# An Immersive Virtual Reality Simulator for Echocardiography Examination
## 2 Materials and Methods
### Multi-User Connection Module  
The echocardiography examination simulator was developed and integrated with a multi-user connectivity module, allowing multiple educators to simultaneously conduct practical training and exercises. This was designed to address limitations in traditional medical education settings, prevent continuous expenses on consumable materials, and resolve ethical issues arising from clinical practice on actual patients. For the development of a multi-user connectivity module, the Normcore library with features such as smooth mutual transformation synchronization, efficient serialization for congestion control, and stable implementation of multiple connections by blocking the unreliable transmission protocol UDP (user datagram protocol) was utilized. Additionally, the Unity XR Interaction Toolkit was used to support the development of interaction among multiple connected users. The app key issued by Normcore was registered to develop a concurrent connection  
Figure 15: Changing the mode of the echocardiography examination view: **(a)** B-mode and **(b)** M-color mode. \begin{table}
\begin{tabular}{c p{284.5 pt}} \hline \hline
**View** & **View area based on probe position and direction** \\ \hline \multirow{3}{*}{PLAX} & Probe: Place the probe in the left parasternal region of the chest, with the orientation marker facing the right shoulder of the patient’s 3D model. \\  & View area: The aortic valve, left atrium and ventricle, and aortic arch are observed. \\ \hline \multirow{3}{*}{PSAX MV} & Probe: Place the probe in the left parasternal region of the chest, with the orientation marker facing the left shoulder of the patient’s 3D model. \\  & View area: The lower left part of the cardiac muscle, specifically the mitral valve and surrounding structures, is visualized. \\ \hline \multirow{3}{*}{PSAX AV} & Probe: Aligned in the same position and orientation as PSAX MV, tilting the probe contact surface downward. View area: Anatomical structures related to the aortic valve, specifically the open state of the aortic valve, are observed. \\ \hline \multirow{3}{*}{PSAX PM} & Probe: Aligned in the same position and orientation as PSAX MV, tilting the probe contact surface upward. View area: The muscles known as the papillary muscles, which are involved in the contraction of the ventricles, are observed. \\ \hline \multirow{3}{*}{PSAX Apical} & Probe: Move down approximately one to two intercostal spaces from the position of the PSAX MV and the orientation marker facing below the right shoulder of the patient’s 3D model. View area: The structures near the top of the ventricles and around the chordae tendineae (chordae tendons) are observed. \\ \hline \multirow{3}{*}{A4C} & Probe: Positioned in the fifth to sixth intercostal space in the lower left chest area, with the orientation marker facing the upper arm of the patient’s 3D model. View area: The right and left atria, as well as the upper and lower ventricles, are simultaneously visualized. \\ \hline \multirow{3}{*}{A3C} & Probe: The contact position for A4C is the same, with the orientation marker facing the right shoulder of the patient’s 3D model. View area: The left atrium, left upper ventricle, and left lower ventricle are observed. \\ \hline \multirow{3}{*}{A2C} & Probe: The contact position for A4C is the same, with the orientation marker facing the head of the patient’s 3D model. View area: The left atrium and left upper ventricle are predominantly observed. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Echocardiography views based on probe 3D model positions and direction. module, and avatars for participants in the echocardiography examination simulator were created. Multiple participants can freely explore the virtual space of the echocardiography examination simulator, and the participant performing the echocardiography can observe the perspectives of other participants, allowing for a collaborative experience.