# Evaluation of HMDs by QFD for Augmented Reality Applications in the Maxillofacial Surgery Domain
## 5 Conclusions  
This article aimed to study the application of HMD in three operative scenarios of the maxillofacial domain. In conclusion, it is possible to get information regarding the medical aspects, as the applied method of analysis has shown sensible differences in the three maxillofacial scenarios, and regarding the readiness of current HMD with their principal flaws to be adequate as medical tools. Onologic and reconstructive surgery has proven to be the most demanding scenario from the evaluation of surgeon requirements. This practice involves two operation sites \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Scenario** & **PRO BT-2000** & **BT-350** & **BT-300** & **XR-3** & **M4000** & **HoloLens 2** & **Magic Leap 1** & **Best Case** \\ \hline Onological and & 5.59 & 5.99 & 5.60 & 5.74 & 8.15 & 7.72 & 8.81 & 11.73 \\ reconstructive surgery & 5.61 & 6.00 & 5.63 & 5.70 & 8.10 & 7.64 & 8.80 & 11.67 \\ \hline Maxillofacial & 5.20 & 5.73 & 5.30 & 5.37 & 7.83 & 7.28 & 8.37 & 11.03 \\ trauma surgery & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Devices’ overall scores for maxillofacial scenarios. (maxillofacial region and fibula) managed by two different medical teams, and so has a larger number of people in the operating room than the other scenarios. Moreover, working on the two different sites requires the amount of data delivered to the surgeon by the device to be doubled (landmarks, medical data, 3D models, etc.) when compared, for example, to the orthognathic scenario. The dual-site aspect of oncological procedures should make it possible to consider the feasibility to equip both teams with a device. That opportunity will improve and enhance the way to exchange information between the surgeons, and so the connectivity of the device will become a milestone. The overall score (Table 7), as planned, is suitable to quickly depict the readiness of the devices, confirming the result with an easier reading. The table illustrates how no device can reach the best-case yet, but three of them have promising scores: (1) the M4000 TM--industrial monocular device with a slightest idea of modularity; (2) the HoloLens 2 TM--renowned HMD used in many applications with a lot of available documentation; (3) the Magic Leap OneTM--powerful HMD which has recently led its manufacturer to pivot the business towards professional customers in order to avoid bankruptcy. Even if HoloLens 2 TM is a more up-to-date device, its scores are lower than the other two high-scoring devices, for instance, the Magic Leap OneTM, mainly because of the available computing power. The hardware features, grouped under the name of computing power, were considered essential to give to the surgeon a trustable and robust instrument. In fact, during an operation, the HMD must always be responsive and avoid stuttering, lagging, FPS drops or any other phenomena that may confuse or hinder the surgeon. The HoloLens 2 TM have the possibility to use the Azure Remote RenderingTM real-time service to improve its performance, but this is heavily dependent on the internet connection. Thus, in the analysis, only the stand-alone capabilities of each device were considered and evaluated accordingly. The analysis recognized three sensors that were fundamental for medical procedures but not yet implemented in any device:  
1. Optical zoom to look at small structures during the vascular anastomosis in oncological surgery. Optical see-through devices have too many difficulties to have a digital magnification overlapped on the scene; although it is easier for video see-through, digital magnification has resolution issues. 2. Blood flux live view to verify during the surgery the proper vascularization of the implanted graft. 3. Non-optical landmarks reader to overcome the need for an appropriate and clean scene are essential to not lose sight of landmarks and, consequently, the registration between reality and virtual elements.