Institute For Biomedical Engineering (IBE)

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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.
Development of a computer vision pipeline for the analysis of Aliivibrio fischeri bioluminescence inhibition on solid media
(Stellenbosch : Stellenbosch University, 2023-11) Parker, Irshaad Ahmad; 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.
Healthcare ecosystem development: exploring SME participation and innovative engagement in digital platform-based ecosystems.
(Stellenbosch : Stellenbosch University, 2023-11) Mbanefo, CC; Grobbelaar, SS; Botha, Alfred ; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
ENGLISH ABSTRACT: The concept of the ecosystem has gained significant traction within the business realm, primarily as a metaphorical structure. It describes an economic community that thrives on interdependent relationships among various organisations, businesses, firms and individuals. These entities interact and integrate their resources to co-create value. In light of this, digital platform ecosystems have found widespread application across diverse sectors, including marketplaces, automobiles, information and communication technology, education, and housing. This, in turn, has facilitated increased involvement of Small and medium-sized enterprises (SMEs) and consumers in the sharing economy. However, existing research has primarily focused on the role of platform orchestrators and the dynamics between firms and customers, mainly neglecting the comprehensive examination of engagement practices among diverse actors driving the ecosystem. Consequently, gaining a holistic understanding of the interplay between subsystems and engagement practices of ecosystem actors becomes challenging. This knowledge gap impedes platform ecosystems' development, support, and sustainability in healthcare delivery. The study adopted Design Science Research as an essential approach for addressing human problems and contributing new knowledge. Within this structure, the Design Science Research Methodology (DSRM) was utilised to facilitate the development of a management tool and guide the overall research process. The DSRM encompasses six distinct activities, each serving a specific purpose in achieving the study’s objectives: problem identification and motivation, definition of solution objectives, design and development, demonstration, evaluation, and communication. From a theoretical standpoint, this study sought to conceptualise a framework that supports the participation and innovation of SMEs within digital platform-based ecosystems. This research enriches the existing literature on healthcare ecosystems by identifying the foundational elements that platform orchestrators and SMEs consider. It sheds light on the intricacies of value co-creation within multisided platforms. The study conducted a comprehensive review of relevant literature to identify and categorise the core elements for platform development and SME participation, encompassing conceptual, systematised, and scoping reviews. Accordingly, the study delved into eight aspects of platform ecosystem development, including dynamic capabilities, enterprise architecture, digital transformation, resource integration, value co-creation, social innovation, community management, and standards, elucidating their contextual applications. The study's response to the research question materialised in a framework and management tool tailored for SMEs engaged in platform ecosystems, known as the SME Participation and Innovation in Platform Ecosystems (SPIPE) framework. The SPIPE framework and management tool were designed to enable platform orchestrators and SMEs to participate and engage in platforms through innovative means actively. Through subject-matter expert reviews, ranking exercises, and a case study of a South African healthcare platform ecosystem, the framework was contextualised within internal and external environmental opportunities, ensuring the adaptability and efficacy of the SPIPE tool in diverse settings, ultimately enabling the attainment of desired outcomes. The study demonstrates that the utilisation of the SPIPE framework offers a systematic and structured approach for effectively integrating multiple actors in developing, implementing, and managing platform ecosystems. By employing the framework and management tool, healthcare delivery and service providers can navigate the intricacies of these ecosystems more efficiently, thereby optimising their operations and enhancing overall healthcare service quality.
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.
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.
Nucleic acid capture and release device.
(Stellenbosch : Stellenbosch University, 2022-04) Rabikoosun, Sagal; Nieuwoudt, MJ; Warren, R; Grobbelaar, M; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
ENGLISH SUMMARY: This project research aims to design a prototype device to extract nucleic acids, mainly from lysed Mycobacterium Tuberculosis cells. The proposed device would be an industry asset that provides a time-saving preparatory step for downstream genome sequencing of Mycobacterium Tuberculosis and its drug-resistant variants. Existing literature indicates that using a positive potential will electrostatically attract nucleic acids due to the negatively charged phosphate backbone in the nucleic structure. The design process is divided into phases, including planning, concept design, embodiment design, detail design, testing, and production. This project focuses on aspects of project planning to detail design; however, recommendations for testing and production are indicated. A series of experiments were developed to demonstrate that a positive potential induces a migration of nucleic acids and to display that a usable quantity of nucleic acids is released when the voltage is reversed. The testing phase includes experiments to determine the impacts of material choice, presence of a coating, the applied voltage, capture/release times, device geometry, and the influence of biological contaminants. A prototype design is proposed from these results, with an acceptance testing plan and suggestions for refinement. The quality and quantity of captured nucleic acid can be determined using several processes. In this project, to quantify changes in nucleic acid concentration, a Qubit fluorometer was used. Observations include that gold and palladium remain viable material choices; however, collection with single uncoated probes with larger surface areas works best. Nafion-coated probes collect a comparable quantity of nucleic acids regardless of the surface area, number of probes, or geometric design. The presence of a surface coating during both capture and release and a buffer during collection improved experimental repeatability. During the release, Nafion coated probes repelled nucleic acids faster than uncoated probes. However, the mean quantity of nucleic acids released is lower than that of the uncoated probe. More rigid probes are less time-consuming to surface coat and are less likely to recapture nucleic acids during the sampling process and released the most nucleic acids. In the 2-probe setup, some of the released nucleic acids are recaptured on the secondary probe once polarity is reversed and voltage lowered by 0.5 V to reduce the power output. Saturation limits were reached during the +2.5 V capture experiment at the 6 min interval on uncoated probes. All probes also reached saturation limits during the Nafion release experiment at the 1 min, 30 s interval. Nafion coatings were found to degrade in 5 % NaClO in 30 min. It is apparent that a single rigid uncoated probe of as large as reasonably possible surface area will attract the most nucleic acid in 6 min. Reversing the polarity of the probe in a buffer capture solution will gradually repel nucleic acids from the probes until an eventual saturation limit is assumed to be released, after the 2 min, 15 s interval has passed. Using a surface coating on a probe and a 2-probe setup is not advised to optimise mass captured or experimental time.
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.
Utilizing virtual reality as a therapeutic tool psychiatry
(Stellenbosch : Stellenbosch University, 2022-04) Du Plessis, Stefan; Van den Heever, D. J.; Schreve, K.; Rosenstein, D.; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
ENGLISH ABSTRACT: The mass production of modern cellphone technology has resulted in a dra matic cost reduction of producing Virtual Reality (VR) head-mounted dis plays. Although VR has been effective in the treatment of phobias, uptake is still far from mainstream. Fear of heights (i.e. acrophobia) is one of the more common forms of phobias in the general population. Up to 28% of people have distress and anxiety when exposed to heights (i.e. visual heights intoler ance (VHI)), with up to 6% of people meeting clinical criteria for the specific phobia. Virtual Reality Exposure Therapy (VRET) for acrophobia has been shown to be effective as early as the 1990s. There are, however, still relatively few randomized controlled studies that have looked at its effectiveness . Even fewer studies look at physiological responses associated with fear cessation. Biofeedback is the process of presenting participants with their physiological responses allowing them to gain a measure of control over them. Biofeedback shows promise as a treatment adjunct for specific phobias. We therefore aim to create a VR height exposure platform, that offers a graduated exposure, is optimized to avoid excessive motion sickness, is cost-effective for widespread use, and is validated by participant reports collected during the exposure. Here we developed and tested a cost effective VR acrophobia environment with biofeedback in a sample of 22 participants, 4 of whom had clinically measurable acrophobia. We constructed an Electrodermal Activity (EDA) biofeedback prototype using two Arduino boards, one being electrically isolated (Nano) to reduce noise and increase safety. The second Arduino (UNO R3) was con nected via USB to a VR workstation running the Unreal Engine 4.24.2. USB connectivity was established via the UE4duino plugin. All participants un derwent clinical screening, excluding for confounding psychopathology except acrophobia. Acrophobia symptoms were evaluated using the Visual Height Intolerance Severity Scale (vHISS) questionnaire. Participants were placed on a VR platform which ascended to 28 meters. Subjective stress responses were recorded during the task as well as VR related motion sickness. Data was en tered into a repeated measures ANOVA to check for within-subject differences in levels of stress, comparing when the platform was on the ground as well as in the air. Afterwards participants experiences were evaluated via a brief questionnaire. Biofeedback based on the mean of the signal consistently informed participants that they were stressed while the platform was elevated. Participants showed a significant increase in mean skin conductance signal while the platform was elevated. Continuous decomposition analysis as well as subjective responses confirmed the accuracy of the biofeedback provided. All participants reported a positive experience using the biofeedback, most perceiving it to be accurate. The present work indicates that biofeedback in VRET is a promising treatment adjunct, which should be explored in further clinical trials.

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