Sensitivity study of a locally developed six electrode focused impedance method.

The Focused Impedance Method (FIM) is a new technique of electrical bioimpedance measurements in the human body. The idea originated in Bangladesh and provides an opportunity for localized measurement of bioimpedance down to reasonable depths from the body surface using skin surface electrodes. This has potential applications for physiological studies of targeted organs in the body and in detecting or diagnosing diseases and disorders. FIM is based on the age-old Tetra-Polar Impedance Measurement (TPIM) but provides a few significant improvements. Technology must be developed indigenously to obtain long-term benefits, particularly in Low and Medium Income countries (LMIC). This paper presents an experimental sensitivity study of the six-electrode version of the Focused Impedance method (FIM-6) with the circuit and phantom indigenously designed in Nepal. The work involved sensitivity studies of both FIM-6 and TPIM with the necessary circuit blocks developed through experimental validation. The sensitivity studies were performed on a simple 2D phantom with different electrode arrangements for FIM-6 and linear TPIM. A cylindrical object was placed at different positions for this study. The FIM-6 gave a high sensitivity in the central part, which remained almost constant within a small region that may be termed as the focused region. On the other hand, TPIM results fell off sharply away from the central point, making it unsuitable for practical measurements on target organs. Besides, there were areas with large negative sensitivities in TPIM, which were much smaller in FIM. The results obtained through this work clearly show the improvement offered by FIM over TPIM.

Probing Deep Lung Regions using a New 6-electrode Tetrapolar Impedance Method.

Probing deep regions of the lung using electrical impedance is very important considering the need for a low cost and simple technique, particularly for the low and medium income countries. Because of complexity and cost, Electrical Impedance Tomography is not suitable for this envisaged application. The simple Tetrapolar Impedance Measurement (TPIM) technique employing four electrodes is the age old technique for bioelectrical measurements. However, it has its limitations in respect of organ localisation and depth sensitivity using skin surface electrodes. Recently, a new 6-electrode TPIM with two current electrodes but two pairs of appropriately connected potential electrodes positioned on the front and back of the thorax, proposed by one of the authors, came with a promise. However, this work gave a qualitative proposal based on concepts of physics and lacked a quantitative evaluation. In order to evaluate the method quantitatively, the present work employed finite element method based COMSOL Multiphysics software and carried out simulation studies using this new 6-electrode TPIM and compared the results with those from 4-electrode TPIM, with electrodes applied either on the front or at the back of the thorax for the latter. Initially, it carried out a sensitivity distribution study using a simple rectangular volume conductor which showed that the 6-electrode TPIM gives better depth sensitivity throughout the lung region. Next it used a near life like thorax model developed by another of the authors earlier. Using this model, extensive studies were carried out to quantify the overall sensitivity over a target lung region, the contribution of the target lung to the total measured impedance, and several other parameters. Through these studies, the 6-electrode TPIM was established on a stronger footing for probing deep regions of the lungs.

Evaluation of adaptive low cost solar water pasteurization device for providing safe potable water in rural households.

This study was conducted to evaluate the effectiveness of a simplified, low cost, pasteurization device in inactivating the diarrheal pathogens present in pond/lake/river water in order to provide safe potable water to people living in the rural areas of low resource countries. In this process, water in polyethylene bags was exposed to sunshine, where UV radiation emissions and heat absorption from the sunshine occurs simultaneously, and maintaining the heating at <60 °C, and minimum UV radiation emissions of 996.2 W/m2 for approximately 30 minutes was found enough to inactivate diarrheal pathogens in water. The synergistic effect of heat, UV radiation emission and holding time causes the destruction of diarrheal pathogens. However, the performance of the device depends on the thickness of the insulation and the air gap between polyethylene bags. Regardless of sample sources, the highest population reduction of Escherichia coli observed in the bacterial challenge study was 6.8 ± 0.4 log CFU/ml. The physicochemical properties were found acceptable compared with USEPA potable water quality except turbidity, which is acceptable according to the BDS standard, and the shelf-life study results demonstrated that 6 months' storage of pasteurization device-treated water at room temperature is possible without compromising water quality. Therefore, this simplified pasteurization device could be useful in potable water-scarce areas of the world.

Probing for Stomach using the Focused Impedance Method (FIM).

For probing deep organs of the body using electrical impedance, the conventional method is to use Electrical Impedance Tomography (EIT). However, this would be a sophisticated machine and will be very expensive when a full 3D EIT is developed in the future. Furthermore, for most low income countries such expensive devices may not deliver the benefits to a large number of people. Therefore, this paper suggests the use of simpler techniques like Tetrapolar Impedance Measurement (TPIM) or Focused Impedance Method (FIM) in probing deeper organs. Following a method suggested earlier by one of the authors, this paper studies the possibility of using TPIM and FIM for the stomach. Using a simplified model of the human trunk with an embedded stomach, a finite element simulation package, COMSOL, was used to obtain transfer impedance values and percentage contribution of the stomach region in the total impedance. For this work, judicious placement of electrodes through qualitative visualizations based on point sensitivity equations and equipotential concepts were made, which showed that reasonable contribution of the stomach region is possible through the use of TPIM and FIM. The contributions were a little over 20% which is of similar order of the cross-sectional area percentage of the stomach with respect to that of the trunk. For the case where the conductivity of the stomach region was assumed about 4 times higher, the contributions increased to about 38%. Through further studies this proposed methods may contribute greatly in the study of deeper organs of the body.

Use of a Conical Conducting Layer with an Electrical Impedance Probe to Enhance Sensitivity in Epithelial Tissues.

Tetra-polar electrical impedance measurement (TPIM) with a square geometry of electrodes is useful in the characterization of epithelial tissues, especially in the detection of cervical cancer at precancerous stages. However, in TPIM, the peak planar sensitivity just below the electrode surface is almost zero and increases to a peak value at a depth of about one third to one half of the electrode separation. To get high sensitivity for the epithelial layer, having thicknesses of 200 µm to 300 µm, the electrode separation needed is less than 1 mm, which is difficult to achieve in practical probes. This work proposes a conical conducting layer in front of a pencil like probe with a square geometry of TPIM electrodes to create virtual electrodes with much smaller separation at the body surface, thus increasing the sensitivity of the epithelial tissues. To understand the improvements, if any, 3D sensitivity distribution and transfer impedance were simulated using COMSOL Multiphysics software for a simplified body tissue model containing a 300 µm epithelial layer. It has been shown that fractional contribution of an epithelial layer can be increased several times placing a cylindrical conducting layer in between the tissue surface and the electrodes, which can further be enhanced using a conical conducting layer. The results presented in this paper can be used to choose an appropriate electrode separation, conducting layer height and cone parameters for enhanced sensitivity in the epithelial layer.

Biofilter for generation of concentrated sulphuric acid from H2S.

Biofilters are used for the conversion of odorous hydrogen sulphide to odourless sulphate in wastewater treatment plants under the right conditions of moisture and pH. One of the consequences of maintaining the suitable pH and moisture content is the production of large volumes of weakly acidic leachate. This paper presents a biofilter with a maximum H2S elimination capacity of 16.3 g m(-3) h(-1) and removal efficiency greater than 95 % which produces small volumes (1 mL of solution L(-1) of reactor day(-1)) of sulphuric acid with a concentration greater than 5.5 M after 150 days of continuous operation. The concentrated sulphuric acid was produced by intermittently trickling a minimum amount of nutrient solution down the upflow biofilter which created a moisture and pH gradient within the biofilter resulting in an environment at the top for the bacterial conversion of H2S, while sulphuric acid was accumulated at the base. Genetic diversity profiling of samples taken from different sections of the biofilter confirms that the upper sections of the biofilter had the best environment for the bacteria to convert H2S to sulphate. The formation of concentrated sulphuric acid presents an opportunity for the recovery of sulphur from the waste stream as a usable product.

A Rare Internal Herniation in Adult: Meckel's Diverticulum.

Intestinal obstruction due to Meckel's diverticulum is the most common presentation in adults. There are various mechanisms by which it can cause intestinal obstruction such as volvulus of small intestine around a fibrous band extending from Meckel's diverticulum to umbilicus, intussusception, and Littre's hernia. We report the case of a young adult operated on emergency for acute intestinal obstruction. The CT scan suggested a nonspecific internal herniation. Surgical exploration confirmed a rare type of obstruction due to Meckel's diverticulum.

Classification of breast tumour using electrical impedance and machine learning techniques.

When a breast lump is detected through palpation, mammography or ultrasonography, the final test for characterization of the tumour, whether it is malignant or benign, is biopsy. This is invasive and carries hazards associated with any surgical procedures. The present work was undertaken to study the feasibility for such characterization using non-invasive electrical impedance measurements and machine learning techniques. Because of changes in cell morphology of malignant and benign tumours, changes are expected in impedance at a fixed frequency, and versus frequency of measurement. Tetrapolar impedance measurement (TPIM) using four electrodes at the corners of a square region of sides 4 cm was used for zone localization. Data of impedance in two orthogonal directions, measured at 5 and 200 kHz from 19 subjects, and their respective slopes with frequency were subjected to machine learning procedures through the use of feature plots. These patients had single or multiple tumours of various types in one or both breasts, and four of them had malignant tumours, as diagnosed by core biopsy. Although size and depth of the tumours are expected to affect the measurements, this preliminary work ignored these effects. Selecting 12 features from the above measurements, feature plots were drawn for the 19 patients, which displayed considerable overlap between malignant and benign cases. However, based on observed qualitative trend of the measured values, when all the feature values were divided by respective ages, the two types of tumours separated out reasonably well. Using K-NN classification method the results obtained are, positive prediction value: 60%, negative prediction value: 93%, sensitivity: 75%, specificity: 87% and efficacy: 84%, which are very good for such a test on a small sample size. Study on a larger sample is expected to give confidence in this technique, and further improvement of the technique may have the ability to replace biopsy.

[Perineal-scrotal gangrene: epidemiological and therapeutic aspects. About 45 cases]. / La gangrène périnéoscrotale: profil épidémiologique et aspects thérapeutiques. À propos de 45 cas.

Perineoscrotal gangrene is an acute disease, a rare and severe affection of the perineum, whose evolution is unpredictable and rapidly extensive. The diagnosis is clinical. The paraclinical examinations allow early diagnosis and assessment of anatomical and biological repercussions. We conducted a retrospective study of 45 patients spread over six years, involving a multidisciplinary team consisting of three specialists (urologists, visceral, plastic surgeons). The average age was 52 years. The largely male dominated our series. Fournier gangrene was the most common etiology. We noted five cases of death (11%) in the acute phase, secondary to septic shock (four patients) or multiple organ failure (one patient). The evolution was favorable in 40 other patients in the series, requiring an initial management in intensive care unit, and surgical treatment. The average hospital stay was 17 days. After the acute phase, all patients underwent a surgery for skin coverage, ranging from guided healing (two patients) to musculocutaneous flap of the gracilis (six patients) via the secondary suture (four patients), the burying the testes (18 patients) and half thick skin graft, with a functional and aesthetic result was acceptable, and minimal sequelae. In our series, the most predictive prognostic factors would be the delay of care, sepsis on admission and associated diseases.

Adult intussusception caused by an inflammatory fibroid ileal polyp.

BACKGROUND: Inflammatory fibroid polyps (IFPs) are rare benign lesions of uncertain origin that may occur in various parts of the gastrointestinal tract that originate from the sub mucosa located in different sites of the digestive tract. They are commonly located in the stomach and small bowel. It is one of the probable diagnoses that should be considered in obstructive tumors of the small intestine causing invagination. METHODS: A case of IFP is presented, causing intestinal invagination in an 39-year-old female patient, admitted with abdominal distension and pain. RESULT: Computerised tomography imaging (CT) demonstrated intussusception of the small bowel. Exploratory laparotomy revealed a bowel intussusception. An ileo-ileal anastomosis was performed after resection of the tumoral segment. Histology of the resected small bowel revealed an inflammatory fibroid polyp. CONCLUSIONS: intussusception secondary to IFPs of the small intestine are difficult to diagnose without recognition of its clinical and pathological characteristics. CT is useful in confirming an anatomical abnormality, histological examination establishes the final diagnosis of IFPs.

Determination of abdominal fat thickness using dual electrode separation in the focused impedance method (FIM).

Subcutaneous fat layer thickness in the abdomen is a risk indicator of several diseases and disorders like diabetes and heart problems and could be used as a measure of fitness. Skinfold measurement using mechanical calipers is simple but prone to error. Ultrasound scanning techniques are yet to be established as accurate methods for this purpose. magnetic resonance imaging (MRI) and computed tomography (CT) scans can provide the answer but are expensive and not available widely. Some initiatives were made earlier to use electrical impedance to this end, but had inadequacies. In the first part of this paper, a 4-electrode focused impedance method (FIM) with different electrode separations has been studied for its possible use in the determination of abdominal fat thickness in a localized region. For this, a saline phantom was designed to provide different electrode separations and different layers of resistive materials adjacent to the electrodes. The background saline simulated the internal organs having low impedance while the resistive layers simulated the subcutaneous fat. The plot of the measured impedance with electrode separation had different 'slopes' for different thicknesses of resistive layers, which offered a method to obtain an unknown thickness of subcutaneous fat layer. In the second part, measurements were performed on seven human subjects using two electrode separations. Fat layer thickness was measured using mechanical calipers. A plot of the above 'slope' against fat thickness could be fitted using a straight line with an R(2) of 0.93. Then this could be used as a calibration curve for the determination of unknown fat thickness. Further work using more accurate CT and MRI measurements would give a better calibration curve for practical use of this non-invasive and low-cost technique in abdominal fat thickness measurement.

Mesenteric appendicitis strangulating small bowel: an exceptional internal herniation.

Primitive internal hernias are a rare cause of intestinal obstruction. They are often paraduodenal even transmesocolic, but only rarely transomental. We present a rare case of an internal abdominal hernia in a young man. The small bowel was strangulated by an intra mesenteric appendicitis. This hernia was revealed by abdominal pain, nausea and vomiting. Plain X-ray of the abdomen showed dilated jejunal and ileal loops with multiple air-fluid levels. The diagnosis of appendicitis was suggested by ultrasound but the internal hernia was found only upon surgical exploration. An appendicectomy and adhesiolysis were performed. The patient recovered fully after 3 days, and had an uneventful postoperative course. The authors discuss the possible cause of this rare intestinal obstruction.

Primary pelvic hydatid cyst an unusual cause of cystic adnexal image (mass).

Hydatid cyst is a parasitic human infection which is endemic in North Africa. It is more frequently localized in the liver and the lung. Involvement of others sites is usually secondary to these primary localizations. We report 2 exceptional cases of primary pelvic hydatid cyst diagnosed respectively in a 37-year-old and in a 48-year-old women. These cases will focus on the different characteristics of the infection, and the benefit of including epidemiologic arguments in using the diagnostical approach of adnexal masses.

The sensitivity of focused electrical impedance measurements.

One of the problems with tetrapolar impedance measurements is the lack of spatial sensitivity within the measured volume. In this paper we compare the sensitivity of tetrapolar measurements and the focused impedance measurements (FIM) proposed by Rabbani et al (1999 Ann. New York Acad. Sci. 873 408-20), which give an improved sensitivity profile. Using a previously validated model of sensitivity based on Geselowitz's lead theory, the sensitivity of FIM using eight, six and four electrodes was investigated. All electrode configurations showed a maximum in the average sensitivity of a plane at a depth of one-third of the drive-receive electrode spacing. No difference was found in the sensitivity value of this maximum between electrode configurations having the same drive-receive electrode spacing. The six- and eight-electrode configurations showed negative sensitivity regions down to half of the drive-receive electrode spacing, whilst the four-electrode measurement showed negative sensitivity regions down to one-third of the drive-receive electrode spacing. The single peak in sensitivity beneath the centre of the electrode configuration became dominant at 0.56, 1.4 and 0.14 of the receive electrode spacing for the eight-, six- and four-electrode configurations respectively. Thus, the four-electrode FIM configuration gives a single peak closest to the surface.

Transmesocolic internal herniation: a rare case of small bowel obstruction, "the Marrakesh hernia".

Internal hernias, including paraduodenal (traditionally the most common), pericecal, foramen of Winslow, and intersigmoid hernias, account for approximately 0.5-5.8% of all cases of intestinal obstruction and are associated with a high mortality rate, exceeding 50% in some series. We report an extremely rare case of an internal abdominal hernia, through the right mesocolon, in a young woman with a right colon with no peritoneal fixation. This hernia was revealing by abdominal pain, nausea, and vomiting. The diagnosis of internal hernia was suggested by computed tomography (CT), but the exact type of internal hernia was confirmed by surgical exploration. The postoperative course was uneventful and the patient fully recovered after 3 days. The patient is free from symptoms and from recurrence, after 12 months of follow-up.

A new four-electrode Focused Impedance Measurement (FIM) system for physiological study.

A recently developed Focused Impedance Measurement (FIM) system (by the authors' group) uses six electrodes to localize a zone of interest. Because of 3D sensitivity it could give physiological information on large organs like stomach, lungs, etc. using surface electrodes in the frontal plane. This paper presents a modified FIM technique using four electrodes placed at the corners of a square matrix. Firstly current is driven through an adjacent electrode pair while the potential is measured across the opposite pair from which an impedance value is obtained. Then a similar measurement is made at 90 degrees to the above by changing connections to the electrode pairs appropriately. The sum of these two impedance values has a dominant contribution from the central region within the square matrix, giving the desired focusing. Experimental sensitivity maps obtained from a 2D phantom have verified the focusing effect. Compared to the previous six-electrode FIM system the focusing effect is slightly less, but this new technique has less negative artifacts in the periphery. This new FIM method can be applied both in the frontal plane and in the transverse plane of the human thorax, giving a further advantage besides requiring fewer electrodes.

A modified formula for defining tissue phantom ratio of photon beams.

Tissue phantom ratio (TPR), for square fields of various dimensions has been determined at varying depths in water. The dose in water has been measured at a fixed source-to-surface distance (SSD) of 100 cm and reference depth of 5 cm for 6 MV photon beam of Siemens Linear Accelerator Primus 11 in German Cancer Research Center (DKFZ), Heidelberg, Germany. A modified formula has been developed to calculate the TPR value for isocentric treatment. The present article describes the conversion of the measured data values into a comprehensive and consistent data set by the modified formula, that gives the TPR from Percentage Depth Dose (PDD) with depth as a function of field sizes from 10 mm x 10 mm upto 300 mm x 300 mm) and depth (from 0 mm to 300 mm).