## 5 Conclusions  
This study presents an alternative method for refining the position of the ETS device, ensuring that the patient maintains a predefined position during treatment, which is crucial for the success of the therapy.  
The innovative approach proposed in this study involves comparing and replacing the initial alignment of the ETS device, typically performed in the CT bulker, with an equivalent procedure executed in a dedicated room. This new procedure is supported by an OTS, which offers greater flexibility and optimization capabilities compared to the traditional method.  
One of the significant advantages of this method is the potential reduction in the time spent on preparatory clinical activities.  
The study was conducted concurrently with the standard method currently employed in the clinical workflow of CNAO. This parallel approach allowed for a direct comparison between the traditional method and the proposed alternative. The residuals between the ETS scan positions achieved with the two methods indicate that the new procedure can accurately align the ETS position. Furthermore, the ability to perform the procedure in a non-clinical environment adds another layer of flexibility to the treatment process. In conclusion, this study demonstrates the potential of the proposed method to enhance the efficiency and flexibility of setup optimization in ocular proton therapy.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & **Pitch [\({}^{\circ}\)]** & **Roll [\({}^{\circ}\)]** & **Yaw [\({}^{\circ}\)]** & **X [mm]** & **Y [mm]** & **Z [mm]** \\ \hline \multirow{2}{*}{Smart-DX} & Mean & 0.01 & 0.06 & \(-\)0.15 & 0.18 & \(-\)0.20 & \(-\)0.15 \\  & Std & 0.26 & 0.07 & 0.17 & 0.24 & 0.53 & 0.56 \\ \hline \multirow{2}{*}{OTS-CT} & Mean & 0.01 & \(-\)0.05 & \(-\)0.08 & 0.06 & 0.04 & \(-\)0.04 \\  & Std & 0.59 & 0.26 & 0.24 & 0.17 & 0.33 & 0.48 \\ \hline \end{tabular}
\end{table}
Table 4: Calibration residues of Smart-DX system compared to the optical-tracking system residues in the CT room.  
**Author Contributions:** Conceptualization, G.S. and A.P.; methodology, G.S. and A.P.; software, G.S.; validation, A.P. and G.B.; formal analysis, G.S., A.P. and G.B.; investigation, G.S. and A.P.; resources, E.O. and G.B.; data curation, G.S.; writing--original draft preparation, G.S. and A.P.; writing--review and editing, all authors; visualization, all authors; supervision, M.P., F.G., M.C., M.R.F., A.C., C.P., M.R., A.V., E.O. and G.B.; project administration, G.S., A.P. and G.B.; funding acquisition, non applicable. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of FONDAZIONE I.R.C.C.S. POLICLINICO \"SAN MATTEO\" (protocol code 37143/2021 and date of approval 14-04-2021).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
The authors declare no conflicts of interest.