Andrea Müns

Cranioplasty using custom-made hydroxyapatite versus titanium: a randomized clinical trial.

OBJECTIVE Cranioplasty is routinely performed in neurosurgery. One of its underestimated problems is the high postoperative complication rate of up to 40%. Due to the lack of good prospective studies and the small number of patients (5-20 each year) who receive alloplastic materials, decisions in favor or against a certain material are based on subjective empirical or economic reasons. The main goal of this study-the first prospective, randomized multicenter study in Germany-of custom-made titanium and hydroxyapatite (HA) implants was to compare local and systemic infections related to the implant within the first 6 months after implantation. Secondary objectives included comparing the reoperation rate, the complication rate, clinical and neurological outcomes, and health-related quality of life. METHODS The study included patient screening and randomization at 6 to 8 weeks before operation; pre-, intra-, and postoperative documentation until discharge; and postoperative follow-ups after 1 and 6 months. Approval for the study was obtained from the local ethics committee. RESULTS A total of 52 patients were included in the study. The rate of local implant-associated wound infection in the HA group was 2 of 26 (7.7%) patients and 5 of 24 (20.8%) patients in the titanium group (p = 0.407). Systemic inflammation within 6 months after operation affected none of the patients in the HA group and 4 of 24 (37.5%) patients in the titanium group (p = 0.107). In both groups, 7 patients required reoperation after the 6-month follow-up (26.9% of the HA group and 29.2% of the titanium group; not significant). Reoperation with an explantation was necessary in 3 patients in each group (11.5% of the HA group and 12.5% of the titanium group; not significant). The results demonstrated a significantly higher number of epidural hematomas in the HA group in comparison with none in the titanium group. Altogether, 46 adverse events were found in 27 patients (54%). An improvement in the neurological outcome after 6 months was experienced by 43% of the patients in the HA group and 26.3% of the patients in the titanium group (p = 0.709). CONCLUSIONS The study emphasizes that cranioplasty is a high-risk intervention. In comparison with titanium, HA shows benefits in terms of the infection rate and the neurological outcome, but at the same time has a higher postoperative risk for epidural hematoma. Depending on the individual conditions, both materials have their place in future cranioplasty therapies. Clinical trial registration no.: NCT00923793 ( clinicaltrials.gov ).

Integration of a 3D ultrasound probe into neuronavigation.

BackgroundIntraoperative ultrasound (iUS) allows the generation of real-time data sets during surgical interventions. The recent innovation of 3D ultrasound probes permits the acquisition of 3D data sets without the need to reconstruct the volume by 2D slices. This article describes the integration of a tracked 3D ultrasound probe into a neuronavigation.MethodsAn ultrasound device, provided with both a 2D sector probe and a 3D endocavity transducer, was integrated in a navigation system with an optical tracking device. Navigation was performed by fusion of preoperatively acquired MRI data and intraoperatively acquired ultrasound data throughout an open biopsy. Data sets with both probes were acquired transdurally and compared.ResultsThe acquisition with the 3D probe, processing and visualization of the volume only took about 2 min in total. The volume data set acquired by the 3D probe appears more homogeneous and offers better image quality in comparison with the image data acquired by the 2D probe.ConclusionsThe integration of a 3D probe into neuronavigation is possible and has certain advantages compared with a 2D probe. The risk of injury can be reduced, and the application can be recommended for certain cases, particularly for small craniotomies.

A neurosurgical phantom-based training system with ultrasound simulation

BackgroundBrain tumor surgeries are associated with a high technical and personal effort. The required interactions between the surgeon and the technical components, such as neuronavigation, surgical instruments and intraoperative imaging, are complex and demand innovative training solutions and standardized evaluation methods. Phantom-based training systems could be useful in complementing the existing surgical education and training.MethodsA prototype of a phantom-based training system was developed, intended for standardized training of important aspects of brain tumor surgery based on real patient data. The head phantom consists of a three-part construction that includes a reusable base and adapter, as well as a changeable module for single use. Training covers surgical planning of the optimal access path, the setup of the navigation system including the registration of the head phantom, as well as the navigated craniotomy with real instruments. Tracked instruments during the simulation and predefined access paths constitute the basis for the essential objective training feedback.ResultsThe prototype was evaluated in a pilot study by assistant physicians at different education levels. They performed a complete simulation and a final assessment using an evaluation questionnaire. The analysis of the questionnaire showed the evaluation result as “good” for the phantom construction and the used materials. The learning effect concerning the navigated planning was evaluated as “very good”, as well as having the effect of increasing safety for the surgeon before planning and conducting craniotomies independently on patients.ConclusionsThe training system represents a promising approach for the future training of neurosurgeons. It aims to improve surgical skill training by creating a more realistic simulation in a non-risk environment. Hence, it could help to bridge the gap between theoretical and practical training with the potential to benefit both physicians and patients.

Evaluation of a novel phantom-based neurosurgical training system

Background: The complexity of neurosurgical interventions demands innovative training solutions and standardized evaluation methods that in recent times have been the object of increased research interest. The objective is to establish an education curriculum on a phantom-based training system incorporating theoretical and practical components for important aspects of brain tumor surgery. Methods: Training covers surgical planning of the optimal access path based on real patient data, setup of the navigation system including phantom registration and navigated craniotomy with real instruments. Nine residents from different education levels carried out three simulations on different data sets with varying tumor locations. Trainings were evaluated by a specialist using a uniform score system assessing tumor identification, registration accuracy, injured structures, planning and execution accuracy, tumor accessibility and required time. Results: Average scores improved from 16.9 to 20.4 between first and third training. Average time to craniotomy improved from 28.97 to 21.07 min, average time to suture improved from 37.83 to 27.47 min. Significant correlations were found between time to craniotomy and number of training (P < 0.05), between time to suture and number of training (P < 0.05) as well as between score and number of training (P < 0.01). Conclusion: The training system is evaluated to be a suitable training tool for residents to become familiar with the complex procedures of autonomous neurosurgical planning and conducting of craniotomies in tumor surgeries. Becoming more confident is supposed to result in less error-prone and faster operation procedures and thus is a benefit for both physicians and patients.

Evaluation of a semi-automatic segmentation algorithm in 3D intraoperative ultrasound brain angiography.

Abstract In this work, we adapted a semi-automatic segmentation algorithm for vascular structures to extract cerebral blood vessels in the 3D intraoperative contrast-enhanced ultrasound angiographic (3D-iUSA) data of the brain. We quantitatively evaluated the segmentation method with a physical vascular phantom. The geometrical features of the segmentation model generated by the algorithm were compared with the theoretical tube values and manual delineations provided by observers. For a silicon tube with a radius of 2 mm, the results showed that the algorithm overestimated the lumen radii values by about 1 mm, representing one voxel in the 3D-iUSA data. However, the observers were more hindered by noise and artifacts in the data, resulting in a larger overestimation of the tube lumen (twice the reference size). The first results on 3D-iUSA patient data showed that the algorithm could correctly restitute the main vascular segments with realistic geometrical features data, despite noise, artifacts and unclear blood vessel borders. A future aim of this work is to provide neurosurgeons with a visualization tool to navigate through the brain during aneurysm clipping operations.

Brain tumor enhancement revealed by 3D intraoperative ultrasound imaging in a navigation system

Introduction. Brain tumour resections are commonly guided using a navigation system based on preoperative MR data. In order to update the brain status which deforms during the surgery, 3D intraoperative ultrasound (3D-iUS) data are acquired. Tumour interpretation in the 3D-iUS data is however complex because of the image noise, artefacts and missing tumour parts. We propose therefore to enhance the visualization of the brain tumour in the 3D-iUS data using the navigation system. Methods. Our method is based on a tumour model generated by semi-automatic segmentation of the tumour in the preoperative MR data. The tumour model is pre-registered into the patient coordinate system using the transform matrix computed by the navigation system. The brain shift is then estimated using a rigid block matching algorithm between the pre-registered tumour model and the 3D-iUS data. The obtained fine-registered tumour model surface is finally described as a mesh and visualized in the navigation system overlapped on the 3D-iUS data. Results. This method was off-line tested on five patient data including 3D-iUS data and enhanced 3D-iUS data acquired with a contrast agent. In order to evaluate our method the Dice Similarity Index (DSI) was respectively computed between manual delineations of the tumours in the 3D-iUS data considered as references and the pre-registered and fineregistered tumour model. Results demonstrated that the DSI values increased after fine registration and in the enhanced 3D-iUS data. Conclusion. The advantage of using a tumour model combined to a rigid registration technique is to be robust to image artefacts and to be able to reconstitute the tumour information when it is missing in the 3D-iUS data. In order to better match the tumour model with the 3D-iUS data, the fine registered model will be used as initialization to a deformable segmentation method.

Improvement of neuronavigation based on ultrasound by means of the digital video interface

Ultrasound represents a convenient real-time modality for intraoperative use, though ultrasound in neuronavigation involves the challenge of a high quality volume reconstruction of the 2D data. The quality can be enhanced by improving the data transfer process to the navigation system. Since the latest ultrasound devices are often equipped with a digital visual interface (DVI), it was embedded in neuronavigation with the aim to evaluate the potential benefit for clinical