# Medical Augmented-Reality Visualizer for Surgical Training and Education in Medicine
## 1 Introduction
Otherwise, eye strain, discomfort, and fatigue can result by excessive use of the lens muscles in the eyes to focus on the correct plane [20]. In this paper, we introduce an AR system called MARVIS (Medical AR VISualizer) that provides support for surgical procedures training by overlaying images of internal structures onto the surface of a phantom organ. The human liver was chosen as the test organ, for which biopsy and thermoablation were considered as exemplary procedures. This study aimed to develop a system that closely resembles the real conditions of a surgeon's workspace. The key aspects of the MARVIS system are the following:  
1. Optical tracking of the user's head while practicing on the organ phantom. Information related to the spatial relationship between the phantom and operator's head is calculated in real time. 2. Projection of internal structures onto the surface of the liver phantom in conjunction with naked-eye observation. This type of observation along with monoscopic motion parallax provides 3D perception through simple motions of either the operator's head or the phantom. No additional goggles or headsets are required. 3. A dedicated phantom composed of segments with different electric conductivities and an electronic module. This subsystem provides objective information about the procedure results in terms of the correct targeting rate of the internal structures. Various AR systems for medical applications have been proposed. In Ref. [21], a system that displays anatomical objects in three dimensions combined with a 2D slicing plane on an external stereoscopic display is introduced. This system allows trainees to feel a virtual patient using their hands through palpation. In addition, projection-based AR systems for medicine have also been proposed. In Ref. [22], an interactive computer-generated intelligent virtual agent is introduced, where visual information is projected onto the physical shell of a head. Another system trains ultrasound-guided needle placement augmented with computer-generated ultrasound imagery, which emulates the physical process of ultrasound scanning on patients [23]. A system presented in Ref. [24] simulates the fermoal palpation procedure in a virtual environment and allows to train needle insertion into the vessel. However, the systems in Refs. [21; 24] show the generated auxiliary data on external monitors, and the operator must constantly switch the viewpoint, possibly leading to problems in long-term perception. The technique described in Ref. [21] needs a wired stylus to manipulate the virtual object. Furthermore, the system in Ref. [24] requires dedicated hardware to deliver tactile feedback. The systems in Refs. [22; 23] do not consider the operator's viewpoint, possibly causing manipulation problems during the virtual medical procedure due to different coordinate systems. Moreover, the approach presented in Ref. [23] renders all information on screen as monochromatic visualization only. The approach we propose in this paper has the abovementioned key aspects and comprises a novel projection-based AR system. The approach is implemented on the MARVIS dedicated system, which allows to visualize previously segmented computer tomography (CT) medical data of internal structures on the liver phantom.