The correct placement of needles is decisive for the success of many minimally-invasive interventions and therapies. These needle insertions are usually only guided by radiological imaging and can benefit from additional navigation support. Augmented reality (AR) is a promising tool to conveniently provide needed information and may thus overcome the limitations of existing approaches. To this end, a prototypical AR application was developed to guide the insertion of needles to spinal targets using the mixed reality glasses Microsoft HoloLens. The system's registration accuracy was attempted to measure and three guidance visualisation concepts were evaluated concerning achievable in-plane and out-of-plane needle orientation errors in a comparison study. Results suggested high registration accuracy and showed that the AR prototype is suitable for reducing out-of-plane orientation errors. Limitations, like comparatively high in-plane orientation errors, effects of the viewing position and missing image slices indicate potential for improvement that needs to be addressed before transferring the application to clinical trials.

Novel input modalities have the potential to take over single tasks more efficiently than clinically established methods. The results of our user study show the relevance of task characteristics such as task complexity on performance with specific input modalities. Accordingly, future work should consider task characteristics to provide a useful gesture interface for a specific use case instead of an all-in-one solution.

intracranial stents have expanded endovascular therapy options for intracranial aneurysms. the braided Accero stent is available for clinical use since May 2015. To date, no clinical reports on the stent are available. Purpose of this study was the evaluation of the safety and efficacy of the Accero stent in stent-assisted coiling. All patients, in whom implantation of the stent was performed, were included. primary endpoints were good clinical outcome (mRS ≤ 2) and aneurysm occlusion grades 1 and 2 (Raymond Roy Occlusion Classification). Secondary endpoints were procedural and device-related complications with permanent disability or death, complications in the course, and the recanalization rate. Between September 2015 and August 2018, thirty-four aneurysms were treated with stentassisted coiling using the Accero. Sixteen aneurysms were untreated, four of these were ruptured. Mild neurological complications occurred in 2/34 (5.9%) treatments. Two stent occlusions occurred during follow-up. No patient had a poor procedure-or device-related outcome. After an average of 15 months of follow-up, 28/30 aneurysms were completely or near-completely occluded. The Accero stent proved to be safe and effective in the treatment of broad-based intracranial aneurysms. The complication rate and the rate of successful aneurysm occlusions are similar to those of other stents. Stent-assisted coiling (SAC) is a long-established therapy option for intracranial aneurysms 1,2. With this method it is possible to endovascularly treat even complex and broad-necked aneurysms, as stents form a scaffold and thus prevent protrusion or dislocation of coils into the parent artery. Over the years, a variety of stents with different properties have been developed. These include laser-cut stents in open-cell or closed-cell design, as well as braided stents 3-5. The requirements for all stents are the same: advancement in the catheter and deployment must be easy, they must provide sufficient coverage of the aneurysm neck and be flexible enough to maintain their shape and ensure complete wall apposition even in tortuous vascular anatomy. But above all, usage of the device must be safe and lead to good clinical results with regard to aneurysm occlusion. We present the first results of SAC with a new, braided stent (Accero, Acandis, Pforzheim, Germany).

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