Mammography is currently used to screen women in targeted risk classes for breast cancer. Computer assisted diagnosis of mammograms attempts to lower the workload on radiologists by either automating some of their tasks or acting as a second reader. The task of mammogram segmentation based on pixel intensity is addressed in this thesis. The mammographic process leads to images where intensity in the image is related to the composition of tissue in the breast; it is therefore possible to segment a mammogram into several regions using a combination of global thresholds, local thresholds and higher-level information based on the intensity histogram. A hierarchical view is taken of the segmentation process, with a series of steps that feed into each other. Methods are presented for segmentation of: 1. image background regions; 2. skin-air interface; 3. pectoral muscle; and 4. segmentation of the database by classification of mammograms into tissue types and determining a similarity measure between mammograms. All methods are automatic. After a detailed analysis of minimum cross-entropy thresholding, multi-level thresholding is used to segment the main breast tissue from the background. Scanning artefacts and high intensity noise are separated from the breast tissue using binary image operations, rectangular labels are identified from the binary image by their shape, the Radon transform is used to locate the edges of tape artefacts, and a filter is used to locate vertical running roller scratching. Orientation of the image is determined using the shape of the breast and properties of the breast tissue near the breast edge. Unlike most existing orientation algorithms, which only distinguish between left facing or right facing breasts, the algorithm developed determines orientation for images flipped upside down or rotated onto their side and works successfully on all images of the testing database. Orientation is an integral part of the segmentation process, as skin-air interface and pectoral muscle extraction rely on it. A novel way to view the skin-line on the mammogram is as two sets of functions, one set with the x-axis along the rows, and the other with the x-axis along the columns. Using this view, a local thresholding algorithm, and a more sophisticated optimisation based algorithm are presented. Using fitted polynomials along the skin-air interface, the error between polynomial and breast boundary extracted by a threshold is minimised by optimising the threshold and the degree of the polynomial. The final fitted line exhibits the inherent smoothness of the polynomial and provides a more accurate estimate of the skin-line when compared to another established technique. The edge of the pectoral muscle is a boundary between two relatively homogenous regions. A new algorithm is developed to obtain a threshold to separate adjacent regions distinguishable by intensity. Taking several local windows containing different proportions of the two regions, the threshold is found by examining the behaviour of either the median intensity or a modified cross-entropy intensity as the proportion changes. Image orientation is used to anchor the window corner in the pectoral muscle corner of the image and straight-line fitting is used to generate a more accurate result from the final threshold. An algorithm is also presented to evaluate the accuracy of different pectoral edge estimates. Identification of the image background and the pectoral muscle allows the breast tissue to be isolated in the mammogram. The density and pattern of the breast tissue is correlated with 1. Breast cancer risk, and 2. Difficulty of reading for the radiologist. Computerised density assessment methods have in the past been feature-based, a number of features extracted from the tissue or its histogram and used as input into a classifier. Here, histogram distance measures have been used to classify mammograms into density types, and ii also to order the image database according to image similarity. The advantage of histogram distance measures is that they are less reliant on the accuracy of segmentation and the quality of extracted features, as the whole histogram is used to determine distance, rather than quantifying it into a set of features. Existing histogram distance measures have been applied, and a new histogram distance presented, showing higher accuracy than other such measures, and also better performance than an established feature-based technique.

Thesis (M.Sc.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 225-238.

Thesis (M.Tech.: Radiography)-Dept. of Radiography, Durban University of Technology, 2007 xxiv, 142 leaves, Annexures A-L / The aim of the study was to evaluate CT-based treatment planning versus digitised image planning (standard planning technique) for carcinoma of the breast, using the four-field breast technique, in terms of the depth of supraclavicular and axillary nodes, the variability of the breast tissue and the dose inhomogeneity at the matchline.

A thesis submitted in fulfilment of the requirements for the degree Master of Technology: Diagnostic Radiography in the Faculty of Health and Wellness Sciences at the Cape Peninsula University of Technology, 2012 / Complete, accurate and justified radiological examination requests are prerequisite to radiological exposures. However, global research shows evidence of high numbers of incomplete and inaccurate requests as well as that up to 77% radiological exposures are unjustified. Plain lumbar spine and plain skull radiology examinations are reported as being procedures that generate high dose and a low diagnostic yield. This study was designed to objectively measure the completeness, accuracy and justification of these two examinations in an effort to make inferences that will contribute to an improved radiology service. This research could therefore have positive effects on optimisation of radiation protection in Zimbabwe. Methodology A non participatory prospective descriptive analytical document review of quota sampled radiological request forms for 200 plain skull and 200 plain lumbar spine examinations was employed. Data was captured using structured data collection instruments designed and tested by the researcher for this study. The instrument was designed using the IAEA-HHS4 (2010) minimum prescribed request data as a framework and adding additional form fields found to be relevant through a review of all identified radiological request template forms in use at the research site. Data analysis involved central tendency measures and inferential statistics. Results: The central tendency demonstrated for the two examinations was that generally referrers for plain lumbar spine and for plain skull radiology would respectively provide 38.9 +/- 0.6% and 40.2+/-0.5% overall examination request information. This information was significantly below expectation. There was however no significant difference between the samples’ means for the two examinations. The tendency demonstrated in patient information for lumbar spine and skull requests was that generally referrers would respectively provide 48.4 +/- 0.8% and 49.5+/- 0.8% patient information. These values were inclusive of each other and they were significantly (p=0.00 Sig.) below expectation. There was however no significant difference between the two examinations’ data. The tendency demonstrated for examination information was that referrers for the research site would generally provide 29.8+/-0.8% (lumbar) and 32.6+/-0.8% (Skull) examination information. These values were significantly (p=0.000 Sig.) below expectation and demonstrated a significant difference between the sample means for the two examinations. With respect to referrer information, the tendency demonstrated was that generally referrers for plain lumbar spine and for plain skull examinations would respectively provide 38+/- 1% and 38.5 +/- 0.8% referrer identification information. These were significantly below expectation (p= 0.000 Sig.) but there was no significant difference between the samples’ means with respect to referrer information. With respect to accuracy of request data, it was observed that 5% plain lumbar spine and 3% plain skull requests were specific in so far as information documented on request forms could unambiguously identify the area to be imaged. It was also observed that 22.5% (lumbar spine) and 12% (skull) examination requests were indicated and therefore justified. All requests forms were found to be legible. Conclusions: Generally, referrers to this research site tend to provide incomplete, inaccurate and unjustified radiological request data. The observed levels of completeness, accuracy and justification of requests were generally consistent between the two examinations relative to expectation. These levels had medico-legal implications and negative effects on optimisation of radiation protection to patients. Further research to establish causes of this variance in referral behaviour is recommended. The researcher also recommends further research to establish whether there is an association between requested examination and completeness, accuracy and justification of diagnostic radiology examination requests. Keywords: Radiation protection, radiological request, complete request, accurate request, justified request, plain skull imaging, plain lumbar spine imaging.

Thesis (MTech (Radiography))--Cape Peninsula University of Technology, 2011 / This thesis records a study undertaken by a radiography lecturer at a satellite campus of a University of Technology (UoT) in the Western Cape Province of South Africa. The study investigated the academic writing practices of first year Radiation Science learners and focused on an intervention to assist learners to enhance their academic writing competence. Three research questions were addressed: 1. What did radiography learners perceive to be the factors that enabled and constrained their academic writing competence during the first year of academic study?; 2. What were the 2010 first year learners’ perceptions of the changes in their academic writing following an academic writing intervention?; and 3. According to the 2010 first year lecturers, how did the academic writing of the learners change following the intervention? To answer these questions, the research comprised two qualitative approaches: firstly a case study approach, to gain an in-depth understanding of learner writing in radiography; then the insights gained allowed for the design of an appropriate academic writing intervention, carried out in two action research spirals. Thereafter the intervention was evaluated for its impact on learners’ writing competence. The findings and interpretations from this study culminated in a forward looking model that is recommended for use by radiography educators to enhance first year learners’ academic writing competence. The model reflects a zone for the optimal enhancement of academic writing competence for entry-level learners. This ‘zone’ is created in the region of overlap of three contributing factors: collaborative guidance and support, peer mentoring and technology. The model also represents applicable underlying theories (critical theory, constructivism, and academic literacies theory) which provide the theoretical framework for enhanced academic writing competence.

Dissertation submitted in fulfilment of the requirements for the degree Master of Technology: Radiography in the Faculty of Health and Wellness Sciences, 2008 / Introduction Research to date has not been able to agree whether spatial abilities can be developed by practice. According to some researchers spatial ability is an inherited cognitive ability, compared to spatial skills that are task specific and can be acquired through formal training. It is commonly assumed that radiographers require general cognitive spatial abilities to interpret complex radiographic images. This research was conducted to investigate second year radiography students’ three-dimensional thinking skills pertaining to film-viewing assessments. Materials and methods The experimental research strategy was mainly applied together with correlation research. Two trials were run (in 2005 and 2006). The sample group consisted of fifteen second year diagnostic radiography students in 2005 and twenty-three second year diagnostic radiography students, of the same institution, in 2006. Each year group was randomly divided into a control group and an intervention group. Two instruments were used, that is a film-viewing assessment and a three-dimensional test, Academic Aptitude Test (University) (AAT) nr. nine: Spatial Perception (3-D). The whole class completed this basic spatial aptitude test, as well as a base-line film viewing assessment, which focused on the evaluation of technique/anatomy of second year specialised radiographic projections. The marks that the students achieved in the fore-mentioned tests were compared, to determine if there was any correlation between their performances in the different tests. A curricular intervention, which was intended to improve applied three-dimensional skills, was subsequently applied. The students executed certain modified radiographic projections on parts of a human skeleton. For each radiographic projection, the students had to draw the relation of the X-ray beam to the specific anatomical structures, as well as the relation of these structures to the film. The related images of these projections were also drawn. With each of the following sessions, films including images of the previous session were discussed with each student. After the intervention, the whole class wrote a second film-viewing assessment. The marks achieved in this assessment were compared to the marks of the initial film-viewing assessment to determine the influence of the intervention on the performance of the intervention group. Following this assessment, for ethical reasons, the same intervention took place with the control group. A third film-viewing assessment was then written by all the diagnostic second year students to evaluate the overall impact of the intervention on the applied three-dimensional skills of the class. The marks of both the 2005 and 2006 classes (intervention classes) were compared to the marks achieved by former classes from 2000 to 2004 (control classes), in film-viewing assessments to evaluate the role of the curricular intervention over the years. The students again completed the three-dimensional test, Spatial Perception (3-D) to evaluate the impact of the intervention on students’ general three-dimensional cognitive abilities. These marks were also compared to the marks of the third filmviewing assessment, to determine if there was any correlation between the students’ performances in the different tests. Results The intervention groups did not perform significantly better in film-viewing assessments after the intervention, compared to the control groups, but reasonable differences, favouring the intervention group, were achieved. Statistical significance was achieved in film-viewing assessments with both year groups after the whole class had the intervention. The intervention year groups also performed significantly better than the previous year groups (without the intervention) in film-viewing assessments. The performance in general three-dimensional cognitive abilities of the group of 2006 improved significantly after the intervention, but on the contrary, the performance of the group of 2005 declined. There was a small intervention effect on the performance of the group of 2006. Only a weak to moderate correlation between the marks of the students achieved in the three-dimensional tests and the marks achieved in the film-viewing assessments, was found. Conclusion The contrasting evidence between the data of the two groups (2005 and 2006) in the three-dimensional tests and the small intervention effect on the performance of the group of 2006, makes the intervention not applicable for the increase of general spatial abilities. The results of this research show that the applied three-dimensional skills of radiography students in interpreting specialised and modified projections can be improved by intensive practice, independent of their inherited spatial abilities.

M.Tech. (Radiography) / Satisfied patients are recognized as an important outcome measure for evaluating the quality of medical care provided in a hospital setting. A satisfied patient is more likely to comply with instructions given and cooperate with medical staff during procedures such as special radiographic examinations in the radiography department. In Malawi, studies on patient satisfaction have mostly been confined to doctor – patient interaction and other aspects of the health care service. Very little research has been conducted to explore the experiences of patients undergoing special radiographic examinations. The purpose of this study was to explore the experiences of patients undergoing special radiographic examinations at Kamuzu Central Hospital. A qualitative, contextual, explorative, descriptive approach was used to collect data from patients undergoing special radiographic examinations at Kamuzu Central Hospital in Malawi. Focus group interviews were employed to collect data from the study participants. A total number of 15 patients took part in the study. A content analysis approach was used to analyze the views of the participants. The themes that emerged from the focus group data were: Concerns about delays from reception to receiving radiography results (Radiographs and report); Patients’ experiences with regards to the quality of patient care they received and Concerns about the hospital environment and resources in the radiography department. Guidelines have been proposed to address the themes identified.

M.Tech. (Radiography) / Systematic implementation of a quality control (QC) programme is crucial for any diagnostic radiology department if consistent optimal equipment performance, quality images, accurate diagnosis and quality services at optimum radiation dose and costs are to be assured. This highlighted the necessity for the Tanzania Atomic Energy Commission (TAEC) to establish a training programme to enable radiographers to implement a QC programme and associated QC measures in their departments. Most radiographers have been trained on the QC programme, however, the level of QC implementation by the radiographers is not established. The aim of this study was to investigate the extent to which the QC programme and associated QC measures are being implemented by radiographers in conventional diagnostic radiography units, in Tanzania. A quantitative cross-sectional study design, using a questionnaire, was conducted on a sample of radiographers who have been trained on the QC programme, and who were practicing in hospitals within Tanzania. The study found that implementation of the QC programme and associated QC measures was poor. Most QC measures were not being performed and that only a few tests were being performed but not consistently. Furthermore, there were no records and procedures available for the QC programme. The challenges identified were negligence by the radiographers, lack of standardized test tools, lack of hospital managerial support, lack of enforcement and lack of motivation and coordination. Multifactor interventions by the TAEC, Ministry of Health and Social Welfare, radiographers and the hospital management teams are needed to improve the implementation of the QC programme.

Radiation from Computed Tomography (CT) is now the major contributor to population radiation dose. Despite controversy around the dose-effect relationship of radiation from CT, the linear non-threshold (LNT) theory is endorsed by many authorities, and constitutes the basis of cancer risk estimates. The purpose of this study was (1) a literature review of radiobiological theories, and methods of dose saving stategies in CT; (2) to highlight the importance of dose saving in CT, and to demonstrate how dose can be saved in a radiology department: Following a 40% reduction in reference X-ray tube current for a CT of the urinary tract, the effecitve dose and estimated lifetime attributable risk of incident cancer due to this CT in a group (n=103) were reduced by 37% and 38% in an age and sex-matched group respectively. The literature review showed that the public health implications of CT radiation exposure remain uncertain. / Health Studies / M.A. (Public Health)

Radiation from Computed Tomography (CT) is now the major contributor to population radiation dose. Despite controversy around the dose-effect relationship of radiation from CT, the linear non-threshold (LNT) theory is endorsed by many authorities, and constitutes the basis of cancer risk estimates. The purpose of this study was (1) a literature review of radiobiological theories, and methods of dose saving stategies in CT; (2) to highlight the importance of dose saving in CT, and to demonstrate how dose can be saved in a radiology department: Following a 40% reduction in reference X-ray tube current for a CT of the urinary tract, the effecitve dose and estimated lifetime attributable risk of incident cancer due to this CT in a group (n=103) were reduced by 37% and 38% in an age and sex-matched group respectively. The literature review showed that the public health implications of CT radiation exposure remain uncertain. / Health Studies / M.A. (Public Health)