Incomplete Gamma Kernels: Generalizing Locally Optimal Projection Operators.

We present incomplete gamma kernels, a generalization of Locally Optimal Projection (LOP) operators. In particular, we reveal the relation of the classical localized L1 estimator, used in the LOP operator for point cloud denoising, to the common Mean Shift framework via a novel kernel. Furthermore, we generalize this result to a whole family of kernels that are built upon the incomplete gamma function and each represents a localized Lp estimator. By deriving various properties of the kernel family concerning distributional, Mean Shift induced, and other aspects such as strict positive definiteness, we obtain a deeper understanding of the operator's projection behavior. From these theoretical insights, we illustrate several applications ranging from an improved Weighted LOP (WLOP) density weighting scheme and a more accurate Continuous LOP (CLOP) kernel approximation to the definition of a novel set of robust loss functions. These incomplete gamma losses include the Gaussian and LOP loss as special cases and can be applied to various tasks including normal filtering. Furthermore, we show that the novel kernels can be included as priors into neural networks. We demonstrate the effects of each application in a range of quantitative and qualitative experiments that highlight the benefits induced by our modifications.

Versatile multi-constrained planning for thermal ablation of large liver tumors.

The surgical planning of large hepatic tumor ablation remains a challenging task that relies on fulfilling multiple medical constraints, especially for the ablation based on configurations of multiple electrodes. The placement of the electrodes to completely ablate the tumor as well as their insertion trajectory to their final position have to be planned to cause as little damage to healthy anatomical structures as possible to allow a fast rehabilitation. In this paper, we present a novel, versatile approach for the computer-assisted planning of multi-electrode thermal ablation of large liver tumors based on pre-operative CT data with semantic annotations. This involves both the specification of the number of required electrodes and their distribution to adequately ablate the tumor region without damaging too much healthy tissue. To determine the insertion trajectory of the electrodes to their final position, we additionally incorporate a series of medical constraints into our optimization, which allows a global analysis where obstacles such as bones are taken into account and damage to healthy tissue is mitigated. Compared with the state-of-the-art method, our method achieves compact ablation regions without relying on assumptions on a potential needle path for optimal global search and, hence, is suitable for guiding clinicians through the planning of the tumor ablation. We also demonstrate the feasibility of our approach in various experiments of clinical data and demonstrate that our approach not only allows completely ablating the tumor region but also reducing the damage of healthy tissue in comparison to the previous state-of-the-art method.

Collaborative VR-Based 3D Labeling of Live-Captured Scenes by Remote Users.

Previous work on interactive 3D labeling focused on improving user experience based on virtual/augmented reality and, thereby, speeding-up the labeling of scenes. In this article, we present a novel interactive, collaborative VR-based 3D labeling system for live-captured scenes by multiple remotely connected users based on sparse multi-user input with automatic label propagation and completion. Hence, our system is particularly beneficial in the case of multiple users that are able to label different scene parts from the respectively adequate views in parallel. Our proposed system relies on 1) the RGB-D capture of an environment by a user, 2) a reconstruction client that integrates this stream into a 3D model, 3) a server that gets scene updates and manages the global 3D scene model as well as client requests and the integration/propagation of labels, 4) labeling clients that allow an independent VR-based scene exploration and labeling for each user, and 5) remotely connected users that provide a sparse 3D labeling used to control the label propagation over objects and the label prediction to other scene parts. Our evaluation demonstrates the intuitive collaborative 3D labeling experience as well as its capability to meet the efficiency constraints regarding reconstruction speed, data streaming, visualization, and labeling.

Constraint-Based Optimized Human Skeleton Extraction from Single-Depth Camera.

As a cutting-edge research topic in computer vision and graphics for decades, human skeleton extraction from single-depth camera remains challenging due to possibly occurring occlusions of different body parts, huge appearance variations, and sensor noise. In this paper, we propose to incorporate human skeleton length conservation and symmetry priors as well as temporal constraints to enhance the consistency and continuity for the estimated skeleton of a moving human body. Given an initial estimation of the skeleton joint positions provided per frame by the Kinect SDK or Nuitrack SDK, which do not follow the aforementioned priors and can prone to errors, our framework improves the accuracy of these pose estimates based on the length and symmetry constraints. In addition, our method is device-independent and can be integrated into skeleton extraction SDKs for refinement, allowing the detection of outliers within the initial joint location estimates and predicting new joint location estimates following the temporal observations. The experimental results demonstrate the effectiveness and robustness of our approach in several cases.

SLAMCast: Large-Scale, Real-Time 3D Reconstruction and Streaming for Immersive Multi-Client Live Telepresence.

Real-time 3D scene reconstruction from RGB-D sensor data, as well as the exploration of such data in VR/AR settings, has seen tremendous progress in recent years. The combination of both these components into telepresence systems, however, comes with significant technical challenges. All approaches proposed so far are extremely demanding on input and output devices, compute resources and transmission bandwidth, and they do not reach the level of immediacy required for applications such as remote collaboration. Here, we introduce what we believe is the first practical client-server system for real-time capture and many-user exploration of static 3D scenes. Our system is based on the observation that interactive frame rates are sufficient for capturing and reconstruction, and real-time performance is only required on the client site to achieve lag-free view updates when rendering the 3D model. Starting from this insight, we extend previous voxel block hashing frameworks by introducing a novel thread-safe GPU hash map data structure that is robust under massively concurrent retrieval, insertion and removal of entries on a thread level. We further propose a novel transmission scheme for volume data that is specifically targeted to Marching Cubes geometry reconstruction and enables a 90% reduction in bandwidth between server and exploration clients. The resulting system poses very moderate requirements on network bandwidth, latency and client-side computation, which enables it to rely entirely on consumer-grade hardware, including mobile devices. We demonstrate that our technique achieves state-of-the-art representation accuracy while providing, for any number of clients, an immersive and fluid lag-free viewing experience even during network outages.

Design and implementation of practical bidirectional texture function measurement devices focusing on the developments at the University of Bonn.

Understanding as well as realistic reproduction of the appearance of materials play an important role in computer graphics, computer vision and industry. They enable applications such as digital material design, virtual prototyping and faithful virtual surrogates for entertainment, marketing, education or cultural heritage documentation. A particularly fruitful way to obtain the digital appearance is the acquisition of reflectance from real-world material samples. Therefore, a great variety of devices to perform this task has been proposed. In this work, we investigate their practical usefulness. We first identify a set of necessary attributes and establish a general categorization of different designs that have been realized. Subsequently, we provide an in-depth discussion of three particular implementations by our work group, demonstrating advantages and disadvantages of different system designs with respect to the previously established attributes. Finally, we survey the existing literature to compare our implementation with related approaches.

Compartment syndrome.

Compartment syndrome is a limb-threatening and occasionally life-threatening injury. It occurs whenever the tissue pressure (referred to as interstitial pressure) within a closed anatomic space is greater than the perfusion pressure. Untreated, compartment syndrome leads to tissue necrosis, permanent functional impairment and, if severe in large compartments, renal failure and death. Compartment syndrome can occur within any muscle group located in a compartment. It is most common following an event that severely damages a muscle, like a crushing or twisting injury. Mechanisms of injury that involve circumferential burns, ischemia and tourniquets can cause compartment syndrome. Motorcyclists who suffer lower-extermity injuries in accidents are a high-risk group. A tough membrane referred to as a fascia covers muscle groups, forming a compartment for the muscle. In normal circumstances, this arrangement allows the muscle to function more efficiently, but if the muscle is injured in any way, the fascia limits the amount of swelling that can occur. This in turn restricts the flow of blood through the affected region. The first compromised function within the compartment is the flow of lymph and venous blood. If there are sensory nerves running through the compartment, they will not function correctly, causing the numbness, tingling and, later, the pain associated with compartment syndrome. With more swelling, arterial flow is compromised, pain worsens and motor function is impaired. An artificial way of producing a compartment syndrome is to place a cast or splint around a damaged extermity, compressing it. This is a way emergency personnel can compromise an injury and cause long-term consequences for the patient. Recovery is achieved by surgically opening the compartment involved (a fasciotomy) and releasing the pressure. The muscle at first will swell outside the compartment, but then it recovers, swelling is reduced and normal function can be recovered. Prehospital treatment of extremity injuries that will prevent or limit compartment syndrome is immobilization, elevation and cooling. Recognition of the syndrome later in its course, as in this case, requires the EMT to remove the patient to an appropriate emergency department. Prehospital providers need to recognize that many mechanisms of injury can produce this syndrome, even those that seem relatively minor. All injured patients should be educated to seek care should the symptoms of numbness, deep pain and coolness to the distal extremity occur. This case involved a patient who, from a relatively minor mechanism of trauma, experienced an internal disruption of the muscle group controlling the thumb (thenar mass). The early swelling in the thenar compartment resulted in the patient experiencing a tingling sensation in his left thumb. In many cases, such an injury would be referred to as a "stinger" (a temporary neurological deficit due to a sudden and excessive stimulation of a neurologic plexus or junction). But this patient had more swelling in the compartment, resulting in a lack of circulation manifested by a cool extremity, poor capillary refill and decreased pulse oximetry. Luckily, this officer recognized the need for medical evaluation of what appeared to be a minor injury and was returned to duty with no permanent impairment.

Hot on the inside.

When a disease process becomes life-threatening, it is termed to be malignant. Hyperthermia is a heat illness that arises from one of two basic causes: 1) the body's normal thermoregulatory mechanisms are overwhelmed by the environment (an exogenous heat load) or, more commonly, by excessive exercise in a moderate-to-extreme environment (an endogenous heat load); or 2) failure of the thermoregulatory mechanisms, such as those encountered in the elderly or debilitated patient. Either cause can lead to heat illnesses such as heat cramps, heat exhaustion or heatstroke. Heat cramps are brief, intermittent and often severe muscular cramps that frequently occur in muscles fatigued by heavy work or exercise. They are believed to be caused by a rapid change in the extracellular fluid osmolarity resulting from sodium and water loss. Heat exhaustion is a more severe form of heat illness characterized by minor changes in mental status (poor judgment, irritability), dizziness, nausea and headache. In severe cases, the patient may have an altered LOC. Just as with heat cramps, profuse sweating is present. Removing the patient from the hot environment and administering fluids will usually result in a rapid recovery. [table: see text] Left untreated, heat exhaustion may progress to heatstroke. Heatstroke results when there is a complete collapse of thermoregulatory mechanisms. This will lead to a rise in body core temperature in excess of 105.8 degrees F (41 degrees C), which will produce multisystem tissue damage and physiological collapse. Severe cases can cause death. The patient in this case had an axillary temperature taken and recorded at 101.4 degrees F. Typically, axillary temperatures are one degree cooler than oral temperatures, which are one degree cooler than core temperatures. This patient, then, had a core temperature of 103 degrees F or higher. There are two types of heatstroke: classic and exertional. Classic heatstroke occurs during periods of sustained high ambient temperatures and humidity. Exertional heatstroke more often occurs in athletes, military personnel and people who work strenuosly in the environment. In these situations, endogenous heat accumulates more rapidly than the body can dissipate it in the environment. Although sweating is usually absent in the classic form of heatstroke, 50% of exertional heatstroke cases have persistent sweating as a result of catecholamine release. The presence of sweating does not preclude the diagnosis of heatstroke, and cessation of sweating is not the cause of it. As the illness progresses, peripheral vasodilation occurs, resulting in hypotension and shunting. As internal temperatures rise, myocardial contractility begins to decrease, manifested by bradycardia and irritability of the myocardium. No matter the age group, the presence of hypotension and decreased cardiac output indicates a poor prognosis for the patient.

Everyone dies.

It's not unusual to be dispatched to one problem and discover something completely different when you arrive. Patients and family members will tell dispatch what they feel is the problem, and dispatch, without the benefit of being on scene, can only pass along the complaint as it was given to them. Upon arrival back at base, the attending paramedic in this case was asking himself questions like, "What if I had done this differently?" and "Did I miss something?" At the conclusion of every patient interaction, there is an opportunity for EMS to review its actions and [table: see text] change its approach to similar cases in the future. The benefit of public-safety agencies providing service in nonemergent situations is the opportunity to "practice" for true crisis incidents. This case, however, did not present many opportunities to improve care or change the outcome. The paramedic's assessment identified the need for the patient to be transported immediately. Immediate packaging of the patient, intubation and pacing were performed on scene--you known this crew was moving. The ED physician concurred that this was a "load and go" situation. The crew is to be commended for taking charge of a critical situation and performing in an expeditious manner. Oxygen, pacing, i.v. and meds were all given in a timely fashion. Unfortunately, this patient's cancer had progressed to a critical point, and the patient was not going to survive even with optimal care. This EMS crew unfortunately walked into an end-of-life event. Despite their best efforts (a total on-scene time of seven minutes and a five-minute transport) and performing every function flawlessly, this patient still died. This patient was given excellent medical service, but perhaps more important, at his critical moment, was in the presence of people who cared. One of the first things we learn in EMS is that people die. Sometimes our job is simply to provide comfort, relieve suffering and communicate with the survivors. Since all humans must die, it is just as important for us to service their needs at that moment in time. From there, we move on to the next call.