Exposure Render: An Interactive Photo-Realistic Volume Rendering Framework

The field of volume visualization has undergone rapid development during the past years, both due to advances in suitable computing hardware and due to the increasing availability of large volume datasets. Recent work has focused on increasing the visual realism in Direct Volume Rendering (DVR) by integrating a number of visually plausible but often effect-specific rendering techniques, for instance modeling of light occlusion and depth of field. Besides yielding more attractive renderings, especially the more realistic lighting has a positive effect on perceptual tasks. Although these new rendering techniques yield impressive results, they exhibit limitations in terms of their exibility and their performance. Monte Carlo ray tracing (MCRT), coupled with physically based light transport, is the de-facto standard for synthesizing highly realistic images in the graphics domain, although usually not from volumetric data. Due to the stochastic sampling of MCRT algorithms, numerous effects can be achieved in a relatively straight-forward fashion. For this reason, we have developed a practical framework that applies MCRT techniques also to direct volume rendering (DVR). With this work, we demonstrate that a host of realistic effects, including physically based lighting, can be simulated in a generic and flexible fashion, leading to interactive DVR with improved realism. In the hope that this improved approach to DVR will see more use in practice, we have made available our framework under a permissive open source license

Pre-operative Planning and Intra-operative Guidance for Shoulder Replacement Surgery

Shoulder joint replacement, or arthroplasty, is indicated in cases where arthritis or trauma has resulted in severe joint damage that in turn causes increased pain and decreased function. However, shoulder arthroplasty is less successful than hip and knee replacement, mostly due to the complexity of the shoulder joint and the resultant complexity of the replacement operation. In this paper we present a complete visualization-oriented pre-operative planning and intra-operative guidance approach for shoulder joint replacement. Our system assists the surgeon by allowing a virtual arthroplasty procedure whilst giving feedback, primarily via patient- and procedure-specific joint range of motion (ROM) simulation and visualization. After a successful planning, our system automatically generates a 3D model of a patient-specific mechanical guidance device that is then produced by a rapid prototyping machine and can be used during the operation. In this way, a computer-based guidance system is not required in the operating room

Visualization of sliding and deformation of orbital fat during eye rotation

PURPOSE: Little is known about the way orbital fat slides and/or deforms during eye movements. We compared two deformation algorithms from a sequence of MRI volumes to visualize this complex behavior. METHODS: Time-dependent deformation data were derived from motion-MRI volumes using Lucas and Kanade Optical Flow (LK3D) and nonrigid registration (B-splines) deformation algorithms. We compared how these two algorithms performed regarding sliding and deformation in three critical areas: the sclera-fat interface, how the optic nerve moves through the fat, and how the fat is squeezed out under the tendon of a relaxing rectus muscle. The efficacy was validated using identified tissue markers such as the lens and blood vessels in the fat. RESULTS: Fat immediately behind the eye followed eye rotation by approximately one-half. This was best visualized using the B-splines technique as it showed less ripping of tissue and less distortion. Orbital fat flowed around the optic nerve during eye rotation. In this case, LK3D provided better visualization as it allowed orbital fat tissue to split. The resolution was insufficient to visualize fat being squeezed out between tendon and sclera. CONCLUSION: B-splines performs better in tracking structures such as the lens, while LK3D allows fat tissue to split as should happen as the optic nerve slides through the fat. Orbital fat follows eye rotation by one-half and flows around the optic nerve during eye rotation. TRANSLATIONAL RELEVANCE: Visualizing orbital fat deformation and sliding offers the opportunity to accurately locate a region of cicatrization and permit an individualized surgical plan

Mri-based visualisation of orbital fat deformation during eye motion

Summary. Orbital fat, or the fat behind the eye, plays an important role in eye movements. In order to gain a better understanding of orbital fat mobility during eye motion, MRI datasets of the eyes of two healthy subjects were acquired respectively in seven and fourteen different directions of gaze. After semi-automatic rigid registration, the Demons deformable registration algorithm was used to derive timedependent three-dimensional deformation vector fields from these datasets. Visualisation techniques were applied to these datasets in order to investigate fat mobility in specific regions of interest in the first subject. A qualitative analysis of the first subject showed that in two of the three regions of interest, fat moved half as much as the embedded structures. In other words, when the muscles and the optic nerve that are embedded in the fat move, the fat partly moves along with these structures and partly flows around them. In the second subject, a quantitative analysis was performed which showed a relation between the distance behind the sclera and the extent to which fat moves along with the optic nerve

Measuring femoral lesions despite CT metal artefacts: a cadaveric study

Objective Computed tomography is the modality of choice for measuring osteolysis but suffers from metal-induced artefacts obscuring periprosthetic tissues. Previous papers on metal artefact reduction (MAR) show qualitative improvements, but their algorithms have not found acceptance for clinical applications. We investigated to what extent metal artefacts interfere with the segmentation of lesions adjacent to a metal femoral implant and whether metal artefact reduction improves the manual segmentation of such lesions. Materials and methods We manually created 27 periprosthetic lesions in 10 human cadaver femora. We filled the lesions with a fibrotic interface tissue substitute. Each femur was fitted with a polished tapered cobalt-chrome prosthesis and imaged twice—once with the metal, and once with a substitute resin prosthesis inserted. Metalaffected CTs were processed using standard back-projection as well as projection interpolation (PI) MAR. Two experienced users segmented all lesions and compared segmentation accuracy. Results We achieved accurate delineation of periprosthetic lesions in the metal-free images. The presence of a metal implant led us to underestimate lesion volume and introduced geometrical errors in segmentation boundaries.MediamaticsElectrical Engineering, Mathematics and Computer Scienc

An on-line machine vision flotation froth analysis platform

Thesis (MEng)--University of Stellenbosch, 1999.ENGLISH ABSTRACT: Froth flotation is a popular process used for the extraction of certain minerals from ore. The effective automatic control of this process has great financial importance. Utilising machine vision as the measurement component of an automatic flotation control system has several advantages: it is a cost effective solution due to its non-contacting sensors and consequent low maintenance, as well as its low initial setup costs; it yields consistent and accurate parameters; and the measurements it makes are available immediately, thus enabling real-time control and minimising the effects of process disturbances rapidly and efficiently. In addition, machine vision can be used as a research tool for investigating froth flotation, a process which is still not fully understood. This work documents the development of an on-line machine vision flotation froth analysis platform that is in use in the industry as the measurement component of an advanced flotation control system and in the academic world as a powerful research tool. Two additional froth analysis applications, namely an embedded froth mobility sensor for use in the flotation industry and a continuous froth video sampling and analysis research platform, are developed in the course of this work. An investigation into continuous video sampling and analysis of flotation froth is performed for the first time and indicates that this mode of froth image acquisition yields more information than traditional froth imaging methods. Recommendations are made with respect to the practical application of continuous froth video sampling and analysis.AFRIKAANSE OPSOMMING: Skuim-flotasie is 'n gewilde proses vir die ontginning van sekere minerale uit erts. Die effektiewe outomatiese beheer van flotasie dra groot finansiele impak. Daar is verskeie voordele verbonde aan die gebruik van rekenaar-visie as die sensor-komponent van so 'n outomatiese flotasie beheerstelsel. Dit is 'n koste-effektiewe oplossing vanwee die feit dat die sensors nie in aanraking is met die flotasie nie en dus min onderhoud vereis. Boonop is die aanvanklike opstellingskoste laag. 'n Masjien-visie stelsel lewer akkurate en betroubare metings en dit kan hierdie metings baie vinnig beskikbaar maak wat intydse beheer van 'n flotasie-aanleg vergemaklik. Daar kan dan baie vinnig op proses-versteurings gereageer word. Masjien-visie is ook waardevol vir navorsing oor flotasie, 'n proses wat nog nie heeltemal verstaan word nie. 'n Praktiese masjien-visie gebaseerde flotasie-skuim analise platform word ontwikkel. Hierdie sagteware word gebruik in die flotasie-industrie as die sensor-komponent van 'n gevorderde flotasie beheerstelsel asook as 'n kragtige navorsings-hulpmiddel in die akademiese wereld. Twee bykomende toepassings word ontwikkel, naamlik 'n intydse flotasie-skuim mobiliteitsensor vir gebruik in die flotasie-industrie en 'n n'avorsingsplatform vir die insameling en analise van kontinue flotasie-skuim video-data. Ondersoek word ingestel na die analise van kontinue flotasie-skuim video-data vir die eerste keer in flotasie-skuim geskiedenis, en die resultate dui daarop dat hierdie metode van datainsameling meer informasie oor die skuim inhou as tradisionele insamelings- en analise metodes. Daar word aanbevelings gemaak omtrent die praktiese toepassing van kontinue flotasie-skuim video monstering