[Show abstract][Hide abstract] ABSTRACT: Patients usually undergo repeated X-ray examinations after their initial X-ray radiographs are rejected due to poor image quality. This subjects the patients to an excess radiation exposure and extra cost and necessitates the need to investigate the causes of reject. The use of reject analysis as part of the overall quality assurance programs in clinical radiography and radiology services is vital in the evaluation of image quality of a well-established practice. It is shown that, in spite of good quality control maintained by the Radiology Department of a Teaching hospital in Ghana, reject analysis performed on a number of radiographic films developed indicated 14.1% reject rate against 85.9% accepted films. The highest reject rate was 57.1 ± 0.7% which occurs in cervical spine and the lowest was7.7 ± 0.5% for lumbar spine. The major factors contributing to film rejection were found to be over exposure and patient positioning in cervical spine examinations. The most frequent examination was chest X-ray which accounts for about 42.2% of the total examinations. The results show low reject rates by considering the factors for radiographic rejection analysis in relation to both equipment functionality and film development in the facility.
[Show abstract][Hide abstract] ABSTRACT: A routine dose computation around brachytherapy seeds employing the Fast Fourier Transform (FFT) has been demonstrated and likened to dose computations in a similar field based on the TG43 recommendations. In applying the FFT convolution model to dose computation, a dose convolution kernel which takes into consideration the anisotropy of the dose distribution around a brachytherapy source in the presence of tissue and applicator heterogeneities was presented. Resulting from the convolution kernel were functions with polynomial and exponential terms. The solution to the convolution integral was thus represented by the Fast Fourier transform. The versatility of the Fast Fourier Transform becomes evident with its speed of dose computation and accuracy evenly matched. It has also been described as ubiquitous; as successful procedures developed in one field could easily be adopted in other fields (E.g. external beam and brachytherapy). In typical dose computation procedures, the dose computation time is usually proportional to the number of sources or dwell positions required for the implants and relatively increases for large number of sources. With a dose convolution kernel developed for a 64x64x64 matrix size with wrap around ordering, the kernel was convoluted with the source distributions also in similar matrix size in 3D. Results from the analysis showed the FFT based convolution method in brachytherapy was comparable in speed with computerized treatment planning system whose model is based on the recommendations of the TG43. Further development on the FFT incorporating techniques such as the Monte Carlo simulation will be required to fine tune the potency of the FFT convolution in studying tumor growth and the aftermath upshots of radiation therapy.
[Show abstract][Hide abstract] ABSTRACT: A robust model to directly represent output from contemporary brachytherapy calculation had been proposed and developed to make clinical implementation practicable. The model was used to minimize inherent uncertainties associated with the AAMP TG-43 formalism, with consolidation of the TG-43 parameters into new parameter to speed up computational time. Analytical computations were performed to hybridize the anisotropy function, F(r,theta) and radial dose function, g(r,theta) into a single new function f(r,theta) for a Nucletron microSelectron High Dose Rate “new or v2” (mHDRv2) 192Ir brachytherapy source. Outputs obtained with the new function were curve fitted with MatLab and compared to those of Monte Carlo serving as the standard to evaluate the average and maximum uncertainties. Dose rate deviations between the Monte Carlo data and MatLab fits, quantified as errors showed minimal deviations less than 0.3%. In comparison with Lliso’s study, this work shows marginal improvement in the deviated values. This work has shown much promise in building robust models to represent outputs from contemporary brachytherapy dosimetry calculations.
[Show abstract][Hide abstract] ABSTRACT: Profiles of 1,671 patients undergoing diagnostic mammography examination at three centres in Accra between May and December 2009 were analysed as preliminary survey to formulate a National Breast Screening Policy for Ghana. Employment category, age, body mass index, clinical history and diagnosis were indices used in the survey. The age profile of the patients ranged from 22 to 90 years, with an average of 51 years, and at 95 % confidence interval, the variance in age was 0.01. The dominant age groups of the patients surveyed were 46 - 50 years (23 %), 41 - 45 years (21 %) and 51 - 55 years (20 %). From the body mass indices, 34 % of the patients were overweight, 49 % were obese, 16 % were of normal weight and only 1 % was under weight. By the clinical history and diagnosis, about 25 % of the cases were attributed to mastalgia (pain in the breast), 4 % already diagnosed of breast cancer, while 45 % were undergoing assessment and evaluation. The probability of an obese individual to develop breast cancer out of the entire population was p = 0.0036. The profiles indicated that breast screening awareness programmes should be targeted towards women between of ages of 41 - 60 years.
[Show abstract][Hide abstract] ABSTRACT: Maximum count rate, accuracy, precision, constancy and linearity measurement have been undertaken on two dose calibrators at the Nuclear medicine department, Korle-Bu Teaching Hospital as part of quality control test. Both calibrators show some dependence on measurement geometry which deminishes with increasing depth in the well. It was observed that the measured activities for Co-57, Cs-137 and Tc-99m, obtained from the VDR-15R were larger than those from the reference dose calibrator, Capintec CRC-25R. It was found that, the maximum depth of sensitivity in the Capintec was 6.8 cm and 5.6 cm for Co-57 and Cs-137.VDR showed a maximum sensitivity depth of 5.2 cm for both Co-57 and Cs-137. For accuracy and precision, it was observed that, the percentage differences for the reference dose calibrator, Capintec CRC-25R was a little different from that of the VDR-15 but both calibrators were in the range of ±5% of the mean measured activity. The main difference was their maximum height of sensitivities with values of 6.8 cm and 5.2 cm for Co-57 and 5.6 cm and 5.2 cm for Cs-137 for Capintec and VDR-15R respectively. From the linearity test, there were systematic departures of the data points from the fitted straight line in the upper part and lower part and such discrepancies indicated non-linearity. These discrepancies in the upper and lower part were due to impurities (Mo-99 contaminants and Tc-99 contaminants respectively) in the Tc-99m used in the test which revealed itself in apparent levelling out of the activity in the final part and beginning part of the graph. Since most of the points fitted in the straight line, it showed that, almost all the individual activities measured in the test were within the range of ±10% of the values corresponding to the straight line fitted in the data points. It was observed that, the measured activities difference for both calibrators were very small which was as a result of the differences in depth of their wells. The dose calibrators can be used for dose measurements.