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 4 Number 1 (2022)
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High-throughput, high-availability automated planning for radiotherapy clinics in low-resource settings
Marquez Barbara, Gay Skylar, Douglas Raphael, Zhang Lifei, El Basha Daniel, Huang Kai, Cardenas Carlos E. and Court Laurence E.
The Radiation Planning Assistant (RPA), a web-based tool for automating the treatment planning process in radiation oncology, can significantly reduce the staff and time needed for treatment planning in low- and middle-income countries. To enable clinical use, the RPA must output radiation plans consistently and reliably, especially as it is deployed to clinics around the world. To test reliability, we performed a thorough capacity study of the RPA for treatment of two disease sites: cervix and head & neck. The RPA architecture consists of several, multi-capacity computing modules (contouring, plan creation, optimization, quality assurance) that process patients serially. Completion times for each module were measured by processing 25 cervix and 25 head and neck (H & N) patient datasets through the entire workflow. Each module was also modelled in a manufacturing discrete event simulator (ManPy) to evaluate serial and parallel workflows. Model accuracy was evaluated by comparing the simulator’s completion times for single- and multi-patient queues to those of the RPA system. Reliable performance of the RPA was reported as number of radiation plans generated in 24 hours assuming all systems were operating. Finally, module downtime scenarios were simulated to determine their impact on baseline performance of the RPA’s daily throughput. An independent t-test showed that the discrete event simulator realistically modelled mean processing times. The model estimated that the RPA could process 483 cervix plans, 255 H & N contours, or 258 H & N plans in 24 hours with all systems operating. Downtime simulations showed that cervix plan generation remained within 5% of its baseline throughput unless any given module (except for the plan/dose quality assurance module) went down for 3 hours or more. H & N contour generation remained within 5% of its baseline when downtime for either of its two contouring modules did not exceed 1 hour. H & N plan generation remained within 5% of its baseline until downtime for at least 2 of 5 available volumetric arc therapy (VMAT) optimization modules exceeded 1 hour, or any other module’s downtime exceeded 3 hours. Plan calculation and report generation downtimes had <5% effect on output through 4 hours of downtime. The RPA architecture is robust to downtime of its individual modules and can provide a reliable service to clinics with limited resources.
Dosimetric Evaluation between Volumetric Modulated-Arc Therapy (VMAT) and Intensity Modulated Radiotherapy (IMRT) Treatment Techniques for High-risk Prostate Cancer Planned in Three Phases
Adeneye Samuel Olaolu, Eseoghene John Awhariado, Joseph Adedayo, Salako Omolola, Habeebu Muhammad, Omojola Daniel, Adeniji Adeoluwa, Adebayo Abe, and Rasak Lawal
The primary objective of this study is to evaluate the conformity and homogeneity indices using VMAT and IMRT treatment techniques for prostate cancer planned in three phases. Eighteen participants participated in retrospective research. Using VMAT and IMRT treatment procedures, three Planning Target Volumes (PTVs) of varying dose prescriptions were planned and calculated individually. The dosimetry parameters were all derived from each plan’s dose-volume histogram (DVH), to calculate and evaluate the conformity index (CI), homogeneity index (HI), and dose to organs at risk (OARs). There was no statistically significant difference in the means of CIs for all the phases (PH 1, PH 2, and PH 3) between the IMRT (1.02 ± 0.01, 1.00 ± 0.0, 1.02 ± 0.05) and VMAT (1.02 ± 0.0, 1.01 ± 0.0, and 1.00 ± 0.0), respectively. There was no statistically significant difference between the means of the HI for all the phases (PH 1, PH 2, and PH 3) of IMRT (1.07 ± 0.01, 1.04 ± 0.0, 1.05 ± 0.03) and VMAT (1.06 ± 0.01, 1.04 ± 0.0, and 1.03 ± 0.0) plans, respectively. A greater percentage reduction in dose to the OARs was recorded for VMAT. VMAT turned out to be superior to IMRT at a lower dose to the OARs for high-risk prostate cases planned in three phases (PTVs).
Effect of Practice of Transferring Patients Scanning Protocols between Computed Tomography Scanners
Ogundipe A. Olugbenga, Nicholas Ade, Oketayo O. Oyebamiji
Radiation protection of patients, as they undergo computed tomography (CT) diagnostic examinations, should be considered to ensure their safety. One way to achieve this is to guide against unhealthy ‘migration’ of scanning protocols between CT scanners, as reported by the International Committee for Radiation Protection. The aim of this study was to determine the effect of migrating CT scanning protocols between CT scanners by estimating and comparing effective doses of selected examinations across eight CT facilities. Eight CT units (GE, Hilight, Hispeed.CT/I (No SmB) (GHH), Toshiba Aquilion 16 (T16), Siemens Sensation 4 (SS4), Picker UltraZ (PUZ), Philip Brilliance 64/40 (PB64), Mx8000IDT/Brilliance 16 (MxIDT), Philips AV. LX, SR7000 (PAV) and GE Pace, Sytec (PS)) were selected. A CT patient dosimetry calculator, CT-RADOSE was used to determine effective dose to the head, chest, abdominal and pelvic regions from CT scanning parameters for 36 patients. Data analysis was done using Microsoft excel package. The estimated effective dose values ranged from 0.32±0.12-0.82±0.31 and 0.89±0.22-2.21±0.55 mSv at 80 kVp and 120 kVp respectively for head CT, 1.76±0.57-3.83±1.24, 4.70±1.12-10.03±2.51 and 5.95±1.21-13.33±3.36 mSv at 80, 120 and 140 kVp respectively for chest CT, 9.70±2.53-14.21±3.55, 14.79±3.15-21.33±4.54 mSv at 80 kVp, 120 kVp and 140 kVp respectively for abdominal CT and 3.43±1.11-4.34±1.39, 8.37±2.18-10.77±2.69 and 12.11±2.76-15.12±3.29 mSv at 80 kVp, 120 kVp and 140 kVp respectively for pelvic CT. Differences in the calculated effective dose values between the eight CT scanners were found to be statistically significant, (p < 0.05). Significant differences in the values of effective dose among the eight CT scanners suggest an increased risk of radiation exposure to patients when CT scanning parameters are indiscriminately transferred between CT scanners.
Radiotherapy Plan Quality Assessment: Current Tools and Future Directions
Gronberg Mary P., Netherton Tucker J., Beadle Beth M., Cao Wenhua, Cardenas Carlos E., Chung Christine, Fuller Clifton D., Garcia John, Hancock Donald, Howell Rebecca M., Jhingran Anuja, Lee Anna, Lim Tze Yee, Moreno Amy C., Olanrewaju Adenike, Peterson Christine B., Whitaker Thomas J., Court Laurence E.
As artificial intelligence is increasingly adopted in radiation oncology, we have the opportunity to turn our attention toward its use in improving the quality of radiation treatment plans. In this work, we present an overview of patient-specific plan quality assessment tools found in the literature and discuss the pros and cons of each. The findings of an institutional consortium of radiation oncologists, dosimetrists, and physicists who reviewed currently available plan quality assessment tools are presented and include the types of tools they found most beneficial in the clinic, improvements they would like to see in currently available tools, where in the treatment planning process plan quality assessment tools should be implemented, and potential novel applications. Finally, future directions are considered, including the role of plan quality assessment tools in clinical trials, education and training, and peer review.
Evaluation of Iodine 131 Absorbed Dose in Graves’s Disease Therapy: A Gate Geant 4 Monte Carlo Simulation Study in Niamey, Niger
Adamou Soli Idrissa, Ousmane Manga Adamou, Moussa Issoufou Djibrillou, Adehossi Eric, Bouyoucef Salaeddine
In this study, a Monte Carlo simulation in Gate Geant4 was used to calculate the Iodine-131 absorbed fractions for beta particles with the mean energy of 167 keV and gammas with a mean energy of 397 keV. The radiation sources are uniformly distributed in ellipsoid phantoms made from PMMA material. The simulations for the electrons and gamma sources were done separately in order to shoe the contribution of each type of radiation. Each patient was administered with the same activity and the volume of the ellipsoidal phantom corresponding to the size of his thyroid. The absorbed dose fractions for beta and gamma were thus evaluated for all the 45 patients referred to the Nuclear Medicine departments of the Radioisotopes Institute in Niger and the University hospital of Bab el Oued, Algiers, for Radioiodine therapy of Graves’ disease. The mean beta absorbed dose fractions was 5.11 E-05 and 4.99E-06 for gammas rays. The S factor is a factor that indicates the value of the energy absorbed in a target organ when a Radionuclide decays in a source organ. The mean S factor in this study was 1.04E-03 for the absorbed dose fractions β and γ. The mean absorbed dose evaluated using MIRD method was 205.01 Gy while the simulations gave an average absorbed dose of 256.35 Gy using for both methods a target dose of 200 Gy. This approach showed that the Gate code GEANT4 is a suitable tool for dose calculations in internal dosimetry in Nuclear Medicine applications, as well as in radiation protection.
Measurement of Computed Tomography Dose Quantities at Some Radiological Units of Abuja Hospitals
Joseph Teryima Iortile and Taofeeq Abdallah Ige
Computed Tomography (CT) is a valuable diagnostic modality used for treatment of patients but has become a potential threat due to cancer risk. To address this concern, measurement of computed tomography dose quantities at five radiological units at Abuja hospitals were investigated using polymethyl methacrylate phantom (PMMA), ion chamber and integrated electrometer labeled A, B, C, D and E respectively. The results obtained for the body phantom for computed tomography dose index (CTDIvol) range from 6.30±0.01 mGy to 10.8±0.004 mGy and its estimated dose index (CTDIw) range from 4.68±0.01 mGy to 20.02±0.01 mGy. While the CTDIvol for head phantom range from 19.18±0.004 mGy to 70.0±0.90 mGy and its estimated dose index (CTDIw) range from 10.38±0.004 mGy to 37.32±0.90 mGy. The dose ratio for the body phantom range from 0.31±0.01 mGy to 1.56± 0.01 mGy, while that of head phantom range from 1.39±0.03 mGy to 1.88± 0.90 mGy. The dose length product (DLP) for body phantom range from 152.08± 0.01 mGy.cm to 677.40±0.01 mGy.cm and that of head phantom range from 230.14±0.004 mGy.cm to 1075.00±0.90 mGy.cm. The results indicate that the body phantom labeled A- C was within the acceptable limits of 10-40 mGy. While that of head phantom was also within the acceptable limits of 40-60 mGy from centres A-D except centre E (70 mGy) that had values above the accepted limits. Similarly, the dose length product (DLP) at centres A, B, C was within the European Diagnostic Reference Levels for body (650mGy.cm) and head (1050mGy.cm) phantoms. Except centres D and E that was above the European Diagnostic Reference Levels for body and head Phantoms respectively. The differences in the results of the study imply a need for optimization of some computed tomography examinations protocol and quality control measures.
Calibration of Various Detectors for Commissioning of Total Body Irradiation for a New Installation in Maggiore Hospital, Trieste-Italy
Festo Kiragga and Rosella Vidimari
Calibration of detectors: Gafchromic EBT3(GAF) and Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) was done under reference conditions for use in Total Body Irradiation (TBI) conditions. Three Source Axis Distances (SAD) were chosen: 5m, 4.5 m, and 4m with minimal or no backscatter from the wall. Lateral-Lateral (LL), gantry angle 90o, collimator angle 0o, and 6 MV energy were chosen with respect to the nature of the bunker. Percentage Depth Doses (PDDs) were evaluated, first with a big water phantom using calibrated dosimetry diode, P and then also with RW3 slab phantom (30 x 30 x 30 cm3) at the three positions using GAF. Afterwards, the PDDs were then compared allowing the beam to be characterized in different setups. MOSFETs calibration factors corresponding to each channel were also obtained by first measuring the average dose with a Farmer chamber under reference conditions in the same position. Then the MOSFETs were cross-calibrated against the Farmer chamber. A length of 140 cm (pediatric) was found to be in the flatness region with a dose variation of 3%. GAF, and MOSFETs were calibrated and a calibration curve was plotted for GAF while a table of calibration factors was made for the MOSFETs to be used in TBI conditions. A dose variation of less than 2% was achieved between the Farmer chamber and GAF readings at similar points in the RW3 phantom. The beam characteristics were important parameters to understand the behavior of the beam in non-reference conditions (TBI conditions). These were within the tolerance range as dose variations of up to ± 10% are allowed in TBI conditions. The doses measured with the calibrated Farmer chamber and GAF were compared with less than 2% difference and this meant that the GAF can be used in any TBI setup. Therefore, the bunker was found fit for carrying out the TBI technique, particularly for pediatrics.
Evaluating the Performance of Transfer-Learning Approaches for Multiclass Classification of Glioma, Meningioma and Pituitary Tumour
Adewole Maruf, Ige A. Taofeeq, Anazodo Udunna, Akpochafor O. Michael, Adewole Adetunji, Adeyomoye Adekunle and Aweda Moses
Brain tumours are one of the deadliest types of cancers as only 36% of brain tumour patients survive five years after diagnosis. Brain tumours are detected and classified by biopsy -an invasive procedure with the potential to impede brain function and introduce infections. Diagnostic imaging approaches using anatomical magnetic resonance imaging (MRI) have minimized the use of pre-treatment biopsies for detection, but current visual classification of brain tumour images using expert readers have not improved classification accuracy enough to eliminate biopsies. Transfer learning is a machine learning technique where a previously trained model serves as the foundation for a model on a new problem. Recent advances in Convolution Neural Network (CNN), offer promise in using brain MRI to accurately classify brain tumours. Here, we evaluated the performance of 26 CNN models previously developed for general image classification in classification of brain tumours. We retrained 3064 T1-weighted contrast-enhanced MR images from 233 patients with either meningioma (708 images), glioma (1426 images), or pituitary tumour (930 images) using pre-trained weights from the ImageNet dataset and compared classification accuracies of the CNN models. This study provides an exhaustive evaluation of various state-of-the-art CNN models using a large publicly available multiclass brain MRI dataset. EfficientNetB3 had the highest accuracy of 98.98% in classifying tumor type among the 26 models tested. DenseNet121, EfficientNetB2, EfficientNetB5, and EfficientNetB4 also showed high accuracy in identifying the tumor type, with all models achieving an accuracy of more than 97%.
Optimizing the CBCT Technique and Analysis for LINAC Synchronized NIPAM 3D Dosimetry
Kawtar Lakrad, Mark Oldham, Hamid Chakir and Justus Adamson
Linac Synchronized NIPAM (LS-NIPAM) 3D dosimetry utilizes on-board CBCT to read 3D dosimeters, while the measured dose is inherently synchronized with the on-board imaging coordinate system. The main issues are the limited signal strength and the lack of reliable and widely available analysis tools. Our goal is to develop a practical LS-NIPAM 3D dosimetry system that is applicable on a wide scale for accurate 3D dosimetry. An initial irradiation consisted of a simple 3-field plan (6 MV-FFF, 25 Gy), then an AAPM TG119 C-Shape plan was used as a clinical verification. We compared iterative and standard reconstruction algorithms as well as the impact of a variety of imaging metrics on NIPAM image quality. VistaAce (v 0.7) was used for data analysis. The Contrast to Noise Ratio (CNR) increased considerably when the iterative reconstruction algorithm was used (4.7 to 11.8). The measured dose agreed with the dose from the treatment planning system for the 3-field plan, with a pass rate of 95.6% for 3%3mm and 94.5% for 5%2mm. The results from VistaAce were verified via a second analysis using MATLAB and 3D Slicer with both analyses methods in agreement. The initial analysis of the TG119 C-Shape plan shows promising agreement. The developed CBCT technique demonstrated high CNR and high agreement with TPS dose which uses averaged pre-irradiation CBCTs subtracted from averaged post-irradiation CBCTs and using an iterative reconstruction technique. The VistaAce software shows promise as a robust and widely applicable 3D dosimetry analysis tool, including for LS-NIPAM 3D dosimetry.
Therapeutic Radiation Needs in Pediatric Oncology
Kristin Schroeder, Palak P. Patel, Bradley Ackerson, Mwitasrobert Gisiri, Nicole Larrier, Nestory Masalu, Nelson Chao, Adam C. Olson, Beda Likonda
Most new pediatric cancer diagnoses are in LMICs, where survival rates range from 5-25%, compared with 80% in high-resource countries. Access to radiotherapy, a key component of cancer treatment, is extremely limited in East Africa. The objective of this study was to assess and describe the need for radiation therapy for pediatric oncology patients at a tertiary referral center in Tanzania. This study conducted a retrospective review of pediatric oncology patients treated at BMC from 2010-2014. The indication for radiation therapy was deduced from contemporary SIOP and COG protocols. Two radiation oncologists estimated the potential benefits of radiotherapy, both for curative and palliative intent, based on age, diagnosis, and stage at presentation. A total of 221 pediatric patients were included. The most common diagnoses were Burkitt lymphoma (n = 36), other non-Hodgkin lymphoma (n = 33), Wilms tumor (n = 32), acute leukemia (n = 28) and retinoblastoma (n = 23). Treatment regimens included chemotherapy only (74%), surgery only (2%), and both (14%). No patients received radiotherapy due to lack of availability. Of the 144 evaluable cases, radiation therapy was found to have been included in the treatment plan for 34% of patients (95% CI: 26-42%). Of these, 84% (95% CI: 74-94%) would have been treated with curative intent and 16% (95% CI: 6-26%) would have benefited from palliative radiotherapy. One-third of the evaluated patients were deemed to benefit from radiation as part of their treatment, with most regarded for curative intent. Introducing radiotherapy has the potential to improve pediatric cancer outcomes in this region.
IAEA-led Advances in Nuclear Technology Applications: A Comprehensive Review of 2019-2022
Williams Igoniye and M. A. Briggs-Kamara
The idea that prosperity is linked to health is supported by a prolonged usage of nuclear technology in the medical industry. Between 2019 and 2022, a detailed evaluation of the global and African trends in nuclear application in the health sector was conducted. The most important advancement in the treatment of gynecological cancer is the introduction of intra-operative instruments like the portable gamma-camera. The IAEA has recently provided Namibia, a new machine to tackle the rise in cancer incidences, particularly skin cancer. To accomplish SDG 3: Promote well-being, the Peaceful Uses Initiative (PUI) has funded 16 programs that aim to combat cancer on a worldwide scale. It’s a great idea to include the electron beam in the IAEA’s external audit service. Brazil, Cuba, Germany, Greece, Indonesia, Italy, Malaysia, Mauritius, Mexico, Spain, and the United States of America are among the countries that are advancing the use of SIT for mosquito control. The participation of Africans in IAEA programs is highly recommended for development.
An Introduction to Physics in Healthcare
Elizabeth M. Parvin
This article is based on an introductory talk given to the Harmattan school in March 2021. It aimed to show undergraduate physics students some of the many ways the concepts and techniques covered in a physics degree course are applicable to important diagnostic and therapeutic techniques used in modern medicine. Medical physics can be said to have begun with the discovery of X-rays in 1896; developments since then have resulted in sophisticated CT scanning. Other diagnostic applications developed by physicists include ultrasound, nuclear medicine, magnetic resonance imaging, endoscopy, and pulse oximetry. Radiotherapy, which uses several different types of ionising radiation, plays an important role in cancer treatment. Another key role for physicists is in radiation protection. Medical physics offers many exciting opportunities for physics graduates, and they are encouraged to consider it as a career path.
Pressure Dependence of Water 1H Spin Relaxation Rates in Model Hydrogel and Intervertebral Spinal Discs
Wilson M. Egadwa, Mark Pearcy and Konstantin Momot
Back pain is a major cause of disability. It is estimated that around 540 million people worldwide are currently suffering from back pains. This numbers are likely to increase especially in the low- and middle-income countries which are experiencing an increase in life expectancy. It is projected that 70–90% of people will have to experience some form of back pain in their lifetime with 10% experiencing disability as a result. Spine stiffness, neck and low back ache are the most common forms of back pain. Most cases of lower back pain have been shown to be associated with inter-vertebral disc (IVD) degeneration. MRI is a tool used to qualitatively detect structural deformities to the IVD resulting from degeneration. However, these deformities manifest in the terminal stages of degeneration. A method is needed to improve the sensitivity of MRI to quantitatively measure progression of degeneration from the onset of the disease which can vastly improve treatment outcomes. It has been observed that a reduction in Nucleus Pulpous (NP) hydrostatic pressure is one indicator of disc degeneration and that there is a direct correlation between fluid pressure inside the Nucleus Pulposus and the axial load on the disc. The NP hydrostatic pressure is currently measured using discography; an invasive procedure with the potential to further damage the IVD. Previous studies have also shown that MR spin relaxations rates of water protons are sensitive to mechanical stress on the Nucleus Pulposus. However, it is still not clear whether this is due to changes in the chemical composition due to water efflux or if it is due to hydrostatic pressure per se. In this study, the dependence of spin relaxation times in model connective tissue on the hydrostatic pressure is presented. Samples of Gelatine Hydrogen 90% w/w and 10% w/w and oxtail Nucleus Pulpous were separately subjected to confined axial compressive stresses and analysis of their relaxation rates made. Measurement was done using NMR relaxation imaging and validated using NMR spectroscopy R1 measurements. R2 measurements were conducted using Spin Echo technique and FOV of 128 pixel x 128 pixels. From Sync 3 pulse, a series of Free Induction decays were acquired and then Fourier transformed. The area in each spectrum indicated the level of magnetization left after polarization pulse. The integration was implemented by use of Bruker Topspin 1.5 software. Plotting areas as a function of time and fitting was done using custom made Mathematica 4.1 (Wolfram research, Inc.) program to the equations. The measurement outcome was inconclusive, with most parts of the experimental results showing that within physiological pressure alone, in the absence of compositional chemical changes, it is not capable of inducing significant changes in relaxation rates. Further studies are proposed to confirm the results.
Assessment of Knowledge and Attitudes of Radiotherapy Professionals Towards Prevention of Incidents during Treatment in Nigeria
Emmanuel O. Oyekunle, Bidemi I. Akinlade and Taofeeq A. Ige
This study assessed the attitudes and knowledge of radiotherapy professionals towards prevention of incidents or accidents during cancer treatment in Nigeria. A cross-sectional study was conducted among Medical Physicists (MPs), Radiation Oncologists (ROs) and Radiation Therapists (RTs) at 9 radiation oncology centers in Nigeria as of December 2018. The questionnaire comprising 50 questions relevant to the study were administered following ethical approval by the Institutional Ethics Committee. SPSS version 20.0 was used for data analysis and results are presented in tables and figures. 83 (65.9%) of 126 population participated in the study. Mean cumulative percentages of 81.33 ± 16.68 and 89.55 ± 8.47 were obtained respectively for participants’ attitude towards radiation safety practices and their knowledge of the role played by MPs in incidents’ prevention. However, of the 83 respondents, 25.3%, 31.3%, 20.5% and 20.5% affirmed previous occurrences of Co-60 retraction failure, off-target dose delivery, interchange in field sizes and dose delivery to a different patient in external beam radiotherapy respectively. The mean difference of knowledge scores between RTs and ROs (p = .012) and between RTs and MPs (p = .000) were statistically significant. Accidents or incidents could occur in radiotherapy due to technical and human errors. This was a maiden work to characterize radiotherapy incidents and various responders in a national study. The study demonstrated that medical physicists, with the cooperation of ROs and RTs have a pivotal role to play in preventing radiotherapy incidents.