Augustine Kwame Kyere’s research while affiliated with University of Ghana and other places

Purpose In vivo dosimetry is a quality assurance tool that provides post-treatment measurement of the absorbed dose as delivered to the patient. This dosimetry compares the prescribed and measured dose delivered to the target volume. In this study, a tissue-equivalent water phantom provided the simulation of the human environment. The skin and entrance doses were measured using GafChromic EBT2 film for a Theratron® Equinox Cobalt-60 teletherapy machine. Methods We examined the behaviors of unencapsulated films and custom-made film encapsulation. Films were cut to 1 cm × 1 cm, calibrated, and used to assess skin dose depositions and entrance dose. We examined the response of the film for variations in field size, source to skin distance (SSD), gantry angle and wedge angle. Results The estimated uncertainty in EBT2 film for absorbed dose measurement in phantom was ±1.72%. Comparison of the measurements of the two film configurations for the various irradiation parameters were field size (p = 0.0193, α = 0.05, n = 11), gantry angle (p = 0.0018, α = 0.05, n = 24), SSD (p = 0.1802, α = 0.05, n = 11) and wedge angle (p = 0.6834, α = 0.05, n = 4). For a prescribed dose of 200 cGy and at reference conditions (open field 10 cm x 10 cm, SSD = 100 cm, and gantry angle = 0º), the measured skin dose using the encapsulation material was 70% while that measured with the unencapsulated film was 24%. At reference irradiation conditions, the measured skin dose using the unencapsulated film was higher for open field configurations (24%) than wedged field configurations (19%). Estimation of the entrance dose using the unencapsulated film was within 3% of the prescribed dose. Conclusions GafChromic EBT2 film measurements were significantly affected at larger field sizes and gantry angles. Furthermore, we determined a high accuracy in entrance dose estimations using the film.

Background and purpose This paper reports on results from the foremost national survey on external beam radiation therapy (EBRT) treatment practice at the three radiotherapy (RT) facilities in Ghana. It is to survey the current EBRT treatment protocols and its resources available in the country for breast cancer treatment. Results are intended to form the foundation for future clinical research into developing standardized institutional and/or National breast cancer treatment planning guidelines. This will introduce uniformity into EBRT protocols across the three facilities in the country for their breast cancer patients. Materials and Methods The survey was conducted with two online-based questionnaires; a general questionnaire that targeted radiation oncology professionals working in the three RT facilities in Ghana and a follow-up specifically for the radiation oncologists. The first survey was rolled out from 21st August 2020 to 31st December 2020. The second survey was conducted from 15th February 2021 to 31st March 2021 after the initial analysis of the responses from the first survey. The first questionnaire had 54 general EBRT breast cancer treatment questions. The second questionnaire had 14 questions focusing on dose fractionation regimens, definition of treatment targets and organs at risk (OAR) delineation. Results The Google web-based questionnaires had in total 11 responses from the targeted radiation oncologists, medical physicists, and radiation therapists working in the three radiotherapy facilities in the country. The facility response rate was 100% for the survey as there were participation from all three RT facilities. CT-based breast planning was considered standard and used in all three facilities. Reference markers to aid patient positioning and target delineations were employed during simulations. Majority of the relevant OAR associated with breast EBRT were very well defined. 3 dimensional conformal radiotherapy (3DCRT) planning with forward-planning field-in-field (FP-FIF) technique has become the preferred planning of choice. From this survey, there were three medical linear accelerators (Linacs) and two Cobalt-60 (Co-60) treatment units used in treating an average of 750 breast cancer patients annually. Conclusion Results from the survey gave an in-depth overview of the current state of EBRT resources available in the treatment and management of breast cancer in Ghana. Minor protocol variations among the facilities were observed. However, there were strong consensus among the facilities regarding majority of their current existing protocols and possible future techniques/technology implementation.

Medical physics has been an indispensable and strategic stakeholder in the delivery of radiological services to the healthcare system of Ghana. The practice has immensely supported radiation oncology and medical imaging facilities over the years, while the locally established training programme continues to produce human resource to feed these facilities. The training programme has grown to receive students from other African countries in addition to local students. Ghana has been recognised by the International Atomic Energy Agency as Regional Designated Centre for Academic Training of Medical Physicists in Africa. The Ghana Society for Medical Physics collaborates with the School of Nuclear and Allied Sciences of the University of Ghana to ensure that training offered to medical physicists meet international standards, making them clinically qualified. The Society has also worked together with other bodies for the passage of the Health Profession’s Regulatory Bodies Act, giving legal backing to the practice of medical physics and other allied health professions in Ghana. The country has participated in a number of International Atomic Energy Agency’s projects on medical physics and has benefited from its training courses, fellowships and workshops, as well as those of other agencies such as International Organization for Medical Physics. This has placed Ghana’s medical physicists in good position to practice competently and improve healthcare.

Volume computed tomography dose index (CTDIvol) represents an average dose within a scan volume for a standardized CTDI phantom. It is a useful indicator of the dose to the standardized phantom for a specific examination protocol. Dose index (CTDIvol) for head and body PMMA phantoms have been estimated in this study and comparison made with corresponding console displayed doses. The study was performed on 40 slice CT system, and measurements were done with 100 mm long pencil ion chamber connected to an electrometer. Doses were estimated using the AAPM Report 96 formalism. Estimated dose for head scan technique (120 kV, 150 mAs) was 44.30 mGy, deviating from the console displayed dose by 4.49%. The body (pelvic) scan technique of 120 kV and 100 mAs produced a dose estimate of 20.08 mGy in the body phantom, deviating by 3.05% from the console displayed dose. The estimated head and body phantom doses were compared to selected international dose reference levels and varying deviations were observed.

Radionuclide activities in the kidney and bladder have been estimated experimentally from practical data 3 h after injection of Tc-99m MDP, using conjugate view methodology. The study involved sixty-five patient images from the database of a nuclear medicine department in Ghana. Time–activity curve was stimulated with MatLab computer program using biokinetic model published in MIRD Report 13. The model was used to determine theoretical activities in kidney and bladder, which were compared with the experimental data. Estimated radionuclide activities for the kidney and bladder were both minimal in the experimental case comparative to the theoretical. The fraction of injected activity in kidney and bladder were less than 1% of injected activity, and hence kidney and bladder could be seen to receive very low doses during bone scans.

The current brachytherapy treatment planning system employs the TG 43 formalism proposed by the American Association of Medical Physicists in Medicine (AAPM). The TG 43 uses dose rate tables which assume cylindrical symmetry of the sources, and the medium in which the calculation is made is water equivalent, with no modification for different heterogeneities and no account for applicator attenuation. The dose rate tables sometimes require interpolation and extrapolation, which may lead to uncertainties in dose calculations. This work aims to fit functions for the Monte Carlo output parameters generated by Lliso et al. (2001) [10], in the quest to develop a functional form which will reduce the number of independent variables, reduce the uncertainties in dose calculation distribution around the Nucletron pulsed dose rate (PDR) 192 Ir brachytherapy source, and hence to facilitate implementation of the TG 43 formalism. The fitting and verifications were done using different software of the computer, e.g., Matlab, MS word, MS excel. We used Matlab fitting tool to fit the functions for the Nucletron PDR MC output parameters generated by Lliso et al. The accuracy of the fit functional form obtained was verified by comparing the dose rate distribution per unit air kerma strength obtained from the fit, to the dose rate distribution per unit air kerma strength obtained directly for the work of Lliso. For the absolute dose rate error calculations, deviation and mean were used. The average discrepancies in the dose rate per unit air kerma strength (in cGyh −1 U −1) obtained from the fit were all found to be less than 1 %, within the TG – 43 recommended statistical uncertainty limit % 2 . The results from this study, it is hoped can be used as input data in TPS, and to verify calculations of TPS for precise brachytherapy treatment planning.