Showing papers in "SA Journal of Radiology in 2010"

Ecological impacts of small dams on South African rivers Part 1: Drivers of change – water quantity and quality

Abstract: Impacts of large dams are well-known and quantifiable, while small dams have generally been perceived as benign, both socially and environmentally. The present study quantifies the cumulative impacts of small dams on the water quality (physico-chemistry and invertebrate biotic indices) and quantity (discharge) of downstream rivers in 2 South African regions. The information from 2 South African national databases was used for evaluating the cumulative impacts on water quality and quantity. Physico-chemistry and biological data were obtained from the River Health Programme, and discharge data at stream flow gauges was obtained from the Hydrological Information System. Multivariate analyses were conducted to establish broad patterns for cumulative impacts of small dams across the 2 regions – Western Cape (winter rainfall, temperate, south-western coast) and Mpumalanga (summer rainfall, tropical, eastern coast). Multivariate analyses found that the changes in macroinvertebrate indices and the stream’s physico-chemistry were more strongly correlated with the density of small dams in the catchment (as a measure of cumulative impact potential) relative to the storage capacity of large dams. T-tests on the data, not including samples with upstream large dams, indicated that the high density of small dams significantly reduced low flows and increased certain physico-chemistry variables (particularly total dissolved salts) in both the regions, along with associated significant reductions in a macroinvertebrate index (SASS4 average score per taxon). Regional differences were apparent in the results for discharge reductions and the macroinvertebrate index. The results suggest that the cumulative effect of a high number of small dams is impacting the quality and quantity of waters in South African rivers and that these impacts need to be systematically incorporated into the monitoring protocol of the environmental water requirements. Keywords: cumulative impacts, regional comparison, macroinvertebrate indices, measures of small-dam impact potential, average score per taxon

Uranium pollution of the Wonderfonteinspruit, 1997-2008 Part 1: Uranium toxicity, regional background and mining-related sources of uranium pollution

Abstract: Even though mining-related uranium (U) pollution in the Wonderfonteinspruit (WFS) has been an ongoing concern since the mid-1960s, media attention has increased considerably recently, focusing on pollution-related health risks that unsettle the general public. In view of recent findings that U might be more toxic than previously thought, such concerns need to be addressed. This even more so as South Africa has embarked on a nuclear expansion programme aimed at, amongst others, extending mining and processing of U. This is Part 1 of a series of papers aimed at the quantification of the extent of U pollution in the WFS, in order to provide a factual base for subsequent risk assessments. This paper provides an overview of recent findings on U toxicity with specific reference to drinking water, together with a critical examination of related international and South African guidelines. Based on a brief description of the study area and the impacts of mining over the past decades, the origin of U from different auriferous ore bodies (reefs) is explored. Using secondary data on historic gold and U production in the West Rand and the Far West Rand, tailings deposits in the 2 goldfields are estimated to contain well over 100 000 tons of U constituting a large reservoir for ongoing future U pollution. Apart from tailings, underground water in contact with uraniferous reefs constitutes another major source of waterborne U pollution. This applies to water pumped from underground mine workings as part of the active de-watering of overlying karst aquifers as well as decanting water from flooded mine voids. The discharge of U-polluted water together with largely uncontrolled outflow of uraniferous seepage from tailings deposits are major sources of water pollution in the WFS catchment.Keywords: uranium, toxicity, gold mining, reefs, karst, de-watering, tailings, slimes dams, Wonderfonteinspruit

Ecological impacts of small dams on South African rivers Part 2: Biotic response – abundance and composition of macroinvertebrate communities

Abstract: This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments. Keywords: cumulative impacts, reduced low flows, environmental water quality, Ephemeroptera, Trichoptera

Uranium pollution of the Wonderfonteinspruit, 1997-2008 Part 2: Uranium in water – concentrations, loads and associated risks

Abstract: Uranium (U) pollution of the surface water and groundwater of the Wonderfonteinspruit (WFS) catchment caused by gold mining over more than a century has been an ongoing concern for several decades. Triggered by a recent increase in media attention, political pressure on governmental authorities has mounted to assess the associated health risks and implement appropriate mitigation measures. However, owing to the complexity of the catchment arising from the presence of a multitude of dischargers, a complex karst hydrology and large-scale modifications thereof by deep-level gold mining, most attempts to address the issue to date have been limited to uncoordinated ad hoc studies generally suffering from a lack of temporal and spatial representivity of the underlying data. Part 2 of a series of 2 papers aimed at quantifying the extent of mining-related U pollution in the WFS catchment, this paper addresses the pollution of surface water, groundwater, as well as mine effluent. Based on close to 3 400 measured U concentrations (mostly unpublished) of water samples gathered between 1997 and 2008, an overview of U levels and associated loads in the WFS catchment is provided. Results indicate that U levels in water resources of the whole catchment have increased markedly, even though U loads emitted by some large gold mines in the Far West Rand have been significantly reduced. A major contributing factor is highly polluted water decanting from the flooded mine void in the West Rand, which was diverted to the WFS. Over the reference period, an average of some 3.5 t of dissolved U has been released into the fluvial system from monitored discharge points alone. However, since the WFS dries up well before it joins the Mooi River this U load does not usually impact on the water supply system of downstream Potchefstroom directly. It may, however, indirectly reach Potchefstroom since much of the water from the WFS recharges the underlying karst aquifer of the Boskop Turffontein Compartment (BTC), the single most important water resource for Potchefstroom. Compared to 1997, groundwater in the BTC showed the highest relative increase in U levels of the whole WFS catchment, resulting in some 800 kg/a of U flowing into Boskop Dam, Potchefstroom’s main water reservoir. Of particular concern is the fact that U levels in the WFS are comparable to those detected in the Northern Cape (South Africa), which have been linked geostatistically to abnormal haematological values related to increased incidences of leukaemia observed in residents of the area.Keywords: uranium, water pollution, load, deep level gold mining, karst, dolomite, risks, leukaemia, Wonderfonteinspruit, West Rand, Far West Rand

Removal of copper(II) from aqueous solution using spent tea leaves (STL) as a potential sorbent

Abstract: In this work spent tea leaves were used as a non-conventional, cost-effective sorbent for removal of Cu(II) from aqueous solutions in batch systems. The sorbent was characterised with respect to surface area, pore volume, density, etc. The equilibrium sorption data were applied to various sorption isotherm models, and the order of fitness was: Langmuir > Temkin > Freundlich. The maximum sorption capacity Q o was found to be almost 90.9 and 68.4, as evaluated using Langmuir isotherms at 27oC and 37oC respectively. The observed decrease in sorption capacity with temperature indicated the exothermic nature of the uptake process. The kinetic uptake data were best interpreted by a pseudo second-order kinetic model with values of rate constants of adsorption of 1.47 x 10 -2 and 3.01 x 10 -2 g/mg∙min, respectively, for the initial sorbate concentrations of 10 and 20 mg∙l -1 at 27oC. The sorption mean free energy was determined from the Dubinin Radushkevich (DR) isotherm model and was found to be 9.91 kJ∙mol -1 , indicating ion exchange/chemisorption nature of uptake process. The Cu(II) uptake was found to increase with the pH of the sorbate solution and maximum sorption was observed in the pH range of 1.0 to 4.8. Finally, thermodynamic parameters like ΔG o , ΔH o , ΔS o were also evaluated. Keywords: Spent tea leaves, copper(II), adsorption, Langmuir model

Comparison of stepped and smooth spillway effects on stream reaeration

Abstract: The oxygen transfer at a hydraulic structure happens by self-aeration through the spillway and by flow aeration in the hydraulic jump downstream of the hydraulic structure. Spillways with their water-air controlling mechanisms are important not only for their structural properties but also for their effects on stream ecology. Spillway types also affect the efficiency of aeration. Decisions on the types of spillway should be made by taking the environmental conditions and flow rates into consideration. This paper compares the aeration efficiency of stepped and smooth spillways. Empirical correlations predicting length of the non-aerated flow region and aeration efficiency are developed. Smooth and stepped spillways cause increased dissolved oxygen (DO) concentrations at the downstream part of the channel. DO concentration changes are shown to depend on the flow types, discharge rates, tail-water depth and travelling times. Keywords: dissolved oxygen, spillway, stream, re-aeration, aeration efficiency

Balancing resource protection and development in a highly regulated river: The role of conjunctive use

Abstract: The central position of water in social and economic development drives the imperative for water storage, particularly in water-stressed parts of the world. A consequence is that rivers are perceived primarily as locations for water storage as we seek to manage risks to social welfare and development. Assurance of supply becomes the dominant paradigm shaping decisions about allocation of water from impoundments. When this paradigm is deeply ingrained it constrains decision-making around flow management for other purposes, particularly for sustaining ecological systems. Ten years ago South Africa introduced progressive legislation for water resource management (the National Water Act of 1998) which enshrines the ecological Reserve. This requirement for the environment is not considered as a water use, because the environment is the resource. However, due to the very complex Reserve determination process, and perhaps a lack of political will, the ecological Reserve has proved difficult to implement and has only now started to be implemented in some river systems. In the case of the lower uMngeni River in KwaZulu-Natal, besides releases to maintain a minimum river flow (the so called ‘compensation flows’, which were never designed as environmental flows), for nearly 20 years there has been an unofficial policy to allow spates on between 1 and 4 days per year to make possible the continuation of the prestigious Dusi Canoe Marathon. The total amount of water involved is just over 1.2% of the river’s virgin MAR, although in years perceived to be dry the releases may be cut to as little as 0.3% of the virgin MAR. While these releases have been tolerated for the continuation of a high-value recreational industry, they are in fact aligned, albeit with a fraction of the necessary volume, with the environmental flows that would be required if the ecological Reserve had been determined. The releases for these events therefore have a dual or conjunctive value, serving both environmental and recreational purposes at the same time. We suggest that considerations of conjunctive use offer practical opportunities for balancing resource protection and development in regulated rivers.Keywords: resource protection, regulated rivers, assurance of supply, conjunctive use, ecological Reserve, environmental water allocation, environmental flows, recreational use, canoeing

Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed reactor – Part 5: Steady-state model

Abstract: This paper describes the development of a steady-state anaerobic digestion model for biological sulphate reduction using primary sewage sludge (PSS) as substrate. The model comprises: a chemical oxygen demand (COD) based hydrolysis kinetics part in which the PSS biodegradable COD and sulphate removals are calculated for given hydraulic and sludge retention times; a C, H, O, N, P, S, COD and charge mass balance stoichiometry part in which the alkalinity generated (from both the HCO3- and HS-) is determined from the COD and sulphate removals; and an inorganic carbon (CO2) and sulphide mixed weak acid/base chemistry part in which the digester pH is calculated from the HCO3- and HS- species formed. From the stoichiometry, it was found that the PSS is carbon limited in that it does not generate sufficient HCO3- alkalinity for the sulphate reduction, i.e., its COD/C ratio is too high which accounts for the observed zero gas (CO2) generation. The H2S/HS- system provides the alkalinity shortfall and establishes the system pH. Once developed and calibrated, the model results were compared with experimental data from 2 laboratory-scale upflow anaerobic sludge bed reactors (operated at 35oC and 20°C respectively) fed PSS and sulphate. The predicted COD and sulphate removals, alkalinity and digester pH correspond very well to the measured data. The model assists in identifying design and operation parameters sensitive to the system and provides a basis for developing an integrated biological, chemical and physical process dynamic model.Keywords: biological sulphate reduction, primary sewage sludge, upflow anaerobic sludge bed reactor, steady state model, kinetics, stoichiometry, mixed weak acid/base chemistry

MRI determination of the vertebral termination of the dural sac tip in a South African population: clinical significance during spinal irradiation and caudal anaesthesia

Abstract: Knowledge of the approximate caudal termination of the dural sac (DS) is important, especially when placing the portal fields during lower craniospinal irradiation (CSI) and performing caudal anaesthesia. The purpose of this investigation was to determine the level of termination of the DS in relation to the spine in a group of South African patients by using magnetic resonance imaging (MRI). We retrospectively reviewed the lumbosacral MR imaging of 309 patients, in each case identifying the tip of the DS. This level was recorded in relation to the adjacent lumbosacral vertebral body i.e. upper-, middle- and lower-third and adjacent intervertebral disc. The overall mean of the DS position was at the middle third of S2. Although the caudal DS tip was at the level of S2 in the majority of patients, a notable percentage (13.9%) had a DS tip level lower than the lower third of S2, and 15.2% had levels higher than the S1-S2 intervertebral disc. This study failed to demonstrate a difference in the DS termination level, compared with the levels reported in various international studies; nor is there a statistical difference between gender, race and age. Our study shows that routine placement of the portal field at the lower border of S2 adequately treats the majority of CSI patients. However, some patients (13.9%) will be undertreated and some patients (15.2%) will be overradiated. Using spinal MRI to establish the lower border of the CSI portal field will, however, benefit patients by ensuring adequate coverage of the entire neuroaxis as well as minimising late gonadal toxicity owing to overradiation.

Changing hydroclimatic and discharge patterns in the northern Limpopo Basin, Zimbabwe

Abstract: Changing regional and global trends in climate and discharge, such as global warming-related declines in annual rainfall in south-eastern Africa, are likely to have a strong influence on water resource availability, and to increase livelihood risk. It is therefore important to characterise such trends. Information can be obtained by examining and comparing the rainfall and runoff records at different locations within a basin. In this study, trends in various parameters of temperature (4 stations), rainfall (10 stations) and discharge (16 stations) from the northern part of the Limpopo Basin, Zimbabwe, were statistically analysed, using the Spearman rank test, the Mann-Kendall test and the Pettitt test. It was determined that rainfall and discharge in the study area have undergone a notable decline since 1980, both in terms of total annual water resources (declines in annual rainfall, annual unit runoff) and in terms of the temporal availability of water (declines in number of rainy days, increases in dry spells, increases in days without flow). Annual rainfall is negatively correlated to an index of the El Nino – Southern Oscillation phenomenon. The main areas of rising risk are an increasing number of dry spells, which is likely to decrease crop yields, and an increasing probability of annual discharge below the long-term average, which could limit blue-water availability. As rainfall continues to decline, it is likely that a multiplier effect will be felt on discharge. Increasing food shortages are a likely consequence of the impact of this declining water resource availability on rain-fed and irrigated agriculture. Declining water resource availability will also further stress urban water supplies, notably those of Zimbabwe’s second-largest city of Bulawayo, which depends to a large extent from these water resources and already experiences chronic water shortages.Keywords: climate variability, climate change, discharge analysis, Pettitt test, rainfall analysis, water resources, Limpopo Basin, Zimbabwe, Southern Africa

Life-history traits of Streptocephalus purcelli Sars, 1898 (Branchiopoda, Anostraca) from temporary waters with different phenology

Abstract: Rock-pools have specific environmental characteristics, usually with multiple short and unpredictable hydroperiods in 1 season. This requires a specific set of life-history adaptations of their permanent inhabitants, which affects species occurrence. In Southern African rock-pools, large branchiopods are usually represented by Branchipodopsis species. During an intensive sampling campaign in 2004 in the Western Cape of South Africa, a population of Streptocephalus purcelli Sars, 1898 was discovered for the first time in a clear rock-pool with a short hydroperiod. Its usual habitat is a more turbid mud-pool with a longer hydroperiod. We investigated under standard laboratory conditions the differences in early life-history traits between the rock-pool population and a conspecific mud-pool population. Dormant eggs of the rock-pool population were smaller than those of the mud-pool population. The smaller larvae also hatched earlier. These characteristics are in accordance with what is expected for populations living in ephemeral systems. The rock-pool population, on the other hand, also exhibited a higher total hatching percentage, a longer hatching duration, a longer maturation time and a lower mortality. Although, deduced from the last mentioned life-history traits, S. purcelli seemed not well-adapted to unpredictable and ephemeral rock-pool habitats, they could probably occur due to the absence of the competitively stronger species in the region or due to dispersal and mass effects. Keywords: Streptocephalus , temporary rock-pools, Anostraca, South Africa

Optimisation of representative elementary area (REA) for the preparation of lineament density map of fractured rock aquifer

Abstract: The lineament density map derived from remote sensing data of the fractured rock terrain plays an important role in the evaluation of the groundwater resource in the associated fractured aquifer. Application of the lineament density map frequently encounters the problems of whether the density map is representative of an area and whether the map can be effectively applied at a regional scale. Lineament data captured from Landsat ETM+ imagery in 7 domain areas in the Table Mountain Group (TMG) sandstone terrain were used to compute and analyse lineament densities. Methods of determining representative elementary area (REA) on a domain-area scale and on a study-area scale were developed, respectively, based on the power law relationship of lineament densities with computing cell sizes, linear relationship of REAs with domain-area sizes, and the power law relationship of REA percentages with domain-area sizes. Using the function convergence criterion of curve slope less than 1o and measuring dimension in units of area (L2) other than units of length (L), the REA of each domain area can be accurately determined. REA scale-effect analysis helps to optimise the determination of REA in a study area, and the optimisation of REAs may in turn improve the lineament density map generated for regional groundwater studies.Keywords: lineament density, representative elementary area (REA), fractured rock aquifer, Table Mountain Group (TMG)

Levels of selected alkylphenol ethoxylates (APEs) in water and sediment samples from the Jukskei River catchment area in Gauteng, South Africa

Abstract: There has been a continual search to develop sensitive analytical methods for detecting and determining organic compounds such as alkylphenol ethoxylates (APEs) in environmental samples, since they occur at very low concentration levels. Studies conducted so far in some South African waters have offered little or no information on APEs. The presence of these compounds in environmental samples is not desirable and therefore, needs to be monitored. Water and sediment samples were collected from different sites in the Jukskei River catchment area in the 2005 summer and winter seasons. Liquid-liquid extraction (LLE) and Soxhlet extraction (SE) methods (using 1:1 dichloromethane and methanol as extracting solvents) were optimised, evaluated and used to determine APEs of interest in water (unfiltered and filtered) and sediment samples, respectively. Mean percentage recoveries obtained for APEs in spiked double-distilled water were between 83.1±1.0 (OPnEOS3) and 108.1±3.5 (OP) and for sediments the range was between 96.6±0.9 (OPnEOS1) and 117.1±0.6 (OPnEOS3). The concentration levels of APEs studied in unfiltered environmental water samples were in the range of 0.25(0.03) ng/ml (NP) to 92.7(1.11) ng/ml (OPnEOS3) and 0.31(0.02) ng/ml (NP) to 60.1(0.51) ng/ml (OPnEOS3) for filtered environmental water samples. Concentration levels obtained in sediments were from 1.94(0.14) ng/gdw to 941(0.50) ng/gdw (OPnEOS3). Analytes adsorbed on the sample bottle gave concentration levels which ranged from 0.02(0.02) ng/ml to 0.42(0.02) ng/ml for APEs. All the compounds studied were found at levels higher than the European Union (EU) set levels for the protection of the aquatic environment. Keywords: APEs, surface water, sediments, liquid-liquid, soxhlet, GC-FID

Sonographic gallbladder wall thickness in normal adult population in Nigeria : original article

Abstract: Aim. The aim of the study was to determine the ultrasonic gallbladder wall thickness in normal adult Nigerians so as to create standards for defining gallbladder abnormalities in Nigerians. Method. Four hundred adults comprising 228 (57%) women and 172 (43%) men aged 16 - 78 years, who had normal clinical history and physical findings, were recruited. The gallbladder wall thickness was obtained in the supine, prone and right anterior oblique positions. Differences in gallbladder wall thickness were determined using the chi-square test, while the relationship between the ultrasound-measured gallbladder wall thickness and the subjects' age, sex, height and weight were analysed using the Pearson product moment correlation. Normal ranges and related statistics were estimated and tabulated according to age group and sex. Results. The mean age of the subjects was 32±13.2 years. The mean gallbladder wall thickness range was 1.8 - 2.8 mm±0.5mm. The thickness range for females was 1.7 - 2.7 mm±0.5 mm, and that for males was 1.9 - 2.9 mm±0.5 mm. There was a statistically significant difference (p<0.05) in the mean wall thickness between males and females. The mean body parameters (height, weight) of males were significantly greater than those of females (p<0.047, p<0.000 respectively). There was no correlation between gallbladder wall thickness and age and height of subjects (r=0.34, p<0.09). Conclusion. Our study was able to establish population-specific ultrasonic values for gallbladder wall thickness in normal adults that can be reliably used as standards to define gallbladder abnormalities in Nigerians.

Macrodystrophia lipomatosa - MR imaging of a rare congenital anomaly : review of 3 cases

Abstract: Macrodystrophia lipomatosa (MDL) results from progressive overgrowth of all the mesenchymal elements, with a disproportionate increase in fibro-adipose tissue. This rare congenital abnormality occurs most frequently in the distribution of the median nerve in the upper, and medial plantar nerve in the lower, extremity. Excess of unencapsulated fibro-adipose tissue on magnetic resonance imaging (MRI) is virtually diagnostic and can differentiate this entity from other diseases with similar presentations. Involvement of the ulnar aspect of the hand, though rare, has been described; however, the lateral aspect of the foot as seen in our second case has not been reported, to the best of our knowledge.

Is computed tomography of the brain necessary in patients with clinically suspected depressed skull fracture and no focal neurological deficit? : original article

Abstract: Objective. The objective of the study was to determine whether computed tomography (CT) of the brain is necessary in all head trauma patients with clinically suspected depressed skull fractures, Glasgow Coma Scale (GCS) scores of 13 and above, and no focal neurological deficits. Design. A retrospective descriptive analysis was undertaken of patients of all ages who presented at the trauma unit of the Pelonomi Hospital Complex in Bloemfontein with GCS of 13 to 15, depressed skull fracture, no clinical focal neurological deficit, and who also underwent CT of the brain. Data were obtained from patients' files, and radiological reports and were analysed by the Department of Statistics, University of the Free State. Results. One hundred and thirty-one patients were included in the study, of whom 56 (42.7%) were found to have substantial intracranial pathology as determined by CT. Twenty-four (18.3%) of these patients had a GCS of 13, of whom 6 (25%) had normal CT scans and 18 (75%) intracranial pathology. Twenty-eight (21.37%) of the 56 patients with intracranial pathology had a GCS of 14, of whom 11 (39.3%) had normal CT scans and 17 (60.7%) intracranial pathology. A GCS of 15 was determined in 79 (60.3%) of the 131 patients, of whom 58 (73.4%) had normal CT scans and 21 (26.6%) intracranial pathology. Conclusion. Based on our findings, CT imaging of the brain in patients with a clinically suspected depressed skull fracture despite any clinical neurological deficit and a GCS of 13 or more is warranted in our setting. The likelihood of injury on CT correlated inversely with the GCS.

Is airway diameter measured accurately on routine axial CT scans? Comparison with true axial diameter using MPR in children with airway compression owing to pulmonary TB

Abstract: Airway compression is a common complication of TB lymphadenopathy in children, and the diagnostic workup of patients with suspected tracheal or bronchial stenoses includes bronchoscopy and CT (computed tomography).2 This process affords the opportunity to study aspects of CT relating to airway stenosis. Axial CT scans produce excellent resolution in the horizontal plane, but the extent of airway disease may be underestimated if only axial images are obtained. An advantage of using multidetector CT (MDCT) is the use of multiplanar reconstruction (MPR) to align the image along the longitudinal axis of the airway. There is also uncertainty if window settings affect the measurement of the airway diameter. We wished to determine if there was a significant difference between the measurements of compressed airway diameter in the axial plane compared with measurements of diameter using MPR for determining longitudinal axis of the airway; and to evaluate how measurements on lung window settings compare with soft tissue window settings.

A case of extensive synovial involvement by tophaceous gout

Abstract: Gout is the most common form of microcrystal arthropathy that results in deposition of uric acid crystals in and around the joints and soft tissues. The most common cause is decreased uric acid clearance by the kidneys. The radiological manifestations of gout are generally well known and have remained unchanged. We describe a case of chronic tophaceous gout with diffuse extensive involvement of the synovium around the knees bilaterally.

Digital teaching files - a useful teaching tool for the modern radiologist : review article

Abstract: Radiologists have always collected copies of model examples and interesting cases encountered in daily practice to use for teaching purposes. A collection of teaching files is an important resource for medical education and the dissemination of knowledge in radiology. Furthermore, the presence of a radiological teaching file is also a requirement at several universities and tertiary institutions in South Africa and abroad, where radiology postgraduate training is conducted.

Use of MR sialography and T2W fat-suppressed MR in parotitis : tips for the radiologist

Abstract: Imaging can be helpful when investigating salivary gland pain and swelling. Typically in such cases, an ultrasound (US) or conventional sialogram would be requested in seeking obstructed or dilated ducts, a ductal calculus or an abscess within the gland. Occasionally a computed tomography (CT) scan is requested. Magnetic resonance imaging (MRI) is usually reserved for investigating clinically palpable masses in the glands. In acute non-obstructive parotitis, the differential diagnosis includes acute non-suppurative parotitis (as found in mumps), early Sjogren's syndrome, or suppurative parotitis as seen following duct obstruction. Sometimes there is strong insistence on retrograde contrast sialography; however, this may exacerbate the pre-existing inflammatory process. The imaging of a young patient expands on these observations.

Extramedullary haematopoiesis causing spinal cord compression

Abstract: A 38-year-old man with thalassaemia intermedia presented with a 6-week history of progressive muscle weakness, back pain, paraesthesia and spasm in both legs. He did not have any bladder dysfunction. The patient had a cholecystectomy at age 34. One of his brothers had died from an unknown cause at age 7 years. However, he had also had thalassaemia. His other brother died from severe cardiac failure brought on by chronic anaemia at age 40 years. On examination, the patient had normal vital signs and normal cardiac and respiratory examination. Hepatosplenomegaly was present. Neurological examination revealed muscle power of 3/5 in the lower limbs in all the muscle groups, brisk tendon reflexes and bilateral positive Babinski reflexes. The sensory level was at T3. Biochemical evaluation showed microcytic hypochromic anaemia. Haemoglobin was 9.5 g/decilitre (normal=13.8 18.8 g/decilitre), mean cell volume was 73.2 fl (normal=79 100 fl), and mean cell haemoglobin was 25.5 picograms (normal=27 35 pg). He also had an elevated total bilirubin of 62 μmol/l (normal=2 26 μmol/l) and elevated conjugated bilirubin of 11 μmol/l (normal=1 7 μmol/l). The serum urate was also elevated at 0.45 mmol/l (normal=0.21 0.43 mmol/l). These changes may be secondary to haemolysis.

Beware the bifid rib! : pictorial interlude

Abstract: A 4-year-old girl was referred to Tygerberg Academic Hospital with a long-standing history of an asymptomatic anterior chest wall 'lump'. On physical examination, a bony mass was palpated in relation to the anterior aspect of the left 4th rib. Plain radiography demonstrated anterior widening of the left 4th rib (Fig. 1). Fearing a sinister cause, a multidetector computed tomography (MDCT) examination of the chest, with 3D reconstruction and volume rendering, was performed (Fig. 2). A congenital bifid left 4th rib was demonstrated.

A new approach to the step-drawdown test

Abstract: In this paper a new approach to perform step-drawdown tests is presented. Step-drawdown tests known to date are performed strictly keeping the value of the pumping rates constant through all the steps of the test. Current technology allows one to let the submerged electric pumps work at a specific revolution per minute (r/min) and to suitably modify the rotation velocity at every step. The new approach presented in this paper is based on the idea of keeping the value of r/min fixed at every step of the test, instead of keeping constant the value of the discharge. This technique has been experimentally applied to a well and a description of the operations and results are presented in detail. This approach, in this unique case, made possible an understanding of how the discharge Q varies as a function of the drawdown s w . It also enables one monitor the approaching of the equilibrium between Q and s w , using both the variation of Q and s w with time. Moreover, it was observed that for the well in question the ratio Q/s w remains almost constant within each step. Keywords: characteristic curve, pumping test, equipment/field techniques, hydraulic testing

Revisiting the stream-aquifer flow problem with a flux-based Green element model

Abstract: This revisit of the stream-aquifer problem is based on a recent flux-based Green element formulation which offers more accurate solutions than previous formulations presented in Taigbenu (2003). Its accuracy also surpasses those provided by finite element and finite difference methods using grids that are coarser. As in all Green element formulations, the current formulation is predicated on the singular boundary integral theory that is implemented in an element-by-element fashion. What is new in the current formulation is that it calculates the fluxes at all nodes and not only at external nodes. While this approach exhibits much improved accuracy, its drawback lies with handling an increased number of unknowns. This drawback is, however, compensated for by the fewer elements required to achieve accuracies comparable to other conventional numerical methods. In this paper, it is demonstrated that with between 20% and 30% of elements used in finite element and finite difference models, comparable accuracy is achieved with this formulation. The main significance of the current computational technique is that it preserves the flux calculations in a manner that is consistent with the stream-aquifer interaction problem. Keywords: stream-aquifer interaction, The Green element method

Case Report: Multimodality imaging and interventional management of a complex congenital vascular malformation

Abstract: Hepatic vascular lesions are not an uncommon finding in children, and represent the most common benign liver tumours to present in infancy. We present a case of a complex vascular malformation with an intrahepatic component suggestive of a venous/arteriovenous malformation as well as a large extrahepatic lesion. The extrahepatic mass was present in both sub- and supra-diaphragmatic locations, with features of a congenital haemangioma. In view of the clinical presentation and different imaging appearances, this case was felt to be interesting in its radiological workup, management and eventual unusual pathology.

The enigma of reversible splenial lesions

Abstract: Focal reversible lesions of the splenium of the corpus callosum have been described in a number of clinical paradigms. Epilepsy and related conditions are the most commonly reported underlying clinical association. Sudden anti-epileptic therapy withdrawal or seizure activity may be presumed to be the predisposing cause. However, an individual susceptibility must also be considered. Although the exact mechanism producing this syndrome is not known, the MRI appearance and course in each of these clinically distinct causative entities is similar. The complete reversibility of the abnormality on follow-up studies is common to all, and many authors suggest that a conservative watchful approach is all that is required. We present here the findings in two patients with similar, completely reversible, splenial lesions.

Uraemic tumoral calcinosis in patients on haemodialysis in the renal unit at Dr George Mukhari Hospital, Pretoria : original article

Abstract: Objective. Uraemic tumoral calcinosis refers to metastatic calcifications that occur rarely on the extensor surfaces of joints in patients undergoing long-term haemodialysis. The aim of the study was to assess the incidence of uraemic tumoral calcinosis in participants undergoing haemodialysis and to investigate any relationship that might exist between the development of uraemic tumoral calcinosis and the length of time on dialysis. Design. Twenty-four of the 25 patients on haemodialysis at the time of the study underwent radiographs of their shoulders and hips to look for calcinosis, which were then read by the researcher and two independent readers to assess for calcinosis. Study setting. Dr George Mukhari Hospital, Pretoria. Results. Eight per cent (N=2) of participants were found to have asymptomatic calcinosis of the hips. No relationship to length of time on dialysis was found. Conclusions. The study was constrained by a small sample size but the presence of calcinosis in 8% of the participants indicates that an extensive study of a larger sample could prove to be useful in determining the true incidence of uraemic tumoral calcinosis in the region. Long-term follow-up could provide more information on the development of calcinosis and length of time on dialysis.

Diabetic mastopathy: A clinical and radiological challenge

Abstract: A 41-year-old woman presented with a lump above the right areola. She also complained of a burning and heavy sensation of the right breast of recent onset. On further history, the patient was an insulin-dependent diabetic of 35 years’ duration. She had no family history of breast disease. On examination, a palpable thickening above the right areola was detected. Bilateral mammography revealed dense fibro-glandular tissue, denser in the right retro-areolar region than the left, with right peri-areolar skin thickening. There was no discreet mass nor suspicious microcalcifications or axillary adenopathy. Ultrasound (US) demonstrated an ill-defined peri-areolar region of decreased echogenicity and posterior shadowing. Core biopsy under US guidance showed abundant thick collagen bands containing epitheloid fibroblasts and a stroma with small capillary-sized and larger muscularised blood vessls, some of which contained peri-vascular lymphocytic inflammatory cells. Small ductal elements and an occasional lobule showed a peri-ductal and a peri- and intra-lobular lymhocytic and plasma cell infiltrate. These features were in keeping with sclerosing lymphocytic mastitis, known also as diabetic mastopathy.