# Production of Synthetic Models for Neuro-Oncology Training by Additive Manufacturing
## 3 Results and Discussion  
The 10 produced models were used in a neuro-oncology practical workshop with 49 medicine students. This workshop was part of the Second Summer School of the BrainIT project (Brain Revealed: Innovative Technologies in Neurosurgery Study). The following images (Figures 9-11) show the main moments of the workshop where the students in neurosurgery simulated the intervention using the synthetic models. All the steps of the real surgery were successfully reproduced. During the craniotomy time, the electric drill and specific cutting tools were used (Figure 9a). No difficulties were encountered in this surgical step, and the used material simulated the bone structure very  
Figure 10: Tumor inside the brain (**a**) and suturing the dura mater once the tumor was removed (**b**). Figure 9: Students cutting the skull in the workshop (**a**) and removing the tumor (**b**). well. The removal of the bony flap was followed by the incision of the dura mater, the thin membrane that covers the brain (Figure 9b). The next surgical step was the intracerebral tumor ablation. In this 3D reconstruction, the tumor had a hard consistency, and therefore the ablation was performed piece by piece, using cutting and dissecting tools (Figure 10a). Total removal of the well-defined tumor formation was performed, and the dura mater was sutured in place using simple interrupted stitches. The material used in this case was very similar to other popular duraplasty materials available on the market (Figure 10b). After the duraplasty, the bone flap was fixed in place using thick sutures, with very satisfactory results (Figure 11a,b). The overall process developed by the students in the summer school is recorded in Video S1. According to the comments of the students and the general observations during the workshop, the experience was very enriching, providing a greater vision of the intervention. They could put in practice their skills in terms of cutting the skull and dura mater, removing the tumor, and sewing both dura mater and skull, with a model quite similar to the real intervention they would face in an operating room. Additionally, the students were asked to reply a five-question survey about their feelings with the 3D synthetic models they had worked with. These questions were focused on the usefulness of the synthetic models as a method for developing neurosurgical skill, evaluating the feelings obtained with the model approach compared to a reality surgery, in addition to evaluating whether this tool was useful for learning and the potentiality of using this method in different medical specializations. Finally, their level of satisfaction was evaluated. The related results are shown in Figure 12, where it can be concluded that the contribution of these models in neurosurgery is necessary and beneficial to improve the skills of future neurosurgeons. In this work, we reflected that 90% of the students considered the 3D models strongly useful to improve their skills in neurosurgery, 40% thought that this model was enough to feel the sensation of being in a real surgery, 100% considered this practical activity necessary in different sectors of medicine, 90% thought that the AM was an effective tool to support training and pre-clinical trial of medicine professionals, and 90% were very satisfied with the practical activity with these 3D models. Figure 11: Final suture of the skull (**a**) with the tumor removed (**b**). Q1. Do you think that the 3D models of the workshop have been useful to improve skills in neurosurgery? Q2. Were these 3D models realistic enough to feel that you were carrying out a surgery close to reality? From the perspective of neurosurgeons, the proposed training approach of real case reconstruction and simulation of surgery brings about important benefits. For resident physicians, it is a very good opportunity to practice basic surgical maneuvers before performing the procedure on the real patient.