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  • 101.
    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
  • 102.
    Nordbrøden, Mats
    KTH, School of Technology and Health (STH).
    Optimization of Magnetic Resonance Diffusion Tensor Imaging for Visualization and Quantification of Periprostatic Nerve Fibers2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Prostatectomy, surgical resection of the whole prostate is a common treatment for high- risk prostate cancer. Common side effects include long-time urinary and or erectile dysfunction due to damage inflicted to periprostatic nerves. The aim of this study was to identify an optimal magnetic resonance diffusion tensor imaging protocol for visualization and quantification of these nerves, as pre-surgery visualization may help nerve-sparing surgery. Both scanner filter, parameters for accelerated scan techniques, diffusion-related acquisition parameters and post- processing tractography parameters were investigated. Seven healthy volunteers were scanned with a state-of-art 3 T MRI scanner with varying protocol parameters. Diffusion data were processed and analysed using Matlab and Explore DTI. The resulting protocol recommendation included a normalized scanner filter, a parallel imaging acceleration factor of 2, partial Fourier sampling of 6/8, a right-left phase encoding direction, a b-value of 600 s/mm2, monopolar gradient polarity with applied eddy current correction, four acquisitions of 12 diffusion- sensitizing gradient directions, and a reverse phase encoding approach for correction of geometrical image distortions induced by static field inhomogeneity. For post-processing tractography, the recommended parameters were a lower limit for fractional anisotropy of 0.05, a minimum tract length of 3 centimetres and a maximum turning angle between voxels of 60 degrees. The limited parameter range that was tested and the low number of volunteers can be regarded as limitations to this study. Future work should address these issues. Furthermore, feasibility of periprostatic nerve tracking with the optimized protocol should be tested in a patient study. 

  • 103.
    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.

  • 104.
    Nylund, Andreas
    KTH, School of Technology and Health (STH), Medical Engineering.
    To be, or not to be Melanoma: Convolutional neural networks in skin lesion classification2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Machine learning methods provide an opportunity to improve the classification of skin lesions and the early diagnosis of melanoma by providing decision support for general practitioners. So far most studies have been looking at the creation of features that best indicate melanoma. Representation learning methods such as neural networks have outperformed hand-crafted features in many areas. This work aims to evaluate the performance of convolutional neural networks in relation to earlier machine learning algorithms and expert diagnosis. In this work, convolutional neural networks were trained on datasets of dermoscopy images using weights initialized from a random distribution, a network trained on the ImageNet dataset and a network trained on Dermnet, a skin disease atlas.  The ensemble sum prediction of the networks achieved an accuracy of 89.3% with a sensitivity of 77.1% and a specificity of 93.0% when based on the weights learned from the ImageNet dataset and the Dermnet skin disease atlas and trained on non-polarized light dermoscopy images.  The results from the different networks trained on little or no prior data confirms the idea that certain features are transferable between different data. Similar classification accuracies to that of the highest scoring network are achieved by expert dermatologists and slightly higher results are achieved by referenced hand-crafted classifiers.  The trained networks are found to be comparable to practicing dermatologists and state-of-the-art machine learning methods in binary classification accuracy, benign – melanoma, with only little pre-processing and tuning. 

  • 105.
    Okan, Julianne
    KTH, School of Technology and Health (STH).
    Development of a Fall-Injury Reducing Flooring System in Geriatric Care: with focus on improving the models used in the biomechanical simulations and evaluating the first test area2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fall accidents are the type of accident in Sweden that cause most deaths, the largest number of hospitalizations, and most visits to the emergency room. The elderly are overrepresented in the statistics and with the aging population the costs are increasing. One way of reducing both the personal suffering and the cost to society is to introduce safety flooring. Svein Kleiven and Hans von Holst, professors at the department of Neuronics at KTH, have developed a new type of flooring system aimed to reduce fall related injuries. A first test area has been installed at a care facility and the Technical Research Institute of Sweden, SP, has conducted drop tests on nine different prototypes and found a reduction in impact force between 60- 75 % compared to a wooden flooring.

    The goals of this Master’s thesis were to conduct material testing to enable a better validation of the finite element (FE) model of the flooring system, validate a FE human body model for a hip impact and conduct fall simulations. The last goal was to evaluate the test area of the flooring system regarding effect on balance and work environment.

    Tensile tests were conducted to increase the knowledge regarding the different rubber mixtures and surface floors used in prototypes of the flooring system. The human body model had to be modified in regards to material models and anatomy of the hip joint before validated. Two fall simulations were conducted, however with low confidence in the results due to the lack of expected response in the model of the flooring system. A walking test was conducted to investigate if the flooring system affected the balance for the elderly and a questionnaire was created to get subjective ratings from the members of staff at the care facility. The results indicate no clear effect on balance and the subjective ratings shows the importance of also consider the work environment before installing the flooring system.

    More work remains in developing the flooring system; however this Master’s thesis has increased the understanding of the flooring system, both in regards to material properties and influence on the daily life at the care facility. This thesis also developed a more realistic human model, to be used in further hip impact simulations. 

  • 106.
    Olsson, Hanna
    KTH, School of Technology and Health (STH).
    Smartphone-based Colorimetric Diagnosis: DEVELOPMENT OF A METHOD FOR AUTOMATIC COMPENSATION OF IMPACT OF LIGHT SETTING2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the last years many mobile health applications have emerged on the market. Most of these collect and compiles physical data that can be followed over time. Now the next generation of health care applications are on their way. With an increasing capacity and high quality sensors, smartphones have the potential to be used as diagnostic tools.

    Calmark Sweden AB is a company that has developed a smartphone based diagnostic platform for analysis of colorimetric assays integrated on a disposable plastic chip. Their first product, the hilda Neo system is a Point of care test (POCT) for semi quantitative measurement of the biomarker Lac- tate dehydrogenase (LDH). The system consists of a disposable colorimetric LDH test with inte- grated chemical assay, a separate light-box for controlled light conditions and a smartphone appli- cation for image acquisition and test analysis.

    The purpose of this Master Thesis project was to develop and evaluate a method for smartphone based semi quantitative colorimetric analysis of the hilda Neo LDH test that would work without the light-box in different light settings. The method was to be implementable as an iPhone applica- tion and should be able do correctly determine LDH activity in the four LDH ranges; 0-300, 300- 600, 600-900 and >900 units per litre (U/L). Also, the computed LDH levels among cards run with the same sample were not to have a standard deviation higher than 50 U/L.

    Two methods based on continuous measurements of the colour stimuli given from the assay site were developed. In both methods, measurements were made by using the iPhone camera for taking an image series following the colour development of the assay over time. The image series was then processed in MATLAB and the LDH level was computed in two different ways.

    None of the two proposed methods did reach the stated objectives. Neither of the methods gave the correct LDH interval in all evaluation cards and the computed LDH levels had a larger standard deviation then aimed for. However the results indicate that the variation in light settings is not the only factor for the unreached objectives. It is believed that with further studies of the colour proper- ties of the hilda Neo assay and with the continuing development of smartphone technology, it is possible to find a method for smartphone-based colorimetric analysis without having to control the light setting. 

  • 107.
    Papanastasiou, Maria
    KTH, School of Technology and Health (STH).
    Use of Deep Learning in Detection of Skin Cancer and Prevention of Melanoma2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Melanoma is a life threatening type of skin cancer with numerous fatal incidences all over the world. The 5-year survival rate is very high for cases that are diagnosed in early stage. So, early detection of melanoma is of vital importance. Except for several techniques that clinicians apply so as to improve the reliability of detecting melanoma, many automated algorithms and mobile applications have been developed for the same purpose.In this paper, deep learning model designed from scratch as well as the pretrained models Inception v3 and VGG-16 are used with the aim of developing a reliable tool that can be used for melanoma detection by clinicians and individual users. Dermatologists who use dermoscopes can take advantage of the algorithms trained on dermoscopical images and acquire a confirmation about their diagnosis. On the other hand, the models trained on clinical images can be used on mobile applications, since a cell phone camera takes images similar to them.The results using Inception v3 model for dermoscopical images achieved accuracy 91.4%, sensitivity 87.8% and specificity 92.3%. For clinical images, the VGG-16 model achieved accuracy 86.3%, sensitivity 84.5% and specificity 88.8%. The results are compared to those of clinicians, which shows that the algorithms can be used reliably for the detection of melanoma.

  • 108.
    Papastathis, Ioannis
    KTH, School of Technology and Health (STH).
    Intention Detection and Arm Kinematic Control in Soft Robotic Medical Assistive Device2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aging in humans is often associated with reduced muscle strength and difficulty in elevating the arm and sustaining it at a certain position. The aim of this master thesis is to propose a number of technical solutions integrated into a complete electronic system which can be used to support the user's muscle capacity and partially resist gravitational load. An electronic system consisting of sensors, a control unit and an actuator has been developed. The system is able to detect the user's motion intention based on an angle detection algorithm and perform kinematic control over the user's arm by adjusting the level of support at different degrees of elevation. A force control algorithm has been developed for controlling the actuating mechanism, providing the user with a natural and intuitive support during arm elevation. The implemented system is a first step towards the development of a medical assistive device for the elderly or patients with reduced muscle strength allowing them to independently perform a number of personal activities of daily life where active participation of the upper limb is required.

  • 109.
    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.

  • 110.
    Pavlopoulos, Alexandros Ikaros
    KTH, School of Technology and Health (STH).
    Characterization of the synaptic connectivity patterns of genetically defined neuron types in circuits that regulate dopamine and serotonin2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Lateral Habenula (LHb) have been implicated in both reward-seeking behavior and in depressive disorders due to its modulatory effects on dopamine rich areas. Excitatory projections from LHb target GABAergic interneurons of both ventral tegmental area (VTA) and rostromedial tegmental nucleus (RMTg) and consequently provide strong inhibition on VTA‟s dopaminergic neurons. These reward related signals are provided to LHb from distinct neuronal populations in internal Globus Pallidus (GPi). Here by using a dual viral combination of an adeno-associated helper virus (AAV) and a genetically modified rabies virus that displays specific transsynaptic retrograde spread we are providing anatomical evidence for a strong innervations of the LHb by VGLUT2+ glutaminergic and SOM+ GABAergic GPi neurons. Our results provide the first direct evidence for both an excitatory and an inhibitory projection m, from GPi to the LHb. Given the importance of the LHb as a modulatory nucleus of the dopaminergic system, the definition of its connectivity and function will give valuable insights in the understanding of both reward-seeking behavior and depressive disorders.

  • 111.
    Peterson, Amanda
    KTH, School of Technology and Health (STH).
    Designing an Experimental Protocol for Separating Active Diameter Response from Passive Response in Small Blood Vessels2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The knowledge of blood vessel biomechanics is used for understanding and developing treatments for cardiovascular disease. The objective of this project was to develop an experimental protocol, for education and research, that separates active diameter response from the passive, as a function of the intraluminal pressure in a pressure myograph.

    The design process was performed in three steps. First the protocol was designed for an artificial vessel and then expanded to include passive properties of blood vessels, finally further developments needed to analyze active blood vessels were suggested. The system was built as a pressure myograph containing a vessel chamber where the vessel was mounted on two cannulas, two pressure sensors for calculating the intraluminal pressure, and one microscope equipped with a camera for diameter observations. Reference data for the artificial vessel material was acquired from a uniaxial tensile test.

    The results was in the form of stress-stretch relations. Both the results from the artificial vessel and the passive blood vessel was in a acceptable reference range. The results indicate that the experimental protocol can be used for testing passive properties of both artificial vessels and small blood vessels. No results were obtained for active blood vessels, thus the experimental protocol can not be used for separating the active response to diameter change of blood vessels. However, further developments of the experimental protocol are discussed.

  • 112.
    Petit, Clemence
    KTH, School of Technology and Health (STH).
    Brain MRI segmentation for the longitudinal follow-up of regional atrophy in Alzheimer’s Disease2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Brain atrophy measurement is increasingly important in studies of neurodegenerative diseases such as Alzheimer’s disease. From this perspective, a regional segmentation framework for magnetic resonance images has recently been developed by the team that I joined for my master thesis. It combines an atlas fusion and a tissue classification. A graph-cuts optimization step is then applied to obtain the final segmentation from the combination probability maps. To begin with neighboring constraints were integrated into the optimization step so as to prevent some labels to be adjacent in accordance with anatomical criteria. They were successfully tested on a restricted list of patient images which previously presented segmentation errors. Secondly, a multigrid tissue classification was implemented in order to compensate for the effects of intensity inhomogeneities. However, the visual observations on a few cases showed little improvement compared to the increased computation time. Consequently another possibility was investigated to modify the classification. An atlas-based classification was implemented and tested both on a small-scale and a large-scale. The efficiency of the proposed method was visually assessed on a few patients, especially regarding the separation between grey and white matter. The process was then applied on a database containing several hundreds patients and the results demonstrated an improved group separation based on grey matter volume, whose reduction is particularly significant with patients suffering from Alzheimer’s Disease. To conclude, several links of the segmentation framework have been upgraded, which promises good results for future regional atrophy studies.

  • 113.
    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.

  • 114.
    Pezzutti, Silvia
    KTH, School of Technology and Health (STH).
    Age–Related Perspectives on the Biomechanics of Traumatic Injury2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Finite element models have the potential to accurately represent the pediatric body, both from the anatomical and topological point of view. They can describe changes in size and shape as well as changes in the biomechanical properties. Starting from the PIPER human body model, whose baseline represents the anatomy of a 6 years old child, a family of five models between the age of 2 and 6 was created with the purpose of investigating how the body reacts to a traumatic impact. To create these models, a detailed knowledge of pediatric biomechanics was needed, so a deep literature research was performed to characterize all the human body tissues with age-related material properties. Then, an environment model was chosen to investigate how injuries are related to the age of the subject. Since car crashes are a leading cause of death among children, a car accident was simulated to reach the aim of the project. The anatomical and biomechanical scaling process, as well as the positioning of the child in the environment model, were performed with the PIPER tools, while simulations were run with Ls-Dyna.

    From the literature, age-dependent material properties were found for almost all the tissues of the human body, allowing the development of a detailed pediatric FE model. Then, biomechanical injury predictors, such as the brain strain, the skull acceleration, the chest displacement, the lung pressure and the Von Mises stress in the limbs, were extracted from the simulations to evaluate how injuries changes with the age. The head showed to be the body segment most affected by the age, with an increasing injury severity with the decreasing of the age. Moreover, it was observed that the probability of bone fractures increases for higher bone stiffness.

  • 115.
    Potoshna, Lisa
    KTH, School of Technology and Health (STH).
    Design and Development of a Tracheostomy Tube Test Device2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the NRC (National Respiratory Centre) department at Danderyds Hospital different standard tracheostomy tubes are customized in order to create a more appropriate fit for the individual patient. This master thesis aims to design a theoretical model and build a first prototype of a tracheostomy tube test device that can be used to analyse and compare the physiological performance of different for tracheostomy tubes.

     

    The theoretical model of the device consisted of an artificial lung, artificial trachea and a ventilator, pressure and flow sensors and a data acquisition device. The first prototype was built using equipment available at the NRC department and three experimental set-ups were assembled: one simulating normal breathing and two set-ups simulating coughing. Two artificial tracheas, a small and a large one together with different tracheostomy tubes were used to evaluate the first prototype.

     

    Results showed that the first prototype could be used to compare cuffed fenestrated and non-fenestrated tracheostomy tubes. However, the first prototype was less effective when comparing uncuffed fenestrated and non-fenestrated tracheostomy tubes, which is due to the lack of airway resistance in uncuffed tubes. Results strongly motivate a further development of the device with equipment described in the theoretical model and the future studies should be focused on improving the device. 

  • 116.
    Prabhakaran, Gokulraj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Imaging Memory Encoding in Mild Cognitive Impairment (MCI) using fMRI2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 117.
    Qu, An
    KTH, School of Technology and Health (STH).
    CUDA Accelerated 3D Non-rigid Diffeomorphic Registration2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Advances of magnetic resonance imaging (MRI) techniques enable visualguidance to identify the anatomical target of interest during the image guidedintervention(IGI). Non-rigid image registration is one of the crucial techniques,aligning the target tissue with the MRI preoperative image volumes. As thegrowing demand for the real-time interaction in IGI, time used for intraoperativeregistration is increasingly important. This work implements 3D diffeomorphicdemons algorithm on Nvidia GeForce GTX 1070 GPU in C++ based on CUDA8.0.61 programming environment, using which the average registration time hasaccelerated to 5s. We have also extensively evaluated GPU accelerated 3D diffeomorphicregistration against both CPU implementation and Matlab codes, and theresults show that GPU implementation performs a much better algorithm efficiency.

  • 118.
    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.

  • 119.
    Raghavendra, Jammalamadaka
    KTH, School of Technology and Health (STH).
    Optomyography: Detection of muscle surface displacement using reflective photo resistor2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A human body can carry out many physiological complex processes which can be mechanical, electrical or bio-chemical. Each mechanical activity generates a signal that describes the characteristics of the particular action in the form of pressure or temperature. Any irregularity in the process changes the usual functioning thus affecting the performance of the system. Several techniques were introduced to evaluate these muscular signals in order to get a deeper understanding of the medical abnormalities. Displacement sensors, laser optics, electrodes, accelerometers and microphones are some of the widely used devices in measuring the electrical and mechanical activities produced in the muscles.

    The aim of this thesis project was to find and implement a simple non-contact optical method to measure and monitor the displacements caused on the surface of the skin due to muscular movements. In this study, a device was developed using photo electric sensors that can record surface changes caused on the skin due to the movements forearm muscles.

  • 120.
    Raghavendra, Jammalamadaka
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Optomyography - Detection ofmuscle surface displacement using reflective photo resistor.2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A human body can carry out many physiological complex processes which can be mechanical, electrical or bio-chemical. Each mechanical activity generates a signal that describes the characteristics of the particular action in the form of pressure or temperature. Any irregularity in the process changes the usual functioning thus affecting the performance of the system. Several techniques were introduced to evaluate these muscular signals in order to get a deeper understanding of the medical abnormalities. Displacement sensors, laser optics, electrodes, accelerometers and microphones are some of the widely used devices in measuring the electrical and mechanical activities produced in the muscles.

    The aim of this thesis project was to find and implement a simple non-contact optical method to measure and monitor the displacements caused on the surface of the skin due to muscular movements. In this study, a device was developed using photo electric sensors that can record surface changes caused on the skin due to the movements forearm muscles.

  • 121.
    Ren, Wuwei
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brain Imaging with a Coded Pinhole Mask2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 122.
    Reuterdahl, Hannah
    KTH, School of Technology and Health (STH).
    Mobile Marker-based Augmented Reality as an Intuitive Instruction Manual2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Instruction manuals are supposed to be used to ensure safe and proper use of medical devices. The instruction manuals could be paper or digital docu- ments, animations or videos. Conveying information and instructions through these media might not be the most efficient approach, especially in healthcare where physicians and nurses experience high cognitive load and prefer hands-on experience with the devices [1].

    This thesis investigates how a possibly more efficient and intuitive instruction manual could be developed using mobile marker-based Augmented Reality; a technology that combines a virtual and physical world.

    By analyzing and comparing different marker-based Augmented Reality sys- tems and Software Development Kits (SDKs), the most suitable system, in terms of availability and functionality, was chosen for the implementation. Two mobile AR instruction manual prototypes were developed, as a proof-of-concept, using Unity3D with Qualcomm’s Vuforia extension.

    The resulting prototypes demonstrate the opportunity to integrate informa- tion and instructions in our physical world and the difficulties associated with the interaction and user experience with the relatively novel Augmented Reality interface. 

  • 123.
    Rigoni, Isotta
    KTH, School of Technology and Health (STH).
    FE-Modelling and Material Characterization of Ice-Hockey Helmet2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this research was to produce a reliable finite element model of a helmet, that could be used to simulate approval tests as well as impacts to investigate the safety offered. A 2D and 3D mesh was generated from the CAD file of an Easton Synergy 380 with HyperWorks, and then checked referring to standard parameter values. A few specimens cut from the liner were tested with the Instron Electropuls E3000 (Instron, High Wycombe, Great Britain) machine to determine Young’s modulus, Poisson’s ratio and the density of the EPP. The numerical model was characterised with appropriate materials with Ls-PrePost, such as ABS for the shell, EPP for the liner and steel for the impact anvil. The foam was implemented both with the *063_CRUSHABLE_FOAM and the *126_MODIFIED_HONEYCOMB card, in two different configurations. The helmet model was coupled with a finite element model of a HIII head form and three impact scenarios were set up. Backward, lateral and pitched impact were simulated and results were compared with those obtained from the experimental tests carried on at the MIPS. The two configurations were tested in all the three scenarios. The correlation between numerical and experimental results was evaluated by analysing the linear and rotational acceleration, and the rotational velocity, recorded by the accelerometer positioned inside the HIII headform. The parameters used were the Pearson correlation coefficient, the peak linear acceleration score, the shape of the curves, the time occurrence of peaks and the percentage of the difference between them. The first configuration showed good correlation scores (>85%) for the backward and lateral impact, for the rotational velocity and acceleration, while lower values were recorded for the pitched impact simulation. Lower values (70.88% and 77.76%) were obtained for the peak linear acceleration score, which stress the need for modifications of the contact definition in Ls-PrePost or a more detailed material testing. Worse results were recorded for the second configuration, but the smaller computational time required suggests that more attempts should be done in this direction. 

  • 124.
    Romero, Vincent
    KTH, School of Technology and Health (STH).
    The Body Profile Score : an assessment of whole body walking patterns in children with cerebral palsy2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Patients with cerebral palsy account for great upper extremities deviationswhile walking. However, the number of studies assessing their upper bodygait kinematics are rare and no studies have been conducted interested inthe whole body kinematics during walking. In this study, we created awhole body index, the Body Profile Score made of modified existing kinematicindexes assessing the gait pattern of children with cerebral palsy. TheBody Profile Score (BPS) is an average of combination of the Gait ProfileScore (GPS), a modified Trunk Profile Score (TPS), a modified Arm PostureScore (APS) and a also new index called Head Profile Score (HPS), basedon a similar calculation. Dierent versions of the BPS were tested on threegroups: a control group, a CP group before botulinum toxin A treatmentand a CP group after botulinum toxin A treatment. The results showed apoor level of linear correlations between the dierent BPS versions and theGait Profile Score, indicating that lower body indexes such as the GPS orGait Deviation Index (GDI) and full body index such as the BPS do not renderthe same information. The BPS is the first index proposing a full bodykinematic analysis and aims at showing that such an analysis is needed ingait assessment of spastic children in order to have a realistic overview ofthe pathological walking condition.

  • 125.
    Röstin, Martin
    KTH, School of Technology and Health (STH).
    Development of a Flexible Software Framework for Biosignal PI: An Open-Source Biosignal Acquisition and Processing System2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As the world population ages, the healthcare system is facing new challenges in treating more patients at a lower cost than today. One trend in addressing this problem is to increase the opportunities of in-home care. To achieve this there is a need for safe and cost-effective monitoring systems. Biosignal PI is an ongoing open-source project created to develop a flexible and affordable platform for development of stand-alone devices able to measure and process physiological signals.

    This master thesis project, performed at the department of Medical Sensors, Signals and System at the School of Technology and Health, aimed at further develop the Biosignal PI software by constructing a new flexible software framework architecture that could be used for measurement and processing of different types of biosignals. The project also aimed at implementing features for Heart Rate Variability(HRV) Analysis in the Biosignal PI software as well as developing a graphical user interface(GUI) for the Raspberry PI hardware module PiFace Control and Display.

    The project developed a new flexible abstract software framework for the Biosignal PI. The new framework was constructed to abstract all hardware specifics into smaller interchangeable modules, with the idea of the modules being independent in handling their specific task making it possible to make changes in the Biosignal PI software without having to rewrite all of the core. The new developed Biosignal PI software framework was implemented into the existing hardware setup consisting of an Raspberry PI, a small and affordable single-board computer, connected to ADAS1000, a low power analog front end capable of recording an Electrocardiography(ECG).

    To control the Biosignal PI software two different GUIs were implemented. One GUI extending the original software GUI with the added feature of making it able to perform HRV-Analysis on the Raspberry PI. This GUI requires a mouse and computer screen to function. To be able to control the Biosignal PI without mouse the project also created a GUI for the PiFace Control and Display. The PiFace GUI enables the user to collect and store ECG signals without the need of an big computer screen, increasing the mobility of the Biosignal PI device.  

    To help with the development process and also to make the project more compliant with the Medical Device Directive a couple of development tools were implemented such as a CMake build system, integrating the project with the Googletest testing framework for automated testing and the implementation of the document generator software Doxygen to be able to create an Software Documentation.   

    The Biosignal PI software developed in this thesis is available through Github at https://github.com/biosignalpi/Version-A1-Rapsberry-PI

  • 126.
    Salhani Maat, Bilhal
    KTH, School of Technology and Health (STH).
    Backprojection-then-filtering reconstruction along the most likely path in proton computed tomography2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The backprojection-then-filtering algorithm was applied to proton CT data to reconstruct a map of proton stopping power relative to water (RSP) in air, water and bone. Backprojections were performed along three commonly used path estimates for the proton: straight line path, cubic spline path, and most likely path. The proton CT data was obtained through simulations using the GEANT4 simulation toolkit. Two elliptical phantoms were inspected, and an accuracy of 0.2% and 0.8% was obtained for the RSP in water and bone respectively in the region of interest, while the RSP of air was significantly underestimated.

  • 127.
    Schlippe, Marius
    KTH, School of Technology and Health (STH).
    A method to estimate in vivo mechanical properties of human tendon in the lower leg using ultrasound imaging combined with motion capture2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Musculoskeletal models and simulations allow for the estimation of forces acting on muscles and joints during human movement and athletic performance. In order to improve the accuracy of these models for a specific application, knowledge about subject-specific in vivo properties of human muscle and tendon is needed. This study presents a method for estimating in vivo mechanical properties of human tendon in the lower leg, using a combination of ultrasound imaging and motion capture. Key mechanical parameters — such as tendon stiffness, moment arm, slack length and force-strain relationship — and the contribution of tendon elongation to ankle mobility of the medial gastrocnemius (MG) and soleus (SOL) aspects of the Achilles tendon were obtained in vivo in 8 typically-developed adults, and the applicability of the method on the tibialis anterior (TA) tendon was investigated. In contrast to previous studies using a comparable method, variable tendon moment arm lengths during passive movement of the ankle joint was taken into consideration. As a novelty, the passive mechanical properties of the Achilles tendon were obtained in vivo in 4 hemiplegic post-stroke subjects and compared to the 8 typically-developed subjects. The estimated mechanical parameters of the MG and SOL aspects of the Achilles tendon were consistent with findings in the literature. In order to estimate stiffness of the TA tendon, it was shown that a larger range of motion (ROM) of the foot during the passive rotation experiments is needed. The comparison between typically-developed and hemiplegic post-stroke subjects revealed significantly lower tendon stiffness and slack angle, and significantly higher contribution of tendon elongation to ankle mobility in the post-stroke group. The developed method enables estimation of in vivo mechanical properties of tendon in the lower leg and contributes to improving the accuracy of subject-specific musculoskeletal models and simulations.

  • 128.
    Schuetz, Carmen
    KTH, School of Technology and Health (STH).
    Improving the alignment of the linear accelerator and the bending magnets in the Elekta Synergy: Förbättring av inriktningen av linjäracceleratorn och böjmagneterna i Elekta Synergy2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Elekta Synergy is a linear accelerator used in radiation therapy. It is constructed fromvarious mechanical components, including a set of 112.5° bending magnets, which need tobe aligned correctly in order to produce an efficient treatment beam. The current alignmentprocess is outdated and results in inconsistencies, which leads to prolonged assembly timesand the need to correct alignment errors. This paper details the study, design andconstruction of a new bending magnet alignment approach and thereby serves to introducea replacement for the current system. The proposed solution consists of an optimizedmechanical jig in conjunction with image processing software.

  • 129.
    Selvaratnam, Thevapriya
    KTH, School of Technology and Health (STH).
    Optimization and characterization of a centrally functionalized quartz crystal microbalance sensor surface for Norovirus detection: Optimering och karakterisering av en centralt funktionaliserad kvartskristall mikrovåg sensoryta för norovirus detektion2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this study a biosensor based on real time quartz crystal microbalance (QCM) monitoring is optimized and characterized for the application in the Norosensor. This biosensor is aimed to recognise, capture and amplify Norovirus (NoV). In an initial step a simplified bioassay was developed that focuses on the latter parts of the assay which consists of DNA-guided probing and amplification of the captured virus and includes the development of an amplification model assay directly to the functionalised crystal surface. A padlock probe with matching sequence to the conjugated oligonucleotide on the quartz crystal surface is used as target in the model assay. Although a number of studies have been carried out based on padlock probe ligation and rolling circle amplification (RCA) based QCM sensing, these studies utilize the entire crystal surface to capture and amplify the biomolecule. In this research work the QCM monitoring is explored on a centrally functionalised electrode surface through conjugation only at the centre of the electrode for increased mass sensitivity. Thus, allowing capture and amplification of the padlock probe only at the centre of the quartz crystal.

    A 14mm diameter, thermoncompensated AT-cut, nonpolished quartz crystal with a 10mm diameter gold surface coating acting as electrode was utilized for QCM measurements. The detection system is based on mass binding and amplification on the QCM to produce a negative frequency shift in the fundamental frequency of the vibrating quartz crystal. The amplification products were additionally fluorescently labelled and fluorescent microscopy images were also obtained at the end of every experiment to verify the presence or absence of DNA capture and amplification.

    Experimental findings show that the current flow chamber with a 15ul capacity is able to detect a specific padlock probe concentration of 1nM on a conjugated region of ~2.5mm diameter. RCA amplified the mass with an average frequency shift of -80Hz in 60mins RCA incubation time. Further, the specificity and sensitivity of the QCM system was explored.

    However, the system has limitations where sensor binding of reaction proteins, such as DNA ligase and BSA, to some extent is observed. The storage stability of the functionalized self-assembled monolayer (SAM) on the QCM is also observed to deteriorate and thus, is of concern. Nevertheless the combination of RCA based amplification with QCM real-time monitoring has the potential for rapid and simple, low cost detection of the Norovirus.

  • 130.
    Sherifova, Selda
    KTH, School of Technology and Health (STH).
    Modeling the Propagation of Aortic Dissection2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aortic dissection is a diseased condition of the aorta in which there is an initial tear to the intimal layer propagating in the radial direction initially then causing delamination of the arterial layers creating a false lumen. It is estimated to effect 30 individuals in one million per year. The dissection is fatal when it ruptures, and 90 % of the patients die within three months if not diagnosed.

    This study presents the first steps towards modeling the propagation of aortic dissection. The aorta was treated as a three-layered fiber-reinforced composite structure, and the Tsai-Wu failure criterion was employed to obtain the 3-D failure surface for the healthy and dissected human aortic media. To be able to obtain Tsai-Wu coefficients, uniaxial tensile tests in the axial, circumferential, and radial direction, and additionally in-plane (axial-circumferential plane) and out-of-plane shear tests in different orientations were performed on human aortic medias. To our knowledge the combination of applied tests and performingof out-of-plane shear tests on aortic tissues is novel.

    The results showed that the aortic media was the weakest in radial direction under tensile loading. Furthermore, the media was much stronger under out-of-plane shear loading than under in-plane shear loading. In order to consider influences of stress coupling between axial and circumferential directions, an optimal specimen geometry was designed for biaxial tensile testing by the help of finite element analyses. A cruciform geometry with a reduced cross-section in the biaxially loaded zone was found to fit our purposes the best. The preparation protocol to achieve this geometry is currently under investigation. For aortic tissues, all compressive strengths and some biaxial tensile strengths needed to be assumed since they are yet not possible to obtain from mechanical tests. Finally, failure surfaces described by the Tsai-Wu criterion were plotted in 2-D using the analyzed experimental data, with different assumptions in compressive and biaxial tensile strengths.

  • 131.
    Sjödahl, Sofie
    KTH, School of Technology and Health (STH).
    A Pilot Study on the Effectiveness of Heart Rate Variability Biofeedback on Healthy Subjects2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Heart Rate Variability (HRV) is a medical term describing the heart’s natural varying time difference between heartbeats (called NN-intervals). A higher HRV i.e. a larger variability between NN-intervals is connected to healthiness, and lower HRV to unhealthy states.

    Biofeedback (BF) is a method that can detect and send physiological signals back to the user on a screen. Every individual has a resonant frequency, and when breathing at this frequency, the interplay between blood pressure and respiration causes HRV to increase momentarily. HRV biofeedback aims at increasing HRV, by measuring heart rhythm and respiration to guide the user in resonant breathing.

    This thesis had the objective to investigate the effectiveness of one 20 minutes long biofeedback session with resonant frequency breathing. The hypothesis was that the time frame would be longer than two hours. It was carried out with 12 healthy volunteers, who participated in a biofeedback session with an Android application, and afterwards 5 minutes long ECG measurements were made every half hour for two hours. A control session was held with the same participants to give the trial more scientific strength.

    The result showed that a 20 min resonant breathing biofeedback session can elevate Standard Deviation of NN intervals (SDNN) significantly (p < 0.05), 2 hours after the biofeedback session. The conclusion was that the hypothesis cannot be rejected, but the result is too weak to strengthen it much. Further research is needed to draw more conclusions about the time frame of HRV elevations in healthy people. 

  • 132.
    Snäll, Jonatan
    KTH, School of Technology and Health (STH).
    Software development of Biosignal Pi: An affordable open source platform for monitoring ECG and respiration2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to handle the increasing costs of healthcare more of the care and monitoring will take place in the patient’s home. It is therefore desirable to develop smaller and portable systems that can record important biosignals such as the electrical activity of the heart in the form of an ECG.

    This project is a continuation on a previous project that developed a shield that can be connected to the GPIO pins of a Raspberry Pi, a credit-card sized computer. The shield contains an ADAS1000, a low power and compact device that can record the electrical activity of the heart along with respiration.

    The aim of this project was to develop an application that can run on the Raspberry Pi in order to display the captured data from the shield on a screen along with storing the data for further processing. The project was successful in the way that the requirements for the software have been fulfilled.

  • 133.
    Sundell, Jonas
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering, Ergonomics.
    Dogan, Dilber
    KTH, School of Technology and Health (STH), Health Systems Engineering, Ergonomics.
    Finns det indikationer på samband mellan företags arbetsmiljöarbete och deras börsvärde?: En studie av arbetsmiljöarbetets-indikatorer och börsvärde hos ett urval svenska företag2015Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of the study was to use SAM-index data and data on factors from the report Det Goda Arbetet from the Swedish Work Environment Authority and identify if there is any relation between listed companies' market values and their systematic work environment management. This master’s work is limited to Forty-seven companies on the Swedish stock market that responded to the Work Environment Authority survey NU2012.

     

    The method in this study is a quantitative approach in which statistical, quantifiable results were sought. The companies that participated in the NU2012 survey was divided into three groups based on their results from: i) Work Environment SAM index data and ii) data on factors from the report Det Goda Arbetet.

     

    Results from SAM- index data show a relation between companies’ systematic work environment management and market capitalization for the year 2012 while the results from Det Goda Arbetet show that scores for the highest average varies between the groups. Results for the years 2008-2011 (the year when we don`t have access to the baseline study) shows that there is a tendency for a relation between share price, turnover, number of employees and work environment for these years.

     

    The main conclusion based on the analyzes of the data on the share price and the work environment in Sweden as well as the literature review included in the study, it is found that companies that have a good work Environment tend to have higher stock price and better stock market performance than companies with poor work environment management.

    Keywords: Work environment, SAM index, Stock price, Quality, Skills, Productivity.

  • 134.
    Suvanen, Johan
    KTH, School of Technology and Health (STH).
    Technical Conditions and Organizational Aspects for Remote Treatment Planning: a Developing Country’s Perspective2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Radiotherapy (RT) is the most common treatment for cancer. The state-of- the-art modality for RT is the linear accelerator. However, the availability for linear accelerators in the developing world is limited due to costs, infrastructure and need for educated personnel. The development in telecommunica- tions can help to increase the availability by connecting radiation RT-centers and have a central treatment planning unit. Scandinavian Care is a com- pany that builds RT-centers in developing countries and has a project in India where three centers should to be connected.

    The thesis objectives were to evaluate technical conditions and discuss or- ganizational aspects for remote treatment planning applied on Scandinavian Care’s project in India. The technical conditions were evaluated with two models derived from Swedish case studies. The models were analyzed using a SWOT-model. The organizational aspects were divided into the organiza- tion of medical physicists and three importtant communication channels.

    The thesis concludes that the technical conditions are possible for the project in India. The best model depends on the frequency of disturbances in the WAN-connection and patient throughput sensitivity. The organization of medical physicists suggests a rotation schedule to promote education, infor- mal communication and variation of tasks. Telemedical conferences and use of software possibilities could ease the feedback. 

  • 135.
    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. 

  • 136.
    Terrin, Massimo
    KTH, School of Technology and Health (STH).
    Micro-CT for small animal imaging: Optimization of the tube voltage for low-contrast imaging2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis evaluated the optimal tube voltage for low-contrast imaging of a micro-CT system (intended for small animal imaging) built at the School of Technology and Health (STH) of the Royal Institute of Technology (KTH).

    The main goal of this work was to calibrate the above-mentioned device (composed moreover by a Hamamatsu microfocus L10951-01 X-ray tube, a CMOS flat panel Hamamatsu C7942CA-22 and using a Cone-Beam CT reconstruction algorithm) for obtaining the best imaging of low-contrast structures. In order to do this, an analytical model, re-adapted from the previous state-of-the-art Micro-CT studies, was evaluated for finding a sub-optimal tube voltage from which to start the experiments, done on a reference Low-Contrast phantom specifically intended for the calibration of Micro-CT devices. 

    Finally, by looking to the results from the experiments, a good tube setting for the optimization of the CT for low-contrast imaging was found. The optimal tube voltage for low-contrast imaging, from the experiments on the QRM phantom, was found to be between 48 and 50 kV. This tube voltage values gave the best CNR and contrast profiles results. 

    Ultimately, we found that the usage of a 1mm Al filtration reduced the absorbed dose without affecting the image quality.

  • 137.
    Thorsteinsdottir, Arnrun
    KTH, School of Technology and Health (STH).
    Motivation and Quantification of Physical Activity for Hospitalised Cancer Patients2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Previous studies have shown the positive effect of increased physical activity for cancer patients during treatments of chemotherapy and stem cell transplantation. Moderate exercise has shown to cause significantly less loss of muscle mass, less symptoms of cancer related fatigue, less need for platelet transfusions during treatment time and shorter hospitalisation. Inactivity at hospital clinics is though still a major concern and it seems like lack of motivation plays a big roll. It has been shown that an overview of activity level, personal goal setting and education on the importance of physical activity can work as a motivation towards increased physical activity. This project aimed to make a prototype that can quantify physical activity of hospitalised cancer patients and represent it in a motivational and informative way. An accelerometer was used to collect activity data; the data was processed and used to train a support vector machine for classification of activities. Activities recognised by the prototype are the postures lying down, sitting and standing as well as recognising when the user is active. Over 90% accuracy was obtained in activity recognition for specific training sets. The prototype was tested on patients at the haematology clinic at the Karolinska hospital in Huddinge. Test subjects rated the classification accuracy and the motivational value of the prototype on a scale of 1-5. The accuracy was rated 4.2 out of 5 and the motivational value 3.25 out of 5. A pilot study to further test the feasibility of the product will be performed in the summer of 2015. 

  • 138.
    Thunholm, Malin
    KTH, School of Technology and Health (STH).
    Pulse Oximetry: Signal Processing in real time on Raspberry Pi2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis introduces the reader into RespiHeart, which is a product under development. RespiHeart is an complement/alternative to the regular Pulse Oximeter and is intended to be used within the health care sector for combined measurements and communication on open inexpensive platforms.

    This thesis evaluates interaction between RespiHeart and a Raspberry Pi 3 Model B to evaluate if the computer is capable of handling the data from RespiHeart and make signal processing.

    Python is used throughout the whole project and is a suitable language for interaction and signal processing in real time.

  • 139.
    Tonin, Luke
    KTH, School of Technology and Health (STH).
    Annotating Mentions of Coronary Artery Disease in Medical Reports2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 140.
    Trowald, Adam
    KTH, School of Technology and Health (STH), Medical Engineering.
    A comparison between synthetic and conventional MRI2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis describes the bene ts and disadvantages of using synthetic Magnetic

    Resonance Imaging (MRI) instead of conventional MRI. The thesis is

    based on a clinical study performed at Orebro University Hospital were 11

    patients diagnosed with Multiple Sclerosis (MS) went through a brain examination

    with both methods. The examination time was measured and compared

    between the two methods, and the quality of the images was analysed by two

    radiologists.

    The study shows that the examination time can be reduced using the synthetic

    method instead of the conventional. The image quality is however not as good

    with the synthetic method which opens a discussion whether the time reduction

    is worth the loss of image quality. However, the conclusions are that the

    method can be useful for patients diagnosed with MS who are examined yearly

    and especially useful as a complement to the conventional sequence to gain

    as much information as possible that can be compared between the patients

    yearly exams. To completely replace other conventional examination types,

    the method has to be further evaluated and equipped with functions that are

    present in the conventional sequences, such as correction for motion artefacts.

  • 141.
    Tsakiraki, Eleni
    KTH, School of Technology and Health (STH).
    Real-time Head Motion Tracking for Brain Positron Emission Tomography using Microsoft Kinect V22016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The scope of the current research work was to evaluate the potential of the latest version of Microsoft Kinect sensor (Kinect v2) as an external tracking device for head motion during brain imaging with brain Positron Emission Tomography (PET). Head movements constitute a serious degradation factor in the acquired PET images. Although there are algorithms implementing motion correction using known motion data, the lack of effective and reliable motion tracking hardware has prevented their widespread adoption. Thus, the development of effective external tracking instrumentation is a necessity. Kinect was tested both for Siemens High-Resolution Research Tomograph (HRRT) and for Siemens ECAT HR PET system. The face Application Programming Interface (API) ’HD face’ released by Microsoft in June 2015 was modified and used in Matlab environment. Multiple experimental sessions took place examining the head tracking accuracy of kinect both in translational and rotational movements of the head. The results were analyzed statistically using one-sample Ttests with the significance level set to 5%. It was found that kinect v2 can track the head with a mean spatial accuracy of µ0 < 1 mm (SD = 0,8 mm) in the y-direction of the tomograph’s camera, µ0 < 3 mm (SD = 1,5 mm) in the z-direction of the tomograph’s camera and µ0 < 1 ◦ (SD < 1 ◦ ) for all the angles. However, further validation needs to take place. Modifications are needed in order for kinect to be used when acquiring PET data with the HRRT system. The small size of HRRT’s gantry (over 30 cm in diameter) makes kinect’s tracking unstable when the whole head is inside the gantry. On the other hand, Kinect could be used to track the motion of the head inside the gantry of the HR system.

  • 142.
    Turco, Anna
    KTH, School of Technology and Health (STH), Medical Engineering.
    Monte Carlo simulations of a small-animal PET scanner: Analysis of performances and comparison between camera designs2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 143.
    Udvardy, Zoltán
    KTH, School of Technology and Health (STH), Medical Engineering.
    Design of a Testbed for Haptic Devices Used by Surgical Simulators2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays surgery simulations are aiming to apply not just visual effects but forcefeedback as well. To carry out force feedback, haptic devices are utilized that are mostlycommercial products for general purposes. Some of the haptic device features are moreimportant than others in case of surgery simulator use. The precision of the output forcemagnitude is one such property. The specifications provided by haptic devicemanufacturers are lacking details on device characteristics, known to cause difficulties inplanning of accurate surgery simulations.This project shows the design of a testbed that is capable of measuring the precision ofoutput forces within the haptic devices’ workspace. With the testbed, a set ofmeasurements can be run on different haptic devices, giving as a result a betterknowledge of the utilized device. This knowledge aids the design of more precise andrealistic surgery simulations.

  • 144.
    Vendrametto, Tobia
    KTH, School of Technology and Health (STH). Politecnico di Milano.
    Robot Assisted Stapedotomy With an Active Handheld Instrument2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Robotic-assisted surgery is a rapid growing field, facing challenging tasks and demands from surgeons, in particular in minimally invasive and microsurgery. However many of the present robotic systems are not well integrated in the surgical workflow, too big or too expensive. Micron is an innovative fully handheld active micromanipulator that helps surgeons to improve position accuracy and precision in microsurgery by cancelling the normal hand tremor. This thesis proposes an improvement and development of Micron, considering as target the stapedotomy procedure, microsurgery performed at the middle ear that aims to restore the hearing impairments. Two tools, a handle and a brace were designed and prototyped and the control was adapted; at the end the entire system was assessed through some experiments. Promising results were obtained in terms of tremor cancellation but further research is needed in order to reach clear advantages. 

  • 145.
    Vinasco Korsfeldt, Ludvig
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Tais, Mazin
    KTH, School of Technology and Health (STH), Medical Engineering.
    The Effects of a Carbon Fiber Table Top on Radiation Dose and Image Quality During Fluoroscopy2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fluoroscopic procedures are commonly used in today’s healthcare and involve ionizing radiation exposure to personnel and patients. During these procedures the patient is placed on a surgical table. The board on which the patient is lying on is referred to as the table top, and how different table top materials affect the image quality and radiation exposure has been investigated in this report. Radiation exposure measurements at different sites have been recorded with both a polymethyl methacrylate (PMMA) and an anthropomorphic phantom representing a patient. Image quality assessment was made in terms of contrast, signal-to-noise ratio and modular transfer function. The result showed that a higher table top attenuation or a higher tube voltage may lead to a lower dose but also a reduction in image quality. The preferred tube voltage and current, and resulting image quality is task dependent, i.e. dependent on the type of clinical procedure, which makes it hard to generalize in the selection of a certain table. Two methods have been proposed when selecting a table, one which can be considered as quantification of the trade-off between image quality and radiation dose, the other one is a fast method for comparing a large amount of tables.

  • 146.
    Voinea, Alexandra
    KTH, School of Technology and Health (STH).
    Effect of GLP-1R Knockout on stroke outcome2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Stroke is the leading cause of disability in adults in westernized societies and it has an important impact on health and economy. Comorbid health conditions such as hypertension, inactive lifestyle, smoking, obesity and diabetes considerably increase the risk of stroke. Moreover, studies have shown an increased probability of stroke occurrence and recurrence in the type 2 diabetes (T2D). Stroke leads to neurological deficits like motor impairments, disabilities and poor quality of life. The need of finding a novel treatment that can assure neuroprotective effects is crucial considering that the incidence of T2D is increasing around the world. Thrombolytic treatment given within 3-4 h from the stroke can assure some protection. Unfortunately, too few patients can benefit of this treatment due to a delayed arrival at the hospital, incorrect diagnoses or other causes. Furthermore, drugs that have shown some neuroprotective effectiveness in the pre-clinical experiments, failed in the clinical trials and today, there is no treatment for stroke based on neuroprotection. Glucagon-like peptide 1 (GLP-1) is a peptide found in L-cells of the small intestine and is secreted after the meal. The activation of its receptor (GLP-1R) increases the glucose-dependent insulin secretion and decreases the glucagon secretion. Exendin-4 (Ex-4) is a GLP-1R agonist that showed efficacy against stroke in diabetes in animal models. Additionally, it has been demonstrated that Ex-4 is acting through the activation of GLP-1R. The aim of the present study was to determine if the receptor itself plays a role in stroke outcome (without Ex-4) and see if the stroke-induced inflammation is affected by the lack of GLP-1R. We compared knockout vs. wild type mice by evaluating the stroke volume and by performing stereological counting of neurons in the striatum and cortex. The results showed no significant differences between the two groups, indicating that the lack of GLP-1R plays no role in stroke outcome.

  • 147.
    Wang, Beien
    KTH, School of Technology and Health (STH).
    3D Scintillation Positioning Method in a Breast-specific Gamma Camera2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In modern clinical practice, gamma camera is one of the most important imaging modalities for tumour diagnosis. The standard technique uses scintillator-based gamma cameras equipped with parallel-hole collimator to detect the planar position of γ photon interaction (scintillation). However, the positioning is of insufficient resolution and linearity for breast imaging. With the aim to improve spatial resolution and positioning linearity, a new gamma camera configuration was described specifically for breast-imaging. This breast-specific gamma camera was supposed to have the following technical features: variable angle slant-hole collimator; double SiPM arrays readout at the front and back sides of the scintillator; diffusive reflectors at the edges around the scintillator. Because slant-hole collimator was used, a new 3D scintillation positioning method was introduced and tested. The setup of the gamma detector was created in a Monte Carlo simulation toolkit, and a library of a number of light distributions from known positions was acquired through optical simulation. Two library-based positioning algorithms, similarity comparison and maximum likelihood, were developed to estimate the 3D scintillation position by comparing the responses from simulated gamma interactions and the responses from library. Results indicated that the planar spatial resolution and positioning linearity estimated with this gamma detector setup and positioning algorithm was higher than the conventional gamma detectors. The depth-of-interaction estimation was also of high linearity and resolution. With the results presented, the gamma detector setup and positioning method is promising in future breast cancer diagnosis.

  • 148.
    Wang, Beien
    KTH, School of Technology and Health (STH), Medical Engineering.
    3D Scintillation Positioning Method in a Breast-specific Gamma Camera2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In modern clinical practice, gamma camera is one of the most important imaging modalities for tumour diagnosis. The standard technique uses scintillator-based gamma cameras equipped with parallel-hole collimator to detect the planar position of γ photon interaction (scintillation). However, the positioning is of insufficient resolution and linearity for breast imaging. With the aim to improve spatial resolution and positioning linearity, a new gamma camera configuration was described specifically for breast-imaging. This breast-specific gamma camera was supposed to have the following technical features: variable angle slant-hole collimator; double SiPM arrays readout at the front and back sides of the scintillator; diffusive reflectors at the edges around the scintillator. Because slant-hole collimator was used, a new 3D scintillation positioning method was introduced and tested. The setup of the gamma detector was created in a Monte Carlo simulation toolkit, and a library of a number of light distributions from known positions was acquired through optical simulation. Two library-based positioning algorithms, similarity comparison and maximum likelihood, were developed to estimate the 3D scintillation position by comparing the responses from simulated gamma interactions and the responses from library. Results indicated that the planar spatial resolution and positioning linearity estimated with this gamma detector setup and positioning algorithm was higher than the conventional gamma detectors. The depth-of-interaction estimation was also of high linearity and resolution. With the results presented, the gamma detector setup and positioning method is promising in future breast cancer diagnosis.

  • 149.
    Wang, Jing
    KTH, School of Technology and Health (STH).
    Design and implementation of an impedance analyzer based on Arduino Uno: A pilot study of bioelectrical impedance analysis2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electrical bioimpedance measurement is widely used today for monitoring body condition. The applications include and go beyond, body composition assessment, nutritional status evaluation, and cancer detection. The modalities for interpreting the impedance information have also developed quickly over the recent decades from single frequency bioimpedance analysis to spectrum and to images.

    Bioimpedance is measured by computing the relationship between voltage and current. In a current based bioimpedance measurement system, the stability of current source has a large influence on the performance of the system. This thesis compared three different voltage controlled current sources: enhanced Howland circuit, load-in-the-loop circuit driven by a current conveyor and double operational amplifiers circuit. These circuits were simulated in Multisim and manufactured into prototypes and tested in lab.

    Effort has also been made to generate and collect signals with digital-to-analog convertor and analog-to-digital convertor. They were controlled by Arduino Uno and impedance was analyzed in Matlab.

  • 150.
    Wemmert, Ellinor
    KTH, School of Technology and Health (STH).
    Comparison of two Fluoroscopic Systems used for EVAR Procedures: an Approach to Analyze X-ray Image Quality Limited to Tube Output2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Image quality in medical x-ray imaging is dependent on the characteristics of the x-ray photons produced  by  the  x-ray  tube,  the  detection  of  the  x-ray  photons  in  the  detector  and  the  image processing. X-ray image guidance during endovascular interventions is usually performed with C-arm fluoroscopy. It is of major importance that the image quality is sufficient for the procedure. The understanding of what affects the image quality could be made easier if the performance of the different parts of the system were to be judged separately, rather than considering the system as a whole.  

    The term Image QualityTube Output that is used throughout this thesis describes the image quality that only depends on the characteristics of the x-ray beam, such as spectral distribution and fluence, without the consideration of detector characteristics or image processing. The aim of this thesis was to  propose  a  method  to  evaluate  the  Image  QualityTube  Output  and  then  compare  two  different fluoroscopy systems used for endovascular interventions with respect to Image QualityTube  Output, patient dose and personnel exposure, all as a function of patient thickness.  

    To limit to the x-ray tube output a third x-ray system was used. In that way detector and image processing would be the same and the differences in image quality would only be due to the tube output. The imaging parameters set by the Automatic Dose Rate Control, ADRC, for various patient thicknesses, was found by using Polymethyl-methacrylate, PMMA, as patient. A test object was introduced and exposed together with the PMMA of varying thickness, using the parameters set by the ADRC. The images were evaluated with respect to low contrast sensitivity and contrast to noise ratio, CNR. The effective dose rate to the patient was calculated using Monte Carlo simulation. Finally, the personnel exposure was measured using active dosimeters.

    The  results  showed  differences  in  the  systems  performance  and  Image  QualityTube  Output.  Also interesting differences in the effective dose rate to the patient was found. Altogether the results indicate that the proposed method is a feasible way to compare the Image QualityTube Output of two fluoroscopic systems. 

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