Browsing by Author "Abbeyquaye, D."

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Patient dose assessment and optimisation of pelvic radiography with computed radiography systems.
(Oxford University Press, 2021) Abbeyquaye, D.; Inkoom, S.; Hammond, N.B.; Fletcher, J.J.; Botwe, B.O.
Patient Dose Assessment and Optimization of Pelvic Radiography with Digital X-Ray Systems
(University Of Ghana, 2018-07) Abbeyquaye, D.
Low doses of ionizing radiation are delivered to the area of clinical interest in projection radiography. However, the application of digital radiography systems (DRS) is characterized by higher doses than film-screen radiography. Radiation exposure of the pelvis is of primary concern because of the radiosensitive reproductive organs in the pelvic region. For the radiation protection of patients, dose monitoring is essential in pelvic radiography and whenever possible, dose and image quality must be optimized to ensure safety of patients. The aim of this study was to assess the entrance surface dose (ESD) and effective dose (ED) to patients undergoing pelvic X-ray examinations with computed radiography (CR) systems, and develop dose and image quality optimization strategies with the aid of an anthropomorphic phantom. Hence, determine the optimum exposure factors for AP pelvic examinations. This was to serve as basis for dose and image quality optimization in pelvic radiography. Patient and phantom radiographic image quality was assessed in terms of signal-to-noise ratio (SNR). The dose and image quality was assessed for 102 patients. Twenty-four different exposures with varying tube potential (kVp), tube current (mAs) and focus-to-detector distance (FDD) were made for the optimization studies. Results of patients‟ dose estimation showed that the 3rd quartile ESD of 2.56 0.60 mGy for pelvis AP radiography was lower than DRLs by at least 24% with ED of 0.27 0.07 mSv. The mean SNR of patients‟ radiographs was 8.5 2.2 which is 70% higher than the recommendation by the Rose model. After the phantom optimization process, the optimum exposure factors were 70 kVp, 12.5 mAs and 100 cm FDD giving ESD and SNR of 1.09 mGy and 16.23 respectively. It was found that the dose could be reduced further by using lower kVp settings than what is currently being used without degradation in image quality of the radiographs. The dose at the optimum exposure factors was reduced by 29.2% with 65 kVp, 12.5 mAs and 105 cm FDD. Thus the SNR of the image reduced by 19.6% to a SNR of 13.0404, which is still of optimum diagnostic quality.
Photocatalytic enhancement mechanisms for novel g-C3N4/ PVK nanoheterojunction
(Materials Chemistry and Physics, 2023) Elloh, V.W.; Boadu, E.O.; Abbeyquaye, D.; Anderson, D.E.; Yaya, A.
The interactions between monolayer graphitic carbon nitride (g-C3N4) and conjugated polymer poly(9- vinylcarbazole) (PVK) have been explored. We investigated the enhanced photocatalytic mechanisms for the novel g-C3N4/PVK nanoheterojunction covering the state-of-the-art of DFT by performing rigorous DFT calcu lations combined with van der Waals corrections (GGA + vdW). The calculated band alignment between g-C3N4 monolayer and PVK monomer clearly reveals that the conduction band minimum and the valence band maximum of g-C3N4 monolayer are higher than those of the conjugated polymer PVK. This predicted band alignment ensures the photogenerated electrons easily migrate from the g-C3N4 monolayer to the PVK monomer, and will lead to high hydrogen-evolution reaction activity. The charge transfer between g-C3N4 monolayer and PVK results in a polarized field within the interface region, which will benefit the separation of photogenerated carriers. The calculated density of electronic states, Lowdin charge transfer and charge density difference certify that this proposed layered nanoheterojunction is an excellent light-harvesting semiconductor. These findings indicate that the conjugated polymer PVK is a promising candidate as a non-noble metal co-catalyst for g-C3N4 photocatalysis. It also provides useful information for understanding the observed enhanced photocatalytic mechanisms in experiments.