2013-05-24T14:09:51Z http://publications.lib.chalmers.se/oai-pmh/general/

oai:publications.lib.chalmers.se:200 2006-08-28 svep:tech svep:med

Modelling of Factors Influencing Foot Ankle Responses and Injuries in Car Crashes Höglund, Niklas foot-ankle injuries toepan intrusion mathematical model parameter study Foot and ankle injuries in frontal car collisions are believed to be caused mainly by occupant contact with the floor and toepan, occupant interaction with the pedals, and the lower leg being deformed between the floor and knee bolster. A better understanding of the causes of foot and ankle injuries is required to design cars for improved safety of the legs. In this study, mathematical models were developed, evaluated by crash tests, and used in parametric studies to examine the factors that influence the injury outcome. The models will serve as a basis for the development of principles for countermeasures effective in a variety of crash situations. Dynamic tests with biological materials were conducted to obtain more information about injury tolerances of the human ankle in dorsiflexion loading. Mathematical vehicle-occupant models were developed in the multi body and finite element software MADYMO. The models were assessed by both crash tests and sled tests. Parametric studies were made using the mathematical models according to statistical methods. Two approaches were used in the mathematical modelling: investigation of the toepan design, and examination of the safety performance of the same car with and without safety systems. <p />All of the toepan design parameters tested were found to have an effect on lower leg responses: the dummy responses also differed significantly depending on the foot position, occupant size and crash severity. To design cars for improved lower leg safety, efforts should be made to reduce the toepan acceleration and intrusion distance in particular. However, the simulations in this study showed that there is an important interaction between the timing of the peak acceleration and the intrusion distance: when the right foot of the driver was resting on the toepan at the time of the crash, the axial force in the right tibia increased with toepan acceleration; the intrusion magnitude was of minor importance. However, when the right foot rested initially on an accelerator that was displaced during the crash, the axial force increased with the intrusion magnitude, and toepan acceleration was of minor importance. Moreover, this study showed that the local deformation of the toepan is a likely cause of lower leg injuries and must be reduced. <p />The interaction effects of the parameters investigated were also obvious in the examination of safety systems. Although an airbag in the toepan area might considerably reduce the tibial responses, the designers have to be aware that using a foot airbag optimized for a severe crash situation can actually increase the load on the lower leg in less severe crash situations. In this study, the foot-ankle load increased in 50% of all crash situations. Therefore, it is desirable to be able to measure the occupant size and crash severity and to adjust the airbag inflation in a crash situation. <p />In the biological tests, lower leg specimens were struck at the plantar side of the foot and the ankle responses were measured. The average dorsiflexion angle at the time of injury was 42° and the average ankle moment in tests with fractures was 61 Nm. <p />The mathematical modelling techniques used in this study proved to be useful tools for investigating lower leg responses in car crashes. The models developed can simulate the complex shape of toepan intrusion and the interaction between the occupant and the vehicle. The investigation of the causes of injury provided valuable information for designing vehicles with better lower leg safety. 2003 http://publications.lib.chalmers.se/publication/200-modelling-of-factors-influencing-foot-ankle-responses-and-injuries-in-car-crashes Chalmers University of Technology, Göteborg Text.Thesis.Doctoral text/html English

oai:publications.lib.chalmers.se:415 2006-10-23 svep:tech svep:med

On the Precision Grip in Manual Transport Hosseini, Nasser The aim of the present study was to investigate the grip and load force relations in the precision grip (between thumb and index finger) in static and dynamic situations, and to develop automatic procedures for the analysis of position and force data from tests involving the precision grip. The goal of the work was to create physiologically based methods for identification and quantitative determination of disturbances in the nervous control of hand motor function. <p />In the static case, the excess grip force used in order to maintain a certain safety margin, lifting a 600 g object using the precision grip, was explored. Special algorithms were developed to automatically determine this safety margin. In the dynamic case, the grip-lift synergy was investigated using a manual transport task. Algorithms were developed to determine and analyze the different phases of the transport. The effect of movement speed on the manual transport task was investigated. Special parameters were defined to examine the significance of this effect. <p />The static and dynamic precision grip methods were used on patients with movement disorders as well as on healthy persons. A safety margin analysis was performed in Rheumatoid Arthritis patients and in healthy persons. Differences were found in motor behavior between the two groups but no correlation was found for the safety margin and a simple timed test (GAT). <p />The correlation coefficient between GF and LF was determined in manual transport phases in movements both in the forward and the backward direction. Parkinson patients in medicated and non-medicated state as well as healthy persons participated. There were higher correlation coefficients between the grip and load forces in the initial phases, before the lift was completely established, as compared to the ballistic phases of the transport. This was evident both in PD patients and healthy persons. Precision grip parameters were calculated for healthy subjects. All of the parameters had a significant relation to the movement speed, which indicates that movement speed can be a regulatory variable for the generation of the grip and load forces. <p />Force-movement analysis is well suited for the study of hand motor function. Dividing the task into appropriate phases opens possibilities to select specific indicators for different CNS disturbances. 2003 http://publications.lib.chalmers.se/publication/415-on-the-precision-grip-in-manual-transport Chalmers University of Technology, Göteborg Text.Thesis.Doctoral text/html English

oai:publications.lib.chalmers.se:519 2006-10-23 svep:tech svep:med

Range Camera Imaging : From Human Body Measurements to Very Large 3D Points Scenes Visualization Neuez, Gaël body scanner range camera structured light anatomical landmarks EASYTEX 3D visualization 2D image projections octree data structure The use of camera range imaging for the purpose of 3-dimensional representation and non-contact measures is widely used in industry, medicine, computer-aided design and other areas. Different range imaging methods can be applied, such as stereo, laser sheet of light, and structured light.<p /> This Thesis presents two applications based on range camera imaging. <p />The first application concerns software for a commercial body scanner. The SYMCAD system, manufactured by Telmat Industrie, France, is a range camera based on structured light. In order to get range measures, a horizontal strip pattern is projected onto the body. A video camera attached to a PC-controlled frame grabber is used for capturing an image of the body with the overlaid strip pattern. By extracting the edges of the strip pattern and defining an effective 3D representation of the body, it is possible to obtain anthropometrical measures. The software developed gives accurate results for conventional body figures and mostly also for diverging body figures such as hunchback and scoliosis. In case of failure, the software enables the operator to correct the measurement by a simple click-procedure. This work was part of the European Telematics/TIDE project EASYTEX (aesthetical, adjustable, serviceable, and mainstay textiles for disabled and elderly). <p />The second application concerns effective software procedures for 3D visualization. The latest evolution of 3D scanners provides highly dense 3D data clouds. Examples of application areas are architecture, archeological or industrial sites. The extreme complexity of these scenes is a problem for reading and apprehending those millions of points. In addition to 3D data, 2D color images of the scene can be registered, with both intrinsic and extrinsic calibration of the camera. This part of the Thesis presents the development of an octree data structure for an easy representation of 3D data and a visualization tool exploiting both 2D and 3D images. The work was realized in the Image & Signal Processing (TSI) group at ENST (Ecole Nationale Supérieure des Télécommunications, Paris, France) during a 18-month period as a visiting scientist. 2002 http://publications.lib.chalmers.se/publication/519-range-camera-imaging-from-human-body-measurements-to-very-large-3d-points-scenes-visualization Chalmers University of Technology, Göteborg Text.Thesis.Doctoral text/html English

oai:publications.lib.chalmers.se:634 2006-10-23 svep:tech svep:med

Pattern Recognition Methods for Oral Lesion Classification using Digital Color Images Chodorowski, Artur supervised classification pattern recognition support vector machines computer-aided diagnosis color shape oral lesions cancer The present thesis addresses the development and application of pattern recognition methods for classification of oral lesions using digital color images as input. The human oral cavity is a site of numerous diseases and two of the common and visually similar lesions are oral leukoplakia and oral lichenoid reactions. The lichenoid reactions, which may occur in different subclasses, are usually harmless lesions while leukoplakia can develop into cancer. An automatic detection of potentially precancerous lesions can enhance the diagnostic process and reduce the need for biopsy. <p />The problems studied represent a two-class classification problem (potentially precancerous vs. harmless lesions) and a four-class problem (complete classification into leukoplakia, atrophic, plaqueformed and reticular lichenoid reactions). Different classifiers are investigated, from classical Fisher linear discriminant to the novel Support Vector Machines. Different shape and color features are extracted from color images and evaluated as to their discrimination power. Using morphological and color features around 90% classification accuracy has been obtained on the two-class problem and 75% on the four-class problem. This corresponds to the performance of a very experienced oral specialist. The obtained 100% sensitivity for leukoplakia corresponded to 68% specificity for lichenoid reactions. Detection of the lesion boundaries was performed both manually and using Active Contour Models (snakes). The conclusion is that the system can be used as a decision support system and an educational tool in odontological practice. The methods developed have been applied to patients' images acquired from the Department of Oral Medicine, Faculty of Odontology, Göteborg University and Karlstad Central Hospital. 2000 http://publications.lib.chalmers.se/publication/634-pattern-recognition-methods-for-oral-lesion-classification-using-digital-color-images Chalmers University of Technology, Göteborg Text.Thesis.Doctoral text/html English

oai:publications.lib.chalmers.se:780 2006-10-23 svep:tech svep:med

On Multidimensional Dynamic Fluorescence Imaging and Quantitative Image Analysis in Wide-Field Microscopy Applications to Studies of Astroglial Cells Khatibi, Siamak fluorescence imaging volumetric image analysis three-dimensional (3D) reconstruction segmentation volume estimation astrocyte calcium wave intercellular signaling Modern biological research has benefited from a renaissance in light microscopy, brought about by the convergence of developments in fields as diverse as electronics, optics, molecular biology, computer science, and reagent chemistry. Integration of these has transformed microscopy into a highly useful, dynamic research tool for biology and medicine. Now it is possible to generate highly resolved functional maps of molecular events in living systems where new types of specimens can be studied quantitatively and non-invasively, with greatly improved spatial and temporal resolution. By micromanipulation techniques in combination with fluorescence microscopy, it is possible to simultaneously visualize, analyze and perturb cell physiology.<p /> Newly discovered cellular signaling systems in the brain are investigated in a multidisciplinary research program. The astrocytes, the most common glial cells, form an extraneuronal cell network in the brain. The main objectives of the program are to investigate these cell networks and to find out about their roles. The investigations require sophisticated techniques and analysis methods based on, and complementing, conventional fluorescence microscopy. These techniques and methods were developed through medical-engineering teamwork.<p /> In this study, new methodology was developed for studying the characteristics of intra- and intercellular calcium signaling. An automated fluorescence microscopy imaging and image analysis system was developed for this purpose. The image analysis techniques were based on fluorescence wide-field microscopy images combined with algorithms developed for image segmentation, intensity analyses of fluorescence images and motion analysis. The developed system was used for the study of cell state and spatial propagation of calcium waves in cultured astroglial cells. The cell state was determined by analyzing the non-linear transient part of the cell state. In this relation, the amplitude of Ca²⁺ increase in cells and the velocity between cells participating in the Ca²⁺ waves showed exponential characteristics. The influence of different chemical substances induced in the areas of Ca²⁺ wave propagation was determined. The results of the automated system were compared with manual measurements, which confirmed the reliability of the developed automated system as a new tool for further investigation of the calcium wave.<p /> Furthermore, a new methodology was developed for studying and performing quantitative estimation of single-cell volume changes of astrocytes in primary culture. The methodology was carried out by developing a three-dimensional (3D) automated fluorescence microscopy imaging and image analysis system. A new accelerated reconstruction method (the Fast Maximum Likelihood Expectation Maximization method, or FML-EM) and new segmentation methods were developed to estimate single-cell volume changes. However, a 3D reconstructed image comes with an axial ambiguity, which provides a problem for automatic segmentation. We suggested a segmentation method in which the segmentation is defined as an intensity estimation problem. A 3D binary image was created from the gray level reconstructed image. For each 2D binary slice the Maximizer of the Posterior Marginals (MPM) estimates were computed by a modified fast optimal bayesian algorithm. The MPM estimates supplied information for the 2D segmentation, which in turn supplied information for complexity value calculation for each slice. By means of the complexity values, final 3D segmentation was generated.<p /> The segmentation method was applied for volume estimation of astrocytes. The astrocytes exposed to hypoosmotic stress responds with an increase in volume, and those exposed to hyperosmotic stress responded with a volume decrease. The estimated values of the volumes reflected the swelling and shrinking in a robust way. The study demonstrated a large variability in volume changes among cells, both with respect to morphological origin and with respect to capacity. The results of the automated system were compared with those of manual measurements, which comparison confirmed the reliability of the developed automated system as a new tool for further investigation of single-cell volume change. The sensitivity and reproducibility of the technique were evaluated by using spherical fluorescent beads with known volumes.<p /> Finally, quantitative studying of spatio-temporal single-cell volume changes of astrocytes was proposed by a new methodology. The 3D imaging and image analysis system was further developed for this purpose. 1999 http://publications.lib.chalmers.se/publication/780-on-multidimensional-dynamic-fluorescence-imaging-and-quantitative-image-analysis-in-wide-field-micro Chalmers University of Technology, Göteborg Text.Thesis.Doctoral text/html English

oai:publications.lib.chalmers.se:918 2006-10-23 svep:tech svep:med

Hearing by Bone Conduction. Physical and Physiological Aspects Stenfelt, Stefan Bone conduction as a phenomenon, physically and physiologically, is of vital importance in both the diagnosis of a hearing impairment and the development of bone conduction hearing aids. Understanding hearing by bone conduction is difficult, involving sound transmission by wave motion in a complex geometrical structure of layered bone covered with soft tissue and cartilage, finally received by the highly delicate cochlea. Current measurement techniques, with computers, FFT analysers, and miniature accelerometers, enable high quality measurements and analyses of complex structures. Objective investigations of a dry skull and of patients equipped with either binaurally or monaurally osseointegrated titanium fixtures, as well as subjective investigations of these patients, have yielded the results of the physical and physiological behaviour of bone conducted sound presented here.<p /> A bone-anchored hearing system with the transducer implanted offers some potential advantages, not only for current users of the bone-anchored hearing aid but also for sensorineural hearing impaired people who use air conduction aids. A bone-anchored hearing aid of present standard does not provide sufficient gain to aid a pure sensorineural loss; however, to implant the system would make it more beneficial. An attachment close to the cochlea improves the transmission by 5 to 10 dB and yields a better directionality. Moreover, in comparison with air conduction, bone conduction has greater loudness sensitivity, with up to 10 dB more efficient transmission in the range 30 to 80 dB HL. This behaviour may be explained by the efferent nerves to the middle and inner-ear.<p /> Although there is linear transmission for normal sound levels in the skull, bone conducted sound can be severely affected by structural characteristics such as the antiresonances of the skull. These antiresonances cause transcranial attenuation of up to 40 dB, resulting in a perceived sound lateralization. Also, a forced low-frequency antiresonance appears in the transmission to the ipsilateral cochlea when a transducer is applied in the mastoid area; this results in perception of the applied tone solely at the contralateral cochlea. For frequencies above the first free skull resonance, bone conducted sound is transmitted primarily by wave motion through the bones of the cranial vault and only secondarily at the base of the skull. The teeth are well suited for transmission of bone conducted sound and have a sensitivity close to that of the skin covered mastoid; both of these, however, are less sensitive than a percutaneous approach at the mastoid for frequencies above 1 kHz. 1999 http://publications.lib.chalmers.se/publication/918-hearing-by-bone-conduction-physical-and-physiological-aspects Chalmers University of Technology, Göteborg Text.Thesis.Doctoral text/html English

oai:publications.lib.chalmers.se:944 2013-05-21 svep:tech svep:med

On Transient Noise and its Reduction in Hearing Aids Gingsjö, Anders transient noise transient reduction signal processing hearing aid speech intelligibility sound exposure gun shots The most important property of a hearing aid is to facilitate verbal communication for hearing impaired people. However, tuning of the acoustical parameters in a hearing aid in order to optimize the speech intelligibility may result in a harsh and unpleasant sound. This is so especially the case in listening environments where intermittent relative high-frequency and high-level transient noise (e.g. chinks) are present.<p /> In this dissertation, a new approach to minimizing the unpleasantness experienced by hearing aid wearers from such transient noise is presented. The approach relies on the selective identification and reduction of transients carried out so as to minimally affect the intelligibility of contemporaneous speech. Simple and straightforward signal processing has been used, which means that the transient suppression method can be implemented as a part of a digital ear-level hearing aid of today's standard without exceeding the available computational capacity.<p /> For real-time evaluation purposes, a two-channel wearable master hearing aid (signal processing unit), based on a general purpose digital signal processor, has been designed. The evaluations conducted in this work, based on a software prototype implementation of the transient suppresser, show that: (1) transients having half the peak level of that of contemporaneous speech can be detected with sufficient precision; (2) a group of moderately cochlear hearing impaired persons showed, in a blind paired comparison test, a clear preference for the transient suppresser over a hearing aid with conventional signal processing; and (3) in a later test with another group of persons having similar hearing impairments, no negative effect was found from the transient suppresser on the ability to understand speech.<p /> In a separate questionnaire study, the hearing condition and the use of ear protection among Swedish hunters in relation to sound exposure from gun shots were investigated. The results implies that the relative few shots fired without hearing protectors do affect the hearing of hunters as a group when compared with normative data. It is noted that approximately 50% of the hunters suffer from either a hearing loss and/or from a permanent or temporary tinnitus. Moreover, it was found that the left ear (in right handed shooters) was exposed to 160 - 163 dB peak sound pressure level (SPL), which is about 4 dB higher peak pressure than the right ear is exposed to. 1997 http://publications.lib.chalmers.se/publication/944-on-transient-noise-and-its-reduction-in-hearing-aids Chalmers University of Technology, Göteborg Technical report - School of Electrical and Computer Engineering, Chalmers University of Technology, Göteborg, Sweden 319 Text.Thesis.Doctoral text English 1001:2003-01-15::svep:med