## 3 Results and Discussion
### VR Environment  
The present section describes the implementation of a VR platform in order to visualize and inspect clinical cases of patient-specific hearts' 3D models. A digital library contains the reconstructed and segmented heart models of all the examined cases, categorizing them in relation to the type of their defect. In general, the VR application provides an immersive and interactive approach for users to meticulously explore patient-specific 3D models or study several heart diseases. The developed application allows the user to interact with the 3D model of a heart in a virtual environment using an Oculus VR headset and controllers as illustrated in Figure 6. More specifically, the user can manipulate the heart's scale, select and edit specific parts of the heart, navigate through the heart, make sections at any point, and even record notes at any location within the heart. To achieve these features, the VR module utilizes the Oculus Integration asset tool, which allows the user to grab, transform, and interact with the investigated 3D model. The heart model is divided into specific parts or child objects, each one with a simplified triggered mesh collider that enables them to interact with the controls. The Oculus Integration Library offers a wide range of applications that can be employed for the heart object, allowing the user to hold, move, and scale the heart via the controllers. In addition, the application includes a feature to visualize each segmented part separately, considering the clustering algorithm presented in a previous paragraph. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Model**} & **Pressure Losses** & \multirow{2}{*}{**Energy Losses**} & **Mass Flow through the** \\  & **(\(\Delta p\))** & & **Descending Aorta** \\ \hline Aorta with CoA & 3906 Pa & 3.685 J/kg & 6.31 g/s \\ Aorta without CoA & 1296 Pa & 1.222 J/kg & 21.1 g/s \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Quantitative values of the influence of the examined defect. Figure 6: The developed VR environment inspecting a segmented human heart and an aorta. A typical application of the cross-section tool is depicted in Figure 7, where a parallelepiped space is defined, thus creating a plane where the cross-section or 'cutting' effect occurs. The 'parent' object for these quads is an intractable entity composed of a cylindrical handle and a 3D rectangular frame. The outcome of the module is not only aesthetically pleasing but also user-friendly. Furthermore, the VR application features an annotation tool for attaching notes either on the surface or within the interior of the heart, providing a virtual keyboard and complemented by speech-to-text capabilities. Another valuable feature for medical professionals is a measurement tool that can be used by clinicians to measure any anatomical feature of interest with great precision, such as the diameter of the aorta. Hereupon, the quick determination of abnormalities, such as aneurysms or stenosis, becomes simpler and more efficient. The ability to measure distances between various points within the heart can also support the planning of surgical procedures, allowing physicians to gain a better understanding of the heart's size and defects. It must be noted that all the above-mentioned software tools of the VR application are provided in an intuitive and user-friendly interface, making it easy for medical professionals to use without extensive training or expertise in VR technology, as shown in the next figure. Another promising feature that the introduced VR tool provides is the investigation of the numerical analysis within the virtual environment, as presented in Figure 8. The outcomes of the CFD analysis can be imported into the application, allowing a medical doctor who is unfamiliar with these technologies to visualize the blood flow distribution and velocity, thus aiding in the diagnosis and treatment of the patient.