Masters Degrees (Institute For Biomedical Engineering (IBE))

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Now showing 1 - 5 of 7
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    Development of a computer vision pipeline for the analysis of Aliivibrio fischeri bioluminescence inhibition on solid media
    (Stellenbosch : Stellenbosch University, 2023-11) Parker, IA; Stone, W; Perold, WJ; Schreve, K; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
    ENGLISH ABSTRACT: The South African Government aims to promote a circular economy, particularly upcycling organic waste, to improve soil quality in the Western Cape. Notably, wastewater sludge, abundant with organic nutrients, also contains harmful micropollutants. Thus, a reliable, on-site toxicity measurement method is essential. This study introduces an in-field technology to assess micropollutant toxicity in soil and water leachate samples and gauge bioremediation or bioaccumulation levels post-sludge application. The study leverages the bioluminescent properties of Aliivibrio fischeri, commonly known as Vibrio fischeri, as a toxicity indicator. Initial experiments using an optical microbial biosensor in liquid media showed inconsistent results due to hypoxic culture conditions. Subsequent experiments on solid media, employing computer vision and machine learning, demonstrated the consistent inhibition of Vibrio fischeri bioluminescence, serving as an effective toxicity marker. Test compounds, zinc sulphate and atrazine, validated the approach, aligning with existing literature on their toxicity levels. Machine learning models predicted treatment states and concentrations accurately using EC50 estimates. This research is foundational for a mobile diagnostic application for farmers to swiftly and accessibly gauge soil and water quality.
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    Strengthening the value chain of medical devices : a conceptual framework
    (Stellenbosch : Stellenbosch University, 2023-03) Turner, Anne Mary Margaret; Grobbelaar, Sara; Nieuwoudt, Martin; Salie, Faatiema; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
    ENGLISH SUMMARY: The medical device value chain (MDVC) describes every value-adding activity (VA) in Idea generation, Research & Development, Production/ Manufacturing, Market, Distribution & Use, Waste Management, and those that occur Systemically. The medical device industry is highly complex and comprises multidisciplinary stakeholders, typically from Academia, Industry, Healthcare or Government. Much literature examines parts of the MDVC or variations thereof. However, a full MDVC map that facilitates a holistic approach to bottleneck alleviation has yet to exist. Additionally, incorporating multiple perspectives is valuable, given the various roles that add value along the chain. This research project addresses the need for a holistic MDVC map by implementing a Design Science Research (DSR) approach to develop a conceptual framework. The MDVC framework, created in this study, structures how insights can be generated from value chain analysis, fishbone analysis, functional analysis and qualitative analysis to support identifying and alleviatingMDVC bottlenecks. By mapping every VA, bottlenecks can be located, targeted and alleviated. The research design implemented is divided into two phases and five components. Phase one is theoretical and incorporates two rigour cycles to inform the first design cycle. A preliminary review, two systematic literature reviews and one conceptual literature review identify the necessary MDVC categories, VAs, bottlenecks, and alleviations used to inform the conceptual framework. The existing frameworks for strengthening MDVCs (or variations thereof) are identified and support the development of domain concepts to which fishbone analysis could contribute. Thereby, an initial framework is developed based on the existing knowledge base. Phase two is evaluative and incorporates three components to refine the MDVC framework and ensure the practical value of the artefact. The MDVC framework is evaluated using two relevance cycles according to the DSR approach. The first relevance cycle validates the MDVC developed through obtaining feedback from an MDVC stakeholder. The second relevance cycle evaluates the efficacy, quality, and generalisability of the initial MDVC framework through expert reviews. The expert reviews consist of semi-structured interviews and surveys with 17 South African stakeholders representative of the multidisciplinary expertise found in the medical devices industry. The expert reviews confirm the quality and efficacy of the MDVC framework and highlight findings such as the need for a structured process for identifying and alleviating bottlenecks. The results are translated into conceptual and structural improvements during the second design cycle to develop suggestions for a refined MDVC framework. Bottlenecks in the Western Cape’s MDVC are identified systematically as a result. This involved value chain-, fishbone-, functional- and qualitative analysis. Alleviations are also suggested as a result of the value chain- and the qualitative analysis. The findings thus contribute to strengthening the Western Cape’s MDVC as bottlenecks are identified across the chain, and alleviations are suggested. This study adds to the foundation of MDVC research. However, future iterations of the MDVC framework and a more vast interviewee pool are necessary to translate these findings into a more meaningful impact. Study limitations and recommendations are discussed last.
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    Cost Analysis of an Additive Manufacturing Laboratory for 3D Printed Anatomical Models in Orthopaedic Pre-Surgical Planning and Surgery.
    (Stellenbosch : Stellenbosch University, 2023-03) Kotze, L; Van der Merwe, J; Venter, RG; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
    ENGLISH ABSTRACT: The primary problem to be investigated is the need to know how much the individual activities of the three-dimensional printing (3DP) production process contribute to the overall cost per patient. How much to quote internal orthopaedic surgeons before performing the 3DP production process is also unknown and the secondary problem to be investigated. Lastly, the tertiary problem to be investigated is the need to know how much samples 3D printed in different filaments would melt or deform after being exposed to low-temperature ethylene oxide (EtO) or autoclave sterilisation. In the 3DP production process, the investigator used dedicated software packages to create virtual 3D anatomical models from patients’ anonymised computed tomography (CT) or magnetic resonance imaging (MRI) scans for Fused Filament Fabrication (FFF) 3DP (designated as simulation models) and EtO or autoclave sterilisation (designated as haptic maps). Afterwards, a cost estimation model was developed to estimate the direct cost per patient, which was validated by comparing the cost estimates to the cost model results of three new patient cases. Furthermore, samples made from acrylonitrile butadiene styrene (ABS), nylon and polylactic acid (PLA) were sterilised by using low-temperature EtO and autoclave sterilisation. Thereafter, samples were measured with a digital vernier calliper to obtain postprinting and post-sterilisation linear measurements in metres (m). Results were expressed as means ± standard deviations for the total linear differences and absolute percentage errors. In the cost model study, image segmentation and manufacturing costs contributed 31 % and 45 % to the direct cost per patient, respectively. The direct costs of two patient cases were overestimated by 61 % and 74 %, respectively. In conclusion, optimising the image segmentation and manufacturing times of the 3DP production process may make medical 3DP more viable for use in orthopaedic applications and reduce the direct cost per patient. Also, the cost model may not be accurate to estimate the direct cost per patient due to the overestimation of costs in the validation dataset. In the dimensional accuracy testing study, ABS (-1,03E-5 ± 1,65E-4 m) and PLA (-1,01E-4 ± 4,62E-4 m) were the most affected by EtO sterilisation and shrunk in mean linear differences as opposed to nylon (6,43E-6 ± 2,08E-4 m). Furthermore, ABS (-2,52E-4 ± 1,28E-3 m) and PLA (-2,30E-4 ± 7,06E-4 m) were the most affected by autoclave sterilisation and shrunk more in mean linear differences as opposed to nylon (-4,20E-5 ± 2,96E-4 m). To conclude, nylon was preferred as a suitable material for both low-temperature EtO (preferably) and autoclave sterilisation to sterilise haptic maps. The primary problem to be investigated is the need to know how much the individual activities of the three-dimensional printing (3DP) production process contribute to the overall cost per patient. How much to quote internal orthopaedic surgeons before performing the 3DP production process is also unknown and the secondary problem to be investigated. Lastly, the tertiary problem to be investigated is the need to know how much samples 3D printed in different filaments would melt or deform after being exposed to low-temperature ethylene oxide (EtO) or autoclave sterilisation. In the 3DP production process, the investigator used dedicated software packages to create virtual 3D anatomical models from patients’ anonymised computed tomography (CT) or magnetic resonance imaging (MRI) scans for Fused Filament Fabrication (FFF) 3DP (designated as simulation models) and EtO or autoclave sterilisation (designated as haptic maps). Afterwards, a cost estimation model was developed to estimate the direct cost per patient, which was validated by comparing the cost estimates to the cost model results of three new patient cases. Furthermore, samples made from acrylonitrile butadiene styrene (ABS), nylon and polylactic acid (PLA) were sterilised by using low-temperature EtO and autoclave sterilisation. Thereafter, samples were measured with a digital vernier calliper to obtain postprinting and post-sterilisation linear measurements in metres (m). Results were expressed as means ± standard deviations for the total linear differences and absolute percentage errors. In the cost model study, image segmentation and manufacturing costs contributed 31 % and 45 % to the direct cost per patient, respectively. The direct costs of two patient cases were overestimated by 61 % and 74 %, respectively. In conclusion, optimising the image segmentation and manufacturing times of the 3DP production process may make medical 3DP more viable for use in orthopaedic applications and reduce the direct cost per patient. Also, the cost model may not be accurate to estimate the direct cost per patient due to the overestimation of costs in the validation dataset. In the dimensional accuracy testing study, ABS (-1,03E-5 ± 1,65E-4 m) and PLA (-1,01E-4 ± 4,62E-4 m) were the most affected by EtO sterilisation and shrunk in mean linear differences as opposed to nylon (6,43E-6 ± 2,08E-4 m). Furthermore, ABS (-2,52E-4 ± 1,28E-3 m) and PLA (-2,30E-4 ± 7,06E-4 m) were the most affected by autoclave sterilisation and shrunk more in mean linear differences as opposed to nylon (-4,20E-5 ± 2,96E-4 m). To conclude, nylon was preferred as a suitable material for both low-temperature EtO (preferably) and autoclave sterilisation to sterilise haptic maps.
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    Investigating the effect organic tissue has on the electromagnetic waves when targeting the visual cortex
    (Stellenbosch : Stellenbosch University, 2023-03) Dreyer, Rita Liezl; Van der Merwe, J.; Van den Heever, Dawie; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
    ENGLISH SUMMARY: The concept of using electromagnets to stimulate the visual cortex to elicit a phosphene response in the visual field is not novel. Instead, it is the basis of one of the prefered non-invasive neurostimulation methods to address vision loss. The problem, however, lies in the lack of effectiveness and specificity of electromagnetic-based prostheses. The current trend is to improve the design of micro-scale magnetic coils. The effect of the organic tissue, explicitly human organic layers over the visual cortex, on electromagnetic waves has not been explored yet. This study aimed to investigate how organic tissues (skin, facia, skull and meninges) affect electromagnetic waves targeting the visual cortex. This effect should be considered when calibrating electromagnetic-based neurostimulation devices. This study focused explicitly on the maximum field strength, RMS (root-mean-square) value of an alternating current (AC) waveform and the difference between the input and output frequencies. The study tested individual layers of organic tissue and the amalgamation of the layers, including a section of the visual cortex, at 5, 10, 15, 20, and 25 Hz. A bloodless pig's head proved to be a reliable test material since it is physiologically and anatomically similar to human tissue. A fluxgate was used as a sensor to detect changes in all three axes, as the visual cortex is a three-dimensional area. To minimise external interference, the experiment was conducted in a wooden box on the premises of the South African National Space Agency (SANSA), as it has buildings that have minimal electromagnetic interference. The frequency and sinusoidal wave format were controlled by a signal generator, while a DC power supply controlled the current and power. A single pig's head was dissected, with each layer placed in a plastic ziplock bag. The individual layers were tested by placing them between the electromagnet and the fluxgate on a wooden frame held up by a wooden jig. Each test was conducted three times while keeping the distance constant. Temperature control was considered; however, due to electromagnetic interference, the set-up was removed. The experiment was conducted instead at a room temperature of 30 °C. The results showed, unexpectedly, that organic tissue generally increased rather than decreased the magnetic field (maximum field strength, RMS). This trend was observed in the z-, y- and x-axes, where the z-axis had the highest magnetic strength, and the x-axis had the lowest. The effect of the organic tissue was dependent on the input frequency and the type of organic tissue used. The results observed in each axis were independent of the other axes. Only organic tissues of the skin, skull, and brain had an impact on the frequency. One could hypothesize that variations in the output frequencies for these particular organic tissues were caused by the resonance frequencies of these tissues. The findings of this thesis can help to calibrate electromagnetic-based visual prostheses in order to increase the effectiveness and specificity of the devices. However, further studies on a human model should be conducted for more precise calibration.
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    The Influence of neck muscle characteristics on head kinematics during lateral impacts : a simulation based analysis
    (2023-03) Bergh, Oloff Charles Wessel; Van der Merwe, Johan; De Jongh, Cornel; Derman, Wayne; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
    ENGLISH SUMMARY: The skull contains the most critical component of the human body, the brain. Large changes in the velocity and acceleration of the skull, specifically in an angular manner, have been associated with an increased risk of concussion or mild traumatic brain injuries. Modifiable risk factors can be defined as intrinsic characteristics that can be altered to decrease the risk of head injury. Previous studies have investigated neck muscle strength as a potential modifiable risk factor in sports research. However, literature appears to be divided regarding the influence of neck muscle strength on head kinematics and injury risk. Additionally, research associated with individuals who demonstrate a decline in neck muscle strength compared to control subjects appears to be scarce, potentially due to ethical concerns. This project aims to contribute to current literature and evaluate the influence of neck muscle characteristics, such as the maximum isometric and eccentric strength, on the kinematics of the skull during laterally induced head collisions through a simulation-based approach. Multibody dynamic computer models were used to determine the influence of neck muscle characteristics on head kinematics and subsequent head injury risks. The models were based on the original Hyoid model in OpenSim by Mortensen, Vasavada and Merryweather (2018), which has been verified and validated against experimental responses with similar total neck muscle strength values. The Normal model in this project demonstrated the same muscle characteristics as the original Hyoid model. The two stronger models, referred to as the Intermediate and Max models, have increases in maximum isometric and eccentric muscle strength compared to the Normal model. The Intermediate model has realistic achievable neck muscle characteristics of an individual who has undergone specific neck training, while the Max model represents a highly trained athlete with significantly strengthened neck musculature. The Decreased model has lower total neck muscle strength compared to the Normal model and is based on the reductions in muscle characteristics of elderly individuals. The static optimization tool within the OpenSim environment was used to determine the optimal muscular activations of the different models. These activations were subsequently used in the forward dynamic tool to determine the influence of the neck muscle characteristics on head kinematics during increasing lateral impacts. The head kinematics were then used to calculate the head injury criterion (HIC15), a commonly used metric to determine the extent of head injuries based on empirical data. The stronger models consistently showed lower head kinematic and HIC15 values compared to the Normal model, while the Decreased model always demonstrated higher kinematics with a greater risk of injury. At a low external force there was a considerable influence of the neck muscle characteristics on head kinematics and injury risk. However, a non-linear trend indicated that the influence of the neck muscles declined as the external force increased. This could indicate that the influence of the neck muscle characteristics might be overshadowed by large external forces, but could still play a role in reducing head kinematics and injury-risk at lower forces.