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Please follow the links to view the publication.10.2 G Sample/s DAQ system for optical scanning acoustic microscopy using 0.35 μm CMOS technology
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080112
This paper presents an ultra-fast CMOS Data- Acquisition system. It has been developed predominately for use in Optical Scanning Acoustic Microscopy, and it is also applicable in RF transceiver systems. The key modules of this system include a sub- sampling sample-and-hold amplifier, and a pulse generator, which is based on a 2.6 GHz PLL with quadrature outputs and provides control signals for the SHA. The DAQ system is implemented in a standard 0.35 μm CMOS process, and achieves 10.2 G Sample/s sampling rate for the 80 MHz periodic laser input. (8 pages)Strategies and tools for multivariate biology: interactive analysis of high dimensional postgenomic data
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060375
Postgenomic biology is characterised by large and diverse datasets presenting many technical challenges in data handling, analysis and integration. Further, there are significant challenges in converting the data into biological knowledge to support model building and hypothesis generation. A basic strategy is to find structure in the data (clusters) representing the coordinated response of system probes (e.g. biomolecules) to given stimuli. Clusters may then be characterised by reference to knowledgebases (such as pathway genome databases). A complementary strategy is to select probes based on extant knowledge (e.g. related by terms in an ontology) and explore the character of their biological response. We have developed an interactive software tool, Vitamin-B (visual, interactive tool for the analysis and mining of bioinformatics data), which provides utilities for both supervised and unsupervised inquiry and links to external resources to promote knowledge acquisition in support of model construction and hypothesis generation. The focus in the tool's design and development is on usability: aiming to lower the barriers for both expert and novice users to interactive exploratory and targeted data analysis through a full complement of analysis methods coupled to linked dynamic graphics. The tool is based on the proven components of R and ggobi and provides enhanced functionality through a custom user interface, flexible data selection, linkage to external resources, undo functionality and the production of summary reports. A key feature of the project is the central role of HCI principles in the interface. Evidence for the effectiveness of the tool (and its components) will be acquired by user evaluation in illustrative goal-driven scenarios.Simultaneous monitoring of mechanical and electrical properties of pregnant uterus
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060341
The presented data acquisition system allows recording of electrohysterographic signals from maternal abdomen and the mechanical contractions via strain gauge transducer. As a research material we collected 108 traces during 24-hour period before labour from the group of patients between 37 and 40 week of gestation. That enabled the detection of contractions in the both signals and comparison of their descriptive parameters. Obtained results shows that these methods demonstrate high agreement only in relation to the number of contractions recognized as being consistent. But, the agreement of detailed contractions parameters is unacceptable to consider these methods as fully alternative. (4 pages)A low-power high precision self-testing data acquisition system for a large seismic exploration grid
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050142
In seismic exploration for oil and gas, a grid of 2,000 to 30,000 nodes is formed to acquire reflected wave signals from the rock layers in the Earth. Each node consists of a sensor, complete data acquisition system with self-test, and telemetry for returning data to a central recording unit. This demanding application requires a highly linear, wide dynamic range data acquisition system with a 0.1-200 Hz bandwidth. A large number of nodes operating simultaneously require that each node consume very low power. The components of each data acquisition node are: a geophone or a hydrophone (sensors for land and marine exploration respectively), a programmable gain differential amplifier, a delta-sigma analog to digital converter, a multi-function decimation filter, and a high precision DAC for calibration and self-test. Each of these components is optimally designed for low power in large sensor arrays. The acquisition node requires self-calibration capability and operation in a synchronous mode where all channels acquire data simultaneously. A data acquisition system that meets these requirements has been designed and tested. The overall performance of the system is better than 112 dB linearity (THD) and 123 dB dynamic range (SNR) at 500 SPS. The power consumption for the data acquisition portion of a single node is 105 mW from a 5 V analog power supply.The use of LabView and Matlab in the development of a novel pneumotachograph
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980592
A novel pneumotachograph is currently under development which exploits the properties of the Wells turbine used in many wave energy projects during the eighties and the nineties. In order to employ a small scale model of the Wells turbine as a highly sensitive flow transducer a suitable constant speed motor controller is required. This controller has best designed and thoroughly analysed using Matlab with Simulink. Typically airflow data, collected from a pneumatachograph, needs further processing before physicians can extract relevant patient diagnostic data. The now data processing software has been developed using LabView because of its built-in capabilities specifically aimed at data acquisition and data processing. (5 pages)Foetal ECG separation
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970066
The extraction of the foetal electrocardiogram (FECG) from skin electrode signals recorded from a pregnant woman is a problem of concern to Signal Processing which accepts a model-based approach. Taking on board the bioelectrical phenomena which rule the cardiac activity and the propagation of heartbeat signals across the body, the FECG reconstruction may be modelled in the context of blind signal separation (BSS). Experimental results show the applicability of such BSS techniques to this biomedical problem. (6 pages)Measurement of multiple velocities in multiphase flow
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960580
The work described consists of investigating an entirely novel technique for measuring the velocity of the flowing components in vertically upward, gas/liquid flows in the “Cap bubble” and “Taylor bubble” flow regimes. The technique consists of mounting an array of 64 axially separated conductivity sensors in a vertical pipe through which an air/water mixture is flowing (water is the continuous component). By cross-correlating the output signals from any two of these conductivity sensors it is possible to obtain the mean Cap bubble (or Taylor bubble) velocity and hence an estimate of the mean gas velocity. The novel element of the work is to demonstrate that by appropriately combining the output signals from the array of 64 conductivity sensors it is possible to determine the output signals that would be obtained from one or more “simulated impedance sensors” that are travelling through the flow at the same speed as the Cap bubbles (or Taylor bubbles). Cross-correlation of the outputs from two of these simulated conductivity sensors, travelling in between the Cap bubbles, allows the liquid velocity relative to these moving sensors to be determined. Since the velocity of the simulated sensors is known, the liquid velocity can be determined. (4 pages)Three phase pipe flow imaging using a capacitance tomography system
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960579
Several tomography systems for pipe flow imaging have been developed which are based on capacitance sensors measuring the permittivity of the flowing components. Several reconstruction techniques for reconstructing the measured capacitances has been developed. The most commonly used reconstruction algorithm is called the linear backprojection (LBP) algorithm and represents a fast and fairly crude algorithm. In this paper it is shown that in using the LBP-algorithm one must be very careful in interpreting the results. Methods for using a capacitance tomography system based an the LBP-algorithm for three phase oil/water/gas pipe flow imaging is outlined and preliminary results are presented. (6 pages)The implementation and application of practical partial discharge data capture systems
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960235
The much greater availability of fast data processing electronics and computer memory has made detailed data capture during partial discharge measurements practical and accessible to both the academic and the industrial user of partial discharge measurements. Different techniques may be used to perform the actual data capture and these each have some advantages and disadvantages. Continuous data sampling throughout a test ensures that a complete record of the signals detected will be obtained. However, such a technique will require further algorithms to be applied to the raw data in order to define such parameters as the discharge rate, mean discharge amplitude, discharge pulse analysis, etc. Since the basic capture mechanism itself does not define the presence of partial discharge pulses separately from the ever-present system noise, the algorithm must also identify when a pulse actually exists. In order to achieve a good time resolution of the pulse information, a suitable sampling rate must be used in the process. (3 pages)Novel technique to improve optical fibre sensor's response for industrial applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_19951515
A general major disadvantage of optical fibre sensors (OFS) is a non-linear (sigmoidal) response which produces a limited useable linear region. This work presents a novel method of overcoming this problem by the use digital instrumentation and signal processing. Previously we have shown that by appropriate selection of eight wave ordinates from the spectral response of an optical fibre pH sensor as inputs to a trained multilayer artificial neural network, the response range of the sensor can be extended from the normal pH 5.0-7.25 range to the full sensitivity of the sensor, i.e. pH 2.51-9.76 range with a worst error of only 0.08 pH. Application of this method is illustrated. The method is currently adopted to a new, simple and portable instrument based on the use of three LEDs as light sources. In this preliminary study, the sensor just simply measures colour changes of thymol blue indicator in an acid-base pH titration. The application of the neural network to process the colour changes of thymol blue indicator in the acid-base titration is illustrated. (6 pages)A moored ‘surface-following’ buoy for spectral wind measurements with satellite and VHF data telemetry
http://dl-live.theiet.org/content/conferences/10.1049/cp_19940581
Discusses the development of a Sonic Buoy. The high quality of the results from the SWALES deployment vindicates the decision to develop the Sonic Buoy. The relation between the calculated wind stress and wind speed is much more clearly defined than in previous ship-based measurements. On the technical side, the buoy design has been proved with respect to survivability, and the redundancy built into the data logging and telemetry has proved its worth.Development of a multi-year deep sea bottom pressure recorder
http://dl-live.theiet.org/content/conferences/10.1049/cp_19940595
A new deep ocean instrument has been developed by the Technology Group of the Proudman Oceanographic Laboratory. MYRTLE (Multi-Year Return Tidal Level Equipment) is a self-contained instrument for long term deployment on the sea bed. It is capable of making continuous measurements of sea pressure and temperature using high precision quartz crystal sensors. The measured data are transferred to solid state memory contained in several buoyant, releasable data capsules (RDC) which provide a means for data retrieval. The capsules can either be recovered on the surface following an acoustic command to a release or can be pre-programmed to release at yearly intervals and relay the data from the sea surface through a satellite telemetry link, thereby avoiding the expense of a recovery ship. Where applicable, well-proven instrumental techniques have been used in the system to ensure reliability. Several new technologies have been applied in the data formatting and storage systems. A novel method of data transfer to the RDC has been employed using infra-red emitters and receivers communicating through the sea-water/glass interface.Integration-plot test for peri-stimulus time histograms in human motor units
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043871
A statistical test is proposed for peri-stimulus time histograms in human motor units for the case where a test stimulus is delivered at a constant interval after a previous discharge. This mathematically described test included the notion of the multiple comparison and thus achieved higher sensitivity than the previously proposed method. With regard to data acquisition, the interval from a sham stimulus to the next discharge was acquired as a control, and the total number of samples was set to be four times as large as that in the test situation to reduce the statistical scattering noise. A newly defined statistical object, the integration plot (timewise accumulation of the test histogram without control subtraction) was used for this statistical test. The integration plot had less noise than the cumulative sum (CUSUM) plot (1/√2 in theory) and thus represented the neural effect. To compare this integration-plot test with that of the CUSUM, a simulation experiment that compared two sample histograms (one of which had a faint structural change from 20 ms) was conducted. As a result, the present test succeeded in detecting the onset of the change point earlier (23 ms on average) than the CUSUM test (27 ms on average), and the detection probability was also higher (9 out of 10) than the CUSUM (6 out of 10). It was therefore confirmed experimentally that the present statistical test had higher sensitivity than that of the CUSUM proposed previously.Cephalometric image analysis and measurement for orthognathic surgery
http://dl-live.theiet.org/content/journals/10.1049/mbec_20013569
Automatic identification of landmarks in cephalometry is very important and useful for orthognathic surgery. A computerised automatic cephalometric analysis system (CACAS), based on image processing, is presented. For an original X-ray image, median filtering and histogram equalisation are used to improve image quality. The edge of an X-ray image is detected by a wavelet transform and Canny filter. Seventeen landmarks in cephalometry are successfully identified by knowledge-based edge tracing and changeable templates. Seventy-three measurements based on distances, angles and ratios between landmarks are computed automatically. The reliability of the landmarks and the validity of the measurements are compared for automatic and manual operation. The values of measurements obtained by CACAS are more precise and reliable: the mean error for linear measurements is less than 0.9 mm; the mean error for angular measurements is less than 1.2 °. The rate of validity is over 80%, even if the image quality is poor. For an image with a high signal-to-noise ratio, the rate of validity of landmarking and measurements using the CACAS system is over 90%.Kinematic study of a reconstructed hip in paediatric oncology
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053974
In 1997, a large portion of the femur of a four-year-old child affected by a Ewing's sarcoma was reconstructed with an innovative technique that used a massive bone allograft, in conjunction with a vascularised fibula autograft that was directly articulated within the acetabulum. The aim of the present study was to assess the kinematic behaviour of the reconstructed hip during flexion, once the acute remodelling process observed after the operation had ceased. A few additional CT slices of the hip joint region, in a flexed position, were taken at month 33 of the follow-up. The helical axes relative to the neutral-flexion motor action were estimated: their relative positions, with respect to the anatomical femoral heads, were compared, and the translation of the anatomical head centres was estimated. The angles spanned by the two femurs were almost equal, as were the translations along the respective helical axis. The main difference between the two femurs was the distance between the estimated femoral head centres and the relative helical axes. This resulted in a non-negligible translation of 2.9 mm of the fibula head inside the acetabulum during flexion, significantly higher than the 0.5 mm found for the intact contralateral femur. The results showed that, although the transplanted fibula grew and remodelled during the follow up, the action of the reconstructed hip joint still cannot be described as a ball-and-socket.Spatiotemporal Hopfield neural cube for diagnosing recurrent nasal papilloma
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053966
Gadolinium-enhanced magnetic resonance imaging (MRI) is widely used to detect recurrent nasal tumours. A specifically designed two-layer Hopfield neural network, called the spatiotemporal Hopfield neural cube (SHNC), is presented, to be used for detecting recurrent nasal papilloma. Differing from conventional, two-dimensional Hopfield neural networks, the SHNC extends the one-layer, two-dimensional Hopfield network in the original image plane into a two-layer, three-dimensional (3D) Hopfield network with pixel classification implemented in its third dimension. With extended 3D architecture, the network is able to use each pixel's spatial information in a pixel labelling procedure. Because the SHNC takes pixel spatial information into consideration, the effects of tiny detail or noise are removed. As a result, the drawback of disconnected fractions can be avoided. Furthermore, owing to the incorporation of competitive learning rules to update neuron states, to avoid the problem of having to satisfy strong constraints, the convergence of the network was improved. In addition, a more accurate signal–time curve, the relative intensity change (RIC), was adopted to represent the gadolinium-enhanced MRI temporal information, and the RIC curves of recurrent nasal papilloma were incorporated into the SHNC. The experimental results showed that the SHNC could obtain a more appropriate, precise position of recurrent nasal papilloma than the k-means, principal components analysis (PCA) or Eigenimage-filtering methods. The average sensitivity and specificity of the 26 cases were 0.9998 and 0.9961, respectively. These values demonstrate the effectiveness of the proposed technique.Sixty-four channel wearable acquisition system for long-term surface electromyogram recording with electrode arrays
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043894
The use of mono- and bi-dimensional electromyogram (EMG) electrode arrays for the assessment of the neuromuscular system can provide an insight into muscle physiology not achieved with classical bipolar surface EMG. Among the advantages of multichannel EMG detection, there is a) the possibility of estimating muscle fibre conduction velocity, even during motor tasks, and b) the possibility to increase the number of detection points on a muscle, improving the performance of pattern-based EMG decomposition methods. For these reasons, the development and use of multichannel surface EMG devices and techniques were chosen as the primary goals within the European RTD Project ‘Neuromuscular assessment in the elderly worker’ (NEW). The specific requirements of Project NEW called for the availability of a user-friendly, small-sized EMG acquisition system for field use, suitable for multichannel EMG recording using electrode arrays from one or more muscles. A market survey established that none of the commercially available EMG acquisition systems featured all the desired specifications, nor could they be easily adapted for specific use. The paper describes the design of an innovative acquisition system for long-term multichannel EMG recording fulfilling these requirements and comprising adhesive electrode arrays for artifact-free EMG acquisition during work activity and a portable, user-friendly, battery-powered acquisition system for multichannel EMG recording and storage on a removable PCMCIA card. The system has been used extensively within Project NEW for laboratory and field tests and can find applications in other fields of basic and applied research, including ergonomics, occupational and sports medicine.Feasibility study of the use of similarity maps in the evaluation of oncological dynamic positron emission tomography images
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053968
A preliminary study is presented on the potential role of similarity mapping (SM) in the evaluation of oncological dynamic <sup xmlns="http://pub2web.metastore.ingenta.com/ns/">18</sup>F-fluorodeoxyglucose positron emission tomography studies, mainly in lesion localisation and detectability. Similarity maps were calculated using previously described (correlation coefficient (COR) and normalised correlation coefficient (NCOR)) and newly introduced similarity measures (sum of squares coefficient (SSQ), squared sum coefficient (SQS), sum of cubes coefficient (SC) and cubed sum coefficient (CS)). The results were evaluated using simulated and clinical data. The study revealed that the best-suited similarity measure for such applications was the CS similarity coefficient, which provided the best parametric images, delineating structures of interest and supporting the visual interpretation of data sets. It was shown that SM and standardised uptake value (SUV) images had comparable diagnostic performance, although SM was able to offer additional time-related information in a single image. For the case of colorectal recurrences (17 cases), the measured contrast values for the CS and SUV images were 2.36±0.47 and 4.12±0.42, respectively, whereas, for three cases of giant cell tumours, these values were 11.6±2.1 and 11.9±1.8, respectively.Automatic estimation of endothelium cell density in donor corneas by means of Fourier analysis
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043932
One of the main clinical parameters expressing the health of a cornea is the cell density of its endothelium. This information is particularly important in an eye bank environment, where donor corneas are screened to assess their suitability as a human graft. Endothelium cell density is conventionally estimated by a long, tedious and error-prone manual counting procedure, performed by cornea experts on specimen images observed through an optical microscope. An alternative solution is proposed: a computer program that provides automatic estimation of cell density in donor corneas by analysing the spatial frequencies contained in the image. A circular band in the 2D discrete Fourier transform of the image is shown to contain the relevant information about the cell density. A system for extracting from this spatial frequency information an estimate of the cell density has been developed. A clinical evaluation of the proposed technique was performed on 18 corneas, where the densities provided by the proposed technique were compared with those manually obtained by two experts. The results showed an average percentage difference of 3% (maximum 19%), a value well within the measured inter-expert range of variability. The proposed automatic procedure confirmed its ability to estimate correctly corneal endothelium cell density.Three-dimensional point localisation in low-dose X-ray images using stereo-photogrammetry
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043852
A stereo-photogrammetric method for three-dimensional reconstruction of points in low-dose digital X-ray images obtained using a scanner with similar imaging geometry to that of computed tomography scan projection radiography, was analysed. A calibration frame containing 25 radio-opaque markers with known three-dimensional locations was scanned, and the accuracy of reconstruction of the marker positions under varying control point configurations and separation angles was assessed. Errors of less than 1 mm were obtained when nine test points were reconstructed, with 16, 11 and 7 control points at a 90° separation angle, and with 16 and 11 control points at 75° and 60° separation angles. The optimum reconstruction, with a resultant error of 0.68 mm, was found to occur at a separation angle of 90°, with the largest number of control points (16) used to calculate the parameters of the transformation. Extrapolation in the scanning direction beyond the space defined by the control points gave errors of less than 2 mm. This method should be suitable for three-dimensional point reconstruction in applications such as cephalometry, brachytherapy planning and assessment of spinal shape.Influence of measurement noise and electrode mislocalisation on EEG dipole-source localisation
http://dl-live.theiet.org/content/journals/10.1049/mbec_20003461
Measurement noise in the electro-encephalogram (EEG) and inaccurate information about the locations of the EEG electrodes on the head induce localisation errors in the results of EEG dipole source analysis. These errors are studied by performing dipole source localisation for simulated electrode potentials in a spherical head model, for a range of different dipole locations and for two different numbers 27 and 148) of electrodes. Dipole source localisation is performed by iteratively minimising the residual energy (RE), using the simplex algorithm. The ratio of the dipole localisation error (cm) to the noise level (%) of Gaussian measurement noise amounts to 0.15 cm/% and 0.047 cm/% for the 27 and 148 electrode configurations, respectively, for a radial dipole with 40% eccentricity. The localisation error due to noise can be reduced by taking into account multiple time instants of the measured potentials. In the case of random displacements of the EEG electrodes, the ratio of dipole localisation errors to electrode location errors amounts to 0.78 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> cm and 0.27 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> cm for the 27 and 148 electrode configurations, respectively. It is concluded that it is important to reduce the measurement noise, and particularly the electrode mislocalisation, as the influence of the latter is not reduced by taking into account multiple time instants.Estimation of the tissue composition of the tumour mass in neuroblastoma using segmented CT images
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043878
Neuroblastoma is the most common extra-cranial, solid, malignant tumour in children. Advances in radiology have made possible the detection and staging of the disease. Nevertheless, there is no method available at present that can go beyond detection and qualitative analysis, towards quantitative assessment of the tissue composition of the primary tumour mass in neuroblastoma. Such quantitative analysis could provide important information and serve as a decision-support tool to the radiologist and the oncologist, result in better treatment and follow-up and even lead to the avoidance of delayed surgery. The problem investigated was the improvement of the analysis of the primary tumour mass, in patients with neuroblastoma, using X-ray computed tomography (CT) images. A methodology was proposed for the estimation of the tissue content of the mass: it comprised a Gaussian mixture model for estimation, from segmented CT images, of the tissue composition of the primary tumour. To demonstrate the potential of the method, the results are presented of its application to ten CT examinations of four patients. The method provides quantitative information, and it was observed that the tumour in one of the patients reduced from 523 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sup> to 81 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sup> in volume, with an increase in calcification from about 20% to about 88% of the tumour volume, in response to chemotherapy over a period of five months. Results indicate that the proposed technique may be of considerable value in assessing the response to therapy of patients with neuroblastoma.Experimental evaluation of computerised tomography point spread function variability within the field of view: parametric models
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043919
The objective of the paper was to validate non-linear parametric models of computerised tomography point spread function (PSF), to investigate the role of model parameters and to verify the effect of different imaging conditions on estimated parameters. These models were then to be used experimentally to estimate the variation of PSF shape within the field of view of a scanner. Two parametric models of the PSF are presented. The Gaussian model is appropriate when PSF values are positive, and the damped cosine model can account for negative values. These models are non-linear and fully two-dimensional and do not assume radial symmetry. The models were fitted to images of a point source. The models accounted for over 99% of the variance in the PSF signal. Errors in modulation transfer function were limited to 5% when the appropriate model was selected. The difference in the blurring characteristics of three image reconstruction filters was well quantified by shape parameters, and position parameters located the PSF with subpixel accuracy. With a point source located 50 mm directly above the centre of the field of view, the PSF was found to be anisotropic.Computerised analysis of auscultatory sounds associated with vascular patency of haemodialysis access
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053962
Vascular access for renal dialysis is a lifeline for about 120 000 individuals in the United States. Stethoscope auscultation of vascular sounds has some utility in the assessment of access patency, yet can be highly skill-dependent. The objective of the study was to identify acoustic parameters that are related to changes in vascular access patency. The underlying hypothesis is that stenoses of haemodialysis access vessels or grafts cause vascular sound changes that are detectable using computerised data acquisition and analysis. Eleven patients participated in the study. Their vascular sounds were recorded before and after angiography, which was accompanied by angioplasty in most patients. The sounds were acquired using two electronic stethoscopes and then digitised and analysed on a personal computer. Vessel stenosis changes were found to be associated with changes in acoustic amplitude and/or spectral energy distribution. Certain acoustic parameters correlated well (correlation coefficient=0.98, p<0.0001) with the change in the degree of stenosis, suggesting that stenosis severity may be predictable from these parameters. Parameters also appeared to be sensitive to modest diameter changes (>20%), (p<0.005, Wilcoxon rank sum test). These results suggest that computerised analysis of vascular sounds may be useful in vessel patency surveillance. Further testing using longitudinal studies may be warranted.Truncated-Newton algorithm for three-dimensional electrical impedance tomography
http://dl-live.theiet.org/content/journals/10.1049/el_19991466
A truncated-Newton algorithm for three-dimensional electrical impedance tomography is presented. Explicit formation of the Hessian, normally a computational bottleneck, is avoided through use of a preconditioned conjugate gradient (PCG) solution of the Levenberg-Marquardt update. The PCG preconditioner is formed as a product of a sparse approximation of the Jacobian by its transpose.Electro-encephalogram disturbances in different sleep–wake states following exposure to high environmental heat
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043875
In this study, cerebral electrical activity or electro-encephalogram (EEG) was studied following exposure to high environmental heat, in three different age groups of freely moving rats. Each age group was subdivided into three groups: the acute heat stress group, subjected to a single exposure of 4 h at 38 °C in the biological oxygen demand incubator; the chronic heat stress group, exposed for 21 days, for 1 h each day, at 38 °C in the incubator; and the handling control group. The polygraphic sleep–wake recordings involved simultaneous recordings of cortical EEG, electro-oculogram (EOG), and electromyogram (EMG), on paper and in digital form on computer hard disk, just after the heat exposure for the acute stressed rats and on the 22nd day for the chronic stressed rats. The power spectrum was calculated for 2 s epochs of the EEG signals. Quantitative analyses of EEG (qEEG) showed that, in all three age groups, changes in higher-frequency components (β<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>) were significant in all sleep–wake states following both acute and chronic heat stress conditions. The power of β<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> activity in all three age groups after acute heat exposure was significantly decreased during slow wave sleep (SWS) (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><0.05) and rapid eye movement sleep (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><0.05), whereas the reverse was observed in the awake state (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><0.05). Following chronic heat exposure, β<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> activity was found to increase in all three sleep–wake stages in all groups of rats (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><0.01 for SWS in the weaning group and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><0.05 for other data). Thus the study demonstrated that the cortical EEG is sensitive to environmental heat, and alterations in EEG frequencies in different states of mental consciousness due to high heat can be differentiated efficiently by EEG power spectrum analysis.Pattern recognition approach to the detection of single-trial event-related functional magnetic resonance images
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043930
Functional magnetic resonance imaging (FMRI) is an imaging technique for determining which regions of the brain are activated in response to a stimulus or event. Early FMRI experiment paradigms were based upon those used in positron emission tomography (PET), i.e. employing a block design consisting of extended periods of ‘on’ against ‘off’ activations. More recent experiments were based on event-related FMRI, harnessing the fact that very short stimuli trains or single events can generate robust responses. FMRI data suffer from low signal-to-noise ratios, and typical event-related experiment paradigms employ selective averaging over many trials before using statistical methods for determining active brain regions. The paper reports a pattern recognition approach to the detection of single-trial FMRI responses without recourse to averaging and at modest field strengths (1.5 T). Linear discriminant analysis (LDA) was applied in conjunction with different feature extraction techniques. Use of the unprocessed data samples as features resulted in single-trial events being classified with an accuracy of 61.0±9.5% over five subjects. To improve classification accuracy, knowledge of the ideal template haemodynamic response was used in the feature extraction stage. A novel application of parametric modelling yielded an accuracy of 69.8±6.3%, and a matched filtering approach yielded an accuracy of 71.9±5.4%. Single-trial detection of event-related FMRI may yield new ways of examining the brain by facilitating new adaptive experiment designs and enabling tight integration with other single-trial electrophysiological methods.All-optical scanning acoustic microscope: rapid phase imaging
http://dl-live.theiet.org/content/journals/10.1049/el_20001451
An all-optical version of a scanning acoustic microscope is described. The electronic data acquisition system is a major advance on that previously reported, in that it is now capable of high speed acquisition of phase as well as amplitude images at 82 and 164 MHz.Space–frequency quantiser design for ultrasound image compression based on minimum description length criterion
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053970
The paper addresses the problem of how the spatial quantisation mode and subband adaptive uniform scalar quantiser can be jointly optimised in the minimum description length (MDL) framework for compression of ultrasound images. It has been shown that the statistics of wavelet coefficients in the medical ultrasound (US) image can be better approximated by the generalised Student t-distribution. By combining these statistics with the operational rate-distortion (RD) criterion, a space–frequency quantiser (SFQ) called the MDL-SFQ was designed, which used an efficient zero-tree quantisation technique for zeroing out the tree-structured sets of wavelet coefficients and an adaptive scalar quantiser to quantise the non-zero coefficients. The algorithm used the statistical ‘variance of quantisation error’ to achieve the different bit-rates ranging from near-lossless to lossy compression. Experimental results showed that the proposed coder outperformed the set partitioning in hierarchical trees (SPIHT) image coder both quantitatively and qualitatively. It yielded an improved compression performance of 1.01 dB over the best zero-tree based coder SPIHIT at 0.25 bits per pixel when averaged over five ultrasound images.Adaptive processing bandwidth adjustment for laser Doppler flowmetry
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043874
A novel laser Doppler flowmetry scheme is reported that adjusts the processing bandwidth adaptively to optimise the estimation of flow. To obtain an adequate processing bandwidth, the Doppler spectra is first fitted to the Lorentzian function, and the bandwidth at half the maximum of the Lorentzian function is used as an indicator of the major frequency range of the signal. The processing bandwidth is then tuned accordingly, and a frequency-weighted algorithm is applied to compute the fluid velocity. To investigate the influence of the processing bandwidth, an <i xmlns="http://pub2web.metastore.ingenta.com/ns/">in vitro</i> experiment was performed. In the experiment, the flow rate was controlled at constant velocity in the range from 0 to 18.52 mm s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, and the fluid velocity indices were calculated using adaptive and fixed processing bandwidths, respectively. The results showed that the adaptive processing bandwidth adjustment, not only significantly reduced the biological zero (9.6% of the case using 100 kHz bandwidth), but also enhanced the sensitivity of the laser Doppler measurement (over 20%) and linearly responded to a wider velocity range (R<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>=0.979 for velocity from 0 to 18.52 mm s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>).Alternative inter-plane data collection protocol for electrical resistance tomography in flow monitoring applications
http://dl-live.theiet.org/content/journals/10.1049/el_19981013
Cross-plane interference is a potential problem when acquiring the data from two planes of electrodes necessary for flow measurement using electrical resistance tomography. Two techniques are proposed to eliminate this problem.Preprocessing of data from spreading-resistance measurements
http://dl-live.theiet.org/content/journals/10.1049/ip-i-1.1980.0019
Spreading-resistance measurements often exhibit a lot of noise which can hinder their analysis. A method is presented for automated elimination of strongly deviating values, and smoothing of the resistance curve, leading in a few filter steps to a more accurate determination of the concentration profile. It is shown that the accuracy of the spreading-resistance technique can be increased by combining several profiles of a sample.microprocessor-based mossbauer fitting program
http://dl-live.theiet.org/content/journals/10.1049/sm.1982.0030
The feasibility is investigated of performing nonlinear least-squares fits of Mossbauer spectra within a microprocessor-based Mossbauer spectrometer. The development of a ROM-based Pascal program for a spectrometer using a Motorola 6800 microprocessor is described. The time taken to fit a 256-channel spectrum to one Lorentzianshaped line is about 100s per iteration. The fitting program is most useful in fitting relatively simple Mossbauer spectra, such as those obtained in most analytical applications, in teaching applications, or where the user does not have easy access to a mainframe computerAutomated measurement of noisy voltages with a preset confidence level
http://dl-live.theiet.org/content/journals/10.1049/el_19770170
A logical way of measuring voltages having varying amounts of noise present, under computer control, has been achieved by evaluating the running standard deviation of the mean in real time and stopping the measurements when a preset threshold has been reached.Direct rotation-rate detection with a fibre-optic gyro by using digital data processing
http://dl-live.theiet.org/content/journals/10.1049/el_19830677
By using digital processing, the dynamic range of gyros with direct rotation-rate detection is no longer restricted. The linearity error is less than ±1% within a rotation range of 300 to 200000/h.High-performance detector read-out at very low temperatures
http://dl-live.theiet.org/content/journals/10.1049/ecej_19920019
An infra-red detection system must be physically colder than the objects it needs to observe. As some of the objects to be observed by the European Space Agency's Infra-red Space Observatory (ISO) might be as cold as a few tens of degrees Kelvin, it is essential that the ISO's detectors should themselves operate at temperatures close to absolute zero. To avoid problems with electromagnetic interference, it is also necessary that detector read-out (i.e. first-stage signal amplification) be located as close as possible to the detectors. As conventional amplifiers cannot work at temperatures close to absolute zero, special techniques had to be used for the ISO's detectors8-electrode capacitance system for two-component flow identification. Part 1: Tomographic flow imaging
http://dl-live.theiet.org/content/journals/10.1049/ip-a-2.1989.0031
An 8-electrode capacitance system for tomographic imaging of two-component flows has been designed based upon a 2-dimensional finite element model. Emphasis is made on the development of a linear back-projection image reconstruction algorithm. Some reconstructed images obtained using this algorithm are given. Limitations and possible future improvements of the system are discussed.Criterion for the performance analysis of synchronous and asynchronous sampling instruments based on nonlinear processing
http://dl-live.theiet.org/content/journals/10.1049/ip-a-3.1992.0025
We propose a criterion for the comparison of different sampling strategies (synchronous, asynchronous and random) and filtering algorithms used in digital instruments which provide the estimate of the time average of a signal processed with a nonlinear conversion of multiple inputs (e.g. wattmeters, RMS voltmeters,…). This criterion uses the Bayesian approach to incorporate, for every sampling strategy, any prior information on the influences of each incidental quantity which can vary the output of the instrument, transforming this output into a statistic. The asymptotic mean-squared error of the measurements has been assumed as an estimator of the error and its general expression, valid for the most common sampling strategies used in practice, has been deduced. This asymptotic error is a function of the frequency response of the digital filter used and, eventually, of the characteristic function of the probability distribution selected for the random variables generating the sampling instants. Finally, the particular formulae for different sampling strategies and filtering algorithms are discussed and compared.Classification techniques for the extraction of nonperiodic transients from noise: an application in electromyography
http://dl-live.theiet.org/content/journals/10.1049/ip-a-3.1992.0014
A new set of techniques for the extraction and classification of transients in a general background of other signals and noise is described. An example of its use in electromyography is described. The automatic signal-processing method classifies nonoverlapping transients from different sources into groups of closely similar shapes using a pattern recognition method. Each transient is described by a set of features to form uncorrelated factors which are then used in an adaptive clustering technique to group together transients from the same source. In particular, motor unit action potentials in a myoelectric signal can be classified into their motor unit groups using this method.On the PSF of a forward-scattering coherent tomographic technique
http://dl-live.theiet.org/content/journals/10.1049/ip-h-2.1988.0074
The resolution and dynamic range performances of a forward-scattering tomographic imaging technique are evaluated by a computeraided reconstruction of the point spread function (PSF), first for a strictly theoretical case and then, taking into account the effect of certain parameters, for real experimental conditions. The width of the main lobe of the PSF is considered as an index of the resolution power of the technique; the ratio between the peak value of the PSF and the maximum value of the ambiguity artifacts is considered as an index of the dynamic range of the technique. The results obtained are summarised in order to be able to appreciate the changes in the features of the PSF as functions of the number of different views, the distance of the scanning area from the rotation axis of the object to be imaged, and the size of the scanning area.Spectral analysis of short-time biomedical data using adaptive filters
http://dl-live.theiet.org/content/journals/10.1049/ip-a-1.1984.0028
Conventional methods of spectral analysis are unable to track small but rapid variations in frequency. The LMS algorithm used as an adaptive line enhancer is found to track these signals, and provides insight into mechanical and physiological effects of the human body, when analysing electrical signals obtained from internally and externally placed electrodes.Aid to diagnosis of foetal bradicardias using the autocorrelation function
http://dl-live.theiet.org/content/journals/10.1049/ip-a-1.1981.0085
Early diagnosis of intense foetal hypoxia, symtoms of which include changes in the foetal heart rate, may constitute a useful tool for the prevention of irreversible damage to the foetus. In the paper three automatic diagnostic methods are described, all based on analysis of the waveform of the autocorrelation function of the sum of signals representing the foetal heart rate and the uterine pressure. The three methods are compared and tested using records taken from a number of patients.Automatic determination of tone period and evaluation of dysphony in pathological voices
http://dl-live.theiet.org/content/journals/10.1049/ip-a-1.1986.0016
The hoarseness of 28 subjects with laryngeal complaints of widely differing severity has been automatically evaluated by using the simple Chebychev norm to compare a 3-component vector representing the subject's voice with a normal template. A second procedure used the absolute values of the parameters without comparison with a standard. The three components of the characteristic vectors were extracted from recorded utterances of the Spanish vowel ‘a’, for which it was necessary to determine the approximate tone period of the signals. Two methods of pitch extraction were used, one based on the autocorrelation function and the other on a SIFT algorithm.Full-wave computed tomography. Part 3: Coherent shift-and-add imaging
http://dl-live.theiet.org/content/journals/10.1049/ip-a-1.1985.0009
The theory of coherent shift-and-add imaging is summarised, is extended to be more generally applicable than in Parts 1 and 2, and is illustrated with the results of computer simulations and laboratory experiments. 2-dimensional images of collections of cylindrical objects (immersed in a water tank into which plastic containers filled with animal offal can be introduced) are reconstructed by shift-and-add (in both its elementary and extended forms) from wideband ultrasonic signals scattered over a wide angle.Random asynchronous sampling strategy for measurement instruments based on nonlinear signal conversion
http://dl-live.theiet.org/content/journals/10.1049/ip-a-2.1989.0025
A random asynchronous sampling strategy is proposed for the digital implementation of broadband measurement instruments which are based on nonlinear signal conversion. A theoretical analysis of the basic features of this method is given by considering discrete-spectrum almost periodic signals. It is shown that, even when the band of the signals extends beyond the average sampling frequency, this sampling strategy does not introduce systematic errors in the measure, but only random noise which can be adequately filtered when the time available for the measurement is long enough. A formula for the evaluation of the standard deviation of the measure in terms of the spectral characteristics of the signals is given. Some of the specific problems related to the practical implementation of the sampling strategy are also discussed. Finally, as a preliminary validation of the technique, the results obtained by simulating the proposed instrument are compared with the theoretical error analysis.8-electrode capacitance system for two-component flow identification. Part 2: Flow regime identification
http://dl-live.theiet.org/content/journals/10.1049/ip-a-2.1989.0032
Following the first paper on tomographic flow imaging, the authors describe a method for identifying the patterns of two-component flows using the same 8-electrode capacitance system, but using a simpler signal-processing system than that for tomographic reconstruction. The measured capacitance vector of an unknown flow is compared with the stored ‘fingerprint’ vectors of various known flow patterns, and, hence, the actual flow regime can be identified.Approximate Fourier transform using square waves
http://dl-live.theiet.org/content/journals/10.1049/ip-a-2.1989.0038
The technique of spectral analysis, by truncated approximations to the sine and cosine functions, is evaluated using a three-level approximation (−1, 0, +1), where the −1 and +1 sections are of equal length, and the length of the zero level is variable. An optimum ratio is found where the zero levels together cover 120° of the cycle length, to give the least amount of ringing, or leakage. The transform that converts the square-wave spectral estimates to the Fourier coefficients is evaluated. In applications where spectral estimates are required only for limited frequency bands, the technique is flexible and efficient. This analysis is also well suited to irregularly spaced samples, and for direct application to analogue signals.Image-processing technique for investigating dielectric breakdown trees
http://dl-live.theiet.org/content/journals/10.1049/ip-a-3.1992.0015
An image-processing system has been used to measure tree branch lengths and fork angles in PMMA. A logarithmic distribution of branch lengths has been found, while the mean value of the forking angle is 65.7°. Treeing is discussed in terms of mechanical and electronic breakdown mechanisms.Directivity of acoustic signals from partial discharges in oil
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_19951356
For partial discharges in oil, the relationship between the apparent discharge magnitude, electrically measured in picocoulombs, and the acoustic signal amplitude from the same discharge, shows large variations. If the acoustic signal is detected with several detectors simultaneously, it is found that the acoustic amplitudes are correlated in a relatively narrow angular range. For larger angular separation, the acoustic amplitudes are uncorrelated and not anticorrelated. Some physical aspects of streamers in oil are illuminated by this observation and some theoretical considerations. The streamer velocity may, for example, be estimated.Analysis of the second heart sound for diagnosis of paediatric heart disease
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_19982326
The second heart sound (S2) consists of two major components, one due to the closure of the aortic valve (A2) and the other due to the closure of the pulmonary valve (P2). The aortic valve normally closes before the pulmonary valve and leads to a time delay between the two sounds. This delay is known as the ‘split’ in the medical community and is of significant diagnostic importance. The authors aim to develop an automatic technique to measure the split and to compare two common splitting patterns (i.e. variable splitting and fixed splitting), in a quantitative manner. A signal model for S2 is proposed. Accordingly, S2 is decomposed into a number of components with an algorithm based on the time–frequency distribution of the signal. A2 and P2 are selected from the model components and from these the split can be estimated. Groups of patients with the two splitting patterns have been investigated. For each patient, the splits of 20 successive cardiac cycles are measured, their mean and standard deviation are then calculated and used to characterise the two splitting patterns. It is found that the two simple statistical quantities can be used to identify the splitting patterns and hence offer important diagnostic information.