**3. In-vitro microsurgical models**

Here we present two sophisticated in-vitro artificial plastic models which closely mimic real vascular conditions and a more complex in-vivo experimental animal bifurcation aneurysm model in rabbits [18]. For initial and basic microvascular training, the poly-vinyl-chloride (PVC) rat model (Microsurgical Developments Foundation, Maastricht, The Netherlands) shows itself to be more or less sufficient [19]. For a more realistic haptic feeling and enhanced specific microvascular training, a model with highly elastic polyvinyl alcohol (PVA) vessels and an anatomical plastic head (Kezlex, Ono & Co., Ltd., Tokyo, Japan) is available [18, 20].

#### **Figure 9.**

*The models can be used as are or in conjunction with an AR app (UpSurgeOn Neurosurgery S.r.l., Milan, Italy) via a QR code as pictured here. The materials used render the models extremely lifelike in haptics and handling. Depicted here is a right-sided pterional approach with craniotomy already performed. The underlying synthetic dura is visible.*

#### **Figure 10.**

*Here the 3D model is fused with a virtual image via the accompanying QR code, allowing the surgeon to explore deeper intracranial structures of the specific surgical approach.*

Additionally, our highly sophisticated in-vivo experimental animal model (rabbit carotid artery bifurcation model) is demonstrated and discussed [21–23].

**Figure 11.** *Hybrid view of one of the 3D models showing a right-sided ICA aneurysm.*
