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Contamination Of Water, Soil And Plants By Contaminants From Gold Mine Tailings In Matjhabeng Local Municipality, South Africa
Get PDFThesisMining of gold in Matjhabeng Local Municipality area (MLM), Free State, South Africa has produced numerous gold mine tailings, which contain a variety of contaminants. This study, investigated the extent of pollution of water bodies and soil by contaminants from gold mine tailings in the MLM area. The uptake of contaminants by plants, such as medicinal plant species, sweet thorn, as well as food crop species, maize, was also investigated. Surface water and soil were assessed at 15 sampling sites, and within five demarcated zones in uncultivated lands in terms of six physical properties, as well as 12 potential harmful elements (PHEs), while contamination in sweet thorn plants was assessed for the PHEs. The contamination of cultivated soil and maize seeds were studied from 12 sampling sites, and within four demarcated zones in cultivated lands in terms of the physical properties and the PHEs. Groundwater contamination was assessed from eight of the 12 sampling sites, and within three of the four zones, in terms of the physical water quality properties, the PHEs, as well as microbiological properties, since groundwater in the area is also used for drinking. Several environmental pollution risk indices, as well as health risk indices were quantified to determine the potential risk of the contamination of surface water and uncultivated soils by PHEs, as well as the health risk of ingesting the different PHEs in sweet thorn leaves samples, which is used for medicinal purposes. The results of this study revealed that the water, soil and plants in the MLM area have been severely contaminated by the contaminants from the gold mine tailings and of much concern is the contamination by the PHEs. The concentrations of As, Co, Cu, Fe, and Zn, were higher than the surface water quality limits, while Fe, Pb, Ca and Mg measured in groundwater exceeded the drinking water quality limits, with Pb and Fe found to be at toxic levels. The overall contamination of groundwater, revealed that majority of the groundwater in the study area is unsuitable for drinking, as confirmed by high Drinking Water Quality Indexes. On the other hand, the concentration of Cr, Cu, Zn and Fe also exceeded the limits and the background concentrations for uncultivated soils in South Africa, while the concentrations of Cu and Zn exceeded the permissible limits for cultivated soil, as well as the background concentrations in South Africa. Concentrations of Pb and Fe measured in leaves of sweet thorn exceeded the limits while the accumulation of Pb and Se in sweet thorn leaves were found in close to 20% of the sampling sites. However, with maize samples, only arsenic exceeded the limit as stipulated by the Australian Standards for Food Safety, at four sampling sites. The high level of contamination of water, soil and plants in the MLM area was also affirmed by the Geo-accumulation Index results for surface water. The Single Factor Pollution Index results indicated a high contamination by As, and exceptionally high contamination by Se for majority of the surface water samples. On the other hand, human health risk indices results indicated severe non-carcinogenic health risk of As, Pb, Co, Cu, Fe and Pb, from the ingestion of sweet thorn leaves for medicinal purposes with Hazard Index (HI) values > 1. The carcinogenic risk for As at 20% of the sampling sites, and at 40% of the sampling sites for Pb exceeded the 1×10-4 value as stipulated by the USEPA, which suggested a significant cancer risk to the local people in the MLM area. To ascertain the total pollution risk in the MLM area, a Combined Risk Index (CRI) was developed. The results of the CRI revealed that majority of the sampling sites in the MLM area have been contaminated by PHEs and therefore poses risk to the environment and human health. The general trend was that the level of contamination decreased away from Zone 1, in the downstream direction in relation to the prevailing wind in the area, with the least level of contamination registered at the control Zone 5, which was in the upstream wind direction. The overall environmental and health risks classification results for each of the 15 sampling sites for the uncultivated lands revealed three sites, S2, S7 and S9, as high risk areas in the MLM area. Additionally, five sites, S4, S5, S10, S11 and S15 were within the low risk category, while the remainder of the sites have been classified moderate risk areas. The findings from this study indicated that gold mine tailings, as well as mining activities are the major source of PHEs contamination in the MLM area. The results from this study provides scientific facts and evidences that can be used as a baseline for further research on remediation and measures to mitigate the level of contamination by PHEs in the MLM area
Private Retirement Facilities In The Mangaung Area: A Corporate Governance Perspective
Get PDFDissertationLimited housing for the elderly in South Africa indicates that all opportunities must be studied both by government and private stakeholders. People move into retirement facilities at a younger age, and this puts further burden on the demand for safe and affordable facilities. Sectional title and life right retirement facilities play an essential role in addressing the housing problem for the elderly. Private retirement facilities often face challenges regarding financial difficulties, mismanagement and not delivering on promised facilities and services. Sound governance is crucial for retirement facilities, for lessening the risk of financial scandals and contributing to the efficiency and effectiveness of the facility.
The main aim of this study was to provide an in-depth understanding of problems and challenges experienced by the role players concerning management, accounting, auditing and corporate governance of the selected retirement facilities in Bloemfontein in the Mangaung district. Furthermore, to develop recommendations for the various role players in the private retirement facility industry. The literature review covered four main areas, namely legal aspects relating to management, accounting and financial reporting aspects, auditing and assurance aspects as well as the applicability of King IV corporate governance on sectional title and life right retirement facilities. The literature review provided the approach for the empirical study by way of interviewing a sample of knowledgeable role players in each selected facility. A qualitative research approach was followed, using a case study design and a thematic content analysis design to evaluate the semi-structured interviews of the selected participants.
The findings of the empirical study revealed unclear, unnecessary and confusing legal aspects that contribute to further financial burden on the facilities. Various practical problems were discovered concerning management, accounting and auditing aspects. The management of most facilities were unaware of the King IV Code and the applicability of the corporate governance principles and practices on the industry; the concern that was raised regarding the application of corporate governance principles was cost versus value creation. Various recommendations are made that may add value to the retirement industry. The findings can also be valuable for further research
Practical Implementation of Hybrid Energy Systems for Small Loads in Rural South Africa
Get PDFDissertationHybrid renewable energy systems (HRESs), are alternative off-grid methods of generating power to remote rural areas, where power lines are not economically viable. Most of the research studies on renewable hybrid systems or microgrids (MGs) in South Africa, focus mainly on the optimal sizing and optimal control of different systems, by making use of renewable energy simulation softwares, however, there is a lack of research carried out on the implementation of these hybrid systems in real time.
The aim is to develop a real time control method for an isolated hybrid system submitted to a variable load, as well as resources. The first step towards achieving this aim, was to critically review available published research works, to describe recent developments in improving the optimum operating concept of microgrid controllers for stand-alone or grid-connected systems. Secondly, to investigate any real-time implementation established by either hierarchical or distributed control. Then to, analyze their reliability and functionality in practical set up of the controller, in managing power in the system to the variable load.
The study provided a brief overview of microgrid prototype systems, microgrid controls, operating modes and multi-DER microgrid types built into a hybrid system, which introduces a number of strategies or techniques for managing remote rural application prototypes in an isolated or grid-connected system. However, hierarchical control was found to be more appropriate for large microgrids with multiple types of distributed energy resources (DERs), compared to distributed control, particularly when combined with energy storage systems (ESSs), in isolated mode.
The rising of hybrid system controllers in real-time renewable energy for the optimum energy management system (EMS), required the design of a real-time controller to operate the entire system in real time. Increasing popularity of renewable energy (RE) has a control strategy that determined the overall efficiency of the hybrid system (HS), although the energy management system of these systems is particularly complex to be managed.
The study's main contribution is to investigate the feasible controller and, later, to present an advanced control strategy for managing and controlling the flow of hybrid renewable energy with a diesel generator (DG) and battery (BT) as a backup in a rural application of SA. EMS would be implemented, using a fuzzy logic controller (FLC) in MATLAB / SIMULINK. This study analysed input and output variables for the design of a controller, with a set of rules and a three-dimension (3D) surface. Simulation results of related studies with different objectives were analysed, with the aim of sussing out an appropriate controller for the current study.
Arduino Mega was used for coding and uploaded to the implementation of practical implementation of the study. The system operated successfully by supplying the load. This study finally answered the question of the feasibility of the controller in real-time applications
Attrition Among First Year University Of Technology Students: A Study Of First Year Somatology And Human Resources Management Students At The Central University Of Technology, Bloemfontein
Get PDFThesisDespite more than 20 years of democracy, universities continue to experience high attrition rates because of poor academic performance, particularly among Performance of First-Time Entering Students (FTEs). This continues to happen even though numbers of students enrolling at universities keep on increasing annually. The study investigated the bearing of the home environment on how FTEs perceive the university environment with reference to their interactions with the Central University of Technology (CUT) staff, their choice of programmes of study as well as the effectiveness of the CUT’s student academic development and support initiatives. The theoretical rationale explored the research problem will be by referring to the research conducted before on attrition, thus also providing guidance on the areas to be studied.
The study reports on a sample drawn from a population of FTEs in Somatology and Human Resources Management (HRM) programmes. Quantitative data were collected by means of a questionnaire made up of both closed-ended and open-ended questions. Document analysis was also done was so that data from various sources can be scrutinised and construed to triangulate and corroborate the knowledge that was presented by previous studies, thus eliminating the potential for bias. The results of the study revealed that the home environment not conducive to learning as well as students not meeting admission requirements have a bearing on academic performance. Also, the nature of student’s interaction with some CUT staff members may have a negative impact on their academic performance. Based on these findings some recommendations were made. The study proposes the development of the System for the Monitoring of Student Progress (SMSP) through a mobile app at a UoT, which will help to identify at risk students with the aim of implementing interventions that will assist them to be successful in their studies. It is hoped that the SMSP will put the university in a better position to assist FTEs to adjust to university life and improve their academic performance
The Impact Of Training And Development Practices On Employee Performance At Inyatsi Construction, Swaziland
Get PDFDissertationThe importance of employee training and development cannot be over emphasised in an organisation. Critical skills knowledge development is relevant for the establishment and sustainability of an organisation and becomes vital for continuous process improvement. Management must understand the requirements of employees at every stage of their job description because this process is part of critical performance evaluation. That said, the main aim of the study paper was to investigate the impact of training and development (T&D) practices on employee performance at Inyatsi Construction. A quantitative research approach adopted, employing survey to purposively collect data from (n=129) stratified sampled population. The survey was conducted from different branches of Inyatsi Construction located in three different countries, namely, Swaziland, Zambia and South Africa. T&D practices as independent variable and Employee performance as a dependant variable. Descriptive statistic tools SPSS were applied on the questionnaire to see the reliability all the constructs have Cronbach's Alpha value greater than 0.700 indicating the reliability of the instrument. The linear regression analysis revealed a significant relationship between the variables as indicated below: (i) the Pearson correlation coefficient between T&D practices and employee performance is .57 (p< 0.01); (ii) there is a significant relationship between Organisational Intentions and Training and development practices (B=0.862, t=8.740, p-value<0.001); (iii) there is a significant relationship between Specific Employee Development Needs and Training and development practices (B=0.713 t=6.839, p-value<0.001); (iv) there is significant relationship between employee key performance areas and Training and development practices (B=0.653 t=4.617, p-value<0.001).
Despite this study’s contribution to the body of knowledge, specifically within the discourse around this topical issue namely, investment in human capital development for strategic purposes, the study further impresses upon management of Inyatsi, especially HR executives and practitioners to draw lessons from the findings of this study to inform and help develop a culture of learning organisation. Every training and development interventions must be aligned with not only career path of employees, importantly aid the process of achieving strategic imperatives for sustainable competitive advantage
An effective control technique for automatic solar tracking
Get PDFThesis (Master of Engineering in Electrical Engineering)--Central University of Technology, 2021Due to global climate change as a result of pollution caused by the burning of fossil fuels, the world has changed its view when it comes to power generation. The focus is now more on natural and clean energy, such as solar photovoltaic (PV) systems. An effective solar PV system is not a simple system, as the sun is not a stationery object. The sun moves from east to west daily, which makes the design and installation of an effective solar PV system challenging for optimal power harvesting.
Harvesting of solar energy from a PV module efficiently is affected not only by varying environmental conditions, but also by the installation angles, load profile, latitude of the location of interest and energy management system. An energy management system may include a maximum power point tracker (MPPT) that is required to adjust a PV module’s output voltage to a value, which enables the maximum energy to be transferred to a given load. PV module energy conversion can further be increased by using solar tracking technologies. Tracking the sun to enable maximum output power from a PV module varies in complexity. However, it is essential to deliver the highest possible power to the load continuously when variations in the insolation and temperature occur, to maintain a high overall system efficiency.
The purpose of this research study was to develop an effective control technique for an automatic solar tracking system in order to maximise the output power yield that may be obtained from a dual-axes tracking-type system. Three fixed-type PV modules (installed at tilt angles of latitude plus 10° (36°), latitude (26°) and latitude minus 10° (16°)) and the direct-tracking system (controlled by Boolean algorithm) served as the baseline for analysing the simulated power results of two selected algorithms (linear regression and fuzzy logic). These tilt angles are utilised based on the recommendations by Heywood and Chinnery in 1971. The Boolean algorithm is developed and programmed in a National Instruments (NI) LabVIEW user interface software to control three linear actuators to meet the requirements for a dual-axes tracker. The two algorithms (fuzzy logic and linear regression) are developed and simulated using Microsoft Excel.
It took 41 functional blocks and four comparison calculations to develop and execute the direct-tracking system. For the direct-tracking system, two comparison calculations per axis of previous and current voltage readings were done to detect if the PV module should move forward or backwards. The direct-tracking system could move the PV module either forward or backward in both axes (X and Y).
The LabVIEW user interface was also used to visualise the measured data. It was designed and developed for this research study pertaining to the operating parameters of PV modules and linear actuators. The system was installed on the top of the Euclid building at the University of South Africa (UNISA), Science Campus, Florida, Johannesburg. The global positioning system (GPS) coordinates of the building are 26, 1586° S, 27, 9033° E.
It was discovered that the daily performance of the fixed system power (16° PV module) was better than the 26° and 36° fixed systems power by 3.49% and 10.69%, respectively. The direct-tracking system power showed 32% improvement over the fixed system power (16°) due to the fact that it was always aligned to the movement of the sun. The daily simulated power for fuzzy logic was 5.31% better than the direct-tracking system power. The direct- tracking system power was better than the simulated power for linear regression by 2.24%. A key recommendation is to align a PV module perpendicular to the sun from sunrise to sunset, using an effective control technique based on fuzzy logic principles, in order to extract the maximum amount of available energy
Remotely Measuring And Controlling Specific Parameters Of Photovoltaic Modules Via A Radio Frequency Link
Get PDFDissertationBackground: The efficiency of PV modules is affected by a number of factors, including installation parameters and the module surface temperature. Installation parameters of PV modules focus primarily on the tilt and orientation angles, which have to be considered for optimum output power. Furthermore, the operating temperature of a PV module must be kept within certain limits, in order to obtain optimum electrical energy efficiency, depending on the module used. Controlling these parameters of a remote PV module can prove challenging. Purpose: The purpose of this study was to measure the instantaneous surface temperature, voltage and current of a remote PV module that can be used to control some of these parameters in order to maintain a high output power. Methodology: An energy monitoring system was developed that received measurement data and sent control signals over an RF link. The PC transceiver of the system featured a CC1101 RF transceiver connected to the PC via an Arduino UNO, using a USB cable. The PV transceiver featured an Arduino Mega 2560, connected to a CC1101 RF transceiver to make the slave transceiver board, which harboured all the sensors of the system. In addition, the graphical user interface was developed for sending and receiving measurements and control signals between the PC transceiver and the PV transceiver. Results: The PV module voltage and current data was verified using a Fluke 115 DMM. The results showed a 4.9% error percentage for voltage measurements and a 3.9% error percentage for current measurements. Furthermore, a 29-day period of data showed the surface temperature to rise significantly higher than the ambient temperature during the day, indicating that there was considerable heating of the PV Module when there was solar radiation. Whereas for low temperatures measured at night, the surface temperature and the ambient temperature were fairly similar. In addition, PV module current measurements were obtained for a sunny and cloudy day of September that showed 2.32 A and 1.98 A at 11:00 am respectively. Control signals were sent using the graphical user interface from the PC transceiver that were used to activate an actuator that can adjust the orientation angle. A single click of the “Move Left” button in the interface provided an extension of 3 cm of the actuator while a single click of the “Move Right” button resulted in the actuator being retracted by 4 cm. The difference in the displacement of the actuator for the “Move Left” and “Move Right” commands was for demonstration purposes only. Control signals from the PC transceiver to activate a water sprayer (to cool the PV module) were confirmed by switching on and off a LED at the PV module transceiver. The cooling method used is but only an example, the review and selection of a cooling method did not form part of this study. Recommendations: The work presented here could be extended by modifying the graphical user interface to form part of a smart city where the adjustment to the actuator and activation of the water sprayer could be automated. Incorporating cloud storage for monitoring of the output power and surface temperature from any location at any time could also be considered
Developing Microstructure- And Dislocation-Based Constitutive Numerical Models For Predicting The Mechanical Behaviour Of Dmls Ti6Al4V(Eli) At Various Strain Rates
Get PDFThesisDirect metal laser sintering (DMLS) is among the new technologies being pursued by many academic research centres, materials scientists and engineers in the aerospace and biomedical industries as a potential replacement of conventional manufacturing technologies. A scrupulous understanding of the DMLS processes and related post- processes is crucial for establishment of this technology as the better alternative manufacturing route for Ti6Al4V(Extra Low Interstitial-ELI), an alloy commonly used in these industries. The success of such processes depends on the achievement of good structural mechanical properties of Ti6Al4V(ELI), comparable or even superior to those of the conventionally produced alloy. The macroscopic properties of materials are largely affected by the microstructure. The microstructure is a very intricate feature with various aspects that influence specific properties in both a synergistic and competing manner. The morphologies and size of grains, crystallographic texture, macro process-residual stresses and defects, which are largely dislocations in nature, are among these aspects.
To accelerate the acceptance of DMLS Ti6Al4V(ELI) in industry, numerical models that can quantitatively describe the interrelationships between the microstructural features, field variables, such as temperature and strain rate, and the mechanical properties are necessary. At the initial stage of the present study, an analytical constitutive model that is sensitive to the microstructure of Ti6Al4V was developed. Various microstructures of DMLS Ti6Al4V(ELI) were produced via heat treatment and characterised to determine critical microstructural parameters of the model. Experimental tests at selected strain rates and temperatures were then undertaken for these microstructures of DMLS Ti6Al4V(ELI) to acquire data for use in determining the critical parameters of this model. The arising refined and validated analytical constitutive model was then implemented as material user subroutine in ABAQUS/Explicit to generate numerical solutions. Simulation tests were then carried out to determine the predictive capacity of the developed model.
Various mechanisms that prevail during yielding and plastic flow in Ti6Al4V were examined. Using these mechanisms, an advanced analytical model was developed to provide a macroscopic description of the flow properties of various microstructures of DMLS Ti6Al4V(ELI) for a wide range of field variables. The critical microstructural features of average α-grain size and initial dislocation density that influence the plastic deformation were explicitly articulated in the formulation of this model.
The effects of the heat treatment processes on the morphologies, size and crystallographic texture of the microstructural grains were first investigated. The microstructures of the non-heat-treated and heat-treated samples of DMLS Ti6Al4V(ELI) were examined using an optical microscope (OM) and a scanning electron microscope (SEM). A SEM equipped with a backscattered electron detector for electron backscatter diffraction (EBSD) analysis was used for crystallographic texture analysis. The β-phase texture from this data was ascertained based on a reconstruction method using the Automatic Reconstruction of Parent Grain for EBSD data (ARPGE) program. The average α՛/α grain-size was observed to increase from a value of < 1.5 μm for the non-heat-treated samples to a value of about 9 μm for the samples that were heat-treated above the α→β grain transformation temperature. The intensity of texture was also seen to increase because of heat treatment, with the maximum unit density (MUD) of the α՛/α-phase in the basal plane (0001) increasing from 4.9 in the non-heat-treated samples to 24 for samples that were heat-treated at the highest temperature. The non-heat-treated samples and those samples that were heat-treated to just below the α→β-grain transformation temperature showed a strong fibrous texture of the reconstructed β-grains with the 〈100〉 directions almost parallel to the build direction. The alignment of the fibrous texture in the build direction disappeared after heat treatment above the α→β-grain transformation temperature.
An analysis of the X-ray diffraction (XRD) profiles of the non-heat-treated and heat-treated microstructures of DMLS Ti6Al4V(ELI) was carried out to determine the level of defects in these microstructures. The modified Williamson-Hall and modified Warren- Averbach methods of analysis were used to evaluate the dislocation densities in these microstructures. The results obtained showed a 73% reduction of dislocation density in DMLS Ti6Al4V(ELI) upon stress-relieving heat treatment at a temperature of 650°C for a period of 3 hours. The density of dislocations further declined in microstructures that were annealed at elevated temperatures, with the microstructures that were heat-treated just below the α→β-grain transformation temperature recording the lowest dislocation densities.
The high cooling rate gradient normally associated with the DMLS process leads to formation of a non-equilibrium martensitic microstructure. Our previous study demonstrated that this microstructure possesses inferior dynamic deformation properties compared to the microstructure arising from use of conventional manufacturing processes. Thus, in the present study the compressive high-strain-rate properties and deformation behaviour of DMLS Ti6Al4V(ELI) were studied for samples that were heat-treated above the martensitic transformation temperature. High-strain- rate compression tests were carried out using a Split Hopkinson Pressure Bar (SHPB) test system at temperatures of 25 °C, 200 °C and 500 °C. The tests at each temperature were conducted at three different average plastic strain rates of 750 s-1, 1500 s-1 and 2450 s-1 and flow stress curves at these test conditions were obtained. Comparative analyses of these flow stress curves for different categories of samples were then carried out. The flow stress curves of all samples tested generally showed the flow stress to increase with increasing strain rate and to decrease with increasing temperature. These observations showed that the microstructures of Ti6Al4V(ELI) are sensitive to both strain rate and temperature. The samples that were heat-treated at lower temperatures showed the highest dynamic yield stress at any temperature and strain rate compared to those that were heat-treated at elevated temperatures. An examination and analysis of the deformed surfaces of tested samples using SEM showed these surfaces to be dominated by adiabatic shear bands (ASBs) that were predominantly inclined at an angle of ≈45° to the loading axis. This suggested that the compressive fracturing of these samples at high strain rate was because of the development of ASBs.
The flow stress curves of different samples were then used to obtain and refine the calibration parameters of the analytical constitutive model that are sensitive to the microstructure of the samples developed here. In these equations, the strain hardening and dynamic recovery that are normally experienced by materials during high-strain-rate deformation were articulated by two model calibration parameters ℎ and 2, respectively. The influence of initial dislocation densities on the flow properties of Ti6Al4V(ELI) according to the models developed here was investigated. It was shown that for high initial dislocation densities, the shape of the stress-strain curve was that of a pronounced peak stress followed by a decreasing flow stress. Lower initial dislocation densities led to a decreased peak stress and, in some cases, this decrease was followed by a state where no strain hardening occurred. The expected decrease of flow stress with increasing temperature was demonstrated well by the model developed here. The upturn of flow stress at high strain rate was taken care of by the introduction of a viscous drag stress component that is sensitive to high strain rates. This stress component for different samples was calibrated with experimental data using two fitting parameters. The microstructure-based constitutive numerical model developed and validated here using experimental data showed good capacity to predict the high- strain-rate flow properties of additively manufactured Ti6Al4V(ELI) alloy. This was demonstrated by the statistical performance measures of the correlation coefficients (2) and the absolute average error (δ). The values of 2 and δ obtained for correlation of the model and experimental values of various samples were >0.976 and <6% , respectively. This high correlation is an indication of the robustness of the model developed here in predicting the high-strain-rate properties of DMLS Ti6Al4V(ELI).
The validated microstructure- and dislocation-based analytical constitutive model was then implemented as a user material subroutine in ABAQUS using VUMAT and VUHARD subroutines. This was followed by verification. Initially, the verification process was conducted for single and multiple element tests with varying prescribed loading conditions. The simulation results obtained were then compared with the analytical solutions which showed a good capacity of both the developed VUMAT and VUHARD subroutines to be used for high-strain-rate simulations. The verification process was then extended further for tests devised to study the dynamic properties of materials at high strain rates, in this case the SHPB test. Comparison between the SHPB simulation of numerical and experimental results showed excellent correlation, with the correlation coefficient and average absolute error being > 0.97 and < 4%, respectively for various samples. This showed that the numerical model is suitable for use in designing the dynamic strength of DMLS Ti6Al4V(ELI) structures for high strain rate applications, by controlling the morphology of its microstructure and the initial dislocation density present in the alloy
Three-Dimensional Conformal Versus Intensitymodulated Radiation Therapy Planning For Left Breast, Chest Wall And Supraclavicular Fossa Of Cancer Patients
Get PDFDissertationIntroduction: The use of radiation therapy has led to the instance where breast cancer
now has a favourable prognosis post-surgery. For later stage breast cancer, radiation
therapy is performed post-mastectomy. In the Oncology Department, University of the
Free State, the use of radiation therapy post-mastectomy is a standard treatment
technique and it includes the axillary nodes as well as the supraclavicular nodes,
where indicated. The planning technique for radiation therapy has changed with the
introduction of Intensity Modulated Radiotherapy (IMRT) for many cancer treatments.
In this study, the use of IMRT for breast cancer was compared to 3-dimensional
conformal radiation therapy (3D-CRT) for post-mastectomy breast cancer patients that
include the supraclavicular fossa on the left-side. The left-side was selected to indicate
the dose to the heart specifically. The study questioned how 3D-CRT planning
compare with IMRT planning for post mastectomy patients receiving radiation therapy
to the left chest wall and supraclavicular fossa.
Aim: The aim of the research study was to compare 3D-CRT- with IMRT treatment
planning techniques for the treatment delivery of post-mastectomy, left breast, chest
wall and supraclavicular fossa for cancer patients. The objectives were to compare (i)
the dose coverage for the planned target volumes (PTV), (ii) clinical target volumes
(CTV), (iii) the dose received by organs at risk (OAR) and (vi) the dose volume
histograms (DVH) created for each patient’s plans. Methodology: The retrospective study was conducted between January 2019 and
June 2020 in the Oncology Department, University of the Free State, after having
obtained ethical approval. The study was conducted in four stages: 1) contouring and
delineation of structures, 2) generating 3D-CRT plans for 30 patients, 3) generating 30
IMRT plans and 4) comparing the data from the DVH’s. A pilot study was conducted
in order to confirm the reliability and validity of methods and materials utilised. The
patients’ scans were utilised to draw in the PTV, CTV and the OAR by an oncologist.
The 3D-CRT plans were generated by the researcher on the XiO treatment planning
system© (TPS) (Version 4.33.02) and the computed medical system (CMS) Elekta
Software. The IMRT plans were derived from the Monaco© treatment planning system
(V5.11.02). Both the 3D-CRT plans as well as the IMRT plans were compared on the
Monaco planning system. The plans were compared for PTV and CTV dose coverage
and dose delivered to the OAR. The plans were approved by an oncologist for
reliability. The data was captured on a Microsoft Excel spreadsheet and analysed by
a statistician. Results: Twenty-six of the thirty patients’ scans conformed to the inclusion criteria and
were used to create the IMRT plans for comparison with the existing 3D-CRT plans.
Four of the IMRT plans were excluded due to unacceptable dose coverage for either
the PTV coverage or OAR. The PTV coverage for the 105% dose was higher for the
IMRT plans with 1.1% versus 0.2% for the 3D-CRT plans. The 95% dose to the PTV
was superior for the IMRT plans with 7.7% for IMRT versus 32.9% for 3D-CRT plans.
The CTV coverage for the 3D-CRT plans and the IMRT plans had mean values of
0.3% and 1.1% for the 105%, respectively. The 3D-CRT plans had a mean difference
of -0.8% and fewer areas of 105% to the PTV compared to the IMRT plans. The 3DCRT
plans produced areas of less than 95% dose with a mean of 14.5%, whereas the
IMRT plans had a mean dose of 0.9%. The V22 for the 3D-CRT to the heart was higher
compared to IMRT with 7.7% versus 2.1%. The mean heart dose was less for 3D-CRT
with 4.9Gy versus 5.4Gy for IMRT. The mean dose to the oesophagus was less for
the 3D-CRT with 5.1Gy versus 9.3Gy for IMRT. The maximum dose was less for the
3D-CRT with 34.6Gy versus 39.4Gy for IMRT. The percentage of both lungs receiving
18.87Gy was less for IMRT plans with 13.7% versus 16.1% for 3D-CRT plans. The
percentage of left lung receiving 18.87Gy was less for the IMRT plans with 28.1%
versus 33.5% for 3D-CRT plans. The maximum dose to the left humeral head was less
for IMRT with 34.6Gy versus 37.4Gy for 3D-CRT. The percentage of 5Gy to the right
breast was less for 3D-CRT versus IMRT with 3.5% versus 11.4%, respectively. The
dose to the spinal cord was less for IMRT with 13.3Gy versus 22.6Gy for the 3D-CRT.
The percentage of the dose delivered to the normal tissue that received 5Gy was less
for 3D-CRT plans with 12.9% versus 24.9% for IMRT plans. Conclusion: This comparative study demonstrated that the IMRT planning technique
for post mastectomy, left breast cancer patients had superior PTV coverage and OAR
sparing compared to the 3D-CRT planning technique. The IMRT planning technique
did however have larger areas of normal tissue and contralateral breast tissue with low
dose radiation. It should be noted though that this low dose radiation is a concern for
secondary malignancies. The study limitations include the use of a single isocenter for
the 3D-CRT plans, which limited the field size when the mastectomy scar extended
beyond the mid-axillary line, in turn limiting the dose to the PTV dose coverage for both
3D-CRT and IMRT plans, respectively. The 7-field IMRT planning technique was
utilised in this study. However there are 9- and 11- field IMRT planning techniques that
could contribute more to this study. The use of 9- to 11-field IMRT plans could benefit
and expand this study for a more in-depth comparison of different 3D-CRT and IMRT
approaches. In future, the use of breathing techniques, such as deep inspiration breath
hold or inspiration gating, should be considered when using IMRT planning techniques
for breast cancer treatment
Emergency Bipap Ventilator For Breathing Assistance
Get PDFJournal ArticleThe paper proposes the concept of a simplified ventilation device that meets the requirements for the
South African Health Products Regulatory Authority (SAHPRA) approval and may be manufactured in
large numbers at moderate cost to meet the requirements of the current or future pneumonic type
pandemics. The paper further describes the development of such a device and presents descriptions
of the final prototype.
The philosophy behind the design was to take an engineering view of the problem of safe ventilation,
which also meets World Health Organisation (WHO) guideline ‘Technical specifications for invasive
and non-invasive ventilators for COVID-19’ (2020), whilst using the human biological responses to
control the aspiration boundaries, thereby avoiding the very complex processes which simulate the
breathing mechanism.
The methodology employed was a conceptual design phase followed by an engineering design
phase, prototyping, testing, and further developments. The concept was based on guidelines from
WHO, 2020: Technical specifications for invasive and non-invasive ventilators for COVID-19: Interim
guidance: paragraphs 2.1.2 and 2.2.2.(2020) and measured against the UK standard of the Medicines
and Healthcare Products Regulatory Agency (MHPRA) ‘Rapidly manufactured ventilator system’
(2020). Each component of the conceptual design was developed in this way and a final prototype
was assembled for independent evaluation and eventual SAHPRA evaluation.
The finished prototype meets WHO guidelines for a Bi-level Positive Airway Pressure (BiPAP) system
and also meets the guideline requirements for portability. The prototype also meets the initial intent
regarding simplicity, functionality and cost. The further developments to mass production will reduce
the part count and assembly processes, with some components to be reconfigured as disposable
items, not for sterilisation or re-use. The project has shown that specialised equipment may be viewed
pragmatically according to the requirement — to treat all breathing difficulties with a full specification
ventilator is not possible or necessary; to assist the majority of ostensibly minor cases with a Bi-PAP
system is both practical and more affordable. The intent is not to compete with the high technology
commercially sourced equipment, or even the rapidly prototyped re-purposed industrial efforts
worldwide, but rather to initiate some progress in the Republic of South Africa to quickly produce an
abundance of these machines, to cope with the possible deficit of medical ventilators expected in
future.
The solution lies in a simple but failsafe device that provides assisted breathing with the option of
oxygen enrichment. It is intended to be locally manufactured with the minimum of skills and is easily
maintained and sterilised