews some of the important perceptual issues that have arisen in the digital reading rooms of the 21st century.

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 microneurosurgical management of vascular lesions using navigated computed tomography angiography. an advanced IGS technology application

BACKGROUND

Image-guided neurosurgery has become a standard practice in the last few years, with more than 2000 surgical navigation stations installed worldwide. In the same time several reports have also demonstrated the efficacy and accuracy of computed tomography angiography (CTA) in assessing cerebral vascular pathologies. Therefore, the CTA data have recently been implemented into the different navigation systems available on the market, making this new technique widely applied. The objective of this paper is to discuss and evaluate the clinical usefulness of navigated CTA in planning and performing surgery of neurovascular lesions.

METHODS

Raw images acquired from an helical CTA are automatically post-processed on an independent workstation by using a three-dimensional (3D) volume-rendering images engine and/or using thresholding and drawing tools.

RESULTS

The data obtained provide useful information in the preoperative stage by reconstructing the vascular tree with regard to lesion volume, aneurysm neck, dome projection, perforating vessels and their relationship with the lesion and the surrounding anatomy. Furthermore, it can help in the identification of an arteriovenous malformation (AVM) nidus and recognition of its feeding and draining vessels.

CONCLUSION

This fascinating technique can give some invaluable advantages on the management of cerebral vascular lesions and provides excellent information not always available on traditional digital subtraction angiography investigation. It has also proved to be very accurate, particularly regarding the correlation between the 3D volume-rendered CT angiography and the intraoperative findings.

Computer-assisted 3D ultrasound-guided neurosurgery: technological contributions, including multimodal registration and advanced display, demonstrating future perspectives

BACKGROUND

Navigation systems are now frequently being used for guiding surgical procedures. Existing neuronavigation systems suffer from the lack of updated images when tissue changes during surgery as well as from user-friendly displays of all essential images for accurate and safe surgery guidance.

METHODS

We have developed various new technologies for improved neuronavigation. Using intraoperative 3D ultrasound (US) imaging, we have developed various registration algorithms for using and updating a complete multimodal and multivolume 3D map for navigation.

RESULTS

We experienced that advanced multimodal visualization makes it easy to interpret information from several image volumes and modalities simultaneously. Using high quality intraoperative 3D ultrasound, essential preoperative information could be corrected due to brain shift. fMRI and other important preoperative data could then be used together with intraoperative ultrasound imaging for more accurate, safer and improved guidance of therapy.

CONCLUSIONS

We claim that new features, as demonstrated in the present paper, using intraoperative 3D ultrasound in combination with advanced registration and display algorithms will represent important contributions towards more accurate, safer and more optimized future patient treatment.

Accurate characterization of the main trunk of the anterior cerebral artery by means of intraoperative sononavigation with Doppler sonography: implications for brain tumor surgery

OBJECTIVE

Doppler sonography can be used for real-time intraoperative localization of arteries within or near brain tumors but is less useful for distinguishing between arteries with similar diameters, such as the main trunk and branches of the anterior cerebral artery (ACA). By contrast, sononavigation provides real-time information in alignment with magnetic resonance imaging scans and may be of use in characterizing the identity of individual arteries on Doppler sonographic images. The goal of this study was to determine whether sononavigation can distinguish the main trunk of the ACA from the branches of the ACA on Doppler sonographic images.

METHODS

Doppler sonography was used in 3 patients undergoing surgical resection of brain tumors involving the main trunk of the ACA. The location of the main trunk of the ACA was characterized by sononavigation.

RESULTS

With these data, tumor resection was performed with preservation of the main trunk of the ACA. Gross total resection was achieved in 1 case.

CONCLUSIONS

Intraoperative sononavigation with Doppler sonography accurately localized the main trunk of the ACA and enabled preservation of this structure during tumor resection. This method may be applicable to the characterization of other critical arteries and may allow tumor resection with decreased morbidity.

Automated Three-dimensional Volume Rendering of Helical Computed Tomographic Angiography for Aneurysms: An Advanced Application of Neuronavigation Technology

OBJECTIVE:

To introduce the possibility of volume-rendered helical computed tomographic (CT) angiographic data sets by use of Medtronic StealthStation Treon surgical navigation technology (Medtronic Surgical Navigation Technologies, Louisville, CO) and to evaluate the clinical usefulness of the method in planning and performing surgical treatment of intracranial aneurysms.

METHODS:

Between November 2002 and July 2003, we studied 15 patients with suspected intracranial aneurysms. All patients but two received conventional digital subtraction angiography, which failed to provide the requested information. Helical CT angiography was performed in all patients, and data sets were transferred to the StealthStation system across an electronic network to be automatically postprocessed by use of three-dimensional (3-D) volume rendering. The 3-D volume-rendered images were accurately analyzed to obtain more complete information about the aneurysm and to provide accurate treatment planning. In all patients, the 3-D volume-rendered model was displayed on the screen of the StealthStation system for the duration of the surgical procedure and compared with the intraoperative image.

RESULTS:

Data sets from CT angiography were automatically postprocessed by the StealthStation in seconds with excellent results, providing us, before and during surgery, with additional information not always available on traditional digital subtraction angiographic investigation. Because of the very short time necessary to complete this process (&lt;5 min to obtain 3-D volume-rendered images), it was possible to perform emergency clipping of the aneurysms in two patients who had been admitted in very compromised neurological conditions. In 12 patients, integrated digital subtraction angiography and automated 3-D volume-rendered images allowed an accurate presurgical evaluation. Furthermore, in all patients on whom surgery was performed, aneurysms were found in the exact location and with the same anatomic features as depicted by the 3-D volume-rendered models.

CONCLUSION:

Reports in the literature indicate that information gathered by CT angiography with volume rendering shows a significant impact on aneurysm management. The StealthStation system upgraded with the adequate algorithm seems to provide a time- and cost-effective method of performing automated 3-D volume rendering of CT angiography and provides an interesting alternative to the available investigation modalities in case of emergency.

Intraoperative magnetic resonance imaging at 0.12 T: is it enough?

Low magnetic field strength MRI provides the anatomic information needed for intracranial procedures in which intraoperative imaging is needed. Stereotactic accuracy is proven. The distinct advantage of this technologic approach is that it allows the neurosurgical team to operate an iMRI system with minimal disruption to the OR routine. Technical improvements are likely to increase the power and versatility of low field strength iMRI. Logic dictates that ergonomics and economics will make this the iMRI technique desired by most neurosurgeons.

Brain Shift Estimation in Image-Guided Neurosurgery Using 3-D Ultrasound

Intraoperative brain deformation is one of the most important causes affecting the overall accuracy of image-guided neurosurgical procedures. One option for correcting for this deformation is to acquire three-dimensional (3-D) ultrasound data during the operation and use this data to update the information provided by the preoperatively acquired MR data. For 12 patients 3-D ultrasound images have been reconstructed from freehand sweeps acquired during neurosurgical procedures. Ultrasound data acquired prior to and after opening the dura, but prior to surgery, have been quantitatively compared to the preoperatively acquired MR data to estimate the rigid component of brain shift at the first stages of surgery. Prior to opening the dura the average brain shift measured was 3.0 mm parallel to the direction of gravity, with a maximum of 7.5 mm, and 3.9 mm perpendicular to the direction of gravity, with a maximum of 8.2 mm. After opening the dura the shift increased on average 0.2 mm parallel to the direction of gravity and 1.4 mm perpendicular to the direction of gravity. Brain shift can be detected by acquiring 3-D ultrasound data during image-guided neurosurgery. Therefore, it can be used as a basis for correcting image data and preoperative planning for intraoperative deformations.

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.

Multimodal image fusion in ultrasound-based neuronavigation: improving overview and interpretation by integrating preoperative MRI with intraoperative 3D ultrasound

OBJECTIVE

We have investigated alternative ways to integrate intraoperative 3D ultrasound images and preoperative MR images in the same 3D scene for visualizing brain shift and improving overview and interpretation in ultrasound-based neuronavigation.

MATERIALS AND METHODS

A Multi-Modal Volume Visualizer (MMVV) was developed that can read data exported from the SonoWand neuronavigation system and reconstruct the spatial relationship between the volumes available at any given time during an operation, thus enabling the exploration of new ways to fuse pre- and intraoperative data for planning, guidance and therapy control. In addition, the mismatch between MRI volumes registered to the patient and intraoperative ultrasound acquired from the dura was qualified.

RESULTS

The results show that image fusion of intraoperative ultrasound images in combination with preoperative MRI will make perception of available information easier by providing updated (real-time) image information and an extended overview of the operating field during surgery. This approach will assess the degree of anatomical changes during surgery and give the surgeon an understanding of how identical structures are imaged using the different imaging modalities. The present study showed that in 50% of the cases there were indications of brain shift even before the surgical procedure had started.

CONCLUSIONS

We believe that image fusion between intraoperative 3D ultrasound and preoperative MRI might improve the quality of the surgical procedure and hence also improve the patient outcome.