Volume 2 Number 1 (2019)
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Challenges of Using Small Gantry Bore Computed Tomography in Simulation of Breast Cancer Patients for Teletheraphy in Resource Poor Environment
Hassan Ibrahim and Rilwanu Idris
The radiation therapy simulator has been an integral component of the treatment planning process for over 30 years. Conventional radiotherapy simulators are currently being replaced by virtual computed tomography (CT) simulators in many centres across the world, and their demand is constantly increasing with the wider adoption of three-dimensional conformal and intensity-modulated radiation therapy. However, in Nigeria the story is not a successful one, because CT scanners with small gantry bores of 70 cm (for diagnostic procedures) were dedicated to linear accelerators in majority of centres across the country. This present an obstacle to the CT simulation process by limiting patient positions, compromising reproducibility and treatment setup errors. This study aim at finding errors that occurred due to change in standard positioning (midline laser alignment) of breast cancer patients during CT simulation. Data were retrospectively collected from treatment planning system (Render 99) of previously planned breast cancer patients. Off midline laser coordinate was redefined to midline on each previous planning CT image and lateral couch movements were determined on both plans (midline and off midline). Data obtained were analysed using SPSS version 20.0 (Chicago L). Sample -t- test was conducted to find any significant differences in couch positioning between the two plans during treatment setup. Mean, standard deviation and standard error of mean were also determined and presented in tabular form. Thirty CT scan images of breast cancer patients planned for chest wall radiotherapy were retrospectively reviewed. They comprise of 16 and 14 CT images of left and right breast respectively. The mean scores, standard deviations and mean standard error of the left lateral couch movements using standard midline coordinates were 7.7 cm (range of 5.8 cm to 9.7 cm ), 1 cm and 0.3 cm respectively as against off midline coordinates of 1.6 cm (range of 0 to 6.1 cm), 1.9 cm and 0.5 cm. Similarly, the mean, standard deviation and standard error of mean for the right lateral couch movement using standard midline coordinates were 6.3 cm (range of 3.7 cm to 8.4 cm), 1.8 cm and 0.5 cm respectively, as against 1.4 (range of 0 to 4.3 cm), 1.5 cm and 0.4 cm for off midline coordinates. A highly significant difference was found in both left and right plans by comparing plans using midline coordinate and off midline coordinates. Small gantry bore (70 cm) CT-simulator dedicated to linear accelerators is a huddle to successful breast cancer patient simulation. It causes deviation from standard laser at midline simulation of breast cancer patients which results in to major treatment setup error.
Participation in IAEA/WHO TLD Postal Dose Audit Programme: A Voice from Nepal
Chaurasia P. P., Chand S. B., Adhikari M. P. and Yadav R. N.
The study determined the variation across the measured output dose of Cobalt-60 and linear accelerator photon beams using IAEA postal TLD. The megavoltage beams of Cobalt -60, 1.25 MEV , Varian 600 C/D , 6MV and Varian 2300 C/D, 6 MV and 20 MV clinically calculated 2Gray dose is delivered to TLDs in 10cm depth in water phantom in a 10cmx10cm field center following the SSD technique from 2007 to 2015 . The results of postal TLD irradiation mean dose with standard deviation 2.056±0.043, 2.018±0.040, 2.056 ± 0.041 and 2.04±0.056 respectively in a total of 18 runs performed against machine output variation was checked and adjusted. Audit was directly effective in identifying the problem and in rectifying new Cobalt 60 output dose. The TLD postal dose audits indicated high levels of accuracy of dose determination in audited Radiotherapy (RT) beams in subsequent audit runs in B. P. Koirala Memorial Cancer Hospital (BPKMCH). It is assured that the basic dose calibration is accurate and within tolerance here to treat patients with more confidence.
Radiation Doses and Risks in Computed Tomography Examinations at three Hospitals in South-Western Nigeria
Mary-Ann E. Ekpo and Rachel I. Obed
This study is aimed at estimating the radiation doses and associated risks in computed tomography examinations at three hospitals in South-western, Nigeria. A total of 238 adult patients’ data were retrieved from three different scanners (Toshiba Aquillion 64-slice, Philips Brilliance 16-slice and GE 8-slice) representing three hospital facilities in Lagos, South-Western Nigeria. Data retrieved were: demographic data and exposure-related parameters. Measurements of CT dose indexes (CTDI) were performed on the scanners and CT-ExPO dosimetry software was used to estimate absorbed dose to the organs. Risk of cancer was also estimated using the mean effective doses and the ICRP 103 conversion factors. Mean organ doses for the brain, eye lens, thyroid, breasts, stomach, ovaries/testicles for head, chest and abdomen CT procedures were (58.1, 74.9, 12.6, 19.5, 25.4, 25.3/3.8) mGy respectively. Mean CTDIvol and DLP values for the head, chest and abdomen procedures from the three hospitals were 43.2±13.9, 14.4±4.86, 14.0±5.31 and 973.1±421.5, 433.2±162.3, 699.1±322.4 respectively. The overall risk of cancer per procedure ranged from (8-30) x 10 -5/Sv, (40-52) x 10 -5/Sv, (9-18) x 10 -5/Sv for head, chest and abdomen CT scans respectively. These values were comparable to other values obtained in literature. Large variations in mean organ doses were observed among same CT procedures in the different hospitals. These variations depended largely on the variations in CT protocols used in the different hospitals and scanner type. Protocols tailored to clinical indication, patient size and scan region will contribute largely to protocol optimization. It is important that facilities optimize exposure parameters so as to stay within acceptable limits of radiation dose.
Clinical Significance of the Abdominal Height Measured With a Locally Made Abdominometer for Risk Evaluation of Subclinical Atherosclerosis
Sirisena Anil U. I., Okeahialam Basil N., Ike Emeka E., Chagok Nestor M.D., Pam Stephen D. and Ani Charles C.
Obesity is considered one of the main risk factors of cardiovascular diseases and anthropometric indices such as waist circumference (WC), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR) and body mass index (BMI) are used to classify the level of obesity in clinical practice. Intima-media thickness (IMT) of common carotid artery measured by B-mode ultrasound is widely used as a surrogate marker to evaluate the risk level of subclinical atherosclerosis. The objective of this study was to determine the clinical utility of abdominal height (AH) as an anthropometric index for risk evaluations among the existing ones. Non elastic measuring tape, bathroom scale and locally made abdominometer were used in taking measurements to determine all the anthropometric indices. A GE Logiq 5 Expert Duplex ultrasound scanner was used to measure the values of right common carotid artery (RCCIMT) of 221 apparently healthy adult Nigerians. IBM SPSS Version21 software was used in data analysis. Correlations as well as receiver operating characteristic (ROC) curves to determine the cut-off values were carried out. It was found that AH had the highest correlation coefficient, R= 0.386 at 0.01 level with RCCIMT than other indices. Moreover, it was found that AH had the greater area under the curve (AUC) in ROC curves (0.712) with higher significance than WHtR and BMI. Therefore, abdominal height can be used in clinical practice with high level of significance and accuracy for subclinical atherosclerotic risk evaluation in obesity
Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) Properties of Undoped and Doped Gamma-Aluminium Oxide (γ-Al2O3)
Aligba Evelyn H., Agba Hemen E. and Fiase Joseph O.
Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of commercially available γ-Al2O3 (99% pure) powder in undoped and doped forms were investigated for the possible use of the material in radiation dosimetry. The samples used for the study were γ-Al2O3 doped with 0.0g, 0.1g, 0.5g, and 1.0g of carbon graphite. The four samples were synthesized to 12000C for four hours. Experiments were performed using the Risø TL/OSL-DA-15 Reader equipped with a 90Sr/90Y beta irradiator. The Risø Analyst and curve fitting technique were used to determine the glow and decay curves, dose response, reproducibility, signal sensitivity, linearity, activation energy and frequency factor of all the samples irradiated up to 10Gy. The result of the investigation showed that dosimetry with the samples provides a wide dose response range up to 10Gy and also good linearity. The dosimetric peaks of the glow curves obtained were predominantly about 2000C (2520C, 2440C, 2880C and 2440C) for all the samples studied. The TL reproducibility of the samples studied were 2.6%, 1.4%, 1.3%, and 1.2% and the OSL reproducibility of the samples studied were 17%, 11%, 7%, and 5% for samples doped with 0.0g, 0.1g, 0.5g, and 1.0g carbon graphite respectively. This technique is particularly attractive due to its low cost, short reaction times and straight forwardness to prepare compared to the commercial fabrication processes. Therefore, a dosimetric material prepared by this method can be used for personnel dosimetry.
Photon Absorption Buildup Factors in Different Concrete Types for Structural Radiation Shielding Application
Olarinoye Oyeleke and Mohammed Bello
Concrete is one of the most widely used materials for structural radiation shielding application. However, the shielding capacity of a concrete has been argued to depend largely on its constituent materials and sometimes its mass density. Hence concretes with different composite materials are expected to perform differently when used for shielding purpose. This research reports the estimation of the equivalent atomic numbers and photon Energy Absorption Buildup Factors (EABF) for eleven different species of concrete. The relationship between equivalent atomic number, density and EABF was also investigated. The concretes considered were categorized into light and heavy concretes based on their mass density. The EABF were calculated using the well-known geometric progression fitting procedure for photon energies from 0.015 MeV to 15 MeV and for penetration depth up to 40 mfp. An appreciable variation in the EABF was observed at different depth, energy and for each concrete type. The EABF were found to be high in the low and high energy regions and maximum in the intermediate energy section. The variation of EABF with energy and depth was attributed to the photoelectric, Compton scattering and pair production interaction modes. Although most high density concretes show lower buildup factor irrespective of depth and energy, an indication of good photon shielding coefficient. However, based on this study, it is the equivalent atomic number that can be best used to accurately compare the buildup factors amongst concrete rather than density.
Entrance Surface Dose Determination for Common Adult Radiography Examination in Selected Tertiary Hospitals in North Eastern Nigeria
Joseph Dlama Zira, Aliyu Yusuf Salisu, Umar Mohammed Sani, Nzotta Christian Chukwuemeka, Josephine Joshua Tunde, Joseph Dimas Skam, Abdullahi Mundi, Umar Ibrahim, Wiam Elshami Hassan, Nkubli Flavious Boboin, Moi Alhamdu Silas, Ogenyi Prince Ameh, Abubakar Matthew Garba
Patients dose survey is critical in ascertaining the dose received by patients in radiography practice especially with increasing practices and technological advances. The objective of the study is to determine the radiation doses received by patients from radiography examinations in two teaching hospitals in Nigeria. Prospective cross-sectional study was conducted in two Nigerian teaching hospitals located in North Eastern Part of Nigeria. One thousand two hundred patients participated in with 60 patients for each procedure. “Thermoluminiscent” dosimeter chips were used to determine the doses received by patients for each examination. Mean and standard deviation for each examination were obtained and student T-test was used to determine the relationship between the doses received by patients in the two hospitals. Statistical significance was set at p <0.05. Mean weight and age were 60.01±9.0kg and 38.10±9.3 years. The total mean dose and standard deviation for major radiographic examinations were 0.45±0.36mGy for posterior anterior chest x-ray, 0.82±0.44 lateral chest, 0.77±0.41posterior anterior skull, 0.69±0.73 lateral skull, 0.40±0.25, 0.46±0.34 for anterior posterior shoulder and 0.50±0.24 lateral shoulder. There is no statistical significant relationship P>0.05 between doses and technical parameters. Entrance surface doses for radiography examinations were high when compared to that of other regions in Nigeria and African countries. Therefore dose surveys are recommended with the objective of improving exposure optimization and technical procedure in Radiography examination.
AJMP is the official journal of FAMPO
Published by the Global Health Catalyst