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  • 1.
    Alaei, Zohreh
    KTH, School of Technology and Health (STH).
    Molecular Dynamics Simulations of Axonal Membrane in Traumatic Brain Injury2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The following project presents in silico investigation of axonal damage in Diffuse Axonal Injury (DAI). When axons face a shear force, orientation of the lipids in the axonal membrane gets disrupted. Depending on the value of the force, a tensile strain causes the axons to get partially or fully deformed and in some cases a pore forms in the membrane. Using Molecular Dynamic (MD) simulation and a coarse grain model, a series of bilayers with various bilayer structure (single bilayer, parallel bilayer and cylindrical bilayer) and similar composition to biological axonal membrane were simulated. This was initially done to investigate the strain rate dependency of the bilayers, and their viscoelastic ability on returning to their original shape from their deformed forms. To achieve this, various deformation velocities were applied to the bilayers reaching 20% strain and relaxing the bilayer after. Additionally, the bilayers were deformed further until they reached a pore. It was found that the bilayers can almost recover from their deformed forms to their original length when they were deformed at 20% strain level. In conjunction, no correlation between the deformation velocity and lipid deformation was observed. Further, it was found that bilayers with different lipid percentage to axonal bilayer has different strain values for water penetration and for pore formation. The strain value for cylindrical bilayer was found very high compared to the strain values found in vitro. The strain for pore formation of parallel and single bilayer was found to be around 80% to 90% and for water penetration was found to be 70% for single bilayer and 50% for parallel bilayer. A slight difference in strain for pore formation between single and parallel bilayer was found which showed the bilayer structure can play a role in simulation results. The effect of the length in the simulations results was also observed where shorter bilayers showed lower strain for pore formation compared to longer bilayers. 

  • 2.
    Buizza, Giulia
    KTH, School of Technology and Health (STH).
    Classifying patients' response to tumour treatment from PET/CT data: a machine learning approach2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Early assessment of tumour response has lately acquired big interest in the medical field, given the possibility to modify treatments during their delivery. Radiomics aims to quantitatively describe images in radiology by automatically extracting a large number of image features. In this context, PET/CT (Positron Emission Tomography/Computed Tomography) images are of great interest since they encode functional and anatomical information, respectively. In order to assess the patients' responses from many image features appropriate methods should be applied. Machine learning offers different procedures that can deal with this, possibly high dimensional, problem.

    The main objective of this work was to develop a method to classify lung cancer patients as responding or not to chemoradiation treatment, relying on repeated PET/CT images. Patients were divided in two groups, based on the type of chemoradiation treatment they underwent (sequential or concurrent radiation therapy with respect to chemotherapy), but image features were extracted using the same procedure. Support vector machines performed classification using features from the Radiomics field, mostly describing tumour texture, or from handcrafted features, which described image intensity changes as a function of tumour depth. Classification performance was described by the area under the curve (AUC) of ROC (Receiving Operator Characteristic) curves after leave-one-out cross-validation. For sequential patients, 0.98 was the best AUC obtained, while for concurrent patients 0.93 was the best one. Handcrafted features were comparable to those from Radiomics and from previous studies, as for classification results. Also, features from PET alone and CT alone were found to be suitable for the task, entailing a performance better than random.

  • 3.
    Charalampidis, Vasileios
    KTH, School of Technology and Health (STH).
    Real-Time Monitoring System of Sedentary Behavior with Android Wear and Cloud Computing: An office case study2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays, prolonged sitting among office workers is a widespread problem, which is highly related to several health problems. Many proposals have been reported and evaluated to address this issue. However, motivating and engaging workers to change health behavior to a healthier working life is still a challenge.

    In this project, a specific application has been deployed for real-time monitoring and alerting office workers for prolonged sitting. The proposed system consists of three distinct parts: The first one is an android smartwatch, which was used to collect sensor data e.g., accelerometer and gyro data, with a custom android wear app. The second one is an android application, which was developed to act as a gateway for receiving the smartwatch’s data and sending them to IBM Bluemix cloud with MQTT protocol. The final part is a Node-Red cloud application, which was deployed for storing, analyzing and processing of the sensor data for activity detection i.e., sitting or walking/standing. The main purpose of the last one was to return relevant feedback to the user, while combining elements from gaming contexts (gamification methods), for motivating and engaging office workers to a healthier behavior.

    The system was firstly tested for defining appropriate accelerometer thresholds to five participants (control group), and then evaluated with five different participants (treatment group), in order to analyze its reliability for prolonged sitting detection. The results showed a good precession for the detection. No confusing between sitting and walking/standing was noticed. Communication, storage and analysis of the data was successfully done, while the push notifications to the participants, for alerting or rewarding them, were always accurate and delivered on time. Every useful information was presented to the user to a web-based dashboard accessed through a smartphone, tablet or a PC.    

    The proposed system can easily be implemented at a real-life scenario with office workers. Certainly, there is a lot space for improvement, considering mostly the type of data registered at the system, the method for sitting detection, and the user interface for presenting relevant information.

  • 4.
    Gao, Bo
    KTH, School of Technology and Health (STH).
    Multigrid reconstruction of micro-CT data2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The group of Medical Imaging at School of Health and Technology is developing a micro-CT scanner for small animal imaging. Micro-CT refers to reconstructing CT image with resolution in scale of micrometer, and this goal is achieved by acquiring projection data with high resolution. Nevertheless, high resolution projection data and high resolution recon- struction image have introduced the problem of memory insufficiency, as more points need to be processed during micro-CT reconstruction.

    For this reason, this paper has investigated how to alleviate the burden on computers memory through applying multi-grid reconstruction algo- rithms, which means to reconstruct region of interest (ROI) with high resolution while reconstructing background with lower resolution. By do- ing that, pixels being considered in the reconstruction space has been decreased and normal computers will be capable to handle reconstruction of micro-CT image.

    Through testing on numerical data (Shepp Logan Phantom), it can be concluded that multi-grid reconstruction algorithm could reconstruct high fidelity ROI with much faster speed comparing to full resolution reconstruction. Moreover, this proposed technique can also give decent reconstruction to data acquired from micro-CT scanner. 

  • 5.
    Hubert, Alexis
    KTH, School of Technology and Health (STH). Elekta AB.
    Spectroscopic Study of Radiation around the Leksell Gamma Knife for Room Shielding Applications2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Any center planning to install a Gamma Knife radiosurgery unit has to provide for an efficient shielding of the treatment room, to protect the patient, the staff and the public, against undesired radiation. The shielding barrier design is controlled by national and international recommendations; the reference documents for gamma ray radiotherapy facilities are the National Council on Radiation Protection and Measurements (NCRP) reports 49 and 151. However, some facts highlighted in this thesis point out that NCRP methods are ill-adapted to the Gamma Knife. Spectroscopic measurements were performed around the Gamma Knife with a Germanium detector. They revealed that the radiation field contains few high energy photons, is highly anisotropic, and that the leakage level is much lower than the NCRP estimation. These observations led to the development of a new approach to determine the necessary shielding, based on the actual and directly measurable radiation field around the unit. This method would reduce the shielding oversizing induced by the unsuitability of the NCRP recommendations for the Gamma Knife.

  • 6.
    Jansson, Magnus
    KTH, School of Technology and Health (STH), Medical Engineering.
    A 3D-ultrasound guidance device for central venous catheter placement using augmented reality2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Central venous catheterization (CVC) is performed frequently in clinical practices in Operation Rooms(OR) and Emergency Rooms(ER). CVC is performed for different reasons such as supply nutrition or medicine. For CVC ultrasound (US), diagnostic device is preferable among other medical imaging technologies. Central Venous Catheterization (CVC) under the 2D US guidance requires skills for catheter placement to avoid damaging non-targeted blood vessels. Therefore, there is a great need for improvements in the CVC field where mechanical complication has a risk of occurring during the procedure, for example misplacement of the needle.

    This master thesis project was performed at Kyushu University department of mechanical engineering and collaboration with Maidashi Kyushu University Hospital department of Advanced Medicine and Innovative Technology in Japan. This thesis is aimed to develop a new simple and cheap guidance system for CVC placement. The system performed on a Tablet PC and will be using already existing Ultrasound machines in Hospitals and Augmented Reality(AR).

    The project developed a simple AR-System for CVC placement with use of the ArUco library. The new developed system takes information from Ultrasound images and constructs a 3D-model of a vein and artery. Then the 3D-model is augmented on the patient through the tablet PC by using the ArUco library. The construction and augmentation is all performed on the tablet PC and has a small computation to complete the necessary procedures for the 3D-blood vessels.

    The AR-system has a simple control where the interface of the system is a simple push and action system. When a good visualization of the blood vessels and Doppler effect is shown on the ultrasound machine, the surgeon presses the screen and the image is saved. After about five images are acquired, the system builds the 3D-model and augments it on the patient using a marker.

    For the development of this system it implemented the waterfall method where each step was tested and checked, before moving to the next step.

    A full functional system was developed and tested. From the tests performed it is shown that there were limitations due to segmentation and depth perception. But the system has possibilities as an aid for CVC placement.

  • 7.
    Karlsson, Frans
    et al.
    KTH, School of Technology and Health (STH).
    Kalmaru, Edvin
    KTH, School of Technology and Health (STH).
    Optimizing an Ultrasound Based Tissue Micro Engineering System: Optimering av ett Ultraljudsbaserat Cellmanipuleringssystem2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The usage of ultrasonic manipulation of cells enables a more in vivo-like study with maintained cell viability compared to ordinary systems based on 2D manipulation. The method can be applied for cell trapping and micro tissue engineering and has applications for medical and biological studies.  

    The current system used at the Department of Applied Physics, Royal Institute of Technology, needs characterization and optimization regarding its subsystems. This thesis has studied the setup in order to map the origins of heat generation, to improve the system arrangement. As a result, an overview of affecting factors has been presented. The thesis is based on temperature and bead measurements with and without the use of an impedance matching circuit and with/without amplifiers. It was found that the system could be optimized with a smaller and less expensive amplifier reducing the overall system costs. The thesis also resulted in a proposition for further work to optimize the system with respect to its subsystems. 

  • 8.
    Katrínardóttir, Hildigunnur
    KTH, School of Technology and Health (STH), Medical Engineering.
    Finite Element Modeling of Chest Compressions in CPR2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Factors affecting the risk of ribcage injury in adult subjects during CPR were investigated using the torso region of the THUMS model, a full human body FE-model, representing an average adult male. The thoracic dynamic response of the model was compared to experimental PMHS hub loading impact data and live-subject CPR data found in the literature. The model was then used to study the risk of obtaining injuries in various simulated CPR conditions, also varying the stiffness of the costal cartilage.

    Parameters that are known to predict induced injuries were extracted from the model simulations, i.e. chest deflections, and maximum 1st principal strain and von-Mises stress in the ribs and sternum, as well as the pressure in the heart muscle. These were compared with values that have been reported to have the potential to cause injury. The predictions were compared to experimental findings of the probability of CPR resulting in fractures of the ribs and sternum.

    The previously mentioned parameters did not reach high enough values to predict fracture occurrences, but interesting trends were highlighted with regards to the different loading conditions investigated. It was demonstrated that human body FE-model simulation studies can be useful for investigating the influence of different CPR related loading conditions on the risk of occurrences of rib and sternal fractures. 

  • 9.
    Mathay, Margaux
    KTH, School of Technology and Health (STH).
    Virtual planning of Total Knee Arthroplasty surgery: Assessment of implant positioning of different implanting types2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Increased workload on our healthcare system calls for more automation, this too in the pre-operative planning of total knee arthroplasty (TKA) surgery. This should keep in mind however that success in TKA is measured through having proper limb alignment. This thesis project implemented a virtual positioning assessment software that provides an initial position based on its bone and implant inputs with their specific landmarks. Positions can be furtherly adapted and evaluated based on flexion facets, obtaining decreased pre-operative workloads. The software was validated through an analysis comparison of the femur positioning of nine cases with the former used analysis tool of the university Hospital of Ghent. The newly implemented software was concluded to approximate the patients’ pre-operative alignment better for all translational and rotational parameters, except anteroposterior translation and internal/external rotation of the femur.

  • 10.
    Mecconi, Alessandro
    KTH, School of Technology and Health (STH).
    Dopamine replacement therapy reduces beta band burst duration in Parkinson’s disease2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the main characteristics of Parkinson's disease (PD) is an exaggerated oscillatory activity in the beta band (12-30 Hz). This activity has been linked to the rise of symptoms such as bradykinesia and akinesia. Even if dopamine replacement therapy (oral intake of dopamine pro-drug levodopa) reverses these symptoms, the effect of the treatment on the beta band activity has still not been completely understood. Therefore, here the temporal dynamics of beta band activity in human patients affected by PD were characterized with and without levodopa treatment. Local-field-potential (LFP) recordings from five patients undergoing dopamine replacement therapy were used. From the LFPs, the extracted beta epochs with significantly higher power than expected from a comparable noisy signal were analyzed. This analysis showed that beta band activity occurred in bursts meaning that high amplitude oscillation alternated with silenced periods. The pathological state also distinguished itself for longer epochs and with power that increased with the length of the epoch. The administration of levodopa reduced the duration of bursts and decreased the overall mean power of the beta band activity. Finally, epochs with the same number of cycles were compared. The Coefficient of Variation prior such epochs suggested that the ongoing activity might lock into a synchronization process prior the burst. These results provide important information to better understand how levodopa alleviates some of the symptoms of PD and pave the way to develop better computational models for the emergence of beta oscillations.

  • 11.
    Mozzi, Giuliana
    KTH, School of Technology and Health (STH).
    Finite Element Modeling of an Innovative Headband: A study about the headband design and its safety properties2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the most recent challenges faced worldwide is the so-called “ageing population” phenomenon. Besides the disabilities and illnesses that the elderly is prone to, traumatic brain injuries represent a common and potentially fatal factor that greatly affects this population. Other subjects are however also likely to experience traumatic brain injuries i.e. people affected by some kinds of diseases and disorders such as epilepsy and dementia that are known to have a high risk of falling. Furthermore, sports accidents can also lead to traumatic brain injuries, for example cycling. Current solutions and devices for head injury prevention are limited and from a design point of view there is space for improvements. The focus of this master thesis is to model an innovative headband meant to be worn around the scalp during various daily life activities and in multiple situations. Its function is to prevent the wearer from traumatic brain injuries. The headband model is a finite element model, created in LS-PrePost. Subsequently, simulations are performed in LS-Dyna to replicate real life head impact scenarios. Different parameters and features of both the impacting condition and the headband are tested for creating the optimal headband structure for head injury prevention.

  • 12.
    Munkhammar, Tobias
    KTH, School of Technology and Health (STH).
    Ground Reaction Force Prediction during Weighted Leg Press and Weighted Squat in a Flywheel Exercise Device2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When performing a biomechanical analysis of human movement, knowledge about the ground reaction force (GRF) is necessary to compute forces and moments within joints. This is important when analysing a movement and its effect on the human body. To obtain knowledge about the GRF, the gold standard is to use force plates which directly measure all three components of the GRF (mediolateral, anteroposterior and normal). However, force plates are heavy, clunky and expensive, setting constraints on possible experimental setups, which make it desirable to exclude them and instead use a predictive method to obtain the full GRF. Several predictive methods exist. The node model is a GRF predictive method included in a musculoskeletal modeling software. The tool use motion capture and virtual actuators to predict all three GRF components. However, this model has not yet been validated during weighted leg press and weighted squat. Furthermore, the normal component of the GRF can be measured continuously during the activity with pressure sensitive insoles (PSIs), which might provide better accuracy of the GRF prediction. The objectives of this thesis were to investigate whether force plates can be exluded during weighted leg press and weighted squat and to investigate whether PSIs can improve the GRF prediction. To investigate this, the node model and a developed shear model was validated. The shear model computes the two shear GRF components based on data from PSIs, an external load acting upon the body and data from a motion capture system. Both the node model and the shear model were analysed with two test subjects performing two successive repetitions of both weighted squat and weighted leg press in a flywheel exercise device. During the leg press exercise, the node model had a mean coeffcient of correlation (Pearson's) ranging from 0.70 to 0.98 for all three directions with a mean root mean square error ranging between 8 % to 20 % of the test person's body weight. The developed shear model had a coeffcient of correlation (Pearson's) between 0.64 to 0.99 and a mean root mean square error between 3 % and 21 % of the test person's body weight. This indicates that it is possible to exclude force plates and instead predict the GRF during weighted leg press. During squat, neither the node model nor the shear model provided accurate results regarding the mediolateral and anteroposterior components of the GRF, suggesting that force plates can not yet be excluded to obtain the full GRF during weighted squat. The results of the normal component during leg press was somewhat improved with the shear model compared to the node model, indicating that using PSIs can improve the results to some extent.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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. 

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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
  • 22.
    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.

  • 23.
    Winther, Viktor
    KTH, School of Technology and Health (STH).
    Translation of Clinical Rupture Risk Factors for the Biomechanics based AAA Simulations2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The abdominal aorta is the largest blood vessel in the abdomen and the main supplier of blood to the lower body. An abdominal aortic aneurysm (AAA) is an unnatural enlargement of the abdominal aorta, which is a serious condition with a high risk of mortality. If the aneurysm exceeds a certain diameter or growth rate, surgical interventions are justified. Use of a diameter-based criterion has been proven to be inaccurate though since some smaller aneurysms can rupture whilst some larger aneurysms remain quiescent. A biomechanical rupture risk assessment (BRRA) that utilizes the finite element method can be used to evaluate the risk of aneurysm rupture. The BRRA calculates the stresses in the aneurysm based upon CT scans and patients blood pressure. Comparing the stresses with the strength of wall in the aneurysm makes it possible to evaluate the risk of rupture. If the stress exceeds the strength, the aneurysm will rupture. To calculate the strength of the vessel wall, a strength equation is used. The strength equation consists of risk factors such as family history, gender, intra luminal pressure and aneurysm diameter. To individualize the assessment further it would be possible to identify and use other risk factors.

    Rupture risk factors were searched for through two spate literature searches. To identify the risk factors the search utilized keywords such as “rupture risk factors” and “abdominal aortic aneurysm” together with “peak wall stress” or “wall stress”. The search also used a state of the art article from previous research, which contained a list of risk factors that could be searched for. For a factor to be used in this study they had to be global risk factors. Instead of increasing the risk of rupture in a localised point in the aneurysm, a global factor affects the aneurysm uniformly throughout its entirety.

    The search focused on statistical trials that evaluate the factors impact on wall stress or wall strength. An AAA wall strength equation was constructed based on the rupture risk factors that were identified. This equation was translated into the Finite element analysis program (FEAP) to evaluate its behaviour. A statistical analysis was performed in Matlab using data from the program A4CLINICS developed by VASCOPS gMBh. Using 41 patients along with known patient characteristics and CT scans Biomechanical rupture risk assessment (BRRA) was conducted using the new strength equation.

    The assessment resulted in a new peak wall rupture index (PWRI). The resulting data was separated into two groups based upon their volume growth rate, one fast growing and one slow growing group. This separation was done for both the VASCOPS strength equation and the new one. Pearson correlation testing was used to test the correlation between both strength equations and volume growth or diameter growth. To evaluate the sensitivity of the strength equation, receiver operating characteristics (ROC) curves were also used.

    The PWRI in fast and slow groups were not different (p-values of 0.1257 for VASCOPS and 0.0679 for the new equation). The Pearson correlation coefficients showed a higher correlation between new PWRI and volume growth compared to diameter growth. The new PWRI had a higher sensitivity for predicting the volume growth compared to the diameter growth. Initial volume and diameter had the highest sensitivity of all predictors.

    The new PWRI could be used to predict volume growth. Volume growth is a potential predictor of aneurysm rupture, which indicates the new PWRI can be used in the BRRA. But to achieve results with statistical significance, new simulations using larger population must be performed and the strength equation must be revised.

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