EFFECTIVE DOSE AND RISK ESTIMATES IN ADULT PATIENTS FROM FOUR RADIOLOGICAL PROCEDURES EXTRAPOLATED OVER TWO POPULATIONS AT SOME SELECTED CENTERS IN LAGOS STATE, NIGERIA.

In this study, risk of exposure to adult patients in some common radiological procedures was estimated at selected diagnostic centers in Lagos State, Nigeria using estimated average effective doses. The results showed that pelvis lateral (LAT) examination with the lowest estimated mean effective dose level (2.61) recorded the highest probability of cancer incidence and mortality occurrences, while lumbar anteroposterior (AP) had the lowest (3.61). A high sum total of probability of fatal cancers and the total weighted probability of non-fatal cancer in a single exposure to low-dose ionizing radiation were recorded in pelvic procedure among others. Also, a high-percentage mortality increase of solid cancers was recorded in chest PA examination (53.7%), while the lowest was in lumbar spine radiography (with lumbar AP = 0.14%, lumbar LAT = 0.15%). The data obtained suggested the possibility of having higher percentage mortality and cancer-related incidence in the chest.

Shielding of beta and bremsstrahlung radiation with transparent Bi2O3-B2O3-TeO2 glasses in therapeutic nuclear medicine.

High-energy beta emitters (yttrium-90, strontium-89 and phosphorus-32) are nowadays increasingly used in therapeutic nuclear medicine. Beta particles and bremsstrahlung (photons produced when beta particles interact with materials) are harmful and should be shielded in order to protect the personnel and public from their harmful effects. This work determined the radiation yield, effective atomic number and range associated with the interaction of beta particles with a transparent xBi2O3-30B2O3-(70-x)TeO2 glass system (where x = 40, 50, 60 and 70 mol%) using the ESTAR database and programme; and other relevant equations. The properties of the studied glass systems were compared with transparent lead glass, which is unwanted in the medical settings because of lead's toxicity. The result of this work showed that the studied glasses are suitable for use in making vials, syringes and other transparent materials, necessary for shielding high-energy beta particles. All the studied glass systems can replace lead glass.

Natural radioactivity in some rocks employed as dimension and decorative stones in the Nigerian building industry.

The natural radioactivity in some selected granites and allied rocks from the Basement Complex of Nigeria for use as dimension/decorative stones was measured by gamma-ray spectrometry. The average activity concentrations observed for the selected rock samples range from 9 to 124 Bq kg⁻¹; 13 to 60 Bq kg⁻¹ and 1360 to 2326 Bq kg⁻¹ for ²²6Ra, ²³²Th and 4°K, respectively. The mean radiological hazard indices were 121.62 nGy h⁻¹; 239.73 Bq kg⁻¹; 0.65 Bq kg⁻¹ and 0.77 Bq kg⁻¹ for the absorbed dose rate, radium equivalent, external hazard and internal hazard, respectively. The results obtained were examined on the basis of existing International recommended limits and compared with data on similar rocks from other parts of the world. The values obtained for the rocks, except one, were found to be lower than the values recommended for building materials, and the rocks are considered safe for use as decorative stones as defined by OECD criteria (NEA-OCED Nuclear Energy Agency Dose Constraints in Optimisation of Occupational Radiological Protection Report by NEA Group Experts, OCED, France (2011)). Results highlight the fact that, despite meeting certain suitability criteria such as colour, texture, etc., the radioactivity content of the rocks is another factor of importance for their continued application in the human environment/building industry.

Radiological study of soils in oil and gas producing areas in Delta State, Nigeria.

Measurements of radioactivity concentrations in soils around the oil and gas producing areas in Delta State of Nigeria were carried out using a high-purity germanium detector gamma-ray spectrometer. Soil samples were collected from 20 locations from the study area and analysed. The radionuclides detected are traceable to the primordial series of (238)U and(232)Th as well as (40)K and traces of globally released (137)Cs. The specific activity values ranged between 7 and 60 Bq kg(-1) with a mean of 24±2 Bq kg(-1) for (238)U; while for (232)Th the range was 7-73 Bq kg(-1) with a mean of 29±3 Bq kg(-1). Relatively higher specific activity values were recorded in (40)K with a range of 15-696 Bq kg(-1), while the mean was 256±37 Bq kg(-1). However, a relatively low-specific radioactivity was obtained from(137)Cs with a range of 1-25 Bq kg(-1) and a mean of 7±1 Bq kg(-1). The estimated dose equivalent obtainable per year from these levels of radioactivity is <5 % of the recommended safe level of 1 mSv per annum. Therefore, the area and the use of the soils as building materials may be considered safe.

Determination of the elemental constituents of a natural dolerite using NIRR-1.

Elemental characterization of natural dolerite obtained from South Western Nigeria has been carried out using Nigeria Research Reactor-1 (NIRR-1) located at the Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria. The measurements showed the presence of aluminum, calcium, magnesium, titanium and iron with concentrations 69,990+/-3499, 61,140+/-8.0, 38,330+/-3929, 13,880+/-1804 and 8319+/-150 ppm, respectively, as the major elements. In addition, 16 other elements, in minor and trace quantities, including Th, a radioactive rare earth element and five other rare earth elements La, Ce, Sm, Dy and Lu were identified. The presence of the rare earth elements may be a confirmation of the previous argument that the observed single but broad glow peak in the glow curve of this rock is rather an overlap of more than one glow peak. The presence of Th suggests the possibility of internal radioactivity in the rock, a necessary criterion for using a material for luminescence dating. Thus, this work indicates that dolerite can be used for luminescence dating if properly developed for the purpose.

Re-usable low density polyethylene arm glove for puerperal intrauterine exploration.

OBJECTIVE: To design a long arm glove that can be used within a puerperal uterus to prevent the health-care worker contracting HIV from an infected patient. The designed long arm glove should be cheap (affordable) and readily available in low resource centres and must have proven sterility assurance and tensile strength to confer protection for the health worker. DESIGN: Prospective study. SETTING: Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria from 1st December 2006 to 31st May, 2007. SUBJECTS: Fifty medical students of both sexes were selected randomly and the average length from the styloid process to the mid upper-arm of each was measured and the average length was later determined. This was to determine the length of the low density polyethylene long arm gloves to be made from virgin polyethylene material. Consecutive cases of patients with retained placentae in the puerperium who were scheduled for manual removal of the placenta within the period. RESULTS: Packs of low density polyethylene (LDPE) long arm gloves were made from virgin polyethylene material. When subjected to bacteriological analysis, three out of four glove packs were contaminated with Staphylococcus, Bacillus and Klebsiella species of bacteria. Gamma irradiation ranging from 28.133 to 83.35 kiloGray of gamma-irradiation (kGy) sterilised all the gloves as postirradiation glove specimens showed no bacterial contamination. However, at doses up to 50 kGy gamma irradiation caused "strengthening" of the polyethylene gloves. While at doses greater than 50 kGy, gamma irradiation caused "embrittlement" of the material. Thus, 50 kGy of gamma irradiation was found to be an ideal dose to strengthen and to sterilise the glove for usage. The sterilized gloves were found to be effective when used in consecutive cases of retained placenta in protecting the health care workers (HCW) from contamination by possibly HIV contaminated blood. CONCLUSION: There is a risk of contracting HIV for the health-care worker while carrying out a procedure within the puerperal uterus. The low density polyethylene arm glove was designed to prevent this in low resource centres as it would be affordable, available, with proven sterility assurance and mechanical properties to confer protection for the health care worker.

Radiological parameters and radiation doses of patients undergoing abdomen, pelvis and lumbar spine X-ray examinations in three Nigerian hospitals.

Thermoluminescent dosemeters (TLDs) have been used to measure the entrance surface doses (ESDs) of patients undergoing pelvis, abdomen and lumbar spine diagnostic X-ray examinations in Nigeria. A total of three public hospitals and 171 patients were included in this investigation. The ages of the patients involved were from 40 years to 85 years, while their weights ranged from 64 kg to 73 kg. Mean, median, first and third quartiles of ESDs are reported. The results showed that in most cases, for each of the examinations, the individual ESD values are found to be comparable with, and higher than, those from Ghana and Tanzania, respectively. The mean ESD values are also found to be within the range of mean ESD values that have been previously been reported from countries outside Africa. When compared with the European Community (EC) reference values, the mean ESDs were found to be below the reference values in only two of the hospitals. The ranges found in this work are high and this indicates more attention needs to be given to X-ray facilities in the country. This also suggests that radiographic departments need to review their radiographic practices in order to bring their doses to optimum levels. Effective doses were also calculated from the ESD values. The mean effective doses were found to be generally low when compared with those found in the literature from other countries including two African countries. The radiographic parameters used for all the patients were also compared with the European criteria. It is recommended that the tube filtration at one hospital be increased. The importance of good regulatory activities and trained personnel is stressed in this work. Apart from the fact that the data provided in this work will be useful for the formulation of national guidance levels, they also provide patient dosimetry information on healthcare level IV countries.

Survey of radiological techniques and doses of children undergoing some common x-ray examinations in three hospitals in Nigeria.

A dosimetric survey has been carried out in order to investigate typical radiation doses for children undergoing a number of common x-ray examinations in Nigeria. The results presented in this work are derived from the data of 226 children from three different hospitals included in the survey. Assuming the sample is representative of national practice patterns, pediatric chest examinations are the most frequent radiological examinations. Doses were measured by attaching thermoluminescent dosimeters to the patient's skin to determine entrance surface dose (ESD). The mean and standard deviation of the individual ESD values are reported. Comparisons were made between these doses and diagnostic reference levels, and also between the doses and those from other countries. The mean ESD values in the present work are found to be generally higher than those found in an UNSCEAR document and the NRPB diagnostic reference levels. The ratio of maximum ESD to minimum ESD, a parameter that characterizes ESD variation, was found to be less than 10 in each of the hospitals, while across the three hospitals the ratio was found to be greater than 10. The reasons for the high mean ESD and the variations in patients' ESD values have been discussed in terms of regulatory control, personnel, difference in radiological techniques, performance of x-ray facility, film processing condition, and the type of film-screen combination used. The results presented in this work will form part of the baseline data needed for deriving national guidance levels of pediatric radiological examination. In addition, it will also serve as a source of additional information on pediatric patient dosimetry. Suggestions are given on how to reduce doses to pediatric patients during x-ray examinations, especially in developing countries.

Background gamma terrestrial dose rate in Nigerian functional coal mines.

Measurements of the background terrestrial gamma radiation dose rates at different indoor and outdoor locations on the surfaces of Okpara underground and Okaba open cast mines in Nigeria were made. Two duly calibrated low-level gamma survey metres were held 1 m above the ground surface for these measurements. Measurements were also made at various locations inside the mine tunnel at the Okpara mine. Results indicate that the indoor background gamma radiation is comparable for both mining environments. The mean outdoor gamma dose rate determined for the Okaba mining environment is 10.4 nGy h(-1) as against 11.7 nGy h(-1) for Okpara. The ranges are 8.5-16.5 nGy h(-1) for the Okpara measurements and 7.5-14.0 nGy h(-1) for Okaba. Thus, the outdoor gamma dose rates appear to be generally lower at the Okaba open cast mine than at Okpara. The indoor dose rate values range from 11.0 to 17.0 nGy h(-1) in both environments. These indoor measurements have nearly the same mean values 14.4 and 14.5 nGy h(-1) for Okpara and Okaba environments, respectively. The indoor to outdoor dose rate ratio is 1.2 for Okpara and 1.4 for Okaba. These values are in consonance with the corresponding ratio given in literature. Dose rate measurements inside the mine tunnel at the Okpara mine are higher than the surface indoor measurements ranging from 13.5 to 20.5 nGy h(-1) with a mean of 16.5 nGy h(-1). The higher dose rate values measured in the mine tunnel are attributable to the concentration of radon in the 'closed' environment of the mine tunnel.

Whole-body doses of occupationally exposed female workers in Nigeria (1999-2001).

The work described in this note is based on the national dose registry of radiation workers in Nigeria kept by the Federal Radiation Protection Service. In each of the three years (1999-2001) used for this analysis, the number of male radiation workers was more than that of female radiation workers in both medicine and industry. The ratio of the number of female radiation workers to that of their male counterparts, however, is smaller in industry. The mean of the annual doses of all radiation workers increased from 3.6 mSv in 1999 to 4.7 mSv in 2000 and to 7.7 mSv in 2001. This increase was a result of the yearly increase in mean annual doses to radiation workers in industry. In the industrial category, the mean annual doses of female radiation workers were higher than those of their male counterparts in 1999 and 2001 in both occupation categories. In 2000, while the mean annual doses were the same for both male and female radiation workers in the medical category, the mean annual dose of male radiation workers was higher than that of female radiation workers in industry. Female radiation workers received the highest annual doses in 1999 and 2001. These results indicate the need for the regulatory authority to pay more careful attention to the control of female radiation workers' exposures.

Analysis of occupational doses of workers on the dose registry of the Federal Radiation Protection Service in 2000 and 2001.

In 2000 and 2001 about 279 and 221 radiation workers, respectively, were monitored by the Federal Radiation Protection Service, University of Ibadan, in Nigeria. The distribution of the occupational doses shows that the majority of workers received doses below 4 mSv in each of the two years. The radiation workers in the two years are classified into two occupational categories: medicine and industry. The mean annual effective doses, collective doses and the collective dose distribution ratios for workers in each category and the entire monitored workers were calculated. The mean annual effective doses were compared with their corresponding worldwide values quoted by UNSCEAR. In each of the two years, a few workers in industry received doses higher than 50 mSv. The collective dose distribution ratio was found to be about 0.49, which is very close to the highest value of 0.5 in the range of values considered by UNSCEAR as normal for this parameter. This suggests that extra measures have to be taken, particularly in industry, to ensure that the proportion of workers at risk does not go outside this normal range. The occupational doses were also modelled by both the log-normal and Weibull distributions. Both distributions were found to describe the data in almost the same way.

Measurements of X ray absorbed doses to dental patients in two dental X ray units in Nigeria.

Measurements of absorbed doses from radiographic examinations to various anatomical sites in the head and neck of patients with an average age of 45 years using intra-oral dental radiography have been carried out. LiF (TLD-100) dosemeters were used for the measurements of the absorbed dose. The measured absorbed doses to the various anatomical sites in the two units are reported, discussed and compared with results from the literature. Quality control measurements were also performed using a Victoreen quality control test device on the X ray units. The tube voltage accuracies for the two units were found to be within acceptable limits (less than +/- 10%). On the other hand the exposure time accuracies for these units have large deviations (>20%). These results and those that have been reported in the literature may be an indication that high patient doses are common in most dental X ray centres and countries. As a result of this, regular compliance and performance checks of dental diagnostic X ray equipment are essential in order to ensure proper performance and to minimise unnecessary patient and operator doses.

A comparative study of elemental composition of human breast milk and infant milk substitutes.

Instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) analysis have been employed to determine the concentration of 13 elements in human breast milk, various infant formulas, and locally produced cereals from Nigeria, as well as from various infant formulas and natural cow and goat milk available in the UK. The study shows that if the locally produced cereal is to be used on a regular basis for babies in Nigeria, then their diet must be supplemented with essential trace elements. Furthermore, parents should be discouraged from giving their infants cow and goat milk because of the high concentration of major elements compared to human breast milk.