Two of the most popular mediums for virtual reality are head-mounted displays and surround-screen projection systems, such as CAVE Automatic Virtual Environments. In recent years, HMDs suffered a significant reduction in cost and have become widespread consumer products. In contrast, CAVEs are still expensive and remain accessible to a limited number of researchers. This study aims to evaluate both objective and subjective characteristics of a CAVE-like monoscopic low-cost virtual reality surround-screen projection system compared to advanced setups and HMDs. For objective results, we measured the head position estimation accuracy and precision of a low-cost active infrared (IR) based tracking system, used in the proposed low-cost CAVE, relatively to an infrared marker-based tracking system, used in a laboratory-grade CAVE system. For subjective characteristics, we investigated the sense of presence and cybersickness elicited in users during a visual search task outside personal space, beyond arms reach, where the importance of stereo vision is diminished. Thirty participants rated their sense of presence and cybersickness after performing the VR search task with our CAVE-like system and a modern HMD. The tracking showed an accuracy error of 1.66 cm and .4 mm of precision jitter. The system was reported to elicit presence but at a lower level than the HMD, while causing significant lower cybersickness. Our results were compared to a previous study performed with a laboratory-grade CAVE and support that a VR system implemented with low-cost devices could be a viable alternative to laboratory-grade CAVEs for visual search tasks outside the user's personal space.

Acquired brain injury (ABI) is one of the main problems of disability and death in the world. Its incidence and survival rate are increasing annually. Thus, the number of chronic ABI patients is gradually growing. Traditionally, rehabilitation programs are applied to postacute and acute patients, but recent publications determine that chronic patients may benefit from rehabilitation. Also, in the last few years, the potential of virtual rehabilitation (VR) systems has been demonstrated. However, until now, no previous studies have been carried out to compare the evolution of chronic patients with acute patients in a VR program. To perform this study, we developed a VR system for ABI patients. The system, vestibular virtual rehabilitation (V2R), was designed with clinical specialists. V2R has been tested with 21 people ranging in age from 18 to 80 years old that were classified in two groups: chronic patients and acute patients. The results demonstrate a similar recovery for chronic and acute patients during the intervention period. Also, the results showed that chronic patients stop their improvement when they finish their training. This conclusion encourages us to direct our developments toward VR systems that can be easily integrated at home, allowing chronic patients to have a permanent VR training program.

The presence of metal artifacts in dental CT prevents the correct exploration and planning of dental interventions. This paper addresses a new paradigm in metal artifact reduction that uses the backprojected data available in the DICOM files. The method, based on variational image registration and morphological lambda reconstruction, enhances the image quality using not only the information of the artifacted image (horizontal approach) but also the information of adjoining images (vertical approach). Some preliminary results involving different CT scanners and patients are presented and discussed.