Abstract
This paper proposes a haptic interaction system for Virtual Reality (VR) based on a combination of tracking devices for hands and objects and a real-to-virtual mapping system for user redirection. In our solution the user receives haptic stimuli by manipulating real objects mapped to virtual objects. This solution departs from systems that rely on haptic devices (e.g., haptic gloves) as interfaces for the user to interact with objects in the Virtual Environment (VE). As such, the proposed solution makes use of direct haptics (touching) and redirection techniques to guide the user through the virtual environment. Using the mapping framework, when the user touches a virtual object in the VE, he will simultaneously be physically touching the equivalent real object. A relevant feature of the framework is the possibility to define a warped mapping between the real and virtual worlds, such that the relation between the user and the virtual space can be different from the one between the user and the real space. This is particularly useful when the application requires the emulation of large virtual spaces but the physical space available is more confined. To achieve this, both the user's hands and the objects are tracked. In the presented prototype we use a head-mounted depth sensor (i.e., Leap Motion) and a depth-sensing camera (i.e., Kinect). To assess the feasibility of this solution, a functional prototype and a room setup with core functionality were implemented. The test sessions with users evaluated the mapping accuracy, the user execution time and the awareness of the user regarding the warped space when performing tasks with redirection. The results gathered indicate that the solution can be used to provide direct haptic feedback in VR applications and for warping space perception within certain limits.

Abstract

Abstract
In this manuscript, we propose to adapt the B-Spline Explicit Active Surfaces (BEAS) framework for semi-automatic kidney segmentation in computed tomography (CT) images. To study the best energy functional for kidney CT extraction, three different localized region-based energies were implemented within the BEAS framework, namely localized Chan-Vese, localized Yezzi, and signed localized Yezzi energies. Moreover, a novel gradient-based regularization term is proposed. The method was applied on 18 kidneys from 9 CT datasets, with different image properties. Several energy combinations were contrasted using surface-based comparison against ground truth meshes, assessing their accuracy and robustness against surface initialization. Overall, the hybrid energy functional combining the localized signed Yezzi energy with gradient-based regularization simultaneously showed the highest accuracy and the lowest sensitivity to the initialization. Volumetric analysis demonstrated the feasibility of the method from a clinical point of view, with similar reproducibility to manual observers.

Abstract
Introduction and Objectives. Laparoscopic surgery has undeniable advantages, such as reduced postoperative pain, smaller incisions, and faster recovery. However, to improve surgeons' performance, ergonomic adaptations of the laparoscopic instruments and introduction of robotic technology are needed. The aim of this study was to ascertain the influence of a new hand-held robotic device for laparoscopy (HHRDL) and 3D vision on laparoscopic skills performance of 2 different groups, naive and expert. Materials and Methods. Each participant performed 3 laparoscopic tasksPeg transfer, Wire chaser, Knotin 4 different ways. With random sequencing we assigned the execution order of the tasks based on the first type of visualization and laparoscopic instrument. Time to complete each laparoscopic task was recorded and analyzed with one-way analysis of variance. Results. Eleven experts and 15 naive participants were included. Three-dimensional video helps the naive group to get better performance in Peg transfer, Wire chaser 2 hands, and Knot; the new device improved the execution of all laparoscopic tasks (P < .05). For expert group, the 3D video system benefited them in Peg transfer and Wire chaser 1 hand, and the robotic device in Peg transfer, Wire chaser 1 hand, and Wire chaser 2 hands (P < .05). Conclusion. The HHRDL helps the execution of difficult laparoscopic tasks, such as Knot, in the naive group. Three-dimensional vision makes the laparoscopic performance of the participants without laparoscopic experience easier, unlike those with experience in laparoscopic procedures.

Abstract
Minimally invasive cardiovascular interventions guided by multiple imaging modalities are rapidly gaining clinical acceptance for the treatment of several cardiovascular diseases. These images are typically fused with richly detailed pre-operative scans through registration techniques, enhancing the intra-operative clinical data and easing the image-guided procedures. Nonetheless, rigid models have been used to align the different modalities, not taking into account the anatomical variations of the cardiac muscle throughout the cardiac cycle. In the current study, we present a novel strategy to compensate the beat-to-beat physiological adaptation of the myocardium. Hereto, we intend to prove that a complete myocardial motion field can be quickly recovered from the displacement field at the myocardial boundaries, therefore being an efficient strategy to locally deform the cardiac muscle. We address this hypothesis by comparing three different strategies to recover a dense myocardial motion field from a sparse one, namely, a diffusion-based approach, thin-plate splines, and multiquadric radial basis functions. Two experimental setups were used to validate the proposed strategy. First, an in silico validation was carried out on synthetic motion fields obtained from two realistic simulated ultrasound sequences. Then, 45 mid-ventricular 2D sequences of cine magnetic resonance imaging were processed to further evaluate the different approaches. The results showed that accurate boundary tracking combined with dense myocardial recovery via interpolation/diffusion is a potentially viable solution to speed up dense myocardial motion field estimation and, consequently, to deform/compensate the myocardial wall throughout the cardiac cycle. Copyright (C) 2015 John Wiley & Sons, Ltd.

Abstract
Pectus Excavatum (PE) is the most common congenital chest wall deformity, affecting 1 in 400 live births. This deformity is commonly corrected using the minimally invasive Nuss procedure, where a bar is positioned under the sternum. Although recent procedure advances based on patientspecific prosthesis were proposed, correct bar placement is still challenging. In this work, we propose a novel augmented reality system to guide the surgeon during PE bar placement. This system combines a 3D sensor with a projector to superimpose the thoracic ribs cage on the chest wall of the patient, thus indicating the optimal insertion and bar placement points. This system was validated in three different scenarios: 1) simulated chest surface models; 2) 3D printed phantom; and 3) 3D commercial thoracic phantom. An error of 3.93 ± 3.44 mm, and 3.08 ± 1.57 mm were obtained in the first and second experiments, respectively. In the final experiment, visual assessment of the result proved that a high similarity was obtained between the projected model and the real ribs cage position. Overall, the proposed system showed high feasibility with low error, proving that 3D projection of the ribs on the patient’s chest wall may facilitate PE bar insertion and ultimately provide useful information to guide Nuss procedure. © 2016 Taylor & Francis Group, London.