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 1 Number 1 (2018)

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Page: 1-7
Radiographic Reject Film Analysis in Radiology Department of a Teaching Hospital in Jos, Plateau State, Nigeria

Mangset W. Emmanuel and Adesida O. Samuel

In X-ray examinations, it is common to find patients undergo repeated X-Ray examinations after the initial X-Rays films were rejected for undiagnosable image quality. This often contributes to the radiation burden of the patients and waste of resources or avoidable extra cost in most radiology departments. This study aimed at evaluating the rate at which radiographic films used for diagnoses are rejected; assess the reasons for rejection and to obtain information for further image quality at the Teaching Hospital. A prospective method was adopted using radiographic films of good and poor diagnostic quality for a period of two years (January 2015 to December 2016). A total number of 5761 radiographs were studied, out of which 5285 were of good diagnostic quality. The 476 rejected films were analyzed with respect to size, type of procedure and reasons for rejection. The analysis of the rejected films indicated that over-exposure; under-exposure, poor positioning as well as poor processing contributed 28.39%, 20.65%, 13.87% and 11.29% respectively to the rejection. The reject rate was found to be 7.76% in 2015 and 8.98% in 2016, which are above the World Health Organisation and within the Conference of Radiation Control Program Directors (CRCPD) recommended permissible rate of 5% and (5-10%) respectively. The reasons identified for the film rejection could be due to incorrect setting of exposure factors, lack of communication between the operator and the darkroom technician and quality control test on the processor could be responsible for producing over and under exposed radiographs. The findings imply that the patients may have been exposed to avoidable radiation doses. Regular training in radiographic techniques and standardization of protocols as well as quality assurance measures in the hospital could help reduce the reported reasons for rejection.

Page: 8-13
How Do Pencil Beam Sizes Influence Central Axis Dose Calculations in Theraplan Plus Treatment Planning System?

Oyekunle O. Emmanuel, Akinlade I. Bidemi, Uwadiae B. Iyobosa and Madu B. Chibuzo

Most radiotherapy treatment planning systems (TPS) utilize pencil beam (PB) algorithm for the computation of dose distributions. Each commercial TPS will differ slightly in approach. This study assesses the influence of different PB sizes on the accuracy of Theraplan plus (TPP) dose calculations. Theraplan plus (version 3.8) at Department of Radiation Oncology, University College Hospital, Ibadan, Nigeria contains measured (published) central axis data (CAD) for a telecobalt unit at depths 0.5 – 30 cm. Dose calculations for CAD were performed by the TPS for radiation square fields 4 – 35 cm2 using PB sizes, 0.5, 0.75, 1.0, 1.25 and 1.50 cm sequentially. Statistical comparisons of the resulting doses with the measured were performed using SPSS. Theraplan plus resulted in calculated doses that are predominantly higher than the measured values. The percentage increase ranged from 0.01 – 0.72 %, with the maximum obtained at 30 cm x 30 cm, depth 10 cm, PB size 1.5 cm. Dose calculation accuracy increased from 99.72 – 99.98 % and 99.82 – 99.91 % as the PB size decreased from 1.5 – 0.5 cm for fields 4 x 4 cm2 and 30 x 30 cm2 respectively. Central axis data comparisons at PB size 0.75 cm showed the greatest resemblance with the pattern obtained at 1.0 cm (by default). Pencil beam sizes greater than 1.0 cm tends to reduce the accuracy of TPP dose calculations. The use of 0.75 cm size in TPS may also be reasonable for dose calculations. Dosimetry evaluation including off-axis data comparisons is suggested for further clarifications.

Page: 14-24
Computational Magnetic Resonance Diffusion Tensor Imaging for Probing Human Brain Microstructure

Raymond Confidence, Dada O. Michael, Adesola O. Adewale and Awojoyogbe O. Bamidele

In recent years, diffusion magnetic Resonance Imaging (dMRI) is becoming an impressive modality for studying biological tissues because it provides unique measurements that is sensitive to the microstructure of tissues such that the in-vivo connectivity of the brain could easily be mapped. dMRI has proved to be very crucial in the probe of microstructural changes associated with early signs of disease or tissue regeneration; such signs are themselves, consequences of physiological processes in normal tissue and the progression to disease state. In spite of many interesting applications of dMRI, the mechanisms governing diffusion of water in tissues, especially in the brain is still not well understood. The complexities and extreme organization of tissues often lead to significant non-Brownian behaviour of diffusion such that the present understanding of diffusion tissues mechanisms require new modifications. To address the problem, the diffusion NMR equation has been solved in the rectangular coordinate for a special type of excitation frequency. Analytical expressions were obtained for the diffusion transverse magnetization and diffusion tensor equations to account for directional flow of water. Based on these analytical solutions, a MATHEMATICA computer program was developed to visualize the diffusion and tensor information for various human brain regions and specifically for 3D printing useful for pre-surgical planning and simulation of tumor treatment.

Page: 25-35
Measurement of Natural Radionuclides Concentration and Radiological Impact Assessment of Fish Samples from Dadin Kowa Dam, Gombe State Nigeria

Orosun M. Michael, Adisa A. Adewale, Akinyose F. Cornelius, Amaechi E. Charles, Ige O. Simon, Ibrahim B. Mark, Martins Gbenga, Adebanjo G. Debo, Oduh O. Victoria, Ademola O. John

Radioactivity concentrations of 40K, 232Th and 238U in two majorly consumed fish samples from the Dadin Kowa-dam in Yamaltu-Deba local government area of Gombe State, North-east Nigeria had been determined by Gamma-ray spectrometry. Some radiological impacts were estimated from the gamma results in order to deduce the radiation hazard posed by consumption of the fish in the study area. The mean estimated average dose rate for Catfish and Tilapia was 0.34 and 0.25 nGyh-1 while the average value of annual effective doses for the ingested radionuclide in Catfish for 5 years, 10 years, 15 years, Adults and Fishermen were66.29, 52.92, 44.89, 39.46 and 367.21μSvy-1, respectively and that of Tilapia were 53.07, 42.48, 36.09, 31.81 and 295.87μSvy-1, respectively. These values were less than the acceptable limits of 1000 μSvy-1 for the general populace which implies that all are within the safe limit. The estimated average values of the excess lifetime cancer risk (x 10-3) for 5 years, 10 years, 15 years, adults and fishermen in Catfish were 0.23, 0.19, 0.16, 0.14 and 1.29 while that of Tilapia were 0.19, 0.15, 0.13, 0.11 and 1.04 respectively which implies that the estimated values for 10 years, 15 years and adults are less than 0.2 x 10-3 which is the world average value. Similarly, the average value of annual gonadal effective dose for the Catfish and Tilapia was 88.96 and 70.49 μSvy-1, respectively while that of gamma index was 0.20 and 0.16, respectively. Furthermore, the average value of the external hazard index for the Catfish and Tilapia was 0.07, 0.06, respectively while the internal hazard index was 0.11 and 0.08, respectively. The results show trends that are generally low for most of the radiological impact parameters estimated as recommended by UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) thresholds. Therefore, there may be no serious immediate radiological effects to the general populace in this area. It should be noted that for all the radiological health parameters estimated, the mean values for Catfish is higher than that of Tilapia. So for this reason, Catfish pose more radiological health effects than Tilapia, thus, it is safer consuming Tilapia than Catfish.

Page: 36-42
Diagnostic Reference Level in Computed Tomography: An Evaluation of CT-Protocol Dose Index in a Diagnostic Facility

Opadele E. Abayomi, Akpochafor O. Michael, Ezike C. Jerry, Aweda A. Moses

Recent surveys in large medical centers have found that Computed Tomography (CT) studies now often account for 25% of all examinations and 60 to 70% of the patient dose received from diagnostic radiology (IAEA, 2009). This has created a sense of urgency and the impetus for establishing Diagnostic Reference Level (DRL) and dose reduction strategies. This study presents the assessment and evaluation of patient radiation doses for common CT examinations and derivation of DRLs for common CT examinations. Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) of common CT examinations including: Abdomen, Abdominopelvis, Brain, C-Spine, Chest amongst others were measured using a calibrated GE CT scanner. Data were collected for 402 patients. The mean CTDIv (mGy) and DLP (mGy.cm) for all the protocols were 17.92 & 684.94, 17.09 & 744.56, 51.19 & 852.96, 20.08 & 423.92, 16.8 & 490.07 respectively. When compared with international standards, the great variation in dose distribution was attributed to CT technical parameters, clinical complexity of the patients and inadequate quality control program. There is a dire need to establish local DRL, which are corrective measures that are required in elimination of radiation that does not contribute to overall profile of the patients.

Page: 43-50
PET Image Reconstruction: Automated Assessment of Lesion Detection Performance

Abubakar Ahmad, Glatting Gerhard, Molina J. Flavia

Positron Emission Tomography (PET) imaging is based on measured sinogram. This sinogram consists of an array of the sums of all the counts along the lines connecting two detectors. Therefore, to turn this measurement into images, an image reconstruction algorithms (such as ordered-subset-expectation maximization [OSEM], TRUEX, and filtered-back-projection [FBP]) with different parameters need to be applied. The lesion detection in PET images can be obstructed due to the limited spatial resolution and low signal-to-noise ratio, which could lead to errors and uncertainties, by the physician in reporting the images. To overcome these errors, a reliable method for lesion detection is highly demanded, especially, in oncology unit. This study is aimed to develop a method to determine the optimal image reconstruction algorithm for visual lesion detection on PET images, taking into account the size of the lesion, ROI pixels intensity/activity concentration, algorithms and its parameters. The raw data measurement of a thorax PET phantom (NEMA/IEC 61675-1, 2001) obtained from PET was used for the reconstructions. The phantom has an activity concentration on the background of 5 kgBq/ml, equivalent to the standard patient of 70 kg at initial injected activity of 350 MBq of [18F] FDG. The activity ratio of 18F between hot lesion spheres and background was set to be 4:1. The image reconstruction was carried out on a Syngo MI.PET/CT 2009C\2012A software/work station using iterative reconstruction algorithms of OSEM and with implemented time of flight (TOF). The parameters used for reconstruction were 21/24 subsets for TOF and non TOF, 400 x 400 image size, 3 mm Gaussian filter, zoom 1, 3 min. scan time and the number of iterations for all as follows: 1, 3, 6, 9 and 12. A MATLAB code was developed to analyse the image data. The data were evaluated using a statistical t-test. An ROC analysis was performed using Metz ROC software (ROCKIT 1.1B2 beta version) to authenticate the test. The ROC area under the curve (AUC), which determines the detection performance of each investigated reconstruction algorithms, was obtained depending on the lesion size. The AUC for 10 mm sphere lesion with OSEM and OSEM-TOF was within the range of 0.88 ± 0.10 and 0.94 ± 0.08, respectively for all iterations. For combine spheres in all iterations, the AUC were within: 0.95 ±0.03 (OSEM) and 0.96 ±0.02 (OSEM+TOF). It shows that the 22 mm sphere lesion has low AUC standard error. The use of t-test approach allows to automate the comparison of different image reconstruction algorithm. The OSEM-TOF algorithm yield a better result in all the tested sphere sizes reconstructed with different iterations. The method could be improved by using measurements with lower contrast and u-test.

Page: 51-57
Estimation of Entrance Surface Dose and Sex Specific Effective Doses during Chest X-Ray Examinations in Diagnostic Radiology Facilities

Essien E. Imeh, Ekanem Imaobong, Inyang O. Samuel and Umoh Ukeme

The use of ionizing radiation in medical diagnosis has been in practice in Nigeria for sometimes now. The Nigerian Nuclear Regulatory Authority (NNRA) recommends regular assessment of radiation doses from radiation emitting devices in our hospitals to ensure radiological safety of the patients, staff and public. The aim of this study is to estimate the entrance surface doses during routine chest x-ray examinations in diagnostic radiology facilities. These facilities included tertiary (1), secondary (2) and private (1). Three hundred and fifty (350) adult patients took part in the study comprising of 188 male patients (53.7%) and 162 female patients (46.3%). The information required for estimating the entrance surface dose (ESD) included the peak tube potential (kVp), tube loading (mAs), focus to skin distance (FSD), x-ray machine output factor Y(d) and the back scattered factor (BSF) that were substituted into a semi empirical formula. The results show variation in the estimated ESD from facility to facility and between genders. The ESD for male and female patients in the tertiary facility ranged from 0.25 – 0.58 mGy with a mean value of 0.43±0.04 mGy and 0.26 – 0.56 mGy and with a mean value of 0.41± 0.05 mGy respectively. Mean ESDs of 0.29±0.01 mGy and 0.24 ±0.02 mGy were obtained for male and female patients respectively in one secondary facility while the mean ESDs of 0.22 ±0.02 mGy and 0.19±0.02 mGy were obtained for the other secondary facility. The mean ESD values obtained from the private facility were 0.17 ±0.01 mGy for male and female patients respectively. The sex estimated effective dose using the recommended tissue weighting factors by the Kramer et al and Xu and Recee shows that the radiation effective dose for female patients could be underestimated when gender of the patients has been not considered.

Page: 58-69
Radiation Doses Received by Adult Patients during Pelvic Radiographic Examinations in Selected Radio Diagnostic Centres within Lagos State, Nigeria

Balogun A. Fatai, Tchokossa Pascal, Adeyemi O. Fredrick3, Olowookere J. Christopher

Quality Control test of facilities for radiodiagnosis and measurement of patient doses are essential in procedure optimization. The study aimed to conduct quality control tests and provide adult patient dose estimates for pelvis examination being carry out at 8 selected x-ray facilities in Lagos metropolis so as to provide an initial assessable indication of each site’s typically achievable radiation safety and quality standard. Exposure and machine parameters were used with Monte Carlo PCXMC software to estimate the mean doses delivered to 278 patients examined during routine radiodiagnostic examinations. Organ and effective doses were determined. Organs that received significant doses during the pelvic AP radiography are urinary bladder and ovaries. Ovaries received mean dose of 1135.1 ± 258 mGy and 1429.6 ± 436 mGy for male and female respectively while urinary bladder received mean doses of 210.9 ± 99.0 mGy and 181.1 ± 71.2 mGy for male and female respectively during pelvic LAT. The significant doses received by these organs are attributable to their location in the pelvic region. The mean entrance surface air KERMA (ESAK) delivered to patient during pelvic lateral examination is greater by a factor of 1.56 than the mean ESAK received during pelvis antero-postero procedure. The results of the study indicate that stochastic health effect of Mean dose to patients resulting from pelvis radiography is projection dependent. Female patients received higher effective dose than their male counterparts did.

Page: 70-77
Reconstruction of Conventional Ultrasound 2-D Images to Ultrasound Tomographic Images Using MATLAB Software

Dunama M. Amina, Liman M. Sanusi, Aliyu S. Abubakar

Ultrasound images modality is an imaging method using mechanical waves that can transmit through different materials like fluid, soft tissue and solids. Ultrasound machines use sound waves with frequency ranging between 2 to 15MHz. ultrasound tomography is an imaging method capable of producing slice images with high spatial resolution. This paper presents examinations of body obtained with the developed ultrasound tomography model. The studies use real biomedical data obtained from Mindray DC-3 ultrasound machine, which enables to obtain three-dimensional images in the same way as in the classical Computed Tomography (CT). The advantage of this method is that patients are not exposing to ionizing radiation. The system uses conventional ultrasound two-dimensional images, normal 2-D probe and tomographic reconstruction software in MATLAB. The image reconstruction is based on implementing Projection Code, Fourier Slice Theorem and Image Reconstruction Algorithms. The method enables to acquire a much larger amount of information and resolution. Based on the results obtained in this study, it is anticipated that ultrasound tomography may contribute to the creation of a new standard of diagnosis of soft tissue without exposing any patient to radiation.

AJMP is the official journal of FAMPO

Published by the Global Health Catalyst