Browsing by Subject "Biomedical Engineering"
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- ItemOpen Access3D approximation of scapula bone shape from 2D X-ray images using landmark-constrained statistical shape model fitting(2016) Wasswa, William; Mutsvangwa, Tinashe E M; Douglas, Tania STwo-dimensional X-ray imaging is the dominant imaging modality in low-resource countries despite the existence of three-dimensional (3D) imaging modalities. This is because fewer hospitals in low-resource countries can afford the 3D imaging systems as their acquisition and operation costs are higher. However, 3D images are desirable in a range of clinical applications, for example surgical planning. The aim of this research was to develop a tool for 3D approximation of scapula bone from 2D X-ray images using landmark-constrained statistical shape model fitting. First, X-ray stereophotogrammetry was used to reconstruct the 3D coordinates of points located on 2D X-ray images of the scapula, acquired from two perspectives. A suitable calibration frame was used to map the image coordinates to their corresponding 3D realworld coordinates. The 3D point localization yielded average errors of (0.14, 0.07, 0.04) mm in the X, Y and Z coordinates respectively, and an absolute reconstruction error of 0.19 mm. The second phase assessed the reproducibility of the scapula landmarks reported by Ohl et al. (2010) and Borotikar et al. (2015). Only three (the inferior angle, acromion and the coracoid process) of the eight reproducible landmarks considered were selected as these were identifiable from the two different perspectives required for X-ray stereophotogrammetry in this project. For the last phase, an approximation of a scapula was produced with the aid of a statistical shape model (SSM) built from a training dataset of 84 CT scapulae. This involved constraining an SSM to the 3D reconstructed coordinates of the selected reproducible landmarks from 2D X-ray images. Comparison of the approximate model with a CT-derived ground truth 3D segmented volume resulted in surface-to-surface average distances of 4.28 mm and 3.20 mm, using three and sixteen landmarks respectively. Hence, increasing the number of landmarks produces a posterior model that makes better predictions of patientspecific reconstructions. An average Euclidean distance of 1.35 mm was obtained between the three selected landmarks on the approximation and the corresponding landmarks on the CT image. Conversely, a Euclidean distance of 5.99 mm was obtained between the three selected landmarks on the original SSM and corresponding landmarks on the CT image. The Euclidean distances confirm that a posterior model moves closer to the CT image, hence it reduces the search space for a more exact patient-specific 3D reconstruction by other fitting algorithms.
- ItemOpen Access4D flow and displacement sensitive MR imaging of upper arm arterio-venous connections for haemodialysis(2016) Jermy, Stephen; Meintjes, Ernesta M; Franz, Thomas; Auger, Daniel AChronic Kidney Disease (CKD) is a disease that causes kidney damage, often leading to the patient requiring haemodialysis treatment. Haemodialysis treatment requires a vascular access method, commonly Arteriovenous (AV) fistulae and grafts. These access methods must be regularly assessed to ensure the access remains unblocked and the flow rate is normal. Phase Contrast MRA (PC-MRA) is a versatile Magnetic Resonance Imaging (MRI) modality which is capable of imaging and quantifying blood flow in vivo. It is for this reason that this imaging technique was used to image blood flow in the vasculature of the upper arm of volunteers and haemodialysis patients with either an AV fistula or graft. This imaging technique is capable of producing temporally resolved Three-dimensional (3D) datasets (known as "Four-dimensional (4D)" flow) of blood flow in major vessels. Velocities are phase encoded between -π and π based on the chosen Velocity Encoding Constant (venc). To successfully characterise all velocities in the volume it is necessary to set the venc to be approximately equal to the highest velocity found in the vessel. Any lower venc value will cause phase wrapping, an imaging artefact causing all higher velocities to be wrapped by a multiple of 2 π. However, the increase in sensitivity to high velocities reduces the overall specificity of the velocities, especially for low velocities. Due to the pulsatile nature of blood flow in arterial vessels, a large range of velocities are encountered, while venous flow is more constant but lower than the peak arterial flow value. For this reason and due to the length of the 4D flow scans, 20-30 minutes, it would be preferable to perform one scan at a relatively low venc and correct any phase wrapping during post-processing. In this study, we performed both Two-dimensional (2D) PC-MRA scans at various locations in the upper arm and 4D PC-MRA scaans with similar venc settings. The purpose of the study was to implement and test several methods of phase unwrapping to remove phase wrapping artefacts from affected areas within the PC-MRA datasets.
- ItemOpen AccessA deep learning algorithm for contour detection in synthetic 2D biplanar X-ray images of the scapula: towards improved 3D reconstruction of the scapula(University of Cape Town, 2020) Namayega, Catherine; Mutsvangwa, Tinashe; Malila, Bessie; Douglas, TaniaThree-dimensional (3D) reconstruction from X-ray images using statistical shape models (SSM) provides a cost-effective way of increasing the diagnostic utility of two-dimensional (2D) X-ray images, especially in low-resource settings. The landmark-constrained model fitting approach is one way to obtain patient-specific models from a statistical model. This approach requires an accurate selection of corresponding features, usually landmarks, from the bi-planar X-ray images. However, X-ray images are 2D representations of 3D anatomy with super-positioned structures, which confounds this approach. The literature shows that detection and use of contours to locate corresponding landmarks within biplanar X-ray images can address this limitation. The aim of this research project was to train and validate a deep learning algorithm for detection the contour of a scapula in synthetic 2D bi-planar Xray images. Synthetic bi-planar X-ray images were obtained from scapula mesh samples with annotated landmarks generated from a validated SSM obtained from the Division of Biomedical Engineering, University of Cape Town. This was followed by the training of two convolutional neural network models as the first objective of the project; the first model was trained to predict the lateral (LAT) scapula image given the anterior-posterior (AP) image. The second model was trained to predict the AP image given the LAT image. The trained models had an average Dice coefficient value of 0.926 and 0.964 for the predicted LAT and AP images, respectively. However, the trained models did not generalise to the segmented real X-ray images of the scapula. The second objective was to perform landmark-constrained model fitting using the corresponding landmarks embedded in the predicted images. To achieve this objective, the 2D landmark locations were transformed into 3D coordinates using the direct linear transformation. The 3D point localization yielded average errors of (0.35, 0.64, 0.72) mm in the X, Y and Z directions, respectively, and a combined coordinate error of 1.16 mm. The reconstructed landmarks were used to reconstruct meshes that had average surface-to-surface distances of 3.22 mm and 1.72 mm for 3 and 6 landmarks, respectively. The third objective was to reconstruct the scapula mesh using matching points on the scapula contour in the bi-planar images. The average surface-to-surface distances of the reconstructed meshes with 8 matching contour points and 6 corresponding landmarks of the same meshes were 1.40 and 1.91 mm, respectively. In summary, the deep learning models were able to learn the mapping between the bi-planar images of the scapula. Increasing the number of corresponding landmarks from the bi-planar images resulted into better 3D reconstructions. However, obtaining these corresponding landmarks was non-trivial, necessitating the use of matching points selected from the scapulae contours. The results from the latter approach signal a need to explore contour matching methods to obtain more corresponding points in order to improve the scapula 3D reconstruction using landmark-constrained model fitting.
- ItemOpen AccessA structured light solution for detecting scapular dyskinesis(2018) Verster, Jaco; Gray, Janine; Sivarasu, Sudesh; Mutsvangwa, TinasheScapular dyskinesis is a common occurrence in overhead athletes, i.e. athletes who participate in any sport where the upper arm and shoulder is used above the athlete’s head. However, no consensus has been reached on how to evaluate scapular dyskinesis quantitatively. In this thesis, we developed a measuring tool that can be used to evaluate certain key clinical parameters specific to scapular dyskinesis. The tool employs a 3D structured light computer vision approach to create a surface map of the soft-tissue across the scapula. This surface map is then analysed using surface curvature analysis techniques to identify the key clinical parameters associated with scapular dyskinesis. The main advantage of this method is that it provides a measurement tool that may facilitate future quantitative analysis of these key parameters. This may aid with diagnosis and monitoring of the condition by allowing measurement data to be collected both before and after treatment and rehabilitation. We expect that this tool will make the monitoring of treatment effectiveness easier while contributing to diagnostic computer vision.
- ItemOpen AccessAirflow limitation in croup(1999) Jaroslawski, ML; Capper, Wayne; Argent, Andrew CThis thesis investigates a mechanism for air flow limitation in children with croup. Croup is a common condition affecting many young children. Infection (usually viral) causes swelling of the mucosa in the subglottic region of the airway with consequent narrowing of the airway. Although researchers have investigated croup for the past sixty years, there is still very little information available on how croup affects air flow dynamics. The current theory assumes that the stenosis formed by croup in the subglottis of infants leads to a dynamic collapse of the extrathoracic trachea (Chernick, 1990). According to this literature, the dynamic collapse of the extrathoracic trachea will limit the inspiratory flow. It was believed that in severe cases of croup, the dynamic collapse may even temporarily block the airways. In order to investigate the mechanism for air flow limitation in croup the author used the intrathoracic pressure - flow traces from twenty patients with croup, four patients who had been intubated for croup and five normal subjects. Laryngeal X-rays from another twenty patients with croup were analysed as well as five videos, made during laryngoscopy, of the subglottic cross-sectional area of an additional five patients with croup requiring intubation. All data used in this project was collected by an experienced paediatrician from the Red Cross War Memorial Children's Hospital who is also the supervisor of this thesis. Both the video and the X-ray data showed that the dynamic collapse of the trachea contributes much less to airflow obstruction than the subglottic swelling itself. The hypothesis investigated in this thesis is that air flow becomes restricted due to wave speed limitation. According to the theory of wave speed limitation, an increase in driving pressure (the intrathoracic pressure) does not increase the flow if the speed of the air particles exceeds the wave speed. In our case the wave speed is the speed of sound within the lumen of the compliant, narrowed airway. In order to test that theory, it was necessary to obtain the flow, the driving pressure in the subglottis and the cross-sectional area of the subglottis of patients with croup. Unfortunately, the measurement of subglottal cross-sectional areas from videos made during laryngoscopies, proved to be impossible due to both ethical and practical constraints. The measurement of the subglottal cross-sectional areas from X-rays was also difficult in practice. Therefore, the cross-sectional area is calculated. The general orifice equation is modified m order to calculate the subglottal cross-sectional areas in patients with croup. Two methods are used to test the hypothesis of wave speed limitation: i) The wave speed limitation formula. The wave speed limitation formula directly calculates the maximum flow from the pressure - flow data. Hereafter the calculated maximum flow is compared with the measured flow. ii) A lumped component model. A nonlinear, lumped component model has been used to calculate the flow from the driving pressure (intrathoracic pressure). Flow is not limited in this model and an increase in driving pressure will result in a corresponding increase in flow. The flow which is calculated using this model has also been compared to the measured flow. It was found that, in children with croup, there is a good correlation (r=0.82) between calculated and measured values of maximum flow using the wave speed limitation model. The slope of the linear fit using a least square's approximation is 0.98 and this linear relationship is valid for a 0.05 level of significance for Conover's nonparametric test (Daniel and Terrell, 1989). The lumped component model was able to fit the inspiratory flow data with a small sum of square error in the case of both normal ((7.56 ± 0.86) · 10⁻⁹ (ml/s)²) and intubated patients ((3.2 ± 0.75)·10⁻⁹ (ml/s)²). However, the error rose dramatically in patients with croup ((2.04 ± 0.5) -10⁻⁸ (ml/s)²) thus indicating that the lumped component model is no longer valid in these patients. It is concluded that the measured flow velocities in patients with croup approach the calculated velocity of sound in the region of the subglottic swelling, and that the wave speed theory accurately describes the flow limitation. Further support of this is the fact that the lumped component model, which does not incorporate a flow limiting mechanism, breaks down in patients with croup.
- ItemOpen AccessAn Attempt to Improve Stance Mechanics of Trans-Tibial Amputee Gait by the Design of a Modular Ankle Joint Prosthetic(2018) During, Alastair B; Vicatos, George; Sivarasu, SudeshBackground: A-priori research shows that trans-tibial (TT) amputees display poor gait parameters when walking with low-cost ankle-foot prosthetics (here referred to as baseline AFP’s). This has drastic implications for the amputee populations in the developing world specifically, as they have limited access to advanced prosthetic technologies. Low-cost AFP’s are unable to adequately replicate natural stance mechanics, and reliance on these devices results in increased energy expenditure, osteoarthritis and lower-limb joint deterioration. Methodology: This project details the design of a novel ankle joint prosthetic (AJP) that serves as an attachment to baseline AFP’s, with the aim of facilitating better stance mechanics via the restoration of ankle joint mechanisms. The work is presented in three core sections: Part 1 explains the rationale as to why adequately replicating natural stance mechanics is an appropriate need; Part 2 presents the design of the modular low-cost AJP that utilises only simple mechanical elements; and Part 3 presents the experimental quantification of the impact the AJP has on stance mechanics of a baseline AFP (Otto Bock 1D10) in a simulation of the TT amputee walking gait cycle, via the use of three able-bodied participants and a pseudo-prosthesis. Results: The results indicate that the AJP significantly improves the stance mechanics of the baseline AFP. During forefoot rollover a stable joint moment and an increase in joint range of motion (RoM) was observed, yielding a decrease in ankle stiffness. During initial weight acceptance of early stance, an increase in joint RoM displays the restoration of controlled plantarflexion, which indicates an improved transition from heelstrike to footflat. This is a critical mechanism that facilitates stability control during weight acceptance, and the results suggest that the designed AJP is performing better in this regard than its closest functional competitor. However, equipment errors limited the ability to accurately report on ankle stiffness of this phase. Conclusions: Overall the final conclusions are that the designed AJP improves rollover shapes of the baseline AFP, eases phase transitions, and facilitates stability control and forward tibial progression. In combination with the low cost price (±50 USD), its ease of assembly and modular design, the AJP is thus a preferable option for low-income amputees in developing countries. Finally, there is significant evidence of functional and mechanical reliability, and therefore testing of the device can progress to a clinical study involving amputee participants.
- ItemOpen AccessAn investigation of the fluorescence emitted by arterial intimas during irradiation by a XeCl excimer laser(1995) Bhagwandin, Niresh; Breuer, H; Bunn, A E; Fincham, J ELaser angioplasty of occluded arteries has been limited by the unacceptably high rate of vessel wall perforation. To overcome this limitation, fluorescence spectroscopy of arterial wall tissue has been proposed as a technique to discriminate between normal and atherosclerotic arteries and thereby prevent arterial wall perforation during laser angioplasty.
- ItemOpen AccessApplication of 3D imaging technology to anterior cruciate ligament surgery(2006) Dawson, Sarah; Vaughan, Christopher Leonard (Kit); Fitzpatrick, DIncludes bibliographical references (leaves 155-160).
- ItemOpen AccessArticulated Statistical Shape Modelling of the Shoulder Joint(2020) Alemneh, Tewodros; Mutsvangwa, Tinashe; Douglas, TaniaThe shoulder joint is the most mobile and unstable joint in the human body. This makes it vulnerable to soft tissue pathologies and dislocation. Insight into the kinematics of the joint may enable improved diagnosis and treatment of different shoulder pathologies. Shoulder joint kinematics can be influenced by the articular geometry of the joint. The aim of this project was to develop an analysis framework for shoulder joint kinematics via the use of articulated statistical shape models (ASSMs). Articulated statistical shape models extend conventional statistical shape models by combining the shape variability of anatomical objects collected from different subjects (statistical shape models), with the physical variation of pose between the same objects (articulation). The developed pipeline involved manual annotation of anatomical landmarks selected on 3D surface meshes of scapulae and humeri and establishing dense surface correspondence across these data through a registration process. The registration was performed using a Gaussian process morphable model fitting approach. In order to register two objects separately, while keeping their shape and kinematics relationship intact, one of the objects (scapula) was fixed leaving the other (humerus) to be mobile. All the pairs of registered humeri and scapulae were brought back to their native imaged position using the inverse of the associated registration transformation. The glenohumeral rotational center and local anatomic coordinate system of the humeri and scapulae were determined using the definitions suggested by the International Society of Biomechanics. Three motions (flexion, abduction, and internal rotation) were generated using Euler angle sequences. The ASSM of the model was built using principal component analysis and validated. The validation results show that the model adequately estimated the shape and pose encoded in the training data. Developing ASSM of the shoulder joint helps to define the statistical shape and pose parameters of the gleno humeral articulating surfaces. An ASSM of the shoulder joint has potential applications in the analysis and investigation of population-wide joint posture variation and kinematics. Such analyses may include determining and quantifying abnormal articulation of the joint based on the range of motion; understanding of detailed glenohumeral joint function and internal joint measurement; and diagnosis of shoulder pathologies. Future work will involve developing a protocol for encoding the shoulder ASSM with real, rather than handcrafted, pose variation.
- ItemOpen AccessAssessing eHealth knowledge diffusion within the public health sector in Kenya using social network analysis(2020) Gitau, Ryan Nyotu; Douglas, TaniaHigh disease morbidity coupled with limited healthcare personnel places the health sector in Kenya under strain, leaving parts of the population with limited access to health services. Electronic health (eHealth), the utilisation of information and communication technologies in healthcare, is an innovation with the potential to improve access to health services. Several examples exist of eHealth projects being undertaken in Kenya. However, eHealth solutions have been poorly adopted in the public healthcare sector, which has partly been blamed on lack of knowledge amongst healthcare providers and patients. The aim of this study was to examine how knowledge is exchanged between the stakeholders currently active within the eHealth implementation space in the Kenyan public sector. The results of the study would aid in identifying communication breakdowns and ways of increasing information flow with regard to eHealth, and ultimately would aid strategies to help improve the uptake of eHealth within the public sector. A mixed methods study was undertaken that combined quantitative social network analysis and qualitative analysis of semi-structured interviews conducted with stakeholders involved in implementation of eHealth projects in Kenya. Publications on implementation of eHealth projects in Kenya from 2001 to 2018 were used to obtain data on relevant organisations. Social network analysis was used to identify prominent actors. Individuals working within such organisations were invited to participate in semi-structured interviews. Further social network analysis was applied to data gathered through the interviews. Foreign universities and foreign not-for-profit organisations were the most commonly identified organisations in the networks generated. The tacit nature of knowledge within networks, low research capacity and output, information guarding, geographical distance between collaborating organisations, and low cohesion were some of the factors found to inhibit knowledge diffusion within the eHealth implementation space in Kenya. The search for capacity and funding were found to contribute to network structure. eHealth knowledge management strategies should be given attention, for enhanced exchange of knowledge within the public health sector in Kenya.
- ItemOpen AccessAssessment of catheter-manometer systems used for invasive blood pressure measurement(1989) Heimann, P A; Murray, W B; Boonzaier, David; Murray, PW le Roux; Poluta, MladenDirect measurement of blood pressure using a fluid-filled catheter and an electromechanical transducer is widely accepted in clinical practice. However, errors associated with the measurement are often not appreciated and these catheter-manometer systems are frequently unable to accurately reproduce applied pressures. To assess the accuracy of catheter-manometer systems used for invasive arterial blood pressure measurements, in vitro and in vivo evaluations were performed. The frequency response (described in terms of damped natural frequency and damping factor) for a variety of cannulae, pressure tubing and stopcocks (and combinations thereof) and their dependence on various parameters (catheter length, lumen diameter, fluid temperature and catheter material) were measured using an hydraulic pressure generator. The design and construction details of the pressure generator are presented. It was found that the damped natural frequency of the catheter-manometer system is directly proportional to lumen diameter of the pressure tubing/catheter. Furthermore, damping factor is inversely related to the damped natural frequency and stiffer catheter material (for identical radius ratios) results in higher damped natural frequency. Catheter length is inversely related to damped natural frequency and the resonant frequency decreases for an increase in fluid operating temperature. It was established that all catheter-manometer systems tested were under-damped (0.15 < β < 0.37) and that the damped natural frequency ranged from 10.5 Hz for 1500 mm to 27.0 Hz for pressure tubing of 300 mm in length. Furthermore, catheter-manometer systems which had pressure tubing in excess of 300 mm in length did not comply with the bandwidth requirements for accurate dynamic blood pressure measurement. For the in vivo assessment of the catheter-manometer system, the blood pressure waveform was analysed in the time and frequency domains. It was established that in 60 percent of the cases, the systolic pressure peak was higher when measured by a narrow bandwidth catheter-manometer system compared to that measured by a wide bandwidth system. Furthermore, values of dp/dt maximum were lower for wide bandwidth catheter-manometer systems than those measured by narrow bandwidth systems for heart rates above 90 beats per minute. In the frequency domain analysis, artifact was sometimes found to occur at frequencies higher than the bandwidth of the catheter-manometer system. This high frequency artifact was found to distort the blood pressure waveform and resulted in false high dp/dt and peak systolic pressures.
- ItemOpen AccessThe biomatrix model : the development and formalisation of a general systems model(1999) Cloete, Anacreon; Jaros, Gyorgy G; Capper, W LThe purpose of this thesis is the further development and formalisation of the biomatrix model as proposed by Jéros and Cloete (1987). It focuses on the formulation and description of the model per se and not its application, and is essentially a conceptual-theoretical study positioned within the broader systems paradigm. The research is conducted within the framework of new paradigm research and the complete model is presented as its central theoretical thesis. The outcome of the research process is the formulation of the biomatrix model into a logically consistent and contextually congruent general systems model: to be viewed as a rigorously defined proposition.
- ItemOpen AccessCharacterisation of dynamics associated with skeletal muscle contraction initiated by Acetylcholine injection Ghabiba Modak.(2011) Modak, Ghabiba; Kellaway, Laurie A; Sachs, NALower motor neuron damage often results in flaccid paralysis in which the affected muscles are unable to be stimulated artificially via the supplying nerve. Such damage is common in patients who suffer from spinal cord injury and Multiple Sclerosis. Current practice for artificial recovery of muscle function involves stimulating the muscles directly by means of Functional Electrical Stimulation (FES), which requires 100-1000 times more current than that required for nerve stimulation, thus presenting the risk of pain receptor activation. A potential alternative exists in chemical stimulation by means of administration of the neurotransmitter, Acetylcholine (ACh). This study investigates the potential of this possibility by examining the response of two muscle types to extracellular administration of ACh.
- ItemOpen AccessCharacterising the structural brain connectome in Alzheimer's disease and its relation to cognitive intra-individual variability.(2022) Lee, Shao-Hsuan Stephanie; Jankiewicz, Marcin; Robertson, Frances; Christ, BjörnResearch on Alzheimer's disease (AD) has shown white matter (WM) degeneration and structural connectome disruptions measured by diffusion tensor imaging (DTI) as well as increased reaction time intra-individual variability (RT IIV) on neurocognitive testing. However, the relationship between these changes measured on these different modalities remains unexplored. To explore possible relationships between these alterations, this study used tractography to identify WM changes, as indexed by fractional anisotropy (FA) and mean diffusivity (MD), followed by a graph theory-based analysis of the brain structural connectome, and investigated the relationship between these graph theory metrics and RT IIV in 16 AD patients and 20 healthy elderly controls. Within AD patients, we identified WM tracts with lower FA and higher MD mostly located in the cortical and subcortical temporal lobes, such as the hippocampus subregions, compared to healthy elderly controls. We also observed higher FA in the WM tracts within the thalamus as well as between the thalamus and brainstem in AD patients. In the structural brain connectome of these patients, there were regions with altered nodal strength, transitivity, and local efficiency relative to the controls' connectome. Conversely to many studies, we found increases in nodal efficiency across multiple regions and higher global efficiency in AD patients compared to healthy elderly controls. Finally, higher global efficiency was correlated with increased RT IIV on the CRT task in AD patients. In AD, a positive relationship between transitivity in the left cingulate cortex and RT IIV as well as between nodal efficiency in the left cortical temporal lobe and mean RT on the CRT task were observed. On the other hand, lower transitivity in the right thalamus and increased RT IIV, as well as lower transitivity and longer mean RT were found on both the SRT and CRT tasks in AD patients. Our results may show evidence of disruptions and compensatory mechanisms in WM tracts and network metrics in AD. Together, these results revealed WM changes, topological alterations of the brain structural connectome in AD and that these findings can be used in combination with IIV to predict cognitive decline or progression of AD.
- ItemOpen AccessCharacterization of the facial phenotype associated with fetal alcohol syndrome using stereo-photogrammetry and geometric morphometrics(2009) Mutsvangwa, Tinashe E M; Douglas, Tania S; Meintjes, ErnestaFetal Alcohol Syndrome (FAS) is a clinical condition caused by excessive pre-natal alcohol exposure and is regarded as a leading identifiable and preventable cause of mental retardation in the Western world. The highest prevalence of FAS was reported in the wine-growing regions of South Africa but data for the rest of the country is not available. Required, therefore, are large-scale screening and surveillance programmes to be conducted in South Africa in order for the epidemiology of the disease to be understood. Efforts to this end have been stymied by the cost and labour-intensive nature of collecting the facial anthropometric data useful in FAS diagnosis. Stereo-photogrammetry provides a low cost, easy to use and non-invasive alternative to traditional facial anthropometry. The design and implementation of a landmark-based stereo-photogrammetry system to obtain 3D facial information for fetal alcohol syndrome diagnosis (FAS) is described. The system consists of three high resolution digital cameras resting on a purpose-built stand and a control frame which surrounds the subject's head during imaging. Reliability and assessments of accuracy for the stereo-photogrammetric tool are presented using 275 inter-landmark distance comparisons between the system and direct anthropometry using a doll. These showed the system to be highly reliable and precise.
- ItemOpen AccessA clinical engineering decision support system(1988) Muller, Johann HeinrichThe use of technology in health-care today is increasing dramatically with a corresponding increase in cost and complexity to provide and support it. The degree to which a hospital manages this technology affects its ability to treat patients, to perform research, to teach and to attract competent staff. This thesis project has identified the role that clinical engineering could play in health-care technology provision and support in South Africa. A system synthesis technique was employed to develop an idealized clinical engineering model (ICE) that would satisfy South African technological requirements. An extensive literature survey of the current status of clinical engineering in both developed and developing countries was undertaken to provide input to the synthesis process. Surveys were then conducted to determine the actual current status of clinical engineering and its environment in the RSA. To enable such an idealised department to function as defined, it must be supported by appropriate and timeous information. The information needs of the idealised clinical engineering model were analysed and a corresponding decision support system (DSS) defined. Further surveys were conducted to test the applicability and acceptability of the idealised clinical engineering model. The feasibility of implementing the idealised clinical engineering model in South Africa was investigated and recommendations were made based on the research results of this thesis to bring the actual status of clinical engineering closer to the idealised model. ii
- ItemOpen AccessCoaxially electrospun heparin-eluting scaffolds for vascular graft application(2022) Krause, Gerhard Jaco; Bezuidenhout, DeonThe use of electrospun scaffolds for small diameter vascular grafts (< 6 mm) has shown promise in the search for alternative solutions, as current synthetic grafts have high failure rates. The inclusion of heparin into such scaffolds can be beneficial for vascular graft applications as it could prevent mid-graft thrombosis, stabilise and potentiate growth factors as well as subdue undue proliferation of smooth muscle cells. Previous attempts at including heparin by chemical modification or inclusion into the bulk of the electrospun fibres (blend or emulsion electrospinning) were successful but resulted in burst release, reduced bioactivity and rapid elution of the heparin due to bulk degradation of the polymers. This project aimed to develop scaffolds comprising electrospun degradable polyurethane fibres with coaxially incorporated heparin sodium (HepNa+ ) with improved release kinetics and heparin activity for application in the tissue engineering of blood vessel substitutes. Scaffold sheets were cut from tubes (ID = 25 mm) produced on a rotating mandrel by coaxial, conventional and blend electrospinning of a degradable polyurethane, DegraPol® (DP30). Three coaxially electrospun groups were produced with DP30 (CHCl3) shells and polyethylene oxide, PEO (H2O/EtOH) cores containing either low (0.3 wt%), high (0.6 wt%) or no HepNa+ . Blend electrospinning was achieved by incorporating heparin (after modification to its tributylamine (TBA) salt for solubility) into DP30 solution (in CHCl3). Lastly, a control group was produced by conventional electrospinning of DP30 (CHCl3). The morphological (fibre diameter, fibre orientation, pore size and porosity), mechanical (tensile stress and strain, suture retention) and thermal (glass transition, melting and crystallization temperature) properties of the scaffolds were characterised and the corresponding in vitro drug release (heparin quantification and activity) and degradation response over 6 weeks in PBS (37 °C) were determined. Subsequently, conditions were optimised in a pilot study to electrospun small diameter (ID = 2.6 mm) tubular grafts and their morphological and mechanical properties (hoop stress, burst pressure and compliance) were determined. Coaxial electrospinning of DP30 with a water core and especially the addition of HepNa+ resulted in a decrease in fibre diameter (40 %), OI (23 %), pore size (39 %) and porosity (20 %) (all P < 0.05), most likely due to increased conductivity and dielectric constant. With one exception, there was no difference in the directional tensile properties between scaffold groups (ultimate tensile stress > 0.9 MPa, maximum strain > 100 %, suture retention > 2.4 N) or within groups between the longitudinal and circumferential tensile properties. After 6 weeks of in vitro degradation, all groups exhibited similar mechanical losses of approximately 40 % in ultimate tensile stress and 80 % in maximum elongation in circumferential and longitudinal directions. The smaller vascular grafts had burst pressures superior to native vasculature and compliances approximating those of healthy arteries. Thermal analyses (DSC) of the different groups showed similar thermograms with little intergroup variation and indicated that the electrospinning process did not unduly affect the thermal properties or crystallinity, of DP30. There was also no major variations in thermograms of degraded samples. Blend electrospun scaffolds showed the expected initial burst release of HepTBA (47.7 %, 3 days) followed by a sustained release (56.1 %, 6 weeks). Coaxially incorporated HepNa+ also exhibited initial burst release (67.5-69.7 %, 3 days) for both the low and high heparin content groups followed by improved sustained release (81.9 - 97.7%, 6 weeks). Coaxial incorporation had a 2× higher heparin encapsulation efficiency than blend incorporation (approaching 100 %). Heparin, post-TBA-modification, did not fully retain its antithrombotic properties (54.9 % reduction), which was further reduced after incorporation and release (24.2 % reduction). HepNa+ , however, retained its full antithrombotic activity post coaxial incorporation and elution. Coaxial electrospinning of heparin in DP30 shows potential for producing small diameter vascular grafts with mechanical properties comparable to small blood vessels. Although some initial burst release occurred, the sustained release over 6 weeks, incorporation of heparin without the need for modification at improved efficiency, and the retained activity of the heparin after electrospinning incorporation and elution; holds promise for vascular graft applications. Future work should aim for the production of continuous cores within fibre morphology and evaluating graft performance in an in vivo model to determine whether an appropriate and sufficient amount of heparin has been included to affect the desired response.
- ItemOpen AccessA comparison of 3D gait models based on the Helen Hayes Hospital marker set(2000) Tabakin, Dudley; Vaughan, Christopher Leonard (Kit)This study compares three commercial gait analysis packages, Vicon Clinical Manager (VCM), GaitLab 2.0 (GL) and Peak Motus 2000 (PM) with a standard model developed using the Vicon BodyBuilder (BB) software package. All these packages use the same modified Helen Hayes Hospital marker set for external marker placement.
- ItemOpen AccessA comparison of methods for the registration of tractographic fibre images(2011) Golding, Dan; Douglas, Tania SDiffusion tensor imaging (DTI) and tractography have opened up new avenues in neuroscience and are allowing previously unexplored areas of neuroanatomy and function to be researched.
- ItemOpen AccessComparison of resting state functional networks in HIV infected and uninfected children at age 9 years(2018) Stoltsz, Werner Heinrich; Meintjes, Ernesta M; du Plessis, LindieOver 2.5 million children are infected with HIV, the majority of whom reside in Sub-Saharan Africa. Treatment coverage is steadily gaining momentum, reducing mortality and morbidity. Yet little is known about brain development in HIV-infected (HIV+) children who are on highly-active antiretroviral therapy (ART), with viral load suppression from a young age. Here, we use resting state fMRI (rs-fMRI) to examine the impact of HIV and ART on the development of functional networks in 9-year-old vertically HIV-infected children compared to age-matched controls of similar socioeconomic status. We present analyses for a sample of 40 HIV+ (9.2 ± 0.20 years; 16 males) children from the Children with HIV Early Antiretroviral (CHER) clinical trial (Cotton et al. 2013; Violari et al. 2008) and 24 uninfected (12 exposed; 12 males; 9.6 ± 0.52 years) controls from an interlinking vaccine trial (Madhi et al. 2010). Scans were performed at the Cape Universities Body Imaging Centre (CUBIC) in Cape Town, South Africa. We investigated HIV-related differences in within- and between-network functional connectivity (FC) using independent component analysis(ICA) and seed-based correlation analysis (SCA). For SCA, seeds were placed in the structural core, in regions implicated in HIV-related between-group differences at age 7 years, and in regions associated with neuropsychological domains impaired in our cohort. In addition, we evaluated associations of past and present immune health measures with within-network connectivity using ICA. We found no HIV-related intra-network FC differences within any ICA-generated RSNs at age 9 years, perhaps as a result of within-network connectivity not being sufficiently robust at this age. We found a positive association of CD4%, both current and in infancy, with functional integration of left lobule 7 into the cerebellum network at age 9 years. Long-term impact of early immune health supports recently-revised policies of commencing ART immediately in HIV+ neonates. ii Compared to uninfected children, HIV+ children had increased FC to several seeds. Firstly, to seeds associated with the planning and visual perception neuropsychological domains. Secondly, to structural core seeds in the extrastriate visual cortex (of the medial visual network) and the right angular gyrus (of the temporoparietal network). Finally, to left paracentral (somatosensory network) and right precuneus (posterior DMN) seeds previously revealing between-group differences at age 7 years. The connections with greater FC in HIV+ children may variously indicate functional recruitment of additional brain capacity, immature excess of short-range connections, and/or immature excess of between-network connections. In conclusion, despite early ART and early virologic suppression, HIV+ children demonstrate instances of abnormal FC at age 9 years. Disruption to visual cortex is marked, consistent with indications from neuropsychological testing that visual perception is disrupted. The profile of HIV- and/or ART-related effects on FC differs considerably between the two ages of 7 and 9 years, but both show characteristics of immature functional organisation compared with age-matched controls.