# Breakthrough and Challenging Application: Mixed Reality-Assisted Intracardiac Surgery
## 1 Introduction  
In recent years, augmented reality (AR), virtual reality (VR), and mixed reality (MR) have emerged as prominent technologies across various fields, including medicine. While AR overlays virtual elements onto the real environment in real-time, VR provides users with an entirely immersive experience [1]. In contrast, MR blends the digital and physical worlds, enabling interactions between the two dimensions. This technology allows virtual objects to be placed in the real environment or facilitates digital presence in the physical world for collaboration across different locations and times [2]. The introduction of such technologies in surgery brings several advantages, including streamlined procedures, enhanced medical training, improved patient data visualization, and surgical support. Several studies [3; 4; 5; 6; 7; 8; 9; 10; 11; 12] examine the utility and clinical value of three-dimensional (3D) reconstruction and printing in aiding diagnosis, medical education, preoperative planning, and intraoperative guidance of surgical interventions. However, there is a scarcity ofliterature regarding concrete applications of MR in the cardiovascular domain due to its nascent stage of study and expansion. In the field of cardiovascular medicine, conventional 2D medical images and their corresponding 3D reconstructions are integral components of an efficient surgical planning system. The segmentation process is at the base of the 3D reconstruction and it can be conducted from different medical imaging techniques such as computed tomography (CT), Magnetic Resonance Imaging (MRI), doppler ultrasound [13], and advance imaging [14]. Moreover, to understand and simulate the physiological behavior of the heart, computational models have been studied to descript electro-physiology [15] and personalized morphology [16]. However, these processes still request deep analysis and development. However, current practices often rely on flat screens for viewing 3D images, resulting in the loss of crucial spatial information necessary for understanding anatomical regions of interest and their associated pathologies. In the last three years, some research studies [10; 17; 18; 19] have already presented the idea of introducing MR or VR in the cardiovascular domain to overcome the limitations of standard surgical procedures. These limitations include the need for continuous switching between CT image visualization and the patient's body, as well as the restricted two-dimensional visualization of complex anatomical regions. The usefulness of the 3D visualization in pre-interventional planning and the assistive intraoperative tool has been already demonstrated in different studies [20; 21; 22]. Surgeons consider favorably this type of application where they can discuss a 3D model at the same time and see the 3D model in a holographic mode during the surgery. This functionality also reduces problems related to miscommunication, limited access to the mapping system, and direct interaction with technical instrumentation [23]. Generally, in VR and MR experiences specifically developed for surgical planning or training, the 3D model is visualized as a hologram and no interactions are considered, although the device allows far more elaborate implementations. The 3D model should be ideally observed in 360 degrees and virtually dissected according to the type of pathology. However, the complexity of the anatomical region and surgical procedures still limits the application of MR in cardiological surgery. The selection of the software for segmentation and the manual intervention is fundamental. [PERSON] and co-workers [24] proposed one of the first MR applications with a 3D model of the heart for the first version of HoloLens. In this study, the segmentation was conducted with an open-source software 3 DSlicer (version number 5.6.2. ), and the inner membranes of the anatomical component are not clearly visible.