Ústav počítačové grafiky a multimédií
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- ItemMathematical model of mechanical testing of bone-implant (4.5 mm LCP) construct(University of Veterinary and Pharmaceutical Sciences in Brno, 2012-09-17) Urbanová, Lucie; Blažek-Fialová, Iva; Srnec, Robert; Pěnčík, Jan; Kršek, Přemysl; Nečas, AloisThe study deals with the possibility of substituting time- and material-demanding mechanical testing of a bone defect fixation by mathematical modelling. Based on the mechanical model, a mathematical model of bone-implant construct stabilizing experimental segmental femoral bone defect (segmental ostectomy) in a miniature pig ex vivo model using 4.5 mm titanium LCP was created. It was subsequently computer-loaded by forces acting parallel to the long axis of the construct. By the effect of the acting forces the displacement vector sum of individual construct points occurred. The greatest displacement was noted in the end segments of the bone in close proximity to ostectomy and in the area of the empty central plate hole (without screw) at the level of the segmental bone defect. By studying the equivalent von Mises stress SIGMAeqv on LCP as part of the tested construct we found that the greatest changes of stress occur in the place of the empty central plate hole. The distribution of this strain was relatively symmetrical along both sides of the hole. The exceeding of the yield stress value and irreversible plastic deformations in this segment of LCP occurred at the acting of the force of 360 N. These findings are in line with the character of damage of the same construct loaded during its mechanic testing. We succeeded in creating a mathematical model of the bone-implant construct which may be further used for computer modelling of real loading of similar constructs chosen for fixation of bone defects in both experimental and clinical practice.
- ItemEfficient Low-Resource Compression of HIFU Data(2018-06-26) Klepárník, Petr; Bařina, David; Zemčík, Pavel; Jaroš, JiříLarge-scale numerical simulations of high-intensity focused ultrasound (HIFU), important for model-based treatment planning, generate large amounts of data. Typically, it is necessary to save hundreds of gigabytes during simulation. We propose a novel algorithm for time-varying simulation data compression specialised for HIFU. Our approach is particularly focused on on-the-fly parallel data compression during simulations. The algorithm is able to compress 3D pressure time series of linear and non-linear simulations with very acceptable compression ratios and errors (over 80% of the space can be saved with an acceptable error). The proposed compression enables significant reduction of resources, such as storage space, network bandwidth, CPU time, and so forth, enabling better treatment planning using fast volume data visualisations. The paper describes the proposed method, its experimental evaluation, and comparisons to the state of the arts.
- ItemIntensity-based non overlapping area registration supporting "drop-outs" in terms of model-based radiostereometric analysis(2018-03-28) Klíma, Ondřej; Novobilský, Petr; Madeja, Roman; Bařina, David; Chromý, Adam; Španěl, Michal; Zemčík, PavelA model-based radiostereometric analysis (MBRSA) is a method for precise measurement of prosthesis migration, which does not require marking the implant with tantalum beads. Instead, the prosthesis pose is typically recovered using a feature-based 2D-3D registration of its virtual model into a stereo pair of radiographs. In this study, we evaluate a novel intensity-based formulation of previously published non-overlapping area (NOA) approach. The registration is capable to perform with both binary radiographic segmentations or non segmented X-ray images. In contrast with the feature-based version, it is capable to deal with unreliable parts of prosthesis. As the straightforward formulation allows efficient acceleration using modern graphics adapters, it is possible to involve precise high-poly virtual models. Moreover, in case of binary segmentations, the non-overlapping area is simply interpretable, useful for indicating the accuracy of the registration outcome. In silico and phantom evaluations were performed using a cementless Zweymüller femoral stem and its reverse engineered (RE) model. For initial pose estimates with difference from the ground-truth limited to 4 mm and 4° respectively, the mean absolute translational error was not higher than 0.042+-0.035 mm. The error in rotation around the proximodistal axis was 0.181+-0.265°, error for remaining axes was not higher than 0.035+-0.037°.
- ItemExperiences in building a mOSAIC of clouds(2013-05-24) Petcu, Dana; Di Martino, Beniamino; Venticinque, Salvatore; Rak, Massimiliano; Máhr, Tamás; Lopez, Gorka; Brito, Fabrice; Cossu, Roberto; Stopar, Miho; Šperka, Svatopluk; Stankovski, VladoThe diversity of Cloud computing services is challenging the application developers as various and non-standard interfaces are provided for these services. Few middleware solutions were developed until now to support the design, deployment and execution of service-independent applications as well as the management of resources from multiple Clouds. This paper focuses on one of these advanced middleware solutions, called mOSAIC. Written after the completion of its development, this paper presents an integrated overview of the mOSAIC approach and the use of its various software prototypes in a Cloud application development process. We are starting from the design concepts and arrive to various applications, as well as to the position versus similar initiatives.
- ItemIndoor and Outdoor Backpack Mapping with Calibrated Pair of Velodyne LiDARs(2019-09-29) Veľas, Martin; Španěl, Michal; Herout, AdamThis paper presents a human-carried mapping backpack based on a pair of Velodyne LiDAR scanners. Our system is a universal solution both for large scale outdoor and also smaller indoor environments. It benefits from a combination of two LiDAR scanners what makes the odometry estimation more precise. The scanners are mounted under different angles, thus larger space around the backpack is scanned. By fusion with GNSS/INS sub-system, the mapping of featureless environments and also the georeferencing of resulting point cloud is possible. By deploying SoA methods for registration and the loop closure optimization it provides sufficient precision for many applications in BIM (Building Information Modeling), inventory check, construction planning, etc. In our indoor experiments, we evaluated our proposed backpack against ZEB-1 solution, using FARO terrestrial scanner as the reference, yielding similar results in terms of precision, while our system provides higher data density, laser intensity readings, and scalability for large environments.