Measurement of Natural Radioactivity and Assessment of Radiological Hazard Indices of Soil Over the Lithologic Units in Ile-Ife Area, South-West Nigeria.

The distribution of natural radioactivity levels of 238U, 232Th, and 40K in soils overlying the 3 lithologic units within Obafemi Awolowo University, Ile-Ife, Nigeria was investigated to characterize the gamma radiation dose distribution over the lithologies and to assess the radiation hazard due to the natural radionuclides. A thallium-doped cesium iodide detector was employed to determine the activity concentrations of 238U, 232Th, and 40K in 21 soil samples. The respective average concentrations of the 3 radionuclides are 37.7, 3.2, and 245.6 Bq kg-1 for granite gneiss, 31.9, 2.8, and 241.1 Bq kg-1 for banded gneiss, and 21.1, 1.7, and 196.7 Bq kg-1 for mica schist. The average concentration of 238U in granite gneiss lithology exceeds the world average value. The evaluated values of radiation hazard parameters including average absorbed dose rate, outdoor annual effective dose and external hazard index are below the recommended limits. The spatial distribution of the radiation hazard parameters evaluated over the lithologies has been delineated. The highest average cancer risk of 1.15 per 10 000 population was obtained for the study area within the soil overlying the banded gneiss lithology. Generally, the radiation hazard from the soils in study area poses no significant health hazard.

Thyroid dose and cancer risk from head and neck computed tomography at two selected centres in Nigeria.

OBJECTIVE: The objective of this study was to evaluate the thyroid glands' radiation dose and the risk of thyroid cancer induction from head or neck computed tomography (CT) examinations. METHODS: In a prospective study, we evaluated all participants of all ages and sex referred for Head or Neck CT Scan at the University College Hospital, Ibadan and Me Cure Healthcare Limited, Ibadan, Oyo State, Nigeria. Thyroid radiation dose was estimated with impact scan calculator, and real-time dose measurement with thermoluminescent badge dosimeters (TLDs). Data were analysed and P < 0.05 was considered statistically significant. RESULTS: One hundred and sixty-three participants (128 adults and 35 children) participated in the study. In most participants (74%), the tube voltage was 120 kVp. The estimated median thyroid gland dose by the imPACT scan calculator was 4.95 mGy (range = 1.20-30.0 mGy) and 4.40 mGy (range = 3.0-5.10 mGy), while the real-time dose measured by the TLD was 4.79 mGy (range = 1.73-96.7 mGy) and 2.33 mGy (range = 1.20-3.73 mGy) at Centre A and B, respectively. The estimated median thyroid cancer risk was 2.88 × 10-6 (maximum range of 52 × 10-6) at centre A and a median value of 3.20 × 10-6 with a cancer risk estimate that may reach 17.9 × 10-6 recorded at centre B, compared to a cumulative thyroid cancer risk of 0.12 × 10-5 among the general Nigerian population. CONCLUSIONS: Scanner specifications and technique may significantly contribute to variations seen in thyroid radiation doses. There may be a need to optimise centre protocols and apply dose reference levels for head and neck CT examinations to reduce thyroid cancer risk in Nigeria.

Determination of Residential Soil Gas Radon Risk Indices Over the Lithological Units of a Southwestern Nigeria University.

Radiation dose from natural sources is mainly from exposure to radon in the environment. Radon has its origin from uranium-bearing bedrocks and overburden. In the present study, assessment of the level of radon over the three lithological units upon which the residential areas of ObafemiAwolowo University Campus, Ile-Ife (OAU) was situated was carried out. Soil gas radon concentration measurement was carried out at a constant depth of 0.80 m across the three lithologies (granite gneiss, grey gneiss and mica schist) using a RAD7 electronic radon detector. A total of 138 in-situ soil gas radon measurements were carried out. Obtained experimental data were analysed and summarised using descriptive and inferential statistics with statistical significance set at p < 0.05. A radon potential map was also developed using existing permeability data of the soils in the area. Soil radon concentration varied across the different lithologies ranging from 0.04 kBq/m3 - 190 kBq/m3 with a mean value of 14 kBq/m3. The mean value of Rn-222 concentration obtained in the three lithologies are 3.5 ± 5.9, 11.5 ± 25.8 and 28.4 ± 37.4 kBq/m3 for granite gneiss, grey gneiss and mica schist respectively. There is a statistically significant difference (p < 0.001) in the mean concentration of radon-222 measured on the three lithologies. The granite gneiss and grey gneiss lithologies have been designated into low radon index, while mica schist lithology has been designated as medium radon index. 34% of the sampled areas exhibit high radon risk based on Swedish risk criteria, thereby warranting protective actions.

Radon risk perception and barriers for residential radon testing in Southwestern Nigeria.

Objectives: The seriousness and long-term health effects of radon exposure are often underestimated due to inaccurate perceptions of radon risk. The aim of this study was to assess radon risk perception and barriers for residential radon levels testing among Obafemi Awolowo University faculty. Study design: A quantitative cross-sectional design was used for this study. Methods: Lecturers' residents of the Obafemi Awolowo University participated in the study. A semi-structured questionnaire was administered to 296 residents to assess their knowledge about radon and determine their perceived susceptibility to radon health risks. Data were analysed and summarised using descriptive and inferential statistics. Results: The respondents' mean age was 43 â€‹± â€‹8.5 years and 71% were male. The study revealed that awareness of radon was low (46%), while 61% of respondents had poor knowledge. Only a fifth (19.5%) of the respondents had a high perceived risk of radon, and 70% were not aware of measures to detect radon in their respective homes. A majority (74%) of the respondents reported not knowing where to get a radon testing kit as a barrier to radon testing. Professional background (p â€‹< â€‹0.001), academic qualification (p â€‹< â€‹0.05) and designation/cadre (p â€‹< â€‹0.001) were the major determinants of radon knowledge among residents. Moreover, religion and profession were statistically significantly related to the perception of residents about radon risk (p â€‹< â€‹0.05). Conclusion: Despite having a high level of education, knowledge/awareness about radon health risks is low in the Obafemi Awolowo University faculty members; furthermore, lack of knowledge about house testing supplies are a significant barrier to residential testing.

Tandem-ring dwell time ratio in Nigeria: dose comparisons of two loading patterns in standard high-dose-rate brachytherapy planning for cervical cancer.

PURPOSE: In high-dose-rate (HDR) brachytherapy (BT), the source dwell times and dwell positions are essential treatment planning parameters. An optimal choice of these factors is fundamental to obtain the desired target coverage with the lowest achievable dose to the organs at risk (OARs). This study evaluates relevant dose parameters in cervix brachytherapy in order to assess existing tandem-ring dwell time ratio used at the first HDR BT center in Nigeria, and compare it with an alternative source loading pattern. MATERIAL AND METHODS: At the Radiotherapy Department, University College Hospital (UCH), Ibadan, Nigeria, a total of 370 standard treatment plans in two alternative sets were generated with HDR basic 2.6 software for one hundred and eighty five cervical cancer patients. The initial 185 individual plans were created for clinical treatment using the tandem-ring dwell time ratio of 1 : 1. Modifying the initial applicator loading ratio, the second set of plans with related dose data were also obtained for study purposes only. Total reference air kerma (TRAK), total time index (TTI), ICRU volume, treatment time, point B dose, ICRU bladder dose, and rectal points dose were evaluated for both sets of plans. RESULTS: The means of all evaluated dose parameters decreased when the existing tandem-ring dwell time ratio (1 : 1) was modified to other dwell weightings (1 : 1 - 3 : 1). These reductions were 13.43% (ICRU volume), 9.83% (rectal dose), 6.68% (point B dose), 6.08% (treatment time), 5.90% (TRAK), 5.88% (TTI), and 1.08% (bladder dose). Correspondingly, coefficients of variation changed by -7.98%, -5.02%, -5.23%, -4.20%, -3.93%, 8.65%, and 3.96% from the existing pattern to the alternative one. CONCLUSION: Tandem-ring dwell time ratio has significant influence on dosimetric parameters. This study has indicated the need to modify the existing planning approach at UCH.

Comparison of doses to the rectum derived from treatment planning system with in-vivo dose values in vaginal vault brachytherapy using cylinder applicators.

PURPOSE: In-vivo measurements to determine doses to organs-at-risk can be an essential part of brachytherapy quality assurance (QA). This study compares calculated doses to the rectum with measured dose values as a means of QA in vaginal vault brachytherapy using cylinder applicators. MATERIAL AND METHODS: At the Department of Radiotherapy, University College Hospital (UCH), Ibadan, Nigeria, intracavitary brachytherapy (ICBT) was delivered by a GyneSource high-dose-rate (HDR) unit with (60)Co. Standard 2D treatment plans were created with HDR basic 2.6 software for prescription doses 5-7 Gy at points 5 mm away from the posterior surface of vaginal cylinder applicators (20, 25, and 30 mm diameters). The LiF:Mg, Ti thermoluminescent dosimeter rods (1 x 6 mm) were irradiated to a dose of 7 Gy on Theratron (60)Co machine for calibration purpose prior to clinical use. Measurements in each of 34 insertions involving fourteen patients were performed with 5 TLD-100 rods placed along a re-usable rectal marker positioned in the rectum. The dosimeters were read in Harshaw 3500 TLD reader and compared with doses derived from the treatment planning system (TPS) at 1 cm away from the dose prescription points. RESULTS: The mean calculated and measured doses ranged from 2.1-3.8 Gy and 1.2-5.6 Gy with averages of 3.0 ± 0.5 Gy and 3.1 ± 1.1 Gy, respectively, for treatment lengths 2-8 cm along the cylinder-applicators. The mean values correspond to 48.9% and 50.8% of the prescribed doses, respectively. The deviations of the mean in-vivo doses from the TPS values ranged from -1.9 to 2.1 Gy with a p-value of 0.427. CONCLUSIONS: This study was part of efforts to verify rectal dose obtained from the TPS during vaginal vault brachytherapy. There was no significant difference in the dose to the rectum from the two methods of measurements.