PATIENT DOSE ASSESSMENT AND OPTIMISATION OF PELVIC RADIOGRAPHY WITH COMPUTED RADIOGRAPHY SYSTEMS

Digital radiography systems can reduce radiation dose, this capability was harnessed to explore dose and image quality (IQ) optimisation strategies. Entrance surface dose (ESD), effective dose (ED) and organ doses were determined by the indirect method for patients undergoing pelvic anteroposterior X-ray examinations with computed radiography systems. The IQ of patients' radiographs was assessed in terms of signal-to-noise ratio (SNR). An anthropomorphic phantom was exposed with varying tube potential (kVp), tube current-time product (mAs), and focus-to-detector distance (FDD) to determine phantom-entrance dose for the optimisation studies. SNR of each phantom radiograph was determined. Patients' mean ESD of 2.38 ± 0.60 mGy, ED of 0.25 ± 0.07 mSv and SNR of 8.5 ± 2.2 were obtained. After optimisation, entrance dose was reduced by 29.2% with 5 cm increment in FDD, and 5 kVp reduction in tube potential. kVp and/or mAs reduction with an increment in FDD reduced entrance dose without adversely compromising radiographic-IQ.

INDOOR RADON CONCENTRATION AND RISK ASSESSMENT IN SOME DWELLINGS OF OBUASI, MINING TOWN

222Rn concentration indoors was measured in 40 dwellings in the Obuasi municipality, a gold-mining town in the Ashanti Region of Ghana using the LR 115 type II strippable detectors for the two major seasons in Ghana, rainy and dry. The detectors were placed in the bed rooms of dwellers for 6 months each. Average indoor radon concentration varied from 63.9 to 364.9 Bqm-3 with a mean of 152.2 ± 10.9 Bqm-3 in the rainy season and 26.1-119.0 Bqm-3 with a mean of 50.5 ± 3.9 Bqm-3 in the dry season. The effective dose of 3.90 ± 0.3 mSvy-1 for the rainy season and for the dry season, effective dose of 0.6 mSvy-1 were recorded. The seasonal variation of 222Rn concentration indoors showed higher values in the rainy season than the dry season. A dependence was observed between the type of building materials used in building and the indoor radon level.

Assessment of levels of occupational exposure to workers in radiofrequency fields of two television stations in Accra, Ghana

A survey of the radiofrequency (RF) radiation was undertaken within the premises of two television (TV) stations, TVA and TVB, in Accra, Ghana. The primary objective of this study was to determine the level of RF exposure to workers in the TV stations. A spectrum analyser, a bi-conical antenna (30-300 MHz) and a log-periodic antenna (200 MHz-2.0 GHz) were used. Results obtained indicated that the wideband electric field strength levels recorded in this work vary between 0.006 and 58.5 V m(-1) at TVA and between 0.007 and 28.5 V m(-1) at TVB. Compared with the results from TVB, TVA recorded relatively higher values in the 30-400 MHz range, whereas TVB produced relatively higher values in the 400 MHz-1.7 GHz range. Generally, results obtained were found to be below the occupational reference levels of the International Commission on Non-Ionizing Radiation Protection, but at some locations, the field intensity was 4.3 times higher than the reference levels for the general public.

Levels of electric field strength within the immediate vicinity of FM radio stations in Accra, Ghana

Heightened awareness of the ever-expanding use of radiofrequency (RF) techniques and technology has led to mounting concerns from the general public and the scientific community regarding the possible health effects that may arise as a consequence of exposure to RF radiations and has drawn the attention of many researchers the world over. A survey of the RF electromagnetic radiation at public access points in the vicinity of 20 frequency-modulated (FM) radio stations has been made in Accra, Ghana. The fundamental object was to determine the levels of RF fields from FM broadcast antennae within 10-200 m radius about the foot of the FM base station and at a height of 1.5 m above the ground at selected locations. A spectrum analyser and a bi-conical antenna element sensitive and effective within the frequency band of 30-300 MHz were used. Results obtained indicated that the levels of electric field strength ranged from 5.4E-04 V m(-1) at FM station 'O' to 7.4E-08 V m(-1) at FM station 'D'. At a transmission frequency range of 88-108 MHz, the variation of power densities is from 2.5E-10 to 1.5E-17 Wm(-2). These values are very low and are far below the reference level set by the International Commission on Non-Ionizing Radiation Protection and therefore do not pose any known hazard to the inhabitants of Accra, Ghana. The electric field levels presented in this work are comparable with those reported from epidemiological studies conducted elsewhere.

Fuel burnup calculation of Ghana MNSR using ORIGEN2 and REBUS3 codes

Ghana Research Reactor-1 core is to be converted from HEU fuel to LEU fuel in the near future and managing the spent nuclear fuel is very important. A fuel depletion analysis of the GHARR-1 core was performed using ORIGEN2 and REBUS3 codes to estimate the isotopic inventory at end-of-cycle in order to help in the design of an appropriate spent fuel cask. The results obtained for both codes were consistent for U-235 burnup weight percent and Pu-239 build up as a result of burnup.

Assessment of the integrity of structural shielding of four computed tomography facilities in the greater Accra region of Ghana

The structural shielding thicknesses of the walls of four computed tomography (CT) facilities in Ghana were re-evaluated to verify the shielding integrity using the new shielding design methods recommended by the National Council on Radiological Protection and Measurements (NCRP). The shielding thickness obtained ranged from 120 to 155 mm using default DLP values proposed by the European Commission and 110 to 168 mm using derived DLP values from the four CT manufacturers. These values are within the accepted standard concrete wall thickness ranging from 102 to 152 mm prescribed by the NCRP. The ultrasonic pulse testing of all walls indicated that these are of good quality and free of voids since pulse velocities estimated were within the range of 3.496±0.005 km s(-1). An average dose equivalent rate estimated for supervised areas is 3.4±0.27 µSv week(-1) and that for the controlled area is 18.0±0.15 µSv week(-1), which are within acceptable values.

Assessment of radiofrequency radiation within the vicinity of some GSM base stations in Ghana

A radiofrequency (RF) electromagnetic radiation safety survey had been carried out at public access points in 46 towns with 76 Global Systems for Mobile communication cell sites in two major cities in Ghana. The objective was to determine the levels of RF field in residential areas, schools and market places, and compare the measured results with the guidelines set by the International Commission of Non-Ionising Radiation (ICNIRP). Measurements were made with log-periodic antenna coupled with spectrum analyzer. The results varied from 0.85 to 1.07 mW m(-2) and 0.78 to 1.19 mW m(-2) for the transmission frequencies of 900 and 1800 MHz, respectively. The result generally shows a compliance with the ICNIRP limit of 0.024 % but was 108 times higher than a similar survey carried out in Ghana 2 y ago.

Optimisation of patient radiation protection in conventional X-ray imaging procedures using film reject analysis: a demonstration of the importance of rare earth screen-film systems

The optimisation of patient protection was studied using a conventional film screen of speed class 200 and a rare earth film screen of speed class 400. The entrance surface dose (ESD) for the two film-screen systems was determined for patients undergoing some common diagnostic procedures (chest, lumbar spine and pelvis series). The ESD was the optimising parameter and its trade off with the image quality assessment of the radiographs. The estimated ESDs were compared with reference levels set by the Commission of the European Communities for a typical standard adult patient. A mean dose reduction of 17-33 % was achieved upon adoption of a rare earth film screen of speed class 400. Regular assessment of patient dose, quality control (QC) of parameters that affect the patient dose and image quality, adoption of faster rare earth screens and optimum radiographic technique are recommended in order to achieve optimisation goals.

Measurement and analysis of radiofrequency radiations from some mobile phone base stations in Ghana

A survey of the radiofrequency electromagnetic radiation at public access points in the vicinity of 50 cellular phone base stations has been carried out. The primary objective was to measure and analyse the electromagnetic field strength levels emitted by antennae installed and operated by the Ghana Telecommunications Company. On all the sites measurements were made using a hand-held spectrum analyser to determine the electric field level with the 900 and 1800 MHz frequency bands. The results indicated that power densities at public access points varied from as low as 0.01 microW m(-2) to as high as 10 microW m(-2) for the frequency of 900 MHz. At a transmission frequency of 1800 MHz, the variation of power densities is from 0.01 to 100 microW m(-2). The results were found to be in compliant with the International Commission on Non-ionizing Radiological Protection guidance level but were 20 times higher than the results generally obtained for such a practice elsewhere. There is therefore a need to re-assess the situation to ensure reduction in the present level as an increase in mobile phone usage is envisaged within the next few years.

Neutron activation analysis for Dy, Hf, Rb, Sc and Se in some Ghanaian cereals and vegetables using short-lived nuclides and Compton suppression spectrometry

A pseudo-cyclic instrumental neutron activation analysis (PCINAA) method has been developed to determine selected elements in various types of cereal and vegetable from Ghana using relatively short-lived nuclides (t1/2<80 s) and the Compton suppression counting. The samples were irradiated for 10 s at the Dalhousie University SLOWPOKE-2 research reactor facility (DUSR) and allowed to decay for 20 s, and counted for 40 s. The process is repeated every 50 s for 4 cycles to quantify Dy, Hf, Rb, Sc and Se through 165mDy, 179Hf, 86mRb, 46mSc, and 77mSe. The detection limits were generally of the order of 1.0 ng g(-1) except for Rb which is about 1 microg g(-1). Both precision and accuracy of the method were found to be good.

National waste management infrastructure in Ghana

Radioactive materials have been used in Ghana for more than four decades. Radioactive waste generated from their applications in various fields has been managed without adequate infrastructure and any legal framework to control and regulate them. The expanded use of nuclear facilities and radiation sources in Ghana with the concomitant exposure to human population necessitates effective infrastructure to deal with the increasing problems of waste. The Ghana Atomic Energy Act 204 (1963) and the Radiation Protection Instrument LI 1559 (1993) made inadequate provision for the management of waste. With the amendment of the Atomic Energy Act, PNDCL 308, a radioactive waste management centre has been established to take care of all waste in the country. To achieve the set objectives for an effective waste management regime, a waste management regulation has been drafted and relevant codes of practice are being developed to guide generators of waste, operators of waste management facilities and the regulatory authority.

Mental Health Nurses: Guardians of Ethics in Managed Care

Managed care produces an ethical dilemma for the mental health nursing profession. High costs must be contained and services increased, yet there are ethical costs and risks to managed care. If patient needs are not being met under managed care, nurses have an obligation to try to change those situations. The threat of managed care can be turned into an opportunity and challenge for mental health nurses to maintain long-established nursing values.

Doses from radiocesium and 40K activities found in some tobacco leaves and cigarettes

It has been found that tobacco leaves and cigarettes contain on the average 1.30 +/- 0.40 Bq.g-1 of 40K which is a beta-gamma emitter. Besides due to the unfortunate Chernobyl accident tobacco leaves may contain 0.04 Bq.g-1 of 137Cs and 0.01 Bq.g-1 of 134Cs depending on their country of origin. From these activities, the annual dose equivalents and the 50 year committed dose equivalents from ingested and inhaled 134Cs, 137Cs and 40K through tobacco consumption are presented.

Shielding for beta-gamma radiation

The build-up factor, B, for lead was expressed as a polynominal cubic function of the relaxation length, mu x, and incorporated in a "general beta-gamma shielding equation." A computer program was written to determine shielding thickness for polyenergetic beta-gamma sources without resorting to the conventional "add-one-HVL" method.

Increase of electrocardiogram voltage and contractile force of the frog's heart induced by chloroquine

The increase in the amplitude of the E.C.G. and ventricular contractile force induced by chloroquine sulphate was studied in frogs. It was shown that changes originated in the midbrain and were mediated through the sympathetic nervous system. The transmitter was recognized as a beta-adrenergic agent. The possible mechanism of action of chloroquine on the CNS responsible for the phenomenon observed was discussed.