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  • 151.
    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.

  • 152.
    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.

  • 153.
    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.

  • 154.
    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. 

  • 155.
    Wikström, Stephanie
    et al.
    KTH, School of Technology and Health (STH).
    Huisman, Simon
    KTH, School of Technology and Health (STH).
    The infant incubator from a hygienic and HTO perspective: Using ATP luminescence to identify problem areas and suggesting solutions2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Healthcare associated infections (HCAI) are a major problem in healthcare today. Preterm infants have problems keeping their body temperature within normal boundaries due to heat-loss. They therefore need special care that is administered with the help of incubators, which help minimise the heat loss via convection. Within neonatology the incubator has been identified as one of the contributing factors to HCAI due to the warm and humid environment, making it easy to spread nosocomial flora.

    To assess if the incubator is a factor in the spreading of HCAI this project has focused on ATP+AMP (total ATP) luminescence measurements to find areas in the incubator that are likely to contribute to the spread of HCAI and suggesting solutions to some of these. Adenosine triphosphate (ATP) is found in both organic debris and bacteria and is therefore a good indicator of a problem area due to organic debris acting as nutrients. Only the incubator box of the Giraffe® OmniBed® incubator was studied.

    The cleaning process was observed on multiple occasions and together with interviews resulted in a number of 29 hypothesised problem areas, on or within the incubator box, that were measured before and after cleaning. The results show that incubators collect a substantial amount of total ATP during its use. Measurements also show that parts that are cleaned by a disinfector are cleaner than those parts that are cleaned manually. Areas on the main compartment became more contaminated after cleaning which further indicated that the design of the incubator needs improving. It was also concluded that there often was residue from soap left on the surface of the main compartment resulting in inhibition of the total ATP luminescence reaction. This resulted in unrealistic low values due to the inclusion of foam and soap in the sample and as a result 45 out of 570 measurements were excluded. Caution is advised when using the Kikkoman total ATP luminescence method, especially on the main body (chassis) of the incubator.

    A steam vapour cleaner and flask cleanser brush could be used to better reach and clean areas such as cavities and around the bed heating element. The use of the steam vapour cleaner could also diminish or eliminate the use of surface disinfectant that causes red irritated eyes and dizziness in the cleaning staff. The functionality of the incubator was found to be excellent but major improvements can be made in the incubator design to make the cleaning of the incubator easier.

  • 156.
    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.

  • 157.
    Wu, Weiling
    KTH, School of Technology and Health (STH).
    Carbon Footprint: A case study on the municipality of Haninge2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    AbstractCarbon Footprints, as an indicator of climate performance, help identify major GHG emission sources and potential areas of improvement. In the context of greatly expanding sub-national climate efforts, research on Carbon Footprint accounting at municipality level is timely and necessary to facilitate the establishment of local climate strategies. This study aims at exploring the methodologies for Carbon Footprint assessment at municipality level, based on the case study of Haninge municipality in Sweden. In the study, a Greenhouse Gas inventory of Haninge is developed and it is discussed how the municipality can reduce its Carbon Footprint. The Carbon Footprint of Haninge is estimated to be more than 338,225 tonnesCO2eq, and 4.5 tonnes CO2eq per capita. These numbers are twice as large as the production-based emissions, which are estimated to be 169,024 tonnes CO2eq in total, and approximately 2.3 tonnes CO2eq per capita. Among them the most important parts are emissions caused by energy use, and indirect emissions caused by local private consumption. It is worth noting that a large proportion of emissions occur outside Haninge as a result of local consumption. Intensive use of biomass for heat production and electricity from renewable sources and nuclear power have significantly reduced the climate impact of Haninge. The major barrier for Carbon Footprint accounting at municipality level is lack of local statistics. In the case of Sweden, several databases providing emission statistics are used in the research, including KRE, RUS, NIR and Environmental Account.

     

  • 158.
    Yang, Liyun
    KTH, School of Technology and Health (STH).
    Development and validation of a novel iOS application for measuring arm inclination2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Work in demanding postures is a known risk factor for work-related musculoskeletal disorders (MSDs), specifically work with elevated arms may cause neck/shoulder disorders. Such a disorder is a tragedy for the individual, and costly for society. Technical measurements are more precise in estimating the work exposure, than observation and self-reports, and there is a need for uncomplicated methods for risk assessments. The aim of this project was to develop and validate an iOS application for measuring arm elevation angle.

    Such an application was developed, based on the built-in accelerometer and gyroscope of the iPhone/iPod Touch. The application was designed to be self-exploratory. Directly after a measurement, 10th, 50th and 90th percentiles of angular distribution and median angular velocity, and percentage of time above 30°, 60°, and 90° are presented. The focused user group, ergonomists, was consulted during the user interface design phase. Complete angular datasets may be exported via email as text files for further analyses.

    The application was validated by comparison to the output of an optical motion capture system for four subjects. The two methods correlated above 0.99, with absolute error below 4.8° in arm flexion and abduction positions. During arm swing movements, the average root-mean-square differences (RMSDs) were 3.7°, 4.6° and 6.5° for slow (0.1 Hz), medium (0.4 Hz) and fast (0.8 Hz) arm swings, respectively. For simulated painting, the mean RMSDs was 5.5°.

    Since the accuracy was similar to other tested field research methods, this convenient and “low-cost” application should be useful for ergonomists, for risk assessments or educational use. The plan is to publish this iOS application on Apple Store (Apple Inc.) for free. New user feedback may further improve the user interface.

  • 159.
    Yang, Zhen
    KTH, School of Technology and Health (STH).
    Ståställningens påverkan på lederna i de nedre extremiteterna: en pilotstudie2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

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

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

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

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

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

  • 160.
    Ye, Luming
    KTH, School of Technology and Health (STH), Medical Engineering.
    Perception Metrics in Medical Imaging2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 161.
    Zheng, Miaomiao
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Ultrasound Contrast Agents: Fabrication, size distribution and visualization2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ultrasound contrast agents composed of micro-bubble filled with gas are introduced to increase the backscattered power from blood. Their intravenously injection results in the improved contrast in the images.

    The aim of this master thesis project is to manufacture MB suspension at varied temperature and shear forces and to inspect the size distribution and concentration of the PVA-shelled micro-bubble with standard methods according to the developed protocol. A pulser-receiver (Panametrics PR 5072) setup combined with two transducers (2.25 MHz and 5 MHz) was used to investigate the backscattered enhancement of the micro-bubble suspension.

    Images were collected with transmission optical microscope (OLYMPUS IX71) with the aid of counting chamber. The diameter and concentration of the micro-bubbles were analyzed by Image J. The pulser-receiver setup was used to test the acoustic response.

    The mean diameter of micro-bubbles was from 2.03 to 4.38 µm with a standard deviation between 0.40 and 1.12 µm and the micro-bubble concentration varied from 0.07× to 5.22× MBs/ml. The enhancement of the ultrasound backscattered power was greater than 20 dB or even reached 30 dB when the energy was increased. 

  • 162.
    Zhong, Xueying
    KTH, School of Technology and Health (STH), Medical Engineering.
    Mucin preparation and assembly into new biomaterials2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mucins, the main macromolecular constituent responsible for gel-forming property in mucus, have great potential to act as new biological hydrogel for medical applications. Click chemistry reaction is an attractive tool to be applied in both bioconjugation and material science to form covalent bonds between molecules. Herein the click chemistry reaction of tetrazine-norbornene ligation was adapted to form click mucin hydrogel using purified commercial available bovine submaxillary mucin (BSM). This study included the characterization, purification and chemical modification of commercial available BSM. The flow filtration purification was chosen after investigating the effectiveness and yields of four different purification strategies. The reactivity of tetrazine and norbornene-functionalized BSM was evident from the formation of robust mucin hydrogel within minutes after mixing the two components. 

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