The EasyGuide Neuro image-guided surgery system

How to objectively evaluate the impact of image-guided surgery technologies

PURPOSE

This manuscript aims to provide a better understanding of methods and techniques with which one can better quantify the impact of image-guided surgical technologies.

METHODS

A literature review was conducted with regard to economic and technical methods of medical device evaluation in various countries. Attention was focused on applications related to image-guided interventions that have enabled procedures to be performed in a minimally invasive manner, produced superior clinical outcomes, or have become standard of care.

RESULTS

The review provides examples of successful implementations and adoption of image-guided surgical techniques, mostly in the field of neurosurgery. Failures as well as newly developed technologies still undergoing cost-efficacy analysis are discussed.

CONCLUSION

The field of image-guided surgery has evolved from solely using preoperative images to utilizing highly specific tools and software to provide more information to the interventionalist in real time. While deformations in soft tissue often preclude the use of such instruments outside of neurosurgery, recent developments in optical and radioactive guidance have enabled surgeons to better account for organ motion and provide feedback to the surgeon as tissue is cut. These technologies are currently undergoing value assessments in many countries and hold promise to improve outcomes for patients, surgeons, care teams, payors, and society in general.

Virtual Reality and Simulation in Neurosurgical Training

Recent biotechnological advances, including three-dimensional microscopy and endoscopy, virtual reality, surgical simulation, surgical robotics, and advanced neuroimaging, have continued to mold the surgeon-computer relationship. For developing neurosurgeons, such tools can reduce the learning curve, improve conceptual understanding of complex anatomy, and enhance visuospatial skills. We explore the current and future roles and application of virtual reality and simulation in neurosurgical training.

Functional Magnetic Resonance Imaging and Diffusion Tensor Tractography Incorporated Into an Intraoperative 3-Dimensional Ultrasound-Based Neuronavigation System

BACKGROUND

Functional neuronavigation with intraoperative 3-dimensional (3D) ultrasound may facilitate safer brain lesion resections than conventional neuronavigation.

OBJECTIVE

In this study, functional magnetic resonance imaging (fMRI) and diffusion tensor tractography (DTT) were used to map eloquent areas. We assessed the use of fMRI and DTT for preoperative assessments and determined whether using these data together with 3D ultrasound during surgery enabled safer lesion resection.

METHODS

We reviewed 51 consecutive patients with intracranial lesions in whom fMRI with or without DTT was used to map eloquent areas. To assess a possible impact of fMRI/DTT, we reviewed and analyzed the quality of the fMRI/DTT data, any change in therapeutic strategies, lesion to eloquent area distance (LEAD), extent of resection, and clinical outcome.

RESULTS

As a result of the fMRI/DTT mapping, the therapeutic strategies were changed in 4 patients. The median tumor residue for glioma patients was 11% (n = 33) and 0% for nonglioma lesions (n = 12). For gliomas, there was a significant correlation between decreasing LEAD and increasing tumor residue. Of the glioma patients, 42% underwent gross total resection (≥ 95%) and 12% suffered neurological worsening after surgery as a result of complications. Of glioma patients with an LEAD of ≤ 5 mm, 24% underwent gross total resection and 10% experienced neurological deterioration.

CONCLUSION

This study demonstrates that preoperative fMRI and DTT had direct consequences for therapeutic strategies and indicates their impact on intraoperative strategies to spare eloquent cortex and tracts. Functional neuronavigation combined with intraoperative 3D ultrasound can, in most patients, enable resection of brain lesions with general anesthesia without jeopardizing neurological function.

Fiducial Versus Nonfiducial Neuronavigation Registration Assessment and Considerations of Accuracy

Objective:

For frameless stereotaxy, users can choose between anatomic landmarks (ALs) or surface fiducial markers (FMs) for their match points during registration to define an alignment of the head in the physical and radiographic image space. In this study, we sought to determine the concordance among a point-merged FM registration, a point-merged AL registration, and a combined point-merged anatomic/surface-merged (SM) registration, i.e., to determine the accuracy of registration techniques with and without FMs by examining the extent of agreement between the system-generated predicted value and physical measured values.

Methods:

We examined 30 volunteers treated with gamma knife surgery. The frameless stereotactic image-guidance system called the StealthStation (Medtronic Surgical Navigation Technologies, Louisville, CO) was used. Nine FMs were placed on the patient's head and four were placed on a Leksell frame rod-box, which acted as a rigid set to determine the difference in error. For each registration form, we recorded the generated measurement (GM) and the physical measurement (PM) to each of the four checkpoint FMs. Bland and Altman plot difference analyses were used to compare measurement techniques. Correlations and descriptive analyses were completed.

Results:

The mean of values for GMs were 1.14 mm for FM, 2.3 mm for AL, and 0.96 mm for SM registrations. The mean errors of the checkpoints were 3.49 mm for FM, 3.96 mm for AL, and 3.33 mm for SM registrations. The correlation between GMs and PMs indicated a linear relationship for all three methods. AL registration demonstrated the greatest mean difference, followed by FM registration; SM registration had the smallest difference between GMs and PMs. Differences in the anatomic registration methods, including SM registration, compared with FM registration were within a mean ± 1.96 (standard deviation) according to the Bland and Altman analysis.

Conclusion:

For our sample of 30 patients, all three registration methods provided comparable distances to the target tissue for surgical procedures. Users may safely choose anatomic registration as a less costly and more time-efficient registration method for frameless stereotaxy.

[Evaluation of a DC pulsed magnetic tracking system in neurosurgical navigation: technique, accuracies, and influencing factors]

Navigation systems are useful instruments in cranial neurosurgery. For specification of position, so-called sensor-based navigation techniques use: (a) a signal emitter that generates a defined electromagnetic field in the area of the operation site; and (b) small sensors that detect the position of various operating instruments in the electromagnetic field. For a long time, owing to a lack of clinical data and long-term studies, electromagnetic systems have been regarded as error-prone and imprecise. With the development of a pulsed direct current (DC) technique, precision levels can now be reached that are comparable with those of established optical and mechanical measuring procedures. However, it must be noted that the influence on the measuring accuracy within the operating field increases with increasing susceptibility of the various metals used in the operating theatre (titanium<aluminium<high-alloy steels<low-alloy steels). The technique, accuracy, and influencing factors of a DC pulsed magnetic tracking system were investigated in more than 200 cases.

Image-to-patient registration techniques in head surgery

Frame-based stereotaxy was developed in neurosurgery at the beginning of the last century, evolving from atlas-based stereotaxy to stereotaxy based on the individual patient's image data. This established method is still in use in neurosurgery and radiotherapy. There have since been two main developments based on this concept: frameless stereotaxy and markerless registration. Frameless stereotactic systems ('navigation systems') replaced the cumbersome stereotactic frame by mechanically and later also optically or magnetically tracked instruments. Stereotaxy based on the individual patient's image data introduced the problem of patient-to-image data registration. The development of navigation systems based on frameless stereotaxy has dramatically increased its use in surgical disciplines other than neurosurgery, but image-guided surgery based on fiducial marker registration needs dedicated imaging for registration purposes, in addition to the diagnostic imaging that might have been performed. Markerless registration techniques can overcome the resulting additional cost and effort, and result in more widespread use of image-guided surgery techniques. In this review paper, the developments that led to today's navigation systems are outlined, and the applications and possibilities of these methods in the field of maxillofacial surgery are presented.

Der anterosigmoidale Zugang

BACKGROUND AND OBJECTIVE

The antero- or persigmoid approach preserves all functional structures of the petrous bone and, therefore, is an alternative to the classic laterobasal approaches for exploring the petroclival region. As high morbidity is assumed and it is a time consuming procedure, this approach is not well known.

METHODS AND PATIENTS

Initially, a cadaver study using computer assisted surgery was used to determine the surgical workflow before we optimized our surgical procedures.

RESULTS

In a series of 7 patients with benign tumors growing from the petrous apex to the petroclival region, we were able to resect all tumors completely via the anterosigmoidal surgical corridor using computer assisted surgery.

CONCLUSIONS

The navigation-guided anterosigmoidal approach is an excellent method, allowing a good overview of the petroclival region. In patients suffering from complex petroclival tumors, it offers a real chance to achieve complete microsurgical tumor resection without functional defects by an interdisciplinary neuro-oto-surgical session.

Frameless stereotactic navigation in transsphenoidal surgery: comparison with fluoroscopy

Surgical navigation systems (frameless stereotaxy) have been used in addition to or instead of fluoroscopy during transsphenoidal surgery. This study compares the intraoperative localization by an optical tracking system (Elekta Viewscope) with fluoroscopy. Viewscope and fluoroscope sagittal images were compared by the establishment of a Cartesian coordinate system based on anatomical landmarks and by the spatial localization of surgically relevant points for 20 patients. The Viewscope was found to have a total deviation of 3.0 +/- 0.6 mm (mean +/- SD) compared to fluoroscopy (p < 0.01). Much of the error resulted from the registration process, which according to the Viewscope software had an expected error of 3.1 +/- 0.8 mm for this series of patients, and from the probe-to-system correlation (error of 1.0 +/- 0.3 mm). Although frameless stereotactic systems give the surgeon useful trajectory data with three-dimensional visualizations, they remain somewhat inaccurate. The multiplanar abilities of the Viewscope provide an additional but not mandatory advantage to the simplicity and accuracy of fluoroscopy during this type of surgery.

Frameless neuronavigation in intracranial endoscopic neurosurgery

OBJECT

Frameless computerized neuronavigation has been increasingly used in intracranial endoscopic neurosurgery. However, clear indications for the application of neuronavigation in neuroendoscopy have not yet been defined. The purpose of this study was to determine in which intracranial neuroendoscopic procedures frameless neuronavigation is necessary and really beneficial compared with a free-hand endoscopic approach.

METHODS

A frameless infrared-based computerized neuronavigation system was used in 44 patients who underwent intracranial endoscopic procedures, including 13 third ventriculostomies, nine aqueductoplasties, eight intraventricular tumor biopsy procedures or resections, six cystocistemostomies in arachnoid cysts, five colloid cyst removals, four septostomies in multiloculated hydrocephalus, four cystoventriculostomies in intraparenchymal cysts, two aqueductal stent placements, and fenestration of one pineal cyst and one cavum veli interpositi. All interventions were successfully accomplished. In all procedures, the navigational system guided the surgeons precisely to the target. Navigational tracking was helpful in entering small ventricles, in approaching the posterior third ventricle when the foramen of Monro was narrow, and in selecting the best approach to colloid cysts. Neuronavigation was essential in some cystic lesions lacking clear landmarks, such as intraparenchymal cysts or multiloculated hydrocephalus. Neuronavigation was not necessary in standard third ventriculostomies, tumor biopsy procedures, and large sylvian arachnoid cysts, or for approaching the posterior third ventricle when the foramen of Monro was enlarged.

CONCLUSIONS

Frameless neuronavigation has proven to be accurate, reliable, and extremely useful in selected intracranial neuroendoscopic procedures. Image-guided neuroendoscopy improved the accuracy of the endoscopic approach and minimized brain trauma.

Computer-assisted neurosurgery by using a noninvasive vacuum-affixed dental cast that acts as a reference base: another step toward a unified approach in the treatment of brain tumors

OBJECT

The purpose of the study was to evaluate the use of the Vogele-Bale-Hohner (VBH) mouthpiece, which is attached to the patient's upper jaw by negative pressure, for patient-image registration and for tracking the patient's head during image-guided neurosurgery.

METHODS

A dynamic reference frame (DRF) is reproducibly mounted on the mouthpiece. Reference points, optimally distributed and attached to the mouthpiece, are used for registration in the patient's absence on the day before surgery. In the operating room, the mouthpiece and DRF are precisely repositioned using a vacuum, and the patient's anatomical structures are automatically registered to corresponding ones on the image. Experimental studies and clinical experiences in 10 patients confirmed repeated (rigid body) localization accuracy in the range of 0 to 2 mm, throughout the entire surgery despite movements by the patient.

CONCLUSIONS

Because of its noninvasive, rigid, reliable, and reproducible connection to the patient's head, the VBH vacuum-affixed mouthpiece grants the registration device an accuracy comparable to invasive fiducial markers.

Restoration of neural output from a paralyzed patient by a direct brain connection

Patients with severe paralysis of limbs, face and vocal apparatus may be intelligent and aware and yet, tragically, unable to communicate. We describe a communication link for such a 'locked-in' patient with amyotrophic lateral sclerosis. We recorded action potentials in her brain over several months by means of an electrode that induces growth of myelinated fibers into its recording tip. She was able to control the neural signals in an on/off fashion. This result is an important step towards providing such patients with direct control of their environment by interfacing with a computer. Additionally, it indicates that restoration of paralyzed muscles may be possible by using the signals to control muscle stimulators.