Michael Vogele

Minimally Invasive Head Holder to Improve the Performance of Frameless Stereotactic Surgery

Frameless stereotactic procedures crucially depend on the firmness of immobilization. Once registered, shifting of the patient leads to inaccuracy, and the patient registration has to be realigned. To overcome the drawbacks of conventional invasive fixation for neurosurgery and the widely accepted fixation with surgical tape in ENT, the Vogele‐Bale‐Hohner (VBH) head holder has been developed. It permits rigid, noninvasive fixation of the head by using an individualized dental cast attached to the upper jaw by vacuum. Oral intubation is uncomplicated. In addition, a special registration device providing well defined reference points can be mounted to the mouthpiece. We report the first promising clinical applications of this device.

Repositioning Accuracy: Comparison of a Noninvasive Head Holder with Thermoplastic Mask for Fractionated Radiotherapy and a Case Report

PURPOSE To compare accuracy, clinical feasibility, and subjective patient impression between a noninvasive head holder (Vogele Bale Hohner [VBH]; Wellhoefer Dosimetry, Schwarzenbruck, Germany) developed at the University of Innsbruck and the thermoplastic mask fixation system for use in fractionated external radiotherapy. We present a case report of an actual patient fixated in the VBH head holder during radiation therapy. MATERIALS AND METHODS The VBH head holder consists of an individualized vacuum dental cast connected to a head plate via two hydraulic arms allowing noninvasive, reproducible head fixation of even uncooperative patients. Accuracy was tested and compared with that of the thermoplastic mask using the Phillips EasyGuide navigation system on five volunteers. Specific external registration points served as landmarks and their positions were compared after each repositioning. System and operator inaccuracy were also taken into account. The times taken for production and repositioning of the respective fixation devices were compared, and subjective impressions were noted. RESULTS Mean VBH head holder repositioning accuracy was 1.02 mm while that of the thermoplastic mask was 3.05 mm. 69% of mask repositionings showed a deviation > 2 mm and 41% > 3 mm (as opposed to 8% and 1% respectively for the VBH head holder) Those points located farthest away from the respective plane of fixation showed the largest deviations. Both production and repositioning times were similar between the systems; depending upon the patient, the VBH head holder was generally better tolerated than the mask system. CONCLUSION Due to its significantly better repositioning accuracy compared to that of the thermoplastic mask, the VBH head holder is especially suited for external radiation requiring precise repositioning due to critical tissues in immediate surrounding of the area to be irradiated.

Computer‐Aided Surgery in the Petrous Bone

Objectives: We demonstrate that computer‐assisted frameless stereotactic navigation with the ISG/ELEKTA Viewing Wand system in the petrous bone is routinely possible with sufficient application accuracy.

Three-Dimensional Image-Guided Endonasal Surgery With a Microdebrider

We report the first intraoperative use of a microdebrider as a stereotactic three‐dimensional (3D) navigation instrument in paranasal and frontobasal surgery. The microdebrider uses rotating blades and an integrated suction device for controlled removal of tissue under video‐endoscopic view. The ISG Viewing Wand uses the patients computed tomography/magnetic resonance (CT/MR) data and a 3D reconstruction thereof and a highprecision position‐sensitive mechanical arm for intraoperative three‐dimensional navigation. We have linked the microdebrider to the Viewing Wand to transform it into a continuously available intraoperative stereotactic localizing device. We discuss the problems related to this extension of the Viewing Wand and demonstrate the practical use in an exemplary polypectomy.

A Simple and Non-Invasive Vacuum Mouthpiece-Based Head Fixation System for High Precision Radiotherapy

Purpose: To demonstrate why conventional non-invasive mouthpiece-based fixation has not achieved the expected accuracy and to suggest a solution of the problem. Patients and Methods: The Vogele Bale Hohner (VBH) head holder is a non-invasive vacuum mouthpiece-based head fixation system. Feasibility and repositioning accuracy were evaluated by portal image analysis in 12 patients with cranial tumors intended for stereotactic procedures, fixated with the newest version (VBH HeadFix-ARC®). Results: Portal image analysis (8 patients evaluated in 2-D, 4 patients in 3-D) showed that even in routine external beam radiation therapy, treatment can be applied to within a mean 2-D and 3-D accuracy of under 2 mm (SD 0.92 mm and 1.2 mm, respectively) with cost and repositioning time per patient and patient comfort comparable to that of common thermoplastic masks. Conclusion: These preliminary results show that high repositioning accuracy does not rule out simple and quick application and patient comfort. Paramount, however, is tensionless repositioning via the vacuum mouthpiece.Ziel: Fixationssysteme, die auf konventionellen (nicht Vakuum-)Mundstücken basieren, erreichen oftmals nicht die erwartete Genauigkeit. Die vorliegende Arbeit beschäftigt sich mit den möglichen Ursachen und bietet entsprechende Lösungen. Patienten und Methoden: Der Vogele-Bale-Hohner-(VBH-)Head-Holder ist ein nicht invasives, auf einem Vakuummundstück (Abbildung 1) basierendes Kopffixationssystem (Abbildungen 2 und 3). Bei zwölf Patienten mit kraniellen Tumoren wurde mit der neuesten Version (VBH HeadFix-ARC®) die Repositionsgenauigkeit mittels Portal Imaging untersucht. Ergebnisse: Die Portal-Imaging-Auswertung (acht Patienten in 2-D, vier Patienten in 3-D) bestätigte, dass eine Bestrahlung im Kopfbereich auch in der klinischen Routine mit einer mittleren Genauigkeit von unter 2 mm (Standardabweichung 0,92 bzw. 1,2 mm) appliziert werden kann, während Kosten, Repositionsdauer und Akzeptanz der Patienten vergleichbar sind mit denen thermoplastischer Masken. Schlussfolgerung: Diese vorläufigen Ergebnisse zeigen, dass eine hohe Repositionierungsgenauigkeit ein einfaches, schnelles und für den Patienten angenehmes System nicht ausschließt. Ausschlaggebend ist die spannungsfreie Lagerung mittels Vakuummundstück.

Three-Dimensional Navigation in Otorhinolaryngological Surgery with the Viewing Wand

We report our experiences with the ISG Viewing Wand intraoperative 3-dimensional navigation device in endonasal endoscopic procedures of the paranasal sinuses, anterior skull base, and petrous bone. In the last 12 months we have routinely used the wand in 90 patients for treatment of polyposis nasi, for biopsies and removal of tumors in the nasal cavity and at the frontal skull base, for endocrine ophthalmopathy, and in 1 case for cholesteatoma. We present our computed tomography, magnetic resonance imaging, and clinical protocols that allow a precise routine use of the Viewing Wand. In all cases, the system was extremely helpful for intraoperative localization and helped to optimize surgery.

VBH Head Holder to Improve Frameless Stereotactic Brachytherapy of Cranial Tumors

Precise target localization is essential for brachytherapy. We have adapted the VBH (Vogele-Bale-Hohner) head holder (Wellhoefer Dosimetry, Schwarzenbruck, Germany), originally developed at the University of Innsbruck, for frameless stereotactic surgery, for use in brachytherapy of cranial tumors. The VBH head holder allows for rigid, noninvasive head fixation by means of an individualized upper dental cast. Registration rods, rigidly attached to the dental cast, provide stable external points of reference. The dental cast is sucked against the upper palate by vacuum, and then the fixated patient is scanned. During simulation, the targeting device can be positioned with respect to the virtual patient using the ISG Viewing Wand. Following simulation, the real patient is repositioned under vacuum control, the targeting device repositioned as well, and the actual brachytherapy initiated. The VBH head holder is well tolerated by patients and simple to use, and various studies have confirmed submillimeter accuracy. The modified head holder in combination with a new targeting device allows for precise and well-planned insertion of hollow needles into a tumor using frameless stereotactic systems as well as being compatible for uses in other fields.

Semi-robotic 6 degree of freedom positioning for intracranial high precision radiotherapy; first phantom and clinical results

BackgroundTo introduce a novel method of patient positioning for high precision intracranial radiotherapy.MethodsAn infrared(IR)-array, reproducibly attached to the patient via a vacuum-mouthpiece(vMP) and connected to the table via a 6 degree-of-freedom(DoF) mechanical arm serves as positioning and fixation system. After IR-based manual prepositioning to rough treatment position and fixation of the mechanical arm, a cone-beam CT(CBCT) is performed. A robotic 6 DoF treatment couch (HexaPOD™) then automatically corrects all remaining translations and rotations. This absolute position of infrared markers at the first fraction acts as reference for the following fractions where patients are manually prepositioned to within ± 2 mm and ± 2° of this IR reference position prior to final HexaPOD-based correction; consequently CBCT imaging is only required once at the first treatment fraction.The preclinical feasibility and attainable repositioning accuracy of this method was evaluated on a phantom and human volunteers as was the clinical efficacy on 7 pilot study patients.ResultsPhantom and volunteer manual IR-based prepositioning to within ± 2 mm and ± 2° in 6DoF was possible within a mean(± SD) of 90 ± 31 and 56 ± 22 seconds respectively. Mean phantom translational and rotational precision after 6 DoF corrections by the HexaPOD was 0.2 ± 0.2 mm and 0.7 ± 0.8° respectively. For the actual patient collective, the mean 3D vector for inter-treatment repositioning accuracy (n = 102) was 1.6 ± 0.8 mm while intra-fraction movement (n = 110) was 0.6 ± 0.4 mm.ConclusionsThis novel semi-automatic 6DoF IR-based system has been shown to compare favourably with existing non-invasive intracranial repeat fixation systems with respect to handling, reproducibility and, more importantly, intra-fraction rigidity. Some advantages are full cranial positioning flexibility for single and fractionated IGRT treatments and possibly increased patient comfort.

Surgical Application of a New Robotic System for Paranasal Sinus Surgery

The applicability of a robotic system for fully automated surgical procedures approaching the sphenoid sinus is evaluated. An integrated robotic system, A73, for computer navigation-guided, fully automated, and telemanipulation robotic performance is described. Details of the system comprising newly designed surgical instruments for robotic operations and preoperative planning protocols are provided. Experiments with an operational accuracy of less than 1 mm were followed by surgical tests, in which the results of fully automated and telemanipulation performances on 5 cadaveric heads are seen. The A73 system has been successfully used for a reproducible and accurate resection of the anterior wall of the sphenoid sinus. Therefore, we conclude that this system is suited for further testing toward approaching fully automated and more complex procedures of paranasal surgery.

Erste Erfahrungen mit computerunterstützter stereotaktischer interstitieller Brachytherapie

PURPOSE To reach an optimal treatment result and to avoid damage to critical structures a homogeneous dose distribution in the tumor volume with a rapid decreasing dose to the surrounding structures is necessary. Fractionated interstitial brachytherapy of tumors in the ENT region employing needles depends on exact localization of the target volume during all fractions. Therefore reproducibility of positioning of the needle(s) plays an important role. MATERIAL AND METHODS We used the ISG Viewing Wand system in combination with the Vogele-Bale-Hohner (VBH) head holder and a new targeting device. Point of entrance, pathway, and target point of the needle were planned and insertion of the needle simulated in advance. To date we have treated 7 patients with inoperable tumors in the ENT region. The actual position of the needle in the control CT was compared to the planned position. RESULTS The accuracy of positioning of the needle depended on the location of the tumor. In a patient with a recurrent retroorbital adenocarcinoma the mean accuracy was 1 mm. Due to soft tissue displacement in the neck region and the resulting necessity to readjust the targeting device the needle was placed with a mean deviation of 15 mm between the planned and the actual position. CONCLUSIONS Computer-assisted frameless stereotactic interstitial brachytherapy allows for precise, reproducible and preplanned insertion of hollow needles into target structures closely adherent to the surrounding tissue, thus avoiding damage of neighbouring structures. This technique is of great advantage in treating deeply seated tumors which are fixed to bony structures, especially at the skull base. Inaccuracy in the neck region caused by soft tissue shift requires improvement of the immobilization in this region.ZusammenfassungFragestellungDie fraktionierte interstitielle Brachytherapie mit Nadeln von Tumoren im HNO-Bereich erfordert eine exakte Lokalisierung des Zielgewebes bei allen Bestrahlungsfraktionen. Eine wichtige Voraussetzung hier für ist die Reproduzierbarkeit der Positionierung der Nadel(n).Material und MethodenZur Ansteuerung verwendeten wir das ISG-Viewing-Wand-Navigationssystem (ISG Technologies Inc., Mississauga, Ontario, Kanada) in Kombination mit der Vogele-Bale-Hohner-(VBH-) Kopfhalterung (Fa. Wellhöfer Dosimetrie, Schwarzenbruck, Deutschland) und einer Zielvorrichtung. Eintrittspunkt, Stichlanal und Zielpunkt werden vor der Bestrahlungssitzung geplant, und das Vorschieben der Nadel wird simuliert. Wir haben diese Methode bei sieben Patienten mit inoperablen Kopf-Hals-Tumoren angewendet und jeweils die Nadellage am Kontroll-CT mit der geplanten Lokalisation verglichen.ErgebnisseDie Abweichung der erreichten von der geplanten Position der Nadel war von der Tumorlokalisation abhängig. Bei einem intraorbitalen, retrobulbären Tumorrezidiv eines Adenokarzinoms wurde eine mittlere Genauigkeit von 1 mm erzielt. Aufgrund der Weichteilverschieblichkeit und der Notwendigkeit der Nachjustierung der Zielvorrichtung war die Positionierung im Bereich des Halses nur mit einer mittleren Genauigkeit von 15 mm möglich.SchlußfolgerungenDie computerunterstützte, rahmenlos stereotaktische interstitielle Brachytherapie erlaubt die exakte, reproduzierbare und vorgeplante Plazierung von Brachytherapiehohlnadeln in wenig verschiebliche Zielstrukturen unter Schonung benachbarten Gewebes. Sie ist daher speziell bei der Therapie von am Knochen adhärenten, tiefliegenden Tumoren, insbesondere an der Schädelbasis, von Vorteil. Die durch Weichteilverschieblichkeit bedingte Ungenauigkeit in der Halsregion erfordert die Verbesserung der Immobilisation in dieser Region.AbstractPurposeTo reach an optimal treatment result and to avoid damage to critical structures a homogenous dose distribution in the tumor volume with a rapid decreasing dose to the surrounding structures is necessary. Fractionated interstitial brachytherapy of tumors in the ENT region employing needles depends on exact localization of the target volume during all fractions. Therefore reproducibility of positioning of the needle(s) plays an important role.Material and MethodsWe used the ISG Viewing Wand system in combination with the Vogele-Bale-Hohner (VBH) head holder and a new targeting device. Point of entrance, pathway, and target point of the needle were planned and insertion of the needle simulated in advance. To date we have treated 7 patients with inoperable tumors in the ENT region. The actual position of the needle in the control CT was compared to the planned position.ResultsThe accuracy of positioning of the needle depended on the location of the tumor. In a patient with a recurrent retroorbital adenocarcinoma the mean accuracy was 1 mm. Due to soft tissue displacement in the neck region and the resulting necessity to readjust the targeting device the needle was placed with a mean deviation of 15 mm between the planned and the actual position.ConclusionsComputer-assisted frameless stereotactic interstitial brachytherapy allows for precise, reproducible and preplanned insertion of hollow needles into target structures closely adherent to the surrounding tissue, thus avoiding damage of neighbouring structures. This technique is of great advantage in treating deeply seated tumors which are fixed to bony structures, especially at the skull base. Inaccuracy in the neck region caused by soft tissue shift requires improvement of the immobilization in this region.