Body composition estimation from selected slices:equations computed from a new semi-automatic thresholding method developed on whole-body CT scans

Background Estimating volumes and masses of total body components is important for the study and treatment monitoring of nutrition and nutrition-related disorders, cancer, joint replacement, energy-expenditure and exercise physiology. While several equations have been offered for estimating total body components from MRI slices, no reliable and tested method exists for CT scans. For the first time, body composition data was derived from 41 high-resolution whole-body CT scans. From these data, we defined equations for estimating volumes and masses of total body AT and LT from corresponding tissue areas measured in selected CT scan slices. Methods We present a new semi-automatic approach to defining the density cutoff between adipose tissue (AT) and lean tissue (LT) in such material. An intra-class correlation coefficient (ICC) was used to validate the method. The equations for estimating the whole-body composition volume and mass from areas measured in selected slices were modeled with ordinary least squares (OLS) linear regressions and support vector machine regression (SVMR). Results and Discussion The best predictive equation for total body AT volume was based on the AT area of a single slice located between the 4th and 5th lumbar vertebrae (L4-L5) and produced lower prediction errors (|PE| = 1.86 liters, %PE = 8.77) than previous equations also based on CT scans. The LT area of the mid-thigh provided the lowest prediction errors (|PE| = 2.52 liters, %PE = 7.08) for estimating whole-body LT volume. We also present equations to predict total body AT and LT masses from a slice located at L4-L5 that resulted in reduced error compared with the previously published equations based on CT scans. The multislice SVMR predictor gave the theoretical upper limit for prediction precision of volumes and cross-validated the results

Dynamic model of the universal motor supplied by a harmonic voltage

In present article a dynamic model of universal motors, based on the measured data is developed. Suppose that the supply voltage is harmonic and motor operate in open circuit loop. After representing of the mathematical model a simulation model based on the Matlab-Simulink is derived; this allows for the determination of the waveforms of the speed current and torque of the machine for different state operation. Induced voltage of the rotor is determined as a function of the magnetic core saturation and of the armature reaction

Registrace povrchů a přenos topologie v geometrické morfometrii

Geometric morphometry serves biologists and anthropologists to rigorously and quantitatively describe shapes. These representations can be treated as a statistical sample, allowing the researchers to study its variability within groups and correlate it to other features. Geometric morphometry uses landmarks as the proxy for shape, with consistent semantics in each specimen. General triangle meshes do not have this property, and as such, semantically consistent remeshes must be created artificially. This thesis deals with the design of an algorithm that consistently resamples a set of surface models for the purpose of statistical analysis. Coherent point drift was employed to perform nonrigid registration, whose result is then used to generate a semantically consistent remeshes. This approach was successfully applied in a number of studies. As CPD is compute-intensive, we propose methods of accelerating both its initialization and processing phases. Also, an extension was introduced, that can map the deviation of the surfaces from perfect bilateral symmetry and analyze it in a sample, which is significant, among others, for quantification of pathologies. Manual trimming of the surfaces and merging datasets results in outlier regions in the individual surfaces and potentially large differences in their vertex...Geometrická morfometrie slouží biologům a antropologům pro rigorózní a kvantitativní popis tvarů. Tyhle reprezentace tvaru je možno považovat za statistický vzorek, co dovoluje studovat jeho variabilitu v skupinách a srovnávat ho s dalšími proměnnými. Geometrická morfometrie používá landmarky pro popis tvaru, u každého jedince s konzistentní sémantikou. Obecné trojúhelníkové sítě tuhle konzistenci nemají, proto je potřeba je uměle převést na konzistentní reprezentace. Tato dizertace pojednává o návrhu algoritmu pro sémanticky konzistentní převzorkování trojúhelníkových sítí, vhodné pro statistickou analýzu tvarů. Coherent point drift byl použit pro nerigidní registraci, jejíž výsledek tvoří základ pro převzorkované modely. Tento algoritmus byl úspěšně využit u několika studií. CPD je výpočetně náročný algoritmus, proto byly navrženy metody pro zrychlení jeho inicializace a zpracování. Také navrhujeme rozšíření mapující odchylku modelů od dokonalé symetrie. S touhle informací je možno také pracovat jako se statistickým vzorkem, což nachází aplikace mimo jiné u kvantifikaci patologií. Ruční ořezávaní modelů a slučování vzorků vytváří odlehlé oblasti u povrchů a potenciálně velké rozdíly v hustotě pokrytí vrcholy. Navrhujeme nový algoritmus pro nerigidní registraci povrchů s lepší robustností na tyhle jevy a s...Department of Software and Computer Science EducationKatedra softwaru a výuky informatikyMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Komprese zvuku

In the last two decades multimedia have become an integral part of our lives. However, we often face the two clashing requirements - limited storage space or internet connection capacity and the demand for reasonable quality of the media. Compression makes these two requirements more compatible by reducing the amount of data neccessary to store the media. This thesis concentrates on sound, particularly lossy or perceptual compression of audio. As opposed to lossless compression schemes, perceptual coders introduce some noise to the signal to make it better compressible by lossless methods. The tradeoff is an impressive coding efficiency provided by most of these coders. The point of interest in designig a lossy audio coder is to make that damage as imperceptible as possible. This is achieved with knowledge of psychoacoustics (exploiting the imperfections of human auditory system), specifically masking thresholds, perceptual entropy, quiet thresholds and many more. This thesis explains some of these phenomena and their practical implementations in modern audio coders. Finally an overview of select modern audio coders is given, including some technical details about their operation and capabilities

Surface registrations for topology transfer in geometric morphometry

Geometric morphometry serves biologists and anthropologists to rigorously and quantitatively describe shapes. These representations can be treated as a statistical sample, allowing the researchers to study its variability within groups and correlate it to other features. Geometric morphometry uses landmarks as the proxy for shape, with consistent semantics in each specimen. General triangle meshes do not have this property, and as such, semantically consistent remeshes must be created artificially. This thesis deals with the design of an algorithm that consistently resamples a set of surface models for the purpose of statistical analysis. Coherent point drift was employed to perform nonrigid registration, whose result is then used to generate a semantically consistent remeshes. This approach was successfully applied in a number of studies. As CPD is compute-intensive, we propose methods of accelerating both its initialization and processing phases. Also, an extension was introduced, that can map the deviation of the surfaces from perfect bilateral symmetry and analyze it in a sample, which is significant, among others, for quantification of pathologies. Manual trimming of the surfaces and merging datasets results in outlier regions in the individual surfaces and potentially large differences in their vertex..

Komprese zvuku

In the last two decades multimedia have become an integral part of our lives. However, we often face the two clashing requirements - limited storage space or internet connection capacity and the demand for reasonable quality of the media. Compression makes these two requirements more compatible by reducing the amount of data neccessary to store the media. This thesis concentrates on sound, particularly lossy or perceptual compression of audio. As opposed to lossless compression schemes, perceptual coders introduce some noise to the signal to make it better compressible by lossless methods. The tradeoff is an impressive coding efficiency provided by most of these coders. The point of interest in designig a lossy audio coder is to make that damage as imperceptible as possible. This is achieved with knowledge of psychoacoustics (exploiting the imperfections of human auditory system), specifically masking thresholds, perceptual entropy, quiet thresholds and many more. This thesis explains some of these phenomena and their practical implementations in modern audio coders. Finally an overview of select modern audio coders is given, including some technical details about their operation and capabilities

Vessel segmentation

Title: Vessel segmentation Author: Ján Dupej Department / Institute: Department of Software and Computer Science Education Supervisor of the master thesis: RNDr. Josef Pelikán, KSVI Abstract: In this thesis we researched some of the blood vessed segmentation and visualization techniques currently available for angiography on CT data. We then designed, implemented and tested a system that allows both semi-automatic and automatic vessel segmentation and visualization. For vessel segmantation and tracking we used a region-growing algorithm that we overhauled with several heuristics and combined with centerline detection. We then automated this algorithm by automatic seed generation. The visualization part is accomplished with an adaptation of the well-known straightened CPR method that we enhanced so that it visualizes the whole cross-section of the blood vessel, instead of just one line of it. Furthermore, we used the Bishop frame to maintain minimal twist of the curve-local coordinate system along the whole vessel. Keywords: vessel segmentation, medical data analysis, volume dat

Morphometric analysis of mesh asymmetry

New techniques of capturing shape geometry for the purpose of studying asymmetry in biological objects bring the need to develop new methods of analyzing such data. In this paper we propose a method of mesh asymmetry analysis and decomposition intended for use in geometric morphometry. In geometric morphometry the individual bilateral asymmetry is captured by aligning a specimen with its mirror image and analyzing the difference. This involves the construction of a dense correspondence mapping between the meshes. We tested our algorithm on real data consisting of a sample of 102 human faces as well as on artificially altered meshes to successfully prove its validity. The resulting algorithm is an important methodological improvement which has a potential to be widely used in a wide variety of morphological studies

Simulation of facial growth based on longitudinal data: Age progression and age regression between 7 and 17 years of age using 3D surface data.

Modelling of the development of facial morphology during childhood and adolescence is highly useful in forensic and biomedical practice. However, most studies in this area fail to capture the essence of the face as a three-dimensional structure. The main aims of our present study were (1) to construct ageing trajectories for the female and male face between 7 and 17 years of age and (2) to propose a three-dimensional age progression (age -regression) system focused on real growth-related facial changes. Our approach was based on an assessment of a total of 522 three-dimensional (3D) facial scans of Czech children (39 boys, 48 girls) that were longitudinally studied between the ages of 7 to 12 and 12 to 17 years. Facial surface scans were obtained using a Vectra-3D scanner and evaluated using geometric morphometric methods (CPD-DCA, PCA, Hotelling's T2 tests). We observed very similar growth rates between 7 and 10 years in both sexes, followed by an increase in growth velocity in both sexes, with maxima between 11 and 12 years in girls and 11 to 13 years in boys, which are connected with the different timing of the onset of puberty. Based on these partly different ageing trajectories for girls and boys, we simulated the effects of age progression (age regression) on facial scans. In girls, the mean error was 1.81 mm at 12 years and 1.7 mm at 17 years. In boys, the prediction system was slightly less successful: 2.0 mm at 12 years and 1.94 mm at 17 years. The areas with the greatest deviations between predicted and real facial morphology were not important for facial recognition. Changes of body mass index percentiles in children throughout the observation period had no significant influence on the accuracy of the age progression models for both sexes