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Masters Degrees (Radiotherapy and Oncology)

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Browsing Masters Degrees (Radiotherapy and Oncology) by Date Accessioned

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    The role of the kallikrein-kinin system in prostate and breast tumourigenesis and tumour-associated angiogenesis..
    (2007) Wright, Jaclyn.; Naidoo, Strinivasen.; Botha, Julia Hilary.
    This thesis consists of three main parts. An introduction to diode-pumped solid-state lasers, thermal modelling of solid-state lasers and rate-equation modelling of solid-state lasers. The first part explains the basic components and operation principles of a typical diode-end-pumped solid-state laser. The stimulated emission process, solid-state laser gain media, various pump geometries and a basic end-pumped laser resonator configuration are among the topics that are explained. Since thermal effects are one of the main limiting factors in the power-scaling of diode-pumped solid-state lasers, the second part of this thesis describes numerical and analytical thermal models that determine the thermal lens and thermally induced stresses in a laser crystal. As a first step, a time-independent numerical thermal model which calculates the three-dimensional temperature distribution in the laser crystal is implemented. In order to calculate the time dependent thermally induced stresses in a laser crystal, a coupled thermal-stress finite element analysis model was implemented. Even though some steady-state analytical solutions for simple crystal geometries do exist, the finite element analysis approach was taken so that the time dependent thermally induced stresses could be calculated for birefringent crystals of various geometries. In order to validate the numerical results, they are compared to experimental data and analytical solutions where possible. In the last part, the population dynamics inside the laser gain medium are described and modelled with a quasi-three-level rate-equation model. A comprehensive spatially resolved rate-equation model is developed and discussed. In order to simplify the implementation of the rate-equation model as a computer simulation, the spatial dependence of the laser parameters is ignored so that the model reduces to a singleelement plane-wave model. The simplified rate-equation model is implemented and solved numerically. The model is applied to a four-level CW and Q-switched Nd:YLF laser as well as a quasi-three-level QCW Tm:GdV04 laser. The models' predictions are thoroughly verified with experimental results and also with analytical solutions where possible.
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    Effects of a prostaglandin precursor, gamma-linolenic acid (GLA), on malignant cells in vitro and in vivo.
    (1985) Ramchurren, Nirasha.; Botha, Julia Hilary.; Robinson, K. M.
    Recent studies have shown that the proliferation of various human and murine tumour lines can be inhibited by the addition of gamma-linolenic acid (GLA) to the culture medium. These findings are consistent with the proposal put forward by Horrobin (1980) that malignant cells lack the enzyme/ A 6 desaturase; which is responsible for the conversion of linoleic acid (LA) to GLA. Since GLA is a prostaglandin (PG) precursor/ inadequate conversion of LA to GLA would result in decreased production of PGs/ particularly PGEi/ which has been shown to have an inhibitory effect on cell growth. Provision of GLA to enzyme deficient malignant cells should therefore bypass this blockade/ increase PGET synthesis and thus "normalise malignant cells". This study was performed to examine further the effects of exogenous GLA on growth of malignant cells in vitro and in vivo. Cells of the continuous murine sarcoma (M52B) line and primary cultures of non malignant fibroblasts were used to investigate effects of GLA in vitro. Cultures were exposed to either single or multiple doses of a range of concentrations of GLA. Radioimmunoassay (RIA) was performed to compare the amounts of PGE and PGF released into the medium by GLA treated and control M52B cultures and thus determine whether the addition of GLA in vitro significantly affected production of these PGs. Athymic BALB/c mice and immunocompetent BALB/c and Biozze mice as well as mice of the "Onderstepoort Strain" were used in various in vivo studies. Tumours were induced by the subcutaneous inoculation of approximately 1 x 106 cells of either the M52B line (into immunocompetent and athymic mice) or human breast carcinoma (NUB 1) line (into athymic mice). Take rates and latent periods were recorded. GLA treatment was initiated after tumours were established. In one study the fatty acid in hydrogenated coconut oil (HCO), which contains no PG precursors/ was administered parenterally (100 ug/ml/day) to Biozze mice. Control mice were either untreated or injected with HCO only. In another study, BALB/c mice and mice of the "Onderstepoort Strain" had their diet supplemented with GLA (in the form of EPO) to an extent of 3.5%. Control mice consumed either standard laboratory chow only or, chow supplemented with either 35% sunflower seed oil (SSO) or 35% HCO/ neither of which contain GLA. All diets were supplied ad libitum. Tumour sizes were measured every 48 hours and at the end of each experiment at which time tumours were excised and examined histologically. GLA was found to produce inhibitory and toxic effects on growth of both M52B cells and non malignant fibroblasts in vitro/ although the effect in the latter was observed only with high concentrations of the fatty acid. The inhibition of malignant cell growth was concentration dependant and was positively related to the duration of exposure to the fatty acid. Prior to death/ cells treated with GLA accumulated vii paranuclear granules which were shown histochemically to be lipid in nature. Electron microscopy confirmed the presence of large lipid deposits. Cultured M52B cells treated with GLA also released more PGE and PGF into the medium than did cells not exposed to the fatty acid. However, analysis of results using the Mann Whitney U test showed these differences to be statistically non significant for both PGE and PGF on two tailed tests. In contrast to the inhibition of M52B cell growth observed in vitro, growth of solid M52B sarcomas and NUB 1 carcinoma xenografts in athymic mice was apparently unaffected by administration of dietary GLA. Analysis of data using an unpaired student's t-test showed that the differences in tumour volumes between control and treated groups were not statistically significant either before or at the end of the experiment. While the inhibition of malignant cell growth caused by GLA in vitro was consistent with Horrobin's proposal that malignant cells may lack this PG precursor, whether or not these actions are mediated by the PGs remains obscure. Although an increase in PGE production by M52B cells was observed following GLA treatment, besides this increase being statistically non significant, it was not possible to determine whether this was due to PGE, (as suggested by Horrobin) or PGE2. It is possible that the effect produced in vitro was due to some factor other than raised PGE production, for example a non-specific fat-overload effect or a change in cell membrane fluidity. The lack of effect of GLA on tumour growth in vivo may have been due to inadequate delivery of the fatty acid to the tumour site. However, whatever the mechanism of action of GLA in vitro/ since oral GLA was supplemented to the maximum tolerated extent and produced no effect in immunodeficient mice inyiyo, it would seem that in a similar clinical situation oral doses which would be practical may be ineffective.
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    Radioactive iodine in the management of thyrotoxicosis.
    (2011) Narsai, Neil Yeshwant.; Motala, Ayesha Ahmed.
    Objective : An audit of the use and outcomes of Radioactive Iodine (RAI) therapy in the definitive management of thyrotoxicosis at Inkosi Albert Luthuli Central Hospital (IALCH), KwaZulu-Natal, South Africa. Methods : The clinical records of all new patients with thyrotoxicosis, referred in a 4 year period between 01/01/2003 and 31/12/2006, were analysed. Response to RAI was monitored using biochemical parameters (namely, Thyroid Stimulating Hormone and Free T4 levels). Rates of euthyroidism (cure), hypothyroidism and hyperthyroidism (treatment failure) were correlated to dose of RAI. Patients were followed-up for at least 2 years or until the onset of hypothyroidism. The follow-up period was until 31/12/2007. Results : One hundred and fourteen patients (37.7%), of a cohort of 302 new thyrotoxic patients treated with RAI, met the inclusion criteria. Ninety-six patients (84.2%) had Graves Disease (GD) whilst 18 had Toxic Nodular Disease (TND). At 2 year follow-up, 91 patients (79.8%) were hypothyroid, 10 (8.8%) were euthyroid and 13 (11.4%) were hyperthyroid. The average dose of RAI to achieve euthyroidism was 10mCi and hypothyroidism, 9.7mCi. The average time to achieve euthyroidism was 5.9 months and 10.1 months to become hypothyroid. Thirty-one patients (27.2%) remained persistently hyperthyroid after one dose of RAI. Patients with GD (88.5%) were more likely to become hypothyroid (p < 0.001) whilst 38.9% of TND patients remained hyperthyroid (p = .001). Baseline TFT values were significant in terms of outcomes correlated with the prescribed RAI dose i.e Low Dose (<8mCi) vs. Intermediate Dose (8-9mCi) vs. High Dose (>9mCi)(TSH p = 0.05; FT4 p = 0.003; FT3 p = 0.001). Conclusion : The majority of patients became hypothyroid over time, in keeping with reported data. In the public health sector, where early access to RAI (in terms of waiting times for appointments for RAI) and follow-up are major problems, early cure is essential to minimize the morbidity of thyrotoxicosis and this may be achieved with an initial high dose of RAI.
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    Predictors of response of AIDS-associated Kaposi sarcoma to standard chemotherapy.
    (2006) El-Koha, Omran Ali.; Mosam, Anisa.
    Predictors of response of AIDS-associated Kaposi-Sarcoma to standard chemotherapy Overview: Kaposi Sarcoma is the most common HIV-associated cancer. Its etiology and pathogenesis is not fully understood. Little is known about what predicts prognosis, survival and therapeutic response in HIV-KS. In South Africa given the high seroprevalence rates of HIV-l and human herpes virus 8 (HHV 8), Kaposi's sarcoma is a significant problem. The majority of patients have been treated solely with palliation due to the poor outcome associated with a diagnosis of HIV-KS, more so in the absence of highly active antiretroviral therapy (HAART). Since the national ARV rollout programme and the availability and accessibility of HAART to all patients with a diagnosis of HIV-KS, a new strategy has to be established to enable adequate patient selection for chemotherapy. There have been a few published studies addressing the predictors of response to chemotherapy in the first world. However, this is the first study of these factors in HIV-l infected African patients with Kaposi's sarcoma. Aim: To identify and assess the potential value of several parameters predictive of outcome, survival and therapeutic response in HIV- infected patients with KS. Clinical, hematological, biochemical, immunological and virological variables were evaluated. Methods: We collected data from 25 patients with AIDS-KS who were enrolled in a phase III randomized controlled trial comparing HAART alone with the combination of HAART and chemotherapy. All patients were from the combination therapy arm. The following variables were evaluated as predictors of prognosis and therapeutic response: age, gender, ethnic origin, Haemoglobin (Hb), white blood cells (WBCs), lymphocytes, neutrophils, platelets, S.albumin, ALP, GGT, CD4 count, HIV viral load. These variables were assessed in patients at baseline and month 6 of therapy. Patients were staged into good risk and poor risk according to the AIDS clinical trial group (ACTG) criteria. The outcomes assessed were response to treatment and mortality. Results: A total of 25 patients participated to the study. Of these 16(64%) were males and 9(36%) were females, with male: female ratio of 2.7:1. Median age was 34 years (24-47); all patients were of Black African origin. Of the 21 patients, 15 (71.4%) were of good prognosis and 6(28.6%) were of poor prognosis. At baseline the median values of the different variables were as follows: Hb 10.9 g/dl, WBCs 5.95x109/L, lymphocytes 1.7 x109/L, neutrophils 3 x10 9 /L, platelets 272 x10 9 /L, S.albumin 30 gil, total protein 88 gil, ALP 64 U/L, and GTT 21 U/L, CD4 count was 255 cells/mm 3 , HIV-RNA viral load was 42000( 4.610gs). At month 6, 22 patients remained alive, their median values were: Hb 12.2 g/dl, WBCs 4.65 x109/L, lymphocytes 1.5 x109/L, neutrophils 3 x10 9 /L, platelets 301 x109/L, S.albumin 36.5 gil, total protein 84.5 gil, ALP 78.5 U/L, GTT 44.5 U/L, CD4 count 288 cells/mm3 , HIV-RNA viral load was 50500( 4.6910gs). The baseline median CD4 and HIV-RNA viral load counts for the 3 patients who died before month 6 were 47 cells/mm3 and 31000(4.610gs); respectively. Response to therapy was evaluated in 21(84%) patients as 4(16%) patients were missing, of the 21 patients 3 (14.3%) had complete response and 18(85.7%) had partial response. With respect to sex 2(14.3%) males had complete response and 12(85.7%) had partial response, 1(14.3%) female had complete response and 6 (85.7%) had partial response. Non-parametric statistics were used because of the small sample size and the skewness of the data. Variables were described using medians and ranges, and compared between two independent groups using Mann-Whitney tests. Baseline and month 6 comparisons were done using Wilcoxon signed ranks tests. Receiver Operating Characteristic (ROC) curves were used to analyze cut points to optimize sensitivity and specificity of a quantitative variable for a dichotomous outcome. Discussion In the univariate analysis age and sex didn't influence prognosis and therapeutic response, the influence of ethnic origin couldn't be assessed as all patients were of the same ethnic origin. Baseline WBCs (P= 0.004) and lymphocytes (P=0.026) were significantly associated with complete response. Higher values of GGT (p=O.OOl); ALP (P=0.006) were associated with more deaths. Baseline CD4 count and HIV viral load were not of predictive value, lthough change CD4 (P=002) and VL (p=.OOO) over time was significant and most likely attributed to response to therapy. 90.9 % of patients reached undetectable HIV-l Viral loads at month 6. CONCLUSION: Neither CD4 count nor HIV viral load at baseline predicted prognosis or survival; however there was a borderline significance of CD4 (P=0.058) towards a better survival.