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Aiming devices enable the use of neuronavigation systems for rigid instrument guidance mimicking the possibilities of a frame-based system without having a stereotactic frame affixed to the skull. The aim of the presented work was to investigate the phantom targeting accuracy of the Vertek aiming device (Medtronic Inc., Louisville, USA) and whether it can be safely and accurately applied in a concept of minimally invasive brain biopsy in which multi-modal image fusion, image-to-patient registration and head immobilization were based on a non-invasive vacuum mouthpiece. A plastic model of a head with 20 target beads broadly distributed around the head volume was used for determination of CT-based targeting accuracy. Every target was punctured 5 times totaling 100 needle positionings. Accuracy was evaluated on postoperative CT scans with the needles in place. The mean normal deviation (n = 100) was 1.5 +/- 0.8 mm and the mean angle of deviation was 1.1 +/- 0.7 degrees. In a preliminary clinical series in ten patients diagnostic biopsy sampling of intracranial lesions with a median diameter of 28 mm (range: 12-90 mm) could be achieved in all patients and no biopsy related complications were recorded. The experimental results showed a similar accuracy to frame-based stereotaxy. The device facilitates trajectory alignment via two pivot joints and the actual depth and location of the biopsy needle can be monitored. Within the limitations of a preliminary study, brain biopsy may be accurately and safely performed for lesions > or = 12 mm.

Objective: Semi-invasive foramen ovale electrodes (FOEs) are used as an alternative to invasive recording techniques in the presurgical evaluation of patients with temporal lobe epilepsy. To maximize patient safety and interventional success, frameless stereotactic FOE placement by use of a variation of an upper jaw fixation device with an external fiducial frame, in combination with an aiming device and standard navigation software, was evaluated by the Innsbruck Epilepsy Surgery Program., Methods: Patients were immobilized noninvasively with the Vogele-Bale-Hohner headholder (Medical Intelligence GmbH, Schwabmünchen, Germany) to plan computed tomography and surgery. Frameless stereotactic cannulation of the foramen and intracranial electrode placement were achieved with the help of an aiming device mounted to the base plate of the headholder. Ease of applicability, safety, and results obtained with foramen ovale recording were investigated., Results: Twenty-six FOEs were placed in 13 patients under general anesthesia. The foramen ovale was successfully cannulated in all patients. One patient reported transient painful mastication after the procedure as a complication attributable to use of the Vogele-Bale-Hohner mouthpiece. In one patient, a persistent slight buccal hypesthesia was present 3 months after the procedure. To pass the foramen, slight adjustments in the needle position had to be made in 10 sides (38.4%). To place the intracranial electrodes, adjustments were necessary six times (23.7%). An entirely new path had to be planned once (3.8%). Seizure recording provided conclusive information in all patients (100%). Outcome in operated patients was Engel Class Ia in six patients, Class IId in one patient, Class IIb in one patient, and Class IVa in one patient (minimum follow-up, 6 mo)., Conclusion: The Vogele-Bale-Hohner headholder combined with an external registration frame eliminates the need for invasive head clamp fixation. FOE placement can be planned "offline" and performed under general anesthesia later. This can be valuable in patients with distorted anatomy and/or small foramina or in patients not able to undergo the procedure under sedation. Results are satisfactory with regard to patient safety, patient comfort, predictability, and reproducibility. FOEs supported further treatment decisions in all patients.

Surgery in the cranial area includes complex anatomic situations with high-risk structures and high demands for functional and aesthetic results. Conventional surgery requires that the surgeon transfers complex anatomic and surgical planning information, using spatial sense and experience. The surgical procedure depends entirely on the manual skills of the operator. The development of image-guided surgery provides new revolutionary opportunities by integrating presurgical 3D imaging and intraoperative manipulation. Augmented reality, mechatronic surgical tools, and medical robotics may continue to progress in surgical instrumentation, and ultimately, surgical care. The aim of this article is to review and discuss state-of-the-art surgical navigation and medical robotics, image-to-patient registration, aspects of accuracy, and clinical applications for surgery in the cranial area.

Purpose: The purpose of this study was to evaluate in vitro the accuracy of 2 methods for computerized tomography (CT)-guided template production via a surgical navigation system., Materials and Methods: Oral implants were planned on CT scans of standard dental stone casts with integrated target pellets. Method 1 used the aiming device of the navigation system for direct positioning of 2-mm surgical bur tubes on the dental stone casts. In method 2, the aiming device was used to guide drillings into the dental stone casts, and the surgical bur tubes were indirectly positioned by metal rods inserted in the drill holes. In both methods the bur tubes were affixed in a resin template. The accuracy of the obtained templates was evaluated by postoperative CT scans using descriptive statistics and the Student t test (P < .05 considered significant)., Results: The mean accuracy (normal deviation from the defined targets) of method 1 was 0.5 +/- 0.3 mm (max 1.2 mm; n = 56). Mean accuracy for method 2 was 0.6 +/- 0.3 mm (max 1.4 mm; n = 56). No significant difference was found between the maxillary and mandibular templates., Discussion: Conventional navigation systems already installed in many hospitals may be used for surgical template production. In contrast to intraoperative tool tracking, there is no need for patient tracking, and the planned implant axis can be rigidly secured as precisely as technically feasible with the help of an aiming device., Conclusion: Both methods of bur tube positioning may represent a precise means for CT-guided template production.

Diagnostic and therapeutic CT- guided percutaneous interventions are clinical routine in interventional radiology. Image-guided navigation systems visualize the internal anatomy during interventions in real time not necessitating continuous image acquisition. Although multiple 3D image-guidance devices have been developed and used by several surgical disciplines in the last few years, they have not yet been fully applied by the interventional radiologist. The aim of this article is to review the currently performed methods of CT-guided percutaneous interventions and to discuss the potential benefits of newly developed 3D- navigation systems.

Objective: Ablative neurosurgical treatment of trigeminal neuralgia, including percutaneous radiofrequency thermocoagulation, requires cannulation of the foramen ovale. To maximize patient security and cannulation success, a frameless stereotactic system was evaluated in a phantom study, a cadaveric study, and a preliminary clinical trial., Methods: Frameless stereotaxy using an optical navigation system, an aiming device, and a noninvasive vacuum mouthpiece-based registration and patient fixation technique was used for the targeting of a test body based on 1-, 3-, and 5-mm axial computed tomographic slices and of the foramen ovale in three cadavers and 15 patients based on 3-mm axial computed tomographic slices., Results: The mean normal (x/y) localization accuracy/standard deviation (n = 360) was 1.31/0.67 mm (1-mm slices), 1.38/0.65 mm (3-mm slices), and 1.84/0.96 mm (5-mm slices). Significantly better results were achieved with 1- and 3-mm slices when compared with 5-mm slices (P < 0.001). The foramen ovale (3 x 6 mm) was successfully cannulated at the first attempt in all cadavers and patients, which indicates clinical localization accuracies better than 1.5 mm in the anteroposterior and 3 mm in the medial-lateral directions., Conclusion: Based on the noninvasive Vogele-Bale-Hohner vacuum mouthpiece, there is no need for invasive head clamp fixation. Imaging, real laboratory simulation, and the actual surgical intervention can be separated in time and location. The presented data suggest that frameless stereotaxy is a predictable and reproducible procedure, which may enhance patient security and cannulation success independent of the surgeon's experience.

The objective of this article was to review the different factors and limitations influencing the accuracy of computer-aided implant surgery. In vitro and in vivo accuracy studies of articles and congress proceedings were examined. Similar results using bur tracking as well as image-guided template production techniques have been reported, and both methods allow for precise positioning of dental implants. Compared to the conventional technique, this sophisticated technology requires substantially more financial investment and effort (computerized tomographic imaging, fabrication of a registration template, intraoperative referencing for bur tracking, or image-guided manufacturing of a surgical template) but appears superior on account of its potential to eliminate possible manual placement errors and to systematize reproducible treatment success. The potential for the protection of critical anatomic structures and the esthetic and functional advantages of prosthodontic-driven implant positioning must also be considered. However, long-term clinical studies are necessary to confirm the value of this strategy and to justify the additional radiation dose, effort, and costs.

Objectives: The objective of this study was to evaluate the accuracy of a novel registration and targeting technique for image-guided template production (IGTP) in a preliminary phantom study., Material and Methods: Registration of four standard dental stone casts with integrated target pellets to the corresponding computed tomography (CT) data was performed via a vacuum mouthpiece and an external reference frame (Medical Intelligence GmbH, Germany). Using the Treon navigation system (Medtronic Inc., Minneapolis, MN, USA) a surgical path with the entry in the centre of the dental crown and the target in the centre of the target pellet was planned on the CT data. An aiming device was adjusted according to the planned trajectory and guided drillings into the dental stone casts. The accuracy was evaluated on postoperative 3D-CT data., Results: The mean fiducial registration error as given by the registration software was 0.4 mm. One hundred and twelve navigated drillings showed a mean accuracy [xy] of 0.42+/-0.26 mm (maximum 1 mm). For the z-axis, a mean accuracy [z] of 0.25+/-0.12 mm (maximum 0.6 mm) was found., Conclusions: Comparing the presented registration technique to existing registration methods in IGTP and burr tracking, no radiographic and registration templates are needed. The procedure is easy and requires only minimal effort. Navigation-controlled drillings could be performed with an accuracy that approaches the intrinsic navigation system's accuracy, a fact that warrants its use for surgical template production. Further accuracy studies of template-guided drillings are necessary before the presented registration technique can be implemented for patient treatment.

Purpose: Diffusion-weighted magnetic resonance imaging (DWI) after focal status epilepticus has demonstrated focal alterations of the apparent diffusion coefficient (ADC) in the epileptogenic zone. We hypothesized that localized dynamic alterations of brain diffusion during the immediate postictal state will be detectable by serial DWI and correlate with the epileptogenic zone., Methods: Nine adult patients (four men, five women) with medically intractable epilepsy were prospectively examined with a total of 25 DWI scans taken 2-210 min after a seizure., Results: The interictal ADC was significantly (p < 0.05) elevated in the ictogenic hippocampus in all patients with temporal lobe epilepsy. The following postictal changes of the ADC were seen: (a) decreases by maximally 25-31%, which were most pronounced in the epileptogenic zone (n = 2); (b) generalized ADC changes after generalized seizures (n = 1) or prolonged complex partial seizures (n = 2); (c) no major changes after short-lived seizures or if the time to first DWI scan was >15 min or both (n = 3); and (d) widespread bilateral ADC increases after a flumazenil-induced seizure (n = 1)., Conclusions: ADC changes seen during serial postictal DWI are complex and appear to reflect origin and spread of the preceding seizure. A delineation of the epileptogenic zone appears to be possible only in complex-partial seizures of >60 s duration that do not secondarily generalize.