BRIDGE methodology-based quality standards to assess aquifer chemical status in the southwest Bengal Basin, Bangladesh.

Assessment of natural background levels (NBLs) of compositional groundwater parameters helps to identify the potential threats to groundwater resources. This study is the first attempt to apply the pre-selection-based BRIDGE (Background cRiteria for the IDentification of Groundwater thrEshold) methodology to calculate the NBLs and threshold values (TVs) of major groundwater constituents in the southwest Bengal Basin, Bangladesh. A database consisting of 78 groundwater samples was used to assess the NBLs and associated TVs of the major groundwater parameters (EC, Ca2+, Mg2+, Na+, K+, Cl-, NO3-, SO42-, PO43-, Mn2+, and Fe2+). NBLs were derived based on 90th and 97.7th percentiles. The status of regional groundwater resources was assessed by applying 90th percentile NBL on a regional dataset (n = 196). Results revealed the "poor" chemical status of shallow aquifers denoting heavy deterioration of the groundwater quality due to anthropogenic interventions. Nitrate contamination and salinization were identified as the major threats to the deep groundwater of the southwest Bengal Basin. Finally, to verify the chemical status of groundwater in a heavily urbanized area, derived TVs were applied throughout the experimental site Khulna. Twenty-five deep groundwater samples were collected for this purpose. Though most of the parameters exhibited "good" chemical status, nitrate demonstrated anthropogenic groundwater contamination in Khulna City. Thus, the developed TVs would provide an early warning system of pollution. On a national scale, it is expected to facilitate the sustainable groundwater management of the country and contribute to achieving the Sustainable Development Goals (SDG) of the United Nations (UN) in Bangladesh.

Rare co-occurrence of dural arteriovenous fistula and arteriovenous malformation with bilateral subcortical and basal ganglia calcification.

The present study describes the imaging findings in a patient with dural arteriovenous fistula (AVR) and arteriovenous malformation (AVM) with bilateral subcortical and basal ganglia calcification. A 29 year old male patient presented with chief complaint of recent onset of generalized tonic clonic seizures and mild disorientation. The imaging studies on MCT demonstrated diffuse, symmetric calcification in the bilateral basal ganglia and subcortical white matter. MR imaging and angiography revealed AVM in parietooccipital region with supply predominantly from left posterior cerebral and middle cerebral arteries. Multiple dural feeders from meningeal branches of occipital and superficial temporal branches of bilateral external carotid and right internal carotid arteries. Calcification is proposed to be due to chronic reflux into the parenchymal veins or vascular steal phenomenon. This rare co-occurrence of subcortical calcification in a patient with a dural AVF and AVM is being reported.

The Bengal Water Machine: Quantified freshwater capture in Bangladesh.

Global food security depends on the sustainability of irrigated agriculture. Rising groundwater withdrawals from seasonally humid, alluvial plains across tropical Asia have enabled dry-season rice cultivation. This groundwater pumpage increases available subsurface storage that under favorable conditions amplifies groundwater replenishment during the subsequent monsoon. We empirically quantified this nature-based solution to seasonal freshwater storage capture described as the "Bengal Water Machine," revealing its potential and limitations. On the basis of a million piezometric observations from 465 monitoring wells, we show that the collective operation of ~16 million smallholder farmers in the Bengal Basin of Bangladesh from 1988 to 2018 has induced cumulative freshwater capture that volumetrically (75 to 90 cubic kilometers) is equivalent to twice the reservoir capacity of the Three Gorges Dam.

Primary epiploic appendagitis: 3 case reports.

Acute Epiploic Appendagitis is a rare self limiting disease that represents ischaemic infarction of an epiploic appendix. It is usually discovered incidentally on imaging of abdomen done for other causes of acute abdominal pain. It is difficult to diagnose clinically due to the lack of pathognomonic clinical features, since it is characterized by a sudden onset of sharp localized pain either in the left or right iliac fossa with minimal gastrointestinal symptoms, which can simulate a surgical clinical picture. Awareness of imaging findings of this entity is important to arrive at a correct diagnosis and to avoid unnecessary hospitalization and surgery. We report cases of three male patients presenting with acute flank pain who were diagnosed as case of Primary epiploic appendagitis. All 3 patients were treated conservatively.

Triphasic computed tomography (CT) scan in focal tumoral liver lesions.

OBJECTIVE: To assess the diagnostic accuracy of triphasic spiral CT in differentiating benign from malignant focal tumoral liver lesions. METHODS: The study was conducted in Department of Radiology of Aga Khan University Hospital and Sind Institute of Urology and Transplantation, Karachi from Feb 2006 to Feb 2007. By convenient sampling, 45 patients found to have focal tumoral liver lesions were recruited for one year period and their triphasic CT scans findings were evaluated and later correlated with histopathology. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of triphasic CT scan were calculated. RESULTS: Among 45 patients, 136 liver lesions (11 benign and 125 malignant) were detected with the help of different enhancement patterns. Out of these, 37(82.2%) patients had malignant while 8 (17.8%) had benign lesions. On later histopathological examination, 35 (77.8%) of the total 45 cases had malignant lesions while 10 (22.2%) were diagnosed as benign lesions. Based on these results, it could be assessed that triphasic CT Scan has a sensitivity of 100%, specificity of 80%, positive predictive value of 94.5%, negative predictive value of 100% and diagnostic accuracy of 95.5% in differentiating benign from malignant liver lesions. CONCLUSION: Triphasic CT Scan is a good non-invasive tool in characterizing and differentiating benign from malignant liver lesions.

Spatiotemporal distribution of boron in the groundwater and human health risk assessment from the coastal region of Bangladesh.

High concentrations of naturally-occurring and man-accentuated boron in groundwater possess a potential threat to the health and well-being of humans worldwide. In Bangladesh, only a few studies focused on the health risks of boron-containing groundwater. Therefore, the present study investigated the spatiotemporal distribution of boron concentrations in groundwater and its associated health risks in the coastal districts of Bangladesh. A total of 268 samples from the shallow and deep wells during the wet and dry season (137 and 131 samples, respectively) were collected to determine the level of boron concentrations and health risk status. The groundwater boron concentrations ranged from 0 to 4.10 mg/L with an average concentration of 0.68 mg/L, which was much lower than the WHO and the values of Bangladesh drinking water standard guideline. The boron concentrations in the shallow wells override the deep ones with insignificant seasonal variation. Boron contamination affected 10% of the shallow wells in the wet season and only 6% of them in the dry season, whereas only 1% of deep wells exceeds the WHO guideline values of 2.40 mg/L during the wet and dry season, respectively. The human health risk of boron was determined by computing estimated daily intake (EDI) and hazard quotient (HQ) values for infants, children, teenagers, and adults. The average HQ value delimitated that children have high risk followed by teenagers, adults, and infants. About 90-95% of the studied samples were free from boron contamination because of having HQ values < 1 and the rest of the samples possess a high risk for children. For the overall study area, the deep wells were found safer than the shallow wells, which were more susceptible to boron contamination aided by localized freshwater inputs.

Spatial distribution of manganese in groundwater and associated human health risk in the southern part of the Bengal Basin.

The scarcity of arsenic and iron-free safe drinking water is an alarming issue in the southern part of the Bengal Basin. The objectives of the present study were to investigate the spatial distribution of manganese (Mn) concentration in the shallow and deep groundwater and its associated health risks for the children and adults of entire southern Bengal Basin. The Mn concentration in the groundwater varied from 0 to 5.4 mg/L with an average value of 0.47 mg/L that exceeded the WHO's and Bangladesh drinking water guideline values of 0.4 and 0.1 mg/L, respectively. Mn concentration in the shallow wells overrode the deep ones. About 23% of the shallow wells and 11% of deep wells exceeded the WHO's safety limit of Mn concentration for human health. The human health risk related to Mn contamination was estimated by computing the average daily dosage (ADD) and hazard quotient (HQ) values for children and adults. The average computed HQ values found 0.108 and 0.099 for children and adults, respectively. The HQ values delimitated that children are posing a higher risk compared to the adults for the shallow wells. Deep wells were found risk-free for both children and adults. The areal coverage of shallow wells with HQ values > 1 was minimal compared to the total study area and covered only a small portion of Patuakhali and Barguna districts. The rest of the site does not pose any health risk due to Mn contamination for children and adults.

Application of novel framework approach for prediction of nitrate concentration susceptibility in coastal multi-aquifers, Bangladesh.

This study aims to construct a novel framework approach for predicting and mapping nitrate concentration susceptibility in the coastal multi-aquifers of Bangladesh by coupling the K-fold cross-validation method and novel ensemble learning algorithms, including Boosting, Bagging and Random Forest (RF). In total, 286 nitrate sampling sites were employed in the model work. The dataset was demarcated into a 75:25 ratio for model construction (75% 3-fold â‰… 214 sites) and (25% 1-fold â‰… 72 sites) for model validation using the 4-fold cross-validation schemes. A total of 14 groundwater causative factors including salinity, depth, pH, EC, As, HCO3-, F-, Cl-, SO42-, PO42-, Na+, K+, Mg2+, and Ca2+ were adopted for the construction of the proposed models. OneR relative importance model was employed to choose and rank critical factors for spatial nitrate modeling. The results showed that depth, pH and As are the most influential causative factors in the elevated nitrate concentration in groundwater. Based on the model assessment criteria such as receiver operating characteristic (ROC)'s AUC (area under curve), sensitivity, specificity, accuracy, precession, F score, and Kappa coefficient, the Boosting model outperforms others (r = 0.92, AUG ≥ 0.90) in mapping nitrate concentration susceptibility, followed by Bagging and RF models. The results of mapping nitrate concentration also demonstrated that the south-central and western regions had an elevated amount of nitrate content than other regions due to depth variation in the study area. During our sampling campaign, we observed hundreds of fish hatcheries operation, a fish landing center and aquaculture farms which are the reasons for overexploitation and excessive agrochemicals used in the study area. Thus, the dependability of ensemble learning modeling verifies the effectiveness and applicability of the proposed novel approach for decision-makers in groundwater pollution management at the local and regional levels.

An Analysis of the Predictors of Major Bleeding After Transcatheter Aortic Valve Transplantation Using the National Inpatient Sample (2015-2018).

Background Transcatheter aortic valve replacement (TAVR) is now a common procedure to treat and improve quality of life, clinical outcomes, and self-sufficiency in high-risk patients with aortic stenosis, and its use has been expanding rapidly in younger and low-risk populations. The aim of this study was to evaluate the outcomes, trends, and predictors of major bleeding in patients undergoing TAVR. Methodology We utilized the National Inpatient Sample (NIS) data from the year 2015 to 2018. International Classification of Disease 10 codes were utilized to extract data. Baseline characteristics were compared using Pearson's chi-square test for categorical variables and independent samples t-test for continuous variables. A multivariable logistic regression model was used to evaluate the predictors of major bleeding. Propensity matching was done for adjusted analysis to compare outcomes in TAVR with and without major bleeding. The outcomes of interest in this study were (1) predictors of major bleeding after TAVR; (2) in-hospital mortality; and (3) resource utilization in terms of cost and length of stay. Results A total of 34,752 weighted hospitalizations for TAVR were included in the analysis. Of the patients undergoing the procedure, 2,294 (6.6%) had a major bleed while 32,458 (93.3%) did not. At baseline, patients with coagulopathy (odds ratio [OR]: 2.03; 95% confidence interval [CI]: 1.82-2.27), congestive heart failure (OR: 1.26; 95% CI: 1.13-1.40), chronic obstructive pulmonary disease (OR: 1.41; 95% CI: 1.29-1.55), liver disease (OR: 1.96; 95% CI: 1.61-2.39), peripheral vascular disease (OR: 1.29; 95% CI: 1.17-1.43), cerebrovascular disease (OR: 1.22; 95% CI: 1.07-1.38), end-stage renal disease (ESRD) (OR: 2.17; 95% CI: 1.82-2.59), and coronary artery disease (OR: 1.17; 95% Cl: 1.06-1.30) had higher adjusted rates of odds of major bleeding. Patients who had major bleeding had a higher median cost of stay (US$60,326 vs. US$45490) and length of stay (seven vs. three days). Conclusions Mortality is higher in patients with major bleeding, and at baseline, coagulopathy and ESRD are significant predictors of a major bleed in patients undergoing TAVR.

Gastro esophageal reflux: an over investigated entity in neonates and infants.

OBJECTIVES: To determine the outcome of clinically suspected gastro esophageal reflux in neonates and infants. To find a protocol for evaluation of these patients in order to reduce unnecessary radiation to neonates and infants. METHODS: Fifty three neonates and infants of up to 1 year of age with clinical suspicion of gastro esophageal reflux (GER) were referred for Upper gastro intestinal barium studies. This retrospective descriptive case study was carried out over a period of one year starting from October, 2006 to September, 2007. Positive cases were followed for another one year to see the final outcome. The neonate and infants of upto one year of age, referred from Neonatal intensive care unit (NICU), Paediatric ward and Out Patient Department (OPD) were included in this study. RESULTS: Out of 53 cases 32 were positive for G.E.R and no reflux could be identified in rest of the patients. Out of these positive cases only 4 had massive or severe G.E.R. These patients were prescribed conservative and medical treatment and were advised to follow up in the O.P.D where on subsequent follow ups the medical treatment was stopped as there were no further complaints .These patients showed normal weight gain on subsequent O.P.D visits. Other positive cases only had mild to moderate G.E.R and they were managed conservatively. These patients showed normal weight gain on subsequent O.P.D visits with complete resolution of symptoms. CONCLUSION: Regurgitation or gastro esophageal reflux is a common finding in the first 3 months of life (especially in preterm infants) and usually resolves by 6-12 months of age and should not be over investigated.

Diagnostic dilemma in sicklers with acute bone crisis: role of subperiosteal fluid collection on MRI in resolving this issue.

OBJECTIVES: To establish MRI criteria to diagnose early osteomyelitis in sickle cell disease patients with acute bone crisis and to differentiate it from normally occurring ischaemic changes in these patients. METHODS: MRI study with and without Gadolinium contrast was carried out in 59 sickle cell disease patients who presented with acute bone crisis from August 2007 to July 2008, and had clinical suspicion of osteomyelitis. We studied the ability of MRI especially the presence of subperiosteal fluid, for the early diagnosis of osteomyelitis and its differentiation from ischaemic changes in these patients. RESULTS: Depending on MRI diagnostic criteria, we diagnosed 32 cases for osteomyelitis. In 26 patients diagnosis was confirmed microbiologically while 6 patients were treated on clinico radiological basis which showed marked improvement on follow up. Five patients with osteomyelitis had established MR features of osteomyelitis while in 27 cases the diagnosis was made on the basis of presence of subperiosteal fluid. CONCLUSION: Early osteomyelitis is a challenging diagnosis clinically and radiologically in patients with sickle cell disease, which can be diagnosed on M.R.I if special emphasis is put on subperiosteal fluid collection.

Drinking appraisal of coastal groundwater in Bangladesh: An approach of multi-hazards towards water security and health safety.

In Bangladesh, groundwater serves as the sole major potable water source. Salinization along with the elevated presence of metals become the major threat for this resource in coastal districts of Bangladesh. Therefore, a multi-hazard approach is planned to appraise the groundwater quality. Probabilistic health risks assessment was employed to quantify risk due to drinking from polluted water in coastal districts. Geostatistical tools, pollution indices, and health risk models were conducted using water quality data from 925 samples (n = 566 in the wet season, and n = 359 in the dry season). Groundwater quality index (GWQI) reveals about 65% of the samples are 'poor to unsuitable' as potable water in the study area. Metals pollution indices are correlated to each other, and demonstrated a diversified outcome. In addition, the multivariate analyses of water quality confirmed the major influencing factors that come from the geogenic processes along with the anthropogenic contribution. Probabilistic health risk assessment results depicted as a medium to high level of non-carcinogenic threats for consumers in the study area. Districts such as Khulna, Satkhira, Bhola, Pirojpur, Bagerhat, Jhalakati, Patuakhali, Barguna, and Lakshmipur possesses a high level of threat due to poor water-quality. Finally, it can be said that the study area is exposed to multi-hazards such as salinization, and elevated metals in groundwater. Substantial human health concerns might arise in the study area due to contaminated water consumption. This study clearly explained the groundwater quality challenges considering the multi-hazard in the coastal districts of Bangladesh, that could be applicable in policy formulation.

Spatiotemporal distribution of fluoride in drinking water and associated probabilistic human health risk appraisal in the coastal region, Bangladesh.

Spatiotemporal distribution of fluoride in drinking water has been posing serious health concerns worldwide. However, in Bangladesh, to date, there is a very limited study reported the probabilistic health risks from fluoride content in drinking water. Therefore, we investigate the spatiotemporal distribution of fluoride concentration in drinking water and associated health risks in the coastal districts of Bangladesh based on randomly collected 840 groundwater samples (Dry-season = 302 and Wet-season = 538). Probabilistic health risk appraisal from fluoride was performed using the Monte-Carlo simulation and sensitivity analysis. Fluoride concentration in 11.89% (Wet-season) and 24.50% (Dry-season) of the samples exceeded the acceptable level of 1.0 mg/L, while 3.90% (Wet-season) and 7.28% (Dry-season) samples surpassed the maximum permissible limit (fluoride: 1.5 mg/L. The deficiency of fluoride content in groundwater (<0.50 mg/L) in Wet-season (60.41%) and in Dry-season (55.63%) was identified from the study area. The seasonality to the spatial change of fluoride concentration in drinking water has been explored. The mean non-carcinogenic risks e.g., hazard quotient (HQ) from the consumption of high fluoride-containing water for infants and children were mostly exceeded the threshold value 1 (HQ > 1) in both seasons. However, the risk of children and infants at the 95th percentile crossed the safe level (SL: 1) in the wet season and the risk of infants, children, teens and adults at the 95th percentile surpassed 1 in the dry season, indicating the potential adverse health effects. Apart from the high exposure, fluoride deficiency might be a severe problem in this region due to the very low concentration of fluoride (<0.50 mg/L) in drinking water. Sensitivity analyses indicate high fluoride-containing drinking water was the most contributing variables affecting the model outcome. Finally, the case-control study should be performed to examine further the health effects from the ingestion of high/low fluoride-bearing groundwater in the study area.

Processes controlling the extent of groundwater pollution with chromium from tanneries in the Hazaribagh area, Dhaka, Bangladesh.

The Hazaribagh industrial area in Dhaka city, the capital of Bangladesh, is considered one of the hotspots of chromium (Cr) pollution, due to excessive discharge of Cr contaminated waste over decades by approximately 150 tanneries. In 2000, elevated Cr concentrations were observed in the underlying Dupi Tila Aquifer (DTA), which is heavily deployed for drinking water supply of Dhaka city's population. In the following years, Cr concentrations in the DTA have dropped and apparently stayed low. In 2010, elevated Cr concentrations were found again in the DTA. This study aims to evaluate the status of the total Cr contamination in the surface waters, groundwater, and soils in the area, to clarify the temporal evolution of the total Cr contamination pattern in the DTA. For this, we collected water and soil samples in 2012, 2013, 2014, and 2019 for (hydro)chemical characterization and analyzed new groundwater level data on the development of the cone of depression below the city. Our study indicates that the temporal evolution of the total Cr contamination in the DTA is closely coupled to the groundwater dynamics. The rapid growth of the cone of depression due to excessive pumping resulted (i) in a disconnection of the groundwater table from the heavily contaminated Hazaribagh soils, and (ii) in an increased gradient between the contaminated surface waters and the groundwater, increasing infiltration into the groundwater. Finally, (iii) the further growth of the cone of depression resulted in an inflow of fresh groundwater from the west of Dhaka city, causing a dilution effect. Although in 2017 tanneries were moved out of the Hazaribagh area, the contaminated soils still pose a threat to groundwater quality when groundwater levels would recover.

Accumulation of iron and arsenic in the Chandina alluvium of the lower delta plain, Southeastern Bangladesh.

Accumulations of iron, manganese, and arsenic occur in the Chandina alluvium of southeastern Bangladesh within 2.5 m of the ground surface. These distinctive orange-brown horizons are subhorizontal and consistently occur within 1 m of the contact of the aerated (yellow-brown) and water-saturated (gray) sediment. Ferric oxyhydroxide precipitates that define the horizons form by oxidation of reduced iron in pore waters near the top of the saturated zone when exposed to air in the unsaturated sediment. Hydrous Fe-oxide has a high specific surface area and thus a high adsorption capacity that absorbs the bulk of arsenic also present in the reduced pore water, resulting in accumulations containing as much as 280 ppm arsenic. The steep redox gradient that characterizes the transition of saturated and unsaturated sediment also favors accumulation of manganese oxides in the oxidized sediment. Anomalous concentrations of phosphate and molybdenum also detected in the ferric oxyhydroxide-enriched sediment are attributed to sorption processes.

Spatio-temporal assessment and trend analysis of surface water salinity in the coastal region of Bangladesh.

The study was designed to collect water samples over two seasons-wet-monsoon season (n = 96) (March-April) and dry-monsoon season (n = 44) (September-October)-to understand the seasonal variation in anion and cation hydrochemistry of the coastal rivers and estuaries contributing in the spatial trend in salinity. Hydrochemical examination of wet-monsoon season primarily revealed Ca-Mg-HCO3 type (66%) and followed by Na-Cl type (17.70%) water. In the dry-monsoon season, the scenario reversed with primary water being Na-Cl type (52.27%) followed by Ca-Mg-HCO3 type (31.81%). Analysis of Cl/Br molar ratio vs. Cl (mg/L) depicted sampling area affected by seawater intrusion (SWI). Spatial analysis by ordinary kriging method confirmed approximately 77% sample in the dry-monsoon, and 34% of the wet-monsoon season had shown SWI. The most saline-intruded areas in the wet-monsoon seasons were extreme south-west coastal zone of Bangladesh, lower Meghna River floodplain and Meghna estuarine floodplain and south-eastern part of Chittagong coastal plains containing the districts of Chittagong and Cox's Bazar adjacent to Bay of Bengal. In addition, mid-south zone is also affected slightly in the dry-monsoon season. From the analyses of data, this study could further help to comprehend seasonal trends in the hydrochemistry and water quality of the coastal and estuarine rivers. In addition, it can help policy makers to obligate some important implications for the future initiatives taken for the management of land, water, fishery, agriculture and environment of coastal rivers and estuaries of Bangladesh.

Megacity pumping and preferential flow threaten groundwater quality.

Many of the world's megacities depend on groundwater from geologically complex aquifers that are over-exploited and threatened by contamination. Here, using the example of Dhaka, Bangladesh, we illustrate how interactions between aquifer heterogeneity and groundwater exploitation jeopardize groundwater resources regionally. Groundwater pumping in Dhaka has caused large-scale drawdown that extends into outlying areas where arsenic-contaminated shallow groundwater is pervasive and has potential to migrate downward. We evaluate the vulnerability of deep, low-arsenic groundwater with groundwater models that incorporate geostatistical simulations of aquifer heterogeneity. Simulations show that preferential flow through stratigraphy typical of fluvio-deltaic aquifers could contaminate deep (>150 m) groundwater within a decade, nearly a century faster than predicted through homogeneous models calibrated to the same data. The most critical fast flowpaths cannot be predicted by simplified models or identified by standard measurements. Such complex vulnerability beyond city limits could become a limiting factor for megacity groundwater supplies in aquifers worldwide.

Safe distances between groundwater-based water wells and pit latrines at different hydrogeological conditions in the Ganges Atrai floodplains of Bangladesh.

BACKGROUND: Groundwater drawn from shallow tubewells in Bangladesh is often polluted by nearby pit latrines, which are commonly used toilets in rural and sub-urban areas of the country. METHODS: To determine the minimum safe distance of a tubewell from a pit latrine in different hydrogeological conditions of Bangladesh, 20 monitoring wells were installed at three study sites (Manda, Mohanpur and Bagmara) with the vertical and horizontal distances ranging from 18-47 to 2-15 m, respectively. Water samples were collected three times in three seasons and tested for faecal coliforms (FC) and faecal streptococci (FS) as indicators of contamination. Soil samples were analysed for texture, bulk density and hydraulic conductivity following standard procedures. Sediment samples were collected to prepare lithological logs. RESULTS: When the shallow aquifers at one of the three sites (Mohanpur) were overlained by 18-23-m-thick aquitards, the groundwater of the monitoring wells was found contaminated with a lateral and vertical distances of 2 and 31 m, respectively. However, where the aquitard was only 9 m thick, contamination was found up to lateral and vertical distances of 4.5 and 40.5 m, respectively. The soil textures of all the sites were mainly composed of loam and sandy loam. The hydraulic conductivities in the first aquifer at Manda, Mohanpur and Bagmara were 5.2-7.3, 8.2 and 1.4-15.7 m/h, respectively. CONCLUSIONS: The results showed that the safe distance from the tubewell to the pit latrine varied from site to site depending on the horizontal and vertical distances of the tubewell as well as hydrogeological conditions of a particular area.

Diffusion weighted MR imaging of ring enhancing brain lesions.

OBJECTIVE: To evaluate the role of diffusion weighted imaging in differentiating the cause of ring enhancing brain lesions. STUDY DESIGN: Analytical, descriptive study. PLACE AND DURATION OF STUDY: Department of Radiology, The Aga Khan University Hospital, Karachi, from March 2007 to July 2011. METHODOLOGY: Diffusion weighted imaging (DWI) was performed on 37 patients having ring enhancing lesions on their post-contrast brain MRI scans. These lesions were characterized into neoplastic and abscess cavity on the basis of diffusion restriction. Correlation of all these findings was done with histopathology obtained in all these patients. Sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of DWI were calculated. Comparisons of mean ADC values of abscess and neoplastic lesions were also done using t-test. RESULTS: DWI had a sensitivity of 94.73%, specificity of 94.44%, positive predictive value of 94.73%, and negative predictive value of 94.44% and diagnostic accuracy of 94.5% in differentiating brain abscess from neoplastic brain lesions. Mean ADC value in central cavity and wall of neoplastic lesions and brain abscesses were calculated with significant p-value of 0.001 and 0.025 respectively. CONCLUSION: Diffusion weighted imaging is non-invasive method with high sensitivity and specificity which can help in differentiation of ring enhancing neoplastic lesions and brain abscesses. This modality should be read in conjunction with conventional imaging.