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  • 1.
    Andersson, Ida
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Hedvall, Anders
    KTH, School of Technology and Health (STH), Medical Engineering.
    Relationships Between Skin Properties and Body Water Level2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A need for a quantitative method to determine body water level has been identified by a team of Clinical Innovation Fellows at the Centre for Technology in Medicine and Health (CTMH). A reliable way to determine body water level would bring great benefits to the healthcare sector, where no optimal method is available at the time of writing. A possible solution is a sensor that would measure alterations in skin properties due to changes in total body water. CTMH has had an idea of such a sensor, which is evaluated in this work. At an early stage of this evaluation process, it became clear that the research regarding correlations between skin properties and body hydration level was not sufficient to warrant the initiation of a sensor development process. Therefore, the main objective of this thesis became to investigate such correlations.

    An extensive literature review is presented, from which an experiment was developed. The experiment was performed on four human test subjects and involved measurements of skin thickness and elasticity parameters, before and after a weight loss of 3.2-3.7 % due to dehydration. The results showed clear decreases in skin thickness and indications of alterations in skin distensibility as well as in the skin’s immediate elastic response to applied negative pressure. It could also be seen that skin at different body sites does not respond in the same way - calves showed more distinct results than thighs and volar forearm.

    The material provided in this thesis encourages further studies of the correlation between the mentioned properties and total body water. If a predictable correlation can be found, a sensor development process could start. A reliable way to determine body water level would bring great benefits to the healthcare sector, where no optimal method is available at the time of writing.

  • 2.
    Ayele, Yohannes Haileyesus
    KTH, School of Technology and Health (STH).
    Region-Based Contrast Transfer Function correction for Electron Microscopy Images2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electron crystallography is one of the methods for determining the structure of membrane proteins. However, the resolution that we get from electron crystallography of membrane proteins is limited by crystal disorder and inaccurate determination of contrast transfer function (CTF) parameters. To overcome these problems, we applied single particle refinement with local averaging for long range variation of the crystals and local region-based CTF correction for the tilted images. These two corrections are done on the Melibiose Permease (MelB) data sets and a resolution of 8.6Å is reported.

  • 3.
    Bennani, Safia
    KTH, School of Technology and Health (STH).
    An evaluation and improvement of an in vitro heart phantom of the hearts coronary circulation.2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis has been to validate the in-vitro heart simulation model of the coronary arteries called Flowlab, identify limitations and potential problems, and to offer suggestions for improvement. Flowlab emulates arterial characteristics such as pressure and flow, providing a simulation environment with the ability to measure the volumetric coronary blood flow and arterial blood pressure. Compared to current simulation systems, this will give a better understanding of both position and severity of the cardiovascular disease, and also provide essential information regarding the hemodynamics in the coronary arteries.

     

    To understand the fluid dynamics of the coronary system and gain a deeper understanding of the arterial function and physiology, the first phase of this thesis will focus on gathering information regarding the anatomy, physiology and hemodynamics of the coronary arteries. This will also be done to provide the Flowlab construction with appropriate measurements for the coronary simulation pipe, and input data for its final design.

     

    The Flowlab construction will then be tested to verify the accuracy of the produced values compared with the sought after values of pressure and flow, to further enable an adjustment of the system.

     

    The results from the test show that the final calibration of the simulation environment was not sufficient to produce an accurate result for both pressure and flow regulation, only flow. The flow had an accuracy of 10 %, while the generated pressure was underestimated at low pressures and overestimated at high pressure at up to 20 %. An accuracy of 10 % for generated flow is satisfying and sufficient; meanwhile the pressure calibration had to be altered for more reliable data.

     

    The analysis also revealed several shortages in the design of the Flowlab system that needed to be adjusted for more consistent pressure and flow measurements.

  • 4.
    Berndtsson, Andreas
    KTH, School of Technology and Health (STH), Medical Engineering.
    Heart Rate Variability Biofeedback for Android2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Heart rate variability (HRV) is the variations in time between consecutive heart beats, and reflects the functioning of the autonomic nervous system. Not only is HRV a good marker for many physiological disorders, but it is well known that HRV can be altered consciously by different approaches even though it is controlled by the autonomic nervous system. Respiration is an important factor in modulating HRV and this property is utilized in HRV biofeedback, which is a method that aims at increasing heart rate variability. HRV biofeedback systems typically measures heart rate variability and display the parameters on a screen, enabling the user to gain control and increase heart rate variations. In this thesis a software for biofeedback of heart rate variability is presented. The software was implemented for Android and runs on a tablet computer to make the biofeedback system portable and more accessible than most other biofeedback systems. The developed software has proven to be fully functional in real-time providing the user with reliable information. A small pilot study on healthy volunteers has also been made to evaluate the effects of the biofeedback training. These measurements give a preliminary indication that biofeedback session with the proposed solution increases HRV. However, a more comprehensive study with a larger population needs to be carried out in order to confidently confirm the positive effects of biofeedback sessions with the software. 

  • 5.
    Bodin, Ida
    KTH, School of Technology and Health (STH), Ergonomics.
    Using Cognitive Work Analysis to identify opportunities for enhancing human-heavy vehicle system performance2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the road transportation industry development is moving towards more advanced technology and the use of automation in the driving environment is increasing. Regarding the safety risks associated with an unconsidered use of a high degree of automation, it is expensive to develop automatic systems dealing with complex situations. As there is still much improvement to do in this area, this thesis aims to contribute to developing safe autonomic systems to assist truck drivers.

    The aim of the study was twofold, namely 1) to use Cognitive Work Analysis to identify opportunities for enhancing human-heavy vehicle system performance and 2) to contribute to improving the possibilities for identifying opportunities for enhancing system performance through the development of a method of prioritizing Activities using a Contextual Activity Template.

    To identify the opportunities for improvement, the first two phases of a Cognitive Work Analysis (CWA) – Work Domain Analysis (WDA) and Control Task Analysis (ConTA), were conducted.

    To complete the WDA, five hours of interviews were conducted with a senior technical adviser from Scania CV AB as well as a two hour interview with an experienced commercial driver. Additionally, an observation study was conducted during which three video cameras were used to capture sixteen hours of footage (per camera) from 35 hours (2500kms) of observation (one driver/day over a four day period). During the observation study, drivers were asked to talk out loud about the information needed, decisions made and to provide some rational for their behavior at that time with respect to their driving activities. A total of 40 minutes of talk out loud video data was collected per driver. Finally, around five hours of follow-up interviews were conduct-ed during which these drivers reviewed the videos collected during the observation study.

    The results from the WDA were presented in an Abstraction Hierarchy. The overall functional purpose of the system was defined as Goods Distribution via Road Transportation with the values and priorities being Effectivity and Efficiency, Safety, Comfort, Laws/regulations, Reputation, and Organizational Regulations. For the WDA in the current thesis, the AH was completed for the first three values listed above. In total the AH included 343 nodes (39 at the Purpose Related Functions level, 77 at the Object Related Processes level, and 211 at the Physical Objects level).

    The means by which the physical objects were used in different situations was described using a Contractual Activity Template. The object related processes defined in the AH were crosschecked with 42 situations identified during the observation study. Eight hours of further interviews were conducted with the previously-observed drivers to better understand the relationship between the object related processes and the situations. The object related process-situations matrix was then prioritized according to importance and frequency. On the basis of this prioritization, a set of potential improvement areas were identified, as for example communication and visibility during highway driving.

  • 6.
    Carniello, Vera
    KTH, School of Technology and Health (STH).
    Tailoring interactions betweendegradable polymers and proteins,exploiting nanodiamond particlesand Quartz Crystal Microbalance2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Quartz Crystal Microbalance (QCM) is a sensitive and effective technique to analyze mass changes at the interface between a solid material and a liquid environment. In this Master thesis, QCM was employed for evaluating the interactions between selected degradable polymers and nanodiamond particles (nDP), fibronectin and the growth factor BMP-2.

     

    Many parameters must be adapted to allow QCM measurements involving degradable polymers. These parameters were then tailored to allow QCM measurements with PLA, poly(LLA-co-CL), poly(TMC-D-LA) and PS.

     

    Moreover, QCM provides quantitative measurements of protein adsorption on degradable polymers. The behavior of PLA and poly(LLA-co-CL) was further evaluated and compared with respect to protein adsorption. This behavior was demonstrated to be different for the two polymers considered and to be dependent on protein concentration in solution.

     

    Eventually, exploiting QCM it was also possible to assess the relationship between nDP and the adsorption of fibronectin and BMP-2 onto PLA and poly(LLA-co-CL).

  • 7.
    Darvish, Darvish
    et al.
    KTH, School of Technology and Health (STH).
    Öçba, F.Nadideh
    KTH, School of Technology and Health (STH).
    Presentation and evaluation of gated-SPECT myocardial perfusion images: Radial Slices - data reduction without  loss  of  information2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

     

    Single photon emission tomography (SPECT) data from myocardial perfusion imaging (MPI) are normally displayed as a set of three slices orthogonal to the left ventricular (LV) long axis for both ECG-gated (GSPECT) and non-gated SPECT studies. The total number of slices presented for assessment depends on the size of the heart, but is typically in excess of 30. 

    A requirement for data presentation is that images should be orientated about the LV axis; therefore, a set of radial slice would fulfill this need. Radial slices are parallel to the LV long axis and arranged diametrically. They could provide a suitable alternative to standard orthogonal slices, with the advantage of requiring far fewer slices to adequately represent the data.

    In this study a semi-automatic method was developed for displaying MPI SPECT data as a set of radial slices orientated about the LV axis, with the aim of reducing the number of slices viewed, without loss of information and independent on the size of the heart. Input volume data consisted of standard short axis slices orientated perpendicular to the LV axis chosen at the time of reconstruction.

     The true LV axis was determined by first determining the boundary on a central long axis slice, the axis being in the direction of the y-axis in the matrix. The skeleton of the myocardium were found and the true LV axis determined for that slice. The angle of this axis with respect to the y-axis was calculated. The process was repeated for an orthogonal long axis slice. The input volume was then rotated by the angles calculated.

    Radial slices generated for presentation were integrated over a sector equivalent to the imaging resolution (1.2 cm); assuming the diameter of the heart is about 8cm then non-gated data could be represented by 20 radial slices integrated over an 18 degree section. Gated information could be represented with four slices spaced at 45 intervals, integrated over a 30 degree sector.

  • 8.
    Elfström, Anna
    et al.
    KTH, School of Technology and Health (STH).
    Grunditz, Anna
    KTH, School of Technology and Health (STH).
    Evaluation of Sternum Closure Techniques Using Finite Element Analysis2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In an open thoracic surgery the surgeon dissociate the sternum, the breastbone, into two halves to be able to perform the operation. At the end of the surgery a standard technique is used which to close the sternum. The technique is based on steel wires that are wrapped around the halves of the sternum to close it. This technique is the most cost effective technique available on the market today but is still not optimal because it can cause infection, wound rupture and pain for the patient.

    The goal with this master thesis was to, with the help of finite element method, to find out which closure technique is the best one to close the sternum and to provide suggestions for improvement. This was done with respect to the aspects of how large the displacement between the sternum halves is and how much the stresses generated by the implants affect the sternum.

    Using literature studies and interviews three techniques were chosen to be simulated; the standard technique, Zipfix and Sternal Talon. Their implants consisted of stainless steel, PEEK and titanium respectively and the materials were simulated with every technique. In the lower part of the sternum it is a greater displacement between the two halves after simulation than in the rest of the sternum. An improvement was hence to simulate Zipfix and Sternal Talon with an extra steel wire in the lower part.

    Zipfix with the implants of titanium and the standard technique with the implants of stainless steel provided the best results with respect to the two aspects. The two improvements produced smaller displacement but the stresses were higher.

  • 9.
    Falck, Josefina
    KTH, School of Technology and Health (STH), Medical Engineering.
    Effect of side windows, stiffening plate and roof sheet on the stiffness of the bus body2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a bus developer, Scania focus to construct a safe vehicle for the passengers, i.e. high strength of the bus structure and good comfort, which is also profitable for the operator, i.e. high passenger capacity and low fuel consumption. The trade-off when developing a bus body structure is to get both high stiffness and low weight. The bus body including exterior panels plays together with the chassis an important role for the stiffness of the bus. By gathering knowledge about how various exterior panels affects the stiffness of the bus body, the design of the panels can be optimized with respect to high stiffness and low weight. Also from a calculation point of view is it of interest to know how important different panels are for the stiffness of the bus body, in order to make conscious simplifications in the calculation model.

    The aim with this master thesis was to investigate how the stiffening plate, side windows and roof sheet influence the strength of the bus body. How the thickness of the side windows affects the stiffness of the bus body is also investigated. The investigations were made as a relative comparison between a complete bus and comparison models.

     

    The results showed that exterior panels participate in distributing load. By distributing the load, the load uptake gets more efficient since a bigger part of the bus structure is used to take up the load. The side windows affect the stiffness for all tested load cases, with increased importance for the load case where a gravity field is applied in the longitudinal direction, for the torsion load case and when a load is applied to the power train in vertical direction. The roof sheet has a high impact on the stiffness in the torsion load case, but has negligible influence on the stiffness of the bus body for the other tested load cases. The stiffening plate has little influence on the stiffness of the bus body in general and is negligible for all tested load cases except for when a lateral load is applied as either a gravity field or locally to the power train.

     

    Thinner side windows are shown to have a positive influence on the stiffness of the bus body.

  • 10.
    Gunnlaugsdottir, Helga
    KTH, School of Technology and Health (STH).
    Spectroscopic determination of pH in an arterial line from a Heart-lung machine2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There is a need for a real-time, non-invasive method to monitor blood pH in a patient line during cardiopulmonary bypass, as today’s methods are both invasive and time consuming. Blood pH is an indicator of physiological and biochemical activity in the body and needs to be kept within a relatively narrow range, typically between 7.35-7.45. A pH value outside this range can be critical for the patient and therefore needs to be carefully monitored throughout the course of cardiopulmonary bypass. In this study the feasibility of using spectroscopic methods for indirect measurement of pH was investigated, and both transmission and reflectance spectroscopy were tested. The results showed that NIR reflectance spectroscopy is a feasible technique for blood pH monitoring during cardiopulmonary bypass. A strong correlation was found between measured pH values and spectral output in the wavelength range 800-930 nm. It was suggested that by means of the statistical partial least square regression method, a model could be created with three regression factors with a cross-validated R2 of 0.906 and a prediction error RMSEP of 0.089 pH units. The results presented here form a foundation for further analysis and experiments with larger sample set and more controlled experimental environment. 

  • 11.
    Hailu, Abebe
    et al.
    KTH, School of Technology and Health (STH).
    Lundqvist, Fredrik
    KTH, School of Technology and Health (STH).
    Prototype Development of an A-Mode Ultrasound Based Intrafraction Motion Management System2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Owing to the steep dose fall-off curves of high precision and accuracy radiation therapy (RT) modalities such as stereotactic body RT (SBRT), treatment plans with extraordinarily small margins to organs at risk (OARs), such as the spinal cord, has been made possible. With this development, patient movements during treatment, i.e. intrafraction motion (IFM), must be monitored more closely. This master thesis was aimed at developing an A-mode ultrasound prototype to detect the motions of the cervical spine as part of an IFM management (IFMM) system. Current IFMM systems have several drawbacks, including invasiveness and indirect measurements.

    The existing prototype was tested in order to identify areas of improvement. The prototype developed was equipped with a preconditioning circuit that retains the frequency information of the signal. Furthermore, software was developed based on wavelet filtering and enveloping using the Hilbert transform. Multiple logic algorithms were added in order to handle lost signals, competing echoes, echoes from soft tissues etc.

    The newly-developed prototype was found to have higher accuracy and precision than the pre-existing prototype. It was also more robust when measuring distance to the spine. A difficulty in segmenting the echo for bone arises for low quality signals. Therefore a compromise exists between setup time, including probe adjustment, and signal quality. Future work includes the manufacturing of a new neck rest to enable robust probe adjustment and fixation.

  • 12.
    Janjic, Jovana
    KTH, School of Technology and Health (STH).
    Design of an In-vitro Set-up for Sonothrombolysis of human blood clots using microbubbles2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Several studies suggest that the use of ultrasound in conjunction with microbubbles (MBs) can induce the lysis of the blood clots through acoustic cavitation and through the production of microjets and microstreaming. However, there is no accordance about the optimal ultrasound parameters that have to be considered in order to achieve the maximum thrombolytic effect, neither a clear agreement about the type of MBs that have to be used.

    This project had two main goals: the design and optimization of an in-vitro set-up for the study of clot lysis within coronary arteries and its testing with ultrasound in conjunction with two different types of MBs. The MBs considered were the 3MiCRON MBs and the SonoVue MBs.

    The ultrasound sequence was developed using a programmable ultrasound architecture (Verasonics, Inc) and was tested using commercially available clinical transducers.

    Using the designed set-up and varying the ultrasound parameters (frequency, pulse length and pulse amplitude) it was possible to study the clot lysis effciency in conjunction with the two types of MBs. For the 3MiCRON MBs no increase in clot lysis was found with the implemented ultrasound parameters, while considering the SonoVue MBs, a 10% increase in clot lysis was found with 10ms long pulse delivered at 50V (peak-to peak value).

    The obtained set-up had several aspects in common with the real situation of occluded coronary arteries, although some limitations were present and further optimizations are required.

    Further work is required in order to assess if different combination of ultrasound parameters are able to lead to an increase in clot lysis when delivered with 3MiCRON or SonoVue MBs.

  • 13.
    KHALID, SYED GHUFRAN
    KTH, School of Technology and Health (STH).
    Quantification of Hyperhidrosis using Electronic Sudometer2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Human skin has various pathologies in the form of acute and chronic diseases. Some are only cosmetic diseases which are not harmful for life but they can affect mental health and disrupt daily activities. Hyperhidrosis is one of these cosmetic diseases which may be caused by diabetes, infections, or thyroid hyper activity, or can be inherited. There are some examinations for testing hyperhidrosis, e.g. gravimetric and minor starch-iodine test. There are some devices that can measure sweat but are not specifically used or even intended for use on hyperhidrosis.

    A non-invasive prototype instrument called Electronic Sudometer using the principle of electrical impedance measurement has been developed. The philosophy behind this prototype is to make an instrument which can detect hyperhidrosis during homeostasis as well as in pathological condition. The device injects a sinusoid electric current and detects the ensuing voltage, which is proportional to the impedance of sweat on top of the skin during hyperhidrosis. For this prototype, the electrode system is made of brass rings mounted on a handle. The signal is then processed in electronic assembly. Processed output is transferred to a Laptop with specially made connecting wire. Computer having Sound Card Oscilloscope (Lab View based software) plots the signal and shows voltage level corresponding to sudor level. The signal output can also be displayed on a SmartPhone having software called Osciprime, requiring another specially made interface.

    Laboratory test results in the form of a plot of output voltage vs. impedance show accuracy of the device. The impedance results can be translated to sweat level because impedance decreases with increasing sweat during hyperhidrosis. The Sudometer was also calibrated using fixed precision resistors over its working range. Laboratory tests were carried out using an artificial skin at various sweat levels and to a yeast tissue model. Hydration of the artificial skin was quantified by weighing precision cut samples on a laboratory balance. Results from two test persons (the author and a student friend) are also included in this Master Thesis. During these experiments, the laptop computer and SmartPhone, respectively, were on internal battery to eliminate electric hazard.

    Any clinical device must be validated for accuracy and evaluated for safety before applying it on patients – the latter has not been done with the prototype. The author is aware of potential electrical risks, and thus the whole system was disconnected from mains 230V during measurements on himself and a student friend. The device output seems to be well correlated to sweat level although electrolytes were not taken into account. Being a palmar hyperhidrosis patient himself, the author applied the Electronic Sudometer on his palms and the results look quite promising. At different environmental temperatures, the author checked elicited sweat responses. Patient safety is always a concern for clinicians regarding new devices. For this reason, the device itself has been made battery operated, and a new version will be entirely powered from a SmartPhone.

  • 14.
    Marra, Marco Antonio
    KTH, School of Technology and Health (STH).
    Study of dens fracture in the elderly and the influence of osteoporosis with a finite element model2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cervical spine injuries are a serious threat, as they may damage the central nervous system. In the elderly, cervical fractures due to falls are very frequent. The overall weakening of the bony and ligamentous spine decreases the resistance to fractures. Fractures of the dens of the second cervical vertebra (C2) are the most frequent individual fractures in the upper spine. Osteoporosis and impaired conditions play the main role in increasing the fracture risk. Several mechanisms may induce dens fractures: hyper-extension, lateral bending, shear, torsion, but the mechanisms of fractures have not been fully understood.

    Osteoporosis reduces overall bone strength. Cortical bone thinning occurs in the vertebræ, and there is a general loss of bone mass. Trabecular micro-architecture of bones loses integration, leading an increasing porosity. Mechanical properties worsen, and failure occurs more easily.

    In this study the role of osteoporosis on the genesis of dens fractures was investigated. An existing finite element (FE) model of the human spine was employed to simulate the effect of parameters associated with osteoporosis on the loading conditions of the dens. A baseline case was first simulated. Then, cortical thickness, cortical and trabecular bulk modulus and shear modulus were decreased in steps. Three impact scenarios were simulated: a lateral fall, a backward fall, and a forward fall. Effects of osteoporotic variations on the ligamentous spine deformations were studied. A mesh convergence analysis was performed to assess the influence of mesh size on the stresses in vertebra C2.

    The effect of reduced cortical and trabecular bulk moduli alone on stress distribution was not that apparent. In the dens, a reduced cortical thickness, in lateral and backward fall, caused higher maximum stresses than in the baseline. Conversely, in forward fall, reduced cortical thickness caused lower stresses than in the baseline. The effect of reducing trabecular bulk and shear moduli altogether was to decrease the stresses in dens trabecular bone. In lateral and backward fall, by reducing cortical bulk and shear moduli altogether, stresses in dens cortex decreased; whereas, in forward fall, stress decreased in dens neck cortex, and increased in dens apex and waist.

    It is concluded that cortical thinning, and reduced bulk and shear moduli of bone compartments considerably alter the stress distribution in C2, as well as the ligamentous spine response. The extent of such variations depends also on the impact scenarios. Finally, stresses in the model were found to be sensitive to the mesh size currently used in the human spine FE model.

  • 15.
    Mohammadianrasanani, Seyedmehrdad
    KTH, School of Technology and Health (STH). University of Pennsylvania, Radiology Department .
    The use of a body-wide automatic anatomy recognition system in image analysis of kidneys2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 16.
    Mohammadianrasanani, Seyedmehrdad
    KTH, School of Technology and Health (STH). Royal Institute of Technology KTH STH, University of Pennsylvania.
    The use of a body-wide automatic anatomy recognition system in image analysis of kidneys2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 17.
    Monnot, Cyril
    KTH, School of Technology and Health (STH), Medical Engineering.
    Development of a data analysis platform for characterizing functional connectivity networks in rodents2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    AbstractThis document addresses the development and implementation of a routine for analyzing resting-state functional Magnetic Resonance Imaging (rs-fMRI) data in rodents. Even though resting-state connectivity is studied in humans already for several years with diverse applications in mental disorders or degenerative brain diseases, the interest for this modality is much more recent and less common in rodents. The goal of this project is to set an ensemble of tools in order to be able for the experimental MR team of KERIC to analyze rs-fMRI in rodents in a well defined and easy way. During this project several critical choices have been done, one of them is to use the Independent Component Analysis (ICA) in order to process the data rather than a seed-based approach. Also it was decided to use medetomidine as anesthesia rather than isoflurane for the experiments. The routine developed during this project was applied for a project studying the effects of running on an animal model of depression. The routine is composed of several steps, the preprocessing of the data mainly realized with SPM8, the processing using GIFT and the postprocessing which is some statistic tests on the results from GIFT in order to reveal differences between groups using the 2nd level analysis from SPM8 and the testing the correlations between components using the FNC toolbox.

     

  • 18.
    Monnot, Cyril Gerard Valery
    KTH, School of Technology and Health (STH).
    Development of a data analysis platform for characterizing functional connectivity networks in rodents2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This document addresses the development and implementation of a routine for analyzing resting-state functional Magnetic Resonance Imaging (rs-fMRI) data in rodents. Even though resting-state connectivity is studied in humans already for several years with diverse applications in mental disorders or degenerative brain diseases, the interest for this modality is much more recent and less common in rodents. The goal of this project is to set an ensemble of tools in order to be able for the experimental MR team of KERIC to analyze rs-fMRI in rodents in a well defined and easy way. During this project several critical choices have been done, one of them is to use the Independent Component Analysis (ICA) in order to process the data rather than a seed-based approach. Also it was decided to use medetomidine as anesthesia rather than isoflurane for the experiments.

    The routine developed during this project was applied for a project studying the effects of running on an animal model of depression. The routine is composed of several steps, the preprocessing of the data mainly realized with SPM8, the processing using GIFT and the postprocessing which is some statistic tests on the results from GIFT in order to reveal differences between groups using the 2nd level analysis from SPM8 and the testing the correlations between components using the FNC toolbox.

  • 19.
    Morén, David
    et al.
    KTH, School of Technology and Health (STH).
    Pehrs, Georg
    KTH, School of Technology and Health (STH).
    Study of Vehicle-to-Pedestrian Interactions with FEM – Evaluation of Upper Leg Test Methods using a Human Body Model2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The European New Car Assessment Programme (Euro NCAP) performs several different tests to evaluate vehicles and rate their safety. Some of these tests are subsystem tests made to mimic different body parts of a pedestrian in an interaction with a vehicle. However, some criticism to the test method for the upper leg has been presented, stating that there is a discrepancy between this test method and a real-life interaction. Therefore, a modified test method for the upper leg has been proposed.

    The aim of this thesis was to evaluate the upper leg test method used today by Euro NCAP, and compare it with the proposed modified test method as well as to computer simulations with a Human Body Model (HBM). The evaluation was performed by comparing different parameters obtained in the two test methods. These have also been compared to computer simulations using a HBM in interaction with a passenger vehicle model.

    Prior to the evaluation of the test methods, the HBM was positioned into different stances to mimic postures in the human walking cycle. The vehicle model was positioned at four different heights, and three different impact points along the bonnet were used. The results showed that the different methods had their own advantages for some parameters. However, no general conclusion of which method showed the closest correlation to the HBM reference simulations could be determined.

  • 20.
    Narangifard, Ali
    KTH, School of Technology and Health (STH).
    The multislice method in transmission electron microscopy simulation: An implementation in the TEM-simulator software package2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report introduces the multislice method for modeling the interaction between an electron and the atoms in the specimen (electron-specimen interaction). The multislice method is an approximation to the full quantum mechanical model for this interaction. After introducing the theory, we discuss how the multislice method is implemented and integrated into TEM-simulator, a software for simulation of Transmission Electron Microscope (TEM) images. 

  • 21.
    Nilsson, Linnéa
    KTH, School of Technology and Health (STH).
    Ex-vivo evaluation of vascular reactivity due to laser exposure2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 22.
    Nordenfur, Tim
    KTH, School of Technology and Health (STH).
    Comparison of Pushing Sequences for Shear Wave Elastography2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Shear wave elastography is a medical imaging modality in which tissue elasticity is estimated by measuring the speed of ultrasound-induced shear waves. This study aimed to implement four shear wave generating pushes and compare their performance according to chosen metrics. The focused push, unfocused push, unfocused comb push and line push were implemented on a Verasonics ultrasound system and tested on a polyvinyl alcohol phantom. Shear wave propagation was imaged using angle-compounded ultrafast imaging. Axial particle velocities were estimated using a 2D autocorrelator and then cross-correlated to obtain local shear wave speed estimates.

    The focused push and line push were found to generate shear waves with 1--3 times higher peak axial particle velocity, implying better signal-to-noise ratios. The focused push, unfocused push and line push were found to exhibit areas 7 mm wide around the pushing beams in which shear wave speed cannot be estimated, whereas the unfocused comb push has no such blind area.

  • 23.
    Paulsen, Martin
    KTH, School of Technology and Health (STH), Medical Engineering.
    Simulation driven pre-operative planning for the treatment of hallux rigidus: A novel concept of implant assessment2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The present study utilizes finite element analysis in order to simulate a surgical operation in the treatment of a hallux rigidus case, as designed and developed by Episurf Medical AB (Stockholm, Sweden). The surgical intervention includes an initial cheilectomy as well as an insertion of an orthopedic implant.

    The goal of the study was to evaluate the current concept of the medical intervention as it is manifested today, as well as to give design suggestions as how to further improve the pre-planning of the surgery. MRI-images of the first metatarsophalangeal joint in the hallux was collected from a patient suffering from hallux rigidus, and used in order to build case-specific geometrical images to be used in the FE analysis. The simulation was setup as to simulate a normal motion in the first metatarsophalangeal joint during a normal gait pattern.

    The first simulation was conducted without any intervention, while the second was conducted after a pre-determined operation plan in accordance with the surgical operation that Episurf Medical AB wants to perform. The results was then compared and analyzed in order to determine the post-surgical effects that such an operation could have on the patient. A third and final simulation was then performed, by using optimization algorithms in order to make suggestions to the pre-planned cheilectomy shape, as well as orientation of the implant.

    Two parameters were being investigated in order to assess the surgical intervention as designed by Episurf Medical AB; the contact stress on the articular side of the metatarsal head, and the strain on the implant shaft.

    The current manifestation of the cheilectomy did not reduce the contact stress compared to the untreated condition, as the implant failed to be a load baring surface due to the two dimensional nature of which it is conceived. Instead, the contact surface area is reduced and positioned medial and lateral to the implant head. The optimization algorithm could reduce the maximum contact stress significantly, from 295MPa and 400MPa in the treated and untreated conditons respectively, to 160MPa after the optimization algorithm.

    It became clear that the angle of the cheilectomy as well as the orientation of the implant angle has an incriminating effect on the post-operative results. However, the shape of the cheilectomy as well as the design of the implant would need to be revised in future embodiments, as the current concept failed to provide joint with a new articulating surface. Further development of the models formulated in this thesis is advised, as well as validating the findings with clinical data.

  • 24.
    Pettersson, Sara
    et al.
    KTH, School of Technology and Health (STH).
    Gistvik, Helena
    KTH, School of Technology and Health (STH).
    Effects of dead elements in ultrasound transducers2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ultrasound is a common modality used in healthcare today. The ultrasound images can be used as a diagnostic tool and the image quality is therefore important. Earlier studies have shown that transducers used clinically are often damaged; a type of damage is dead elements in the transducer. In this study, it has been evaluated how the number and the placement of the dead elements impact the beam profile and how this is reflected in the image quality. This has been performed with two types of simulations, one simulated beam profiles and the other simulated dead elements in a transducer used to create real images. The results showed that the beam profile was affected by both the number and the placement of dead elements. It has not been determined how the altered beam profile affected the image quality, but there were indications that the image quality deteriorated when there were dead elements in the transducer. As both the number of dead elements and their placement affected the beam profile, an acceptance level could not be suggested regarding the number of dead elements.

  • 25.
    Rabbani, Seyedeh Parisa
    KTH, School of Technology and Health (STH).
    Effect of image variation on computer aided detection systems2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Computer Aided Detection (CAD) systems are expecting to gain significant importance in terms of reducing the work load of radiologists and enabling the large screening programs. A large share of CAD systems are based on learning from examples, to enables the decision making between the images with or without disease. Images are simplified to numerical descriptors (features vectors) and the system is trained with these features. The common practical problem with CAD systems is training the system with a data from a specific source and testing it on a data from a different source; the variations between sources usually affect the CAD system function. The possible solutions for this problem are (1) normalizing images to make them look more equal, (2) choosing less variation sensitive features and (3) modifying the classifier so that it classifies the data from different sources more accurately.

    In this project the effect of image variations on the developed CAD system on chest radio graphs for Tuberculosis is studied at Diagnostic Image Analysis Group. Tuberculosis is one of the major healthcare problems in some parts of the world (1.3 million deaths in 2007) [1]. Although the system has a great performance on the train and test data from the same source, using different sub dataset for training and testing the system does not lead to the same result. To limit the effect of image variation of the CAD systems three different approaches are applied for normalizing the images: (1) Simple normalization, (2) local normalization and (3) multi band local normalization. All three approaches enhance the performance of the system in case of various sub datasets for training and testing purposes. According to the improvement achieved by applying normalization it is suggested as a solution for the stated problem above.

    Although the outcome of this study has satisfactory result, there is always room for further investigations and studies; in specific testing different approaches for finding less variation sensitive features and modifying the classification procedure to a more variation tolerant process.

  • 26.
    Svantesson, Oscar
    KTH, School of Technology and Health (STH), Medical Engineering.
    Software platform for gait evaluation using MATLAB and off-the-shelf MEMS sensors2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a real time software program written in MATLAB using off-the-self MEMS sensors from Shimmer-Research®. Parallel to the software development, a proof of concept was conducted using the produced program to quantify stride length, stride length variance and stride time for patients diagnosed with Parkinson's disease. Results from testing showed that the system measured the mean stride length error to 2.4% of stride length and a standard deviation of 13.7% of stride length. Results from testing further showed a stride time error of 2.70% of individual stride times with a standard deviation of 1.89%. The system shows promise as a pedagogical, gait analysis training tool for physiotherapists as well as in academic teaching. The system is flexible and data processing functions can be readily re-programmed with other or additional processing features while maintaining user feedback, storage and plotting functionalities implemented in the current version of the program. 

  • 27.
    Yang, Zhen
    KTH, School of Technology and Health (STH).
    Ståställningens påverkan på lederna i de nedre extremiteterna: en pilotstudie2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Barn med en allvarlig cerebral pares (CP) diagnos har begränsad eller obefintlig förmåga att stå självständigt. Tillståndet medför även en stor risk för subluxation i höftlederna. En befintlig teori bland ortopeder och sjukgymnaster idag är att hjälpmedel för ståträning för barn med CP, såsom ståskal, med höfter i ett abducerade läge kan motverka höftledernas negativa utveckling. Hittills saknas det dock vetenskapliga bevis för denna teori.

    TeamOlmed Barn & Ungdom tillverkar ståskal med 30 graders abduktionsvinkel enligt teorin ovan. Men kunskaperna inom området är begränsade och företaget önskade undersöka om hypotesen stämmer och hur de biomekaniska förutsättningarna påverkas av ståskalen.

    Detta examensarbete fokuserar på olika ståställningar i abduktion för en frisk person och dess inverkan i de nedre extremiteterna i syfte att undersöka den befintliga teorin. Rörelseanalyssystemet Vicon Nexus användes för datainsamling och analys av moment kring knälederna. Vid analys av krafterna i höftlederna användes OpenSim, ett simuleringsprogram för det muskuloskeletala systemet i 3D.

    Resultatet från Vicon visar att knäna har ett inre varusmoment i frontalplanet, vilket är ofarligt för knälederna, i såväl abducerade som vanlig höftposition. Simuleringsresultatet från OpenSim visar att kraftvektorernas riktningar ändras i samband med ändringar av abduktionsvinklar. Detta betyder att kraftvektorernas riktningar i höfterna, uttryckta i femurs koordinatsystem, är snarlika för ståpositioner med olika abduktionsvinklar. Beloppet av kontaktkraften ökade dock med ökande höftabduktionsvinkel.

    Momenten som uppstår vid olika ståställningar är ofarliga för knälederna och kraftvektorernas riktningar i höfterna är oberoende av abduktionsvinklarna för en frisk person. Den enda skillnaden i höftbelastning med stående i höftabduktion var ökade belopp av höftkontaktkrafter. För att noggrannt kunna utvärdera huruvida en ökad kontaktkraft kan påverka höftens tendens att migrera ur led, samt huruvida liknande observationer finns hos patienter med CP skador i sina ståskal, krävs det vidare studier. Tack vare observationerna av denna pilotstudie kan man ställa mer relevanta studiefrågor kring biomekaniska mekanismer i en större studie med barn med CP-diagnoser.

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