Now showing 1 - 5 of 19
- ItemEvaluation of BCL-2 and PARP-1 as potential therapeutic targets to radiosensitise lung cancer(Stellenbosch : Stellenbosch University, 2021-12) Guillaume, Muteba Mpolesha; Akudugu, John M.; Serafin, Antonio M.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Nuclear Medicine.ENGLISH SUMMARY : Lung cancer remains the most incident malignancy worldwide, representing 13% of all cancers. It is also the leading cause of death in the world, accounting for 18 18.2% of global cancer-related deaths. The burden of lung cancer in Africa is increasing due to ag ageing an and population growth, increased prevalence of risks factors such as smoking, occupational exposure, infections, lifestyle changes, and environmental pollutants. The efficacy of many therapeutic strategies has been hindered by normal tissue toxicity and treatment resistance. For many cancer patients, radiotherapy has been the chosen therapeutic option to minimise cancer cell spread by shrinking the tumour while ensuring protection of normal tissue. There is evidence that small molecule inhibitor s can effectively target cell survival signa signalling pathways, but cancer cell cells manage to find molecular escape routes to either repair the damage or evade cell death. Combination therapy appears to be an appropriate approach to address these challenges. Therefore, targeting more than one component of the cell survival signa signalling pathways could potentially sensitise cancer cells to irradiation and improve the outcome of radiotherapy. The purpose of this study was to evaluate the role of targeting the anti-apoptotic (B-cell lymphoma 2 (Bcl -2)) pathway and the DNA repair (poly (ADP ADP-ribose) polymerase 1 (PARPPARP-1)) pathway with specific inhibitors in modulating the radiosensitivity of a lung cancer cell line ( and an apparently normal lung cell line ( For this, Bcl -2 and PARP PARP-1 were inhibited using ABT ABT-737 and ABT ABT-888, respectively. At a dose of 2 Gy, the typical fractional dose in conventional radiotherapy, combined inhibition of Bcl-2 and PARP-1 or inhibition of Bcl-2 alone resulted in significant radio-sensitisation in only the A549 cells. However, at a larger radiation dose of 6 Gy (a potentially useful fractional dose in hypo-fractionated radiotherapy), inhibition of Bcl-2 and PARP-1 markedly radio-sensitised the apparently normal (L132) and malignant (A549) cell lines, respectively. These findings suggest that use of Bcl-2 and PARP-1 inhibitors might be beneficial when combined with conventional radiotherapy, but not with hypo-fractionated radiotherapy when large fractional radiation doses are employed. However, validation of these results with a larger panel of cell lines is warranted.
- ItemSemiquantitative analysis of FDG PET brain scans using Neurostat and SPM(Stellenbosch : Stellenbosch University, 2021-12) Munemo, Lionel Tapiwa; Doruyter, Alex G. G.; Warwick, James; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Nuclear Medicine.ENGLISH SUMMARY : Background: Positron emission tomography using Fluorine-18 2-Fluoro-2-Deoxy-D-Glucose (FDG-PET) has an established role in the investigation of multiple neurological conditions such as neurolupus and epilepsy. FDG PET brain scans are interpreted visually and semi-quantitatively using tools such as Neurostat or SPM. The normal databases used in Neurostat were created over 20 years ago, however since this time there has been a steady advance in camera technology and reconstruction algorithms for semiquantitative analysis. It is possible that results obtained with semiquantitative analysis using Neurostat (old PET databases) are different from results obtained with semiquantitative analysis using SPM (using a new PET database). The aim of this study was to evaluate whether there are differences in study interpretation when the same scans are read in combination with a Neurostat analysis, compared to when they are read in combination with an SPM analysis using a database built with new scan data. Methods: First, a local normal database was built with healthy control data using MATLAB R2014b and SPM12. These scans were obtained from previous research projects and prospectively enrolled participants. All scans were acquired on a Philips Gemini-TF Big bore PET/CT scanner. Second, a test dataset, comprising a mixture of clinical scans and scans of prospectively enrolled participants (other than those included in the normal database), was used to compare interpretation of results when using the SPM-based normal database (SPM) to interpretation results when using Neurostat (NS). Results: A database of normal FDG Brain PET/CT studies for the 19-35 year age group was created from a total of 26 healthy controls (13 men and 13 women – optimally matched for age and gender). The test dataset was comprised of 20 scans in the same age range: 15 clinical cases and 5 controls. Next, two expert readers read scans in the test dataset with the assistance of both the NS outputs and the SPM outputs, in separate reading sessions. There was no statistically significant difference in whether a scan was called normal or abnormal using either Neurostat or SPM. There was also no significant difference when comparing the number of lesions identified. SPM scored lesions as less severe than Neurostat (p=0.006). Conclusion: SPM-based analysis using a locally-developed normal database (with scans acquired on a modern PET-CT scanner) yielded similar results to Neurostat, justifying its continued use. Further evaluation to determine if these results are applicable to older patients with neurodegenerative conditions such as Alzheimer’s disease is planned.
- ItemInfluence of acquisition time and smoothing parameters on Ga-68 wholebody PET/CT image quality(Stellenbosch : Stellenbosch University, 2020-12) Diale, Boitshoko Phenyo; Moalosi, Tumelo C. G.; Mix, Michael; Ellmann, Annare; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Nuclear Medicine.ENGLISH SUMMARY : PET/CT image optimization has been extensively investigated for 18F–FDG PET imaging. Although 68Ga–tracers are already widely used in PET, optimized imaging and reconstruction are still missing. The aim of this research was to optimize image quality for 68Ga scans under the constraint that the administered dose to a patient and acquisition time are limited. Materials and Methods : A Gemini TF Big Bore PET/CT system manufactured by Philips was used to acquire the images. The experimental data was formulated by retrospectively collecting data from patient scans, who had undergone wholebody (WB) PET/CT using 68Ga–DOTANOC for oncological imaging. The patient data sets were analyzed for this study to plan phantom measurements which simulated a typical activity distribution like in the patient scans. The NEMA (IEC) body phantom filled with low contrast and high contrast activity ratios was scanned on the Gemini TF Big Bore PET/CT scanner using the patient acquisition protocol. The data was reconstructed using a default WB reconstruction protocol with different smoothing parameters and varying scan acquisition times for low and high contrast data. Additionally a HN protocol with smaller voxel sizes was also used on high contrast data. The set images were analyzed using R Studio. Image quality parameters such as coefficient of variation (COV%), contrast to noise ratio (CNR), signal to noise ratio (SNR), recovery coefficient (RC%) and uniformity in terms of standardized uptake value (SUV) were acquired. Results: For low contrast COV%, CNR, SNR values varied as follows: 0.89 – 0.99%, 0.96 – 1.08, 0.99 – 1.05, respectively. Values for high contrast varied as follows: 1.03 – 1.16%, 0.84 – 0.91, 0.80 – 0.97. When comparing COV%, CNR and SNR, low contrast images appeared to be superior to high contrast images. The RC% was found to be consistent in both low contrast and high contrast irrespective of the smoothing parameter. Conclusion: The results obtained from the phantom study demonstrated the Philips Gemini TF Big Bore PET scanner’s stability of good uniformity when assessing maximum activity concentration among the different acquisitions, and ability of the scanner to detect or recover radioactivity in low and high contrast images for all reconstruction parameters. From the phantom study results, incorporating the smoothing reconstruction parameter ”smooth” on low contrast images, allowed the reduction of acquisition time to 180 seconds while maintaining acceptable image quality.
- ItemMonitoring various eluate characteristics of the iThemba LABS SnO2-based 68Ge/68Ga generator over time and validation of quality control methods for the radiochemical purity assessment of 68Ga-labelled DOTA peptide formulations(Stellenbosch : Stellenbosch University, 2017-03) Davids, Claudia Ruby; Rubow, Sietske Margarete; Rossouw, Daniel; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Nuclear MedicineENGLISH SUMMARY : PET imaging with gallium-68 (68Ga) has become widely used due to the availability of 68Ge/68Ga generators and DOTA-derivatised peptide ligands for radiolabelling. The purpose of this study was to monitor the eluate of two iThemba LABS 68Ge/68Ga generators over a period of 12 months to ascertain whether all quality parameters of the 68Ga eluate remained stable and to validate different analytical methods used to determine the radiochemical purity of 68Ga-labelled peptides. Two 1850 MBq (50 mCi) generators were eluted daily with 0.6 M HCl and metal contaminants, 68Ge breakthrough, 68Ga yield, pH, sterility and endotoxin concentrations were determined on a monthly basis. The radiochemical purity of 68Ga-labelled peptides was ascertained using high performance liquid chromatography (HPLC) and instant thin layer chromatography (iTLC). iTLC experiments were performed using both dried and undried iTLC plates. iTLC was also carried out on labelled peptide solution that was spiked with 68GaCl3. These results were also compared with those using HPLC. After 12 months the 68Ga yields, total metal contaminants, sterility and endotoxin concentration remained within European Pharmacopoeial limits. The 68Ge breakthrough increased as the generator aged. This can however be minimised by fractionated elution and post-labelling processing of the eluate by anion or cation exchange chromatography. Separation between 68GaCl3 and 68Ga-labelled peptides was obtained using both 0.1 M citrate buffer pH 5.0 (mobile phase 1) and 1 M ammonium acetate : methanol (1:1) (mobile phase 2). The results also showed that the distribution of radioactivity on the iTLC strip could be determined using a dose calibrator when a TLC scanner is not available. Experiments performed using both undried and dried iTLC-SG chromatography paper, demonstrated that despite the statistically significant difference between the sets of results, in practice either undried or dried iTLC may be used. When purified 68Ga-labelled peptides were spiked with 2% of 68GaCl3, separation between the two was obtained on both HPLC and iTLC. However, iTLC underestimated and HPLC overestimated 68GaCl3 content. Of the two iTLC methods investigated, the method using mobile phase 2 was able to separate colloidal 68Ga impurities from the 68Ga-labelled peptides while the method using mobile phase 1 and the HPLC method could not. In conclusion, the iThemba LABS 68Ge/68Ga generator can be considered stable and of use for up to one year after its manufacture. Both the iTLC method and the HPLC method could detect 68GaCl3 amounts less than 2%. The pharmacopoeia states that 68Ga must be less than 3 % on iTLC and less than 2 % on HPLC. Either dried or undried iTLC strips can be used and if a radio-TLC scanner is not available, the iTLC strips developed with mobile phase 1 can be cut at a suitable distance from the origin and the activity on each section can be read in a dose calibrator. iTLC chromatography using ammonium acetate/methanol seems to be the optimal system for routine analysis of 68Ga labelled DOTA-peptides, as it separates both 68GaCl3 and colloidal impurities from the labelled peptides and is a fast and easy technique.
- ItemEvaluation of the effect of low and intermediate frequency electromagnetic waves on radiosensitivity(Stellenbosch : Stellenbosch University, 2016-12) Chinhengo, Angela; Akudugu, John M.; Serafin, Antonio M.; Stellenbosch University. Faculty of Medicine and Health Science. Dept. of Medical Imaging and Clinical Oncology. Nuclear Medicine.ENGLISH SUMMARY : The incidence of epidemic Kaposi’s sarcoma in HIV/AIDS patients is high due to their compromised immune system. HIV-positive individuals presenting with cancer tend to be more sensitive to ionizing radiation and are at a higher risk of developing severe side effects during radiotherapy, and there is a need to develop non-invasive methods to preferentially sensitize cancer cells and reduce therapeutic doses. Here, the effects of 100 and 1000 Hz electromagnetic fields (EMF) broadcast via an argon plasma ray tube at 50 W on the radio sensitivity of apparently normal Chinese hamster lung fibroblasts (V79) and human malignant melanoma cells (MeWo) were evaluated using the colony forming assay. Pre-exposure of the fibroblasts to both fields had no effect on their radio sensitivity, if X-ray irradiation followed within 2 h or at 6 h. Significant radio sensitization was observed when X-rays were administered 4 h after EMF exposure. For the MeWo cells, pre-exposure to 100 Hz resulted in a significant radioprotection when irradiation followed within 6 h. However, treatment of these cells with a 1000 Hz field significantly potentiated the effect of X-rays. When cells were irradiated prior to EMF exposure, the V79 cells were marginally protected by the 100 Hz field and sensitized by the 1000 Hz field. In contrast, the melanoma cells were slightly protected by the 1000 Hz field and sensitized by the 100 Hz field. The survival rate of the normal fibroblasts when treated with 2 Gy, in two fractions of 1 Gy 6 h apart, was similar to those obtained when cells received an acute dose of 2 Gy 6 h prior to or after exposure to both EMF frequencies. On the other hand, the melanoma cells were significantly sensitized when they were either treated with a combination of X-rays and then 100 Hz EMF 6 h later or with a combination of either of the EMF frequencies and then X-rays 6 h later. These data suggest that use of electromagnetic fields may sensitize tumours to radiation therapy and reduce normal tissue toxicity. Informed and well-designed combinations of low-medium frequency electromagnetic fields and radiation therapy might be beneficial in the management of cancers, especially epidemic Kaposi’s sarcoma.