African Journal of Medical Physics
African Journal of Medical Physics (AJMP) publishes novel and high-quality research papers and other material on all topics relating to medical physics, biomedical sciences, medical imaging and molecular imaging for diagnosis, therapy and disease management. The journal provides an effective way to publish original research articles, review articles, short communication, rapid communication, letter to the editor, case report etc. It strives with a passion to publish articles on diverse themes of theoretical, computational, experimental and related clinical research from across the globe on a sole platform where there will be a wide scope to share ideas Involved from latest on-going research. It is the goal of the journal to provide an international forum for education and training in medical physics, radiation oncology, radiation detection, radiation protection, radiation shielding, and radiation response, new technologies development and applications, diagnostic and radiotherapy physics and applications.
Volume 3 Number 2 (2021)
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Low Dose Radiation Therapy for COVID-19 Pneumonia: The Pros and Cons
Samuel Omenka Ode and Taofeeq Ige
To consider the efficacy and detrimental impact of low-dose lung irradiation as an adjunctive treatment in interstitial pneumonia in patients with COVID-19 and to improve the PAO2/FIO2 ratio (Arterial Oxygen Partial Pressure to Fractional Inspired Oxygen), an in-depth review is imperative to satisfy the global health safety. Some medical X-rays like extremity, chest and dental radiographs, involve effective doses of just a few micro sieverts. However, organ doses and effective doses can be tens of millisieverts for extensive fluoroscopic or CT examinations. The impact of the use of LDRT for COVID-19 patients is captured in this work, both the Linear No Threshold hypothesis and hormesis to avert cytokine storm during radiotherapeutic process. It also details reducing inflammation and explains why the general scientific consensus is currently in check of the LNT model as the most appropriate dose–response relationship for radiation protection purposes at low doses, considering the pros and the cons for appropriate medications.
Acceptance Testing and Commissioning of the New Elekta Flexitron Co-60 High Dose Rate Brachytherapy Unit
George F. Acquah, Philip K. Oppong, Bismark Djan, Ruth N. M. Quaye, Adam C. Shulman and Michael Tassotto
A comprehensive acceptance and commissioning was performed on the Elekta’s brand new afterloading brachytherapy platform: Flexitron High Dose Rate (HDR) treatment unit with a Co-60 source (flexisource). This HDR unit makes it possible to accurately deliver very high doses to target volume whiles sparing surrounding organs at risks (OAKs). But to eliminate any systematic uncertainty during treatment delivery, there is the need to carefully perform acceptance testing and commissioning of this unit installed at the Sweden Ghana Medical Centre, Accra, Ghana before clinical use. The process started with acceptance testing to ensure the facility, HDR unit and its components, meets the standard requirements, functions perfectly and conforms to the manufacturer’s specifications. It included checking of ordered inventory and equipment review, visual and mechanical inspections of all components, applicator assembly, functionality checks, facility’s integrity and source strength survey. Then commissioning was done to test the HDR unit’s accuracy, establish baseline parameters and to develop quality assurance (QA) protocols. This process included the commissioning of all treatment applicators, transfer tubes, Treatment Planning System (TPS), and the Co-60 source. All equipment specifications and safety standards were met and functioned as expected prior to commissioning. Air Kerma strength of the newly installed Co-60 source exhibited a deviation of -2.5% as compared to the source strength from the manufacturer’s certificate. The ‘sweet spot’ of the well-type chamber was also determined at 1136 mm dwell position (equivalent to 19.32 nA). Positional accuracy for all applicators was offset by less than ±3 mm and measured dwell times within ±1 sec. After commissioning, the Flexitron unit was put into clinical use and intended radiation doses delivered to target are within planned doses for all applicators. The purpose of this work is to highlight the comprehensive rigorous commissioning and acceptance tests for this new HDR brachytherapy unit as well as the new cobalt – 60 source.
Quantitative Magnetic Resonance Spectroscopy with In Situ Acquisition of Metabolite and Reference Unsuppressed-water Signals from the Human Brain: Implication for Studies of Psoriatic Arthritis
Abdul Nashirudeen Mumuni, Rajeev Krishnadas and Jonathan Cavanagh
Estimation of absolute metabolite concentrations in magnetic resonance spectroscopy (MRS) is a challenging procedure primarily due to the choice and acquisition of the reference signal, against which metabolite peak areas are converted to concentration units. Methods currently available are either complex or take longer data acquisition times, and these situations defeat the clinical utility of quantitative MRS. This study developed and implemented a quantification scheme that involved the extraction of the reference unsuppressed water signal from a standard clinical single-voxel 1H-MRS acquisition, and used novel means of correcting this reference signal for relaxation losses. Both relaxation-corrected metabolite and unsuppressed water peak areas were then used in a model, which was corrected for voxel tissue fraction and their relative proton numbers, to estimate absolute concentrations of N-acetyl aspartate (NAA), creatine, choline, glutamate and myo-inositol in the human brain. Data was acquired from the anterior cingulate cortex (ACC) with TE/TR = 35/2000 ms and bilateral hippocampus with TE/TR = 144/2000 ms of healthy controls and psoriatic arthritis patients (n = 16 in each group), using the standard PRESS localization sequence with CHESS water suppression. The study found lower ACC creatine levels in patients at baseline (p = 0.01), and after receiving anti-inflammatory medication (p = 0.03), compared to healthy controls. Concentrations in the left and right hippocampi were not significantly different (p > 0.05) in both groups. Across the three voxel positions, NAA and choline varied significantly before and after medication respectively. There were no significant gender and age associations with concentrations. Generally, concentration estimates in this study compared with published estimates, indicating that the method is accurate and clinically applicable.
Development of Artificial Intelligence Algorithm for Computer Aided Diagnosis of Brain Tumour (CADbrat) Using Tensor Flow, TFlearn Library and Magnetic Resonance Images
Raymond Confidence, Dada O. Michael, Musa Emmanuel, Oni O. Michael and Awojoyogbe O. Bamidele
Early diagnosis of a brain tumour is very important. It improves patient’s quality of life and offers diverse options for treatment and reduces the financial burden of tumour treatment. In recent years, computational resources have improved, and they are capable of handling large amount of data which are generated during clinical diagnosis. Furthermore, the recent advances in machine learning have made large data analysis in medicine more tractable and interesting. Automated deep learning-based computer-aided diagnosis (CADx) can be deployed as a crucial and reliable tool used for early detection. In this study, a CADx algorithm with high accuracy and sensitivity has been developed to provide assistance to health care givers in the timely diagnosis of brain tumours. The artificial intelligence algorithm made use of Tensor Flow, TFlearn Library and Magnetic Resonance Images as such model optimization was achieved by cascading the convolutional layers with a down-sampling layer (Max pooling) and higher filter number at the inception convolution layer to extract high level features and provide translational invariance down the network. With this model, an average F1-score of 99.49% was obtained despite training the network on a CPU. This amounts to a slightly improved performance of a similar model which was, however, trained on NVIDIA Tesla K40 server (2880 CUDA cores and 12GB memory). To demonstrate the application of the developed convolutional neural network (CNN) algorithms in clinical scenarios, a graphic user interface (GUI) using Flask application programming interface (API) was developed for easy brain tumour diagnosis with MRI scans.
Validation of Machine Performance Check’s Rotation-Induced Couch Shift on Two TrueBeam Linear Accelerators
Kukiriza Grace, Valenti Marco and Parisotto Marco
Daily quality assurance (QA) is an essential requirement of modern radiotherapy. Validation of the performed QA tests is equally fundamental. Machine Performance Check (MPC) measurements were performed on VARIAN’s TrueBeam (TB) STX LINAC, equipped with a PerfectPitch Couch with 6 degrees of freedom (DoF), and TB with 4 DoF couch commissioned in August 2018 and February 2019 respectively. TB STX was routinely used for stereotactic treatments in the department. The MPC’s rotation-induced couch shift results acquired on TB STX and TB, using an IsoCal phantom, was compared with independent QA tests performed using EBT3 Gafchromic Film placed on the couch at SSD 100 cm with 2 cm of RW3 phantom slices as build-up material. The digitized Film was analysed with a home-made MATLAB script. The independent QA tests were performed on five (05) days spread over a month. The mean difference in the rotation-induced couch shift measured with MPC and the Film was computed and graphs plotted. The observed mean difference and standard deviation in the rotation-induced couch shift measured with MPC and the Film was 0.02 mm ±0.02 and 0.04 mm ±0.04 on TB STX and TB respectively. The uncertainty of the Film method resulted to 0.02 mm, and precision was within 0.01mm. The good agreement between rotation-induced couch shifts measured with MPC and the Film validates MPC as a good tool for daily QA tests. The department decided to use EBT3 Gafchromic Film for long term verification of MPC’s rotation-induced couch shift.