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Task-oriented repetitive movements can improve muscle strength and movement co-ordination in patients with impairments due to neurological lesions. The application of robotics and automation technology can serve to assist, enhance, evaluate and document the rehabilitation of movements. The paper provides an overview of existing devices that can support movement therapy of the upper extremities in subjects with neurological pathologies. The devices are critically compared with respect to technical function, clinical applicability, and, if they exist, clinical outcomes. [ABSTRACT FROM AUTHOR]

The paper describes a spherical harmonic-based finite element scheme for solving Poisson-type equations throughout volumes characterised by irregularly shaped inner and outer surfaces. The inner and outer surfaces are defined by spherical harmonics, and the volume in between these surfaces is divided into nested shells that are weighted averages of the inner and outer surfaces. The resulting mesh comprises hexahedral elements, wherein each hexahedral element is defined by inner and outer shells in the radial direction and divisions in the polar and azimuthal directions. The spacing between shells can be set to any desired value. Similarly, the size of the polar and azimuthal divisions can be specified. A test of the scheme on an anisotropic sphere, meshed with 720 nodes, yielded a relative error of 0.78% on the sphere's surface. As a comparison, a previously published combined finite element/boundary element scheme with a 946-node mesh produced a corresponding error of 3.57%. [ABSTRACT FROM AUTHOR]

The cardio-circulatory system of chronotropic incompetent patients is unable to adapt heart rate adequately to the level of strain. A common therapy is the implantation of a pacemaker that stimulates the heart at a rate derived from a strain related sensor signal. The paper describes a new pacemaker concept that uses a well-defined time interval in the electrogram as a sensor parameter, the atrioventricular conduction time (AVCT). Identification experiments with patients delivered the stationary and dynamic behaviour of AVCT subject to variations in the exercise rate and the pacing frequency. Furthermore, it was demonstrated that AVCT is perturbed by respiratory activity. The new rate-responsive algorithm, which uses the internal model control principle, explicitly takes into account the closed-loop nature of the underlying system. The major design objectives were: extended range of the individual heart rate; effective attenuation of the respiratory-related disturbance; and stability. Seven patients undergoing incremental exercise were paced with this AVCT-based algorithm. The experiments confirmed the suitability of this concept with respect to the design goals. The patients' peak intrinsic heart rate at exercise was 100 +/- 20min(-1). When paced with the AVCT algorithm, the paced heart rate was 126 +/- 12min(-1). The increase was significant (26 +/- 13min(-1); 15 to 53 min(-1)), which clearly demonstrated the potential of this concept to restore chronotropic competence. [ABSTRACT FROM AUTHOR]

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 50mm directly above the centre of the field of view, the PSF was found to be anisotropic. [ABSTRACT FROM AUTHOR]

The paper presents an algorithm for reducing false alarms related to changes in arterial blood pressure (ABP) in intensive care unit (ICU) monitoring. The algorithm assesses the ABP signal quality, analyses the relationship between the electrocardiogram and ABP using a fuzzy logic approach and post-processes (accepts or rejects) ABP alarms produced by a commercial monitor. The algorithm was developed and evaluated using unrelated sets of data from the MIMIC database. By rejecting 98.2% (159 of 162) of the false ABP alarms produced by the monitor using the test set of data, the algorithm was able to reduce the false ABP alarm rate from 26.8% to 0.5% of ABP alarms, while accepting 99.8% (441 of 442) of true ABP alarms. The results show that the algorithm is effective and practical, and its use in future patient monitoring systems is feasible. [ABSTRACT FROM AUTHOR]

The electro-encephalographic (EEG) activity of people who stutter could provide invaluable information about the association of neural processing and stuttering. However, the EEG has never been adequately studied during speech in which stuttering naturally occurs. This is owing, in part, to the masking of the EEG signal by artifact from sources such as the speech musculature and from ocular activity. The aim of this paper was to demonstrate the ability of independent component analysis (ICA) to remove artifact from the EEG of stuttering children recorded while they are speaking and stuttering. The EEG of 16 male children who stuttered and 16 who did not stutter was recorded during a reading task. The recorded EEG that contained artifact was then subjected to ICA. The results demonstrated that the EEG assessed during stuttered speech had substantially more noise than the EEG of speech that did not contain stuttering (p < 0.01). Furthermore, it was shown that ICA could effectively remove this artifact in all 16 children (p < 0.01). The results from one child highlight the findings that ICA can be used to remove dominant artifact that has prevented the study of EEG activity during stuttered speech in children. [ABSTRACT FROM AUTHOR]

The paper presents a study of global system for mobile (GSM) phone radiofrequency effects on human cerebral activity. The work was based on the study of auditory evoked potentials (AEPs) recorded from healthy humans and epileptic patients. The protocol allowed the comparison of AEPs recorded with or without exposure to electrical fields. Ten variables measured from AEPs were employed in the design of a supervised support vector machines classifier. The classification performance measured the classifier's ability to discriminate features performed with or without radiofrequency exposure. Most significant features were chosen by a backward sequential selection that ranked the variables according to their pertinence for the discrimination. Finally, the most discriminating features were analysed statistically by a Wilcoxon signed rank test. For both populations, the N100 amplitudes were reduced under the influence of GSM radiofrequency (mean attenuation of -0.36 microV for healthy subjects and -0.60 microV for epileptic patients). Healthy subjects showed a N100 latency decrease (-5.23 ms in mean), which could be consistent with mild, localised heating. The auditory cortical activity in humans was modified by GSM phone radiofrequencies, but an effect on brain functionality has not been proven. [ABSTRACT FROM AUTHOR]

The paper studies a surface electromyogram (SEMG) decomposition technique suitable for identification of complete motor unit (MU) firing patterns and their motor unit action potentials (MUAPs) during low-level isometric voluntary muscle contractions. The algorithm was based on a correlation matrix of measurements, assumed unsynchronised (uncorrelated) MU firings, exhibited a very low computational complexity and resolved the superimposition of MUAPs. A separation index was defined that identified the time instants of an MU's activation and was eventually used for reconstruction of a complete MU innervation pulse train. In contrast with other decomposition techniques, the proposed approach worked well also when the number of active MUs was slightly underestimated, if the MU firing patterns partly overlapped and if the measurements were noisy. The results on synthetic SEMG show 100% accuracy in the detection of innervation pulses down to a signal-to-noise ratio (SNR) of 10 dB, and 93+/-4.6% (mean+/-standard deviation) accuracy with 0 dB additive noise. In the case of real SEMG, recorded with an array of 61 electrodes from biceps brachii of five subjects at 10% maximum voluntary contraction, seven active MUs with a mean firing rate of 14.1 Hz were identified on average. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper presents a technique for the segmentation of the fibro-glandular disc in mammograms based upon a statistical model of breast density. The density function of the model was represented by a mixture of up to four weighted Gaussians, each one corresponding to a specific density class in the breast. The parameters of the model and the number of tissue classes in the breast were determined using the expectation-maximisation algorithm and the minimum description length method. Grey-level statistics of the pectoral muscle were used to determine the tissue categories that are likely to represent the fibro-glandular disc. The method was applied to 84 medio-lateral oblique mammograms from the Mini-MIAS database. The results of the segmented fibro-glandular disc were assessed by a radiologist using the original and the segmented images, with reference to a ranking table categorising the results of segmentation as: 1: excellent; 2: good; 3: average; 4: poor; and 5: complete failure. Of the 84 cases analysed, 64.3% were rated as excellent, 16.7% were rated as good, 10.7% were rated as average, and 4.7% were rated as poor; only 3.6% of the cases were rated as a complete failure with regard to segmentation of the fibro-glandular disc. [ABSTRACT FROM AUTHOR]

The paper provides a new technique based on a least-squares approach for the accurate estimation of a force platform calibration matrix using simple manual procedures, when the direction of the applied loads cannot be perfectly aligned with the axes of the platform. This new procedure can be applied to all force platforms and allows the combined application of vertical and horizontal forces, both static and time-varying. The robust calibration method includes the angular errors in the least-squares parameter vector, thus reducing the bias in the estimated calibration matrix parameters. The performance of the robust method was compared with the conventional one, using a numerical simulation approach starting from a known calibration matrix. With the conventional approach, in noiseless conditions, the maximum error due to load misalignment (SD = 3 degrees) was 6% for the direct terms and over 10% for the cross-talk terms. With the robust method, these errors reduced to zero and were always below 0.4%, even when realistic noise was superimposed on the measures. With perfectly aligned loads and realistic output noise, the confidence intervals of the calibration matrix parameters were very similar for the two methods, demonstrating that the increased number of parameters did not affect the reliability of the estimate. [ABSTRACT FROM AUTHOR]

The heart rate is a non-stationary signal, and its variation can contain indicators of current disease or warnings about impending cardiac diseases. The indicators can be present at all times or can occur at random, during certain intervals of the day. However, to study and pinpoint abnormalities in large quantities of data collected over several hours is strenuous and time consuming. Hence, heart rate variation measurement (instantaneous heart rate against time) has become a popular, non-invasive tool for assessing the autonomic nervous system. Computer-based analytical tools for the in-depth study and classification of data over day-long intervals can be very useful in diagnostics. The paper deals with the classification of cardiac rhythms using an artificial neural network and fuzzy relationships. The results indicate a high level of efficacy of the tools used, with an accuracy level of 80-85%. [ABSTRACT FROM AUTHOR]

A numerical model able to investigate the influence of biomechanical factors on the long-term secondary stability of implants would be extremely useful for the design of new cementless prosthetic devices. A purely biomechanical model of osseo-integration has been developed, formulated as a rule-based adaptation scheme. Due to its complexity, the problem was divided into three steps: preliminary implementation of the model (proof of concept); implementation of the complete model and investigation of the model solution; and model validation. The paper describes the first of these three steps. The model was implemented as a discrete-states machine, and the few parameters required were derived from the literature. It was then applied to a real clinical case. The study was conducted using the frictional contact finite element model of a human femur implanted with a cementless anatomical stem. A stable solution was achieved after between three and 15 iterations for all initial positions considered. Similar initial conditions yielded similar final configurations. The model predicted all initial configurations, with the exception of a partial osseo-integration, ranging between 62% (distal fit) and 78% (proximal fit) of the viable interface. This is in good agreement with the values reported in the literature that never exceed 75%, even in the best conditions, and report better clinical results for proximal fit. For the varus configuration, which lacks cortical support, the algorithm predicted a completed loosening. [ABSTRACT FROM AUTHOR]

The fundamental goal of ultrasound thermal therapy is to provide proper thermal lesion formations for effective tumour treatment. The quality of the therapy depends mostly on its positional precision. To date, most ultrasound thermal therapy treatments have focused on the formation of power or temperature patterns. The non-linear and time-delay effects of thermal dose formation prohibit direct control of the thermal dose distribution. In the paper, the control of thermal lesions by regulation of the temperature of a pilot point is proposed. This scheme utilises the high correlation between temperature elevation and thermal dose at the forward boundary of thermal lesions. To verify the feasibility, a 2D ultrasound phased array system was used to generate thermal lesions of various sizes, and the temperature elevation required to generate a thermal dose threshold was investigated. Results showed that the required temperature elevation was found to be a reasonably constant value of 52.5 degrees C under differing conditions when the focal area was small. When the focal area under consideration was large, the required temperature elevation became a monotonic function of blood perfusion rate, ranging from 49.2 to 52.5 degrees C. When the reference temperature of the pilot point was set at a conservative value (52.5 degrees C), the thermal lesions were controlled precisely under a wide range of blood perfusion and power pattern changes, tested by using a more realistic model that takes into account thermal-induced attenuation and blood perfusion changes. This changed the complex thermal dose control problem into a simple temperature regulation problem, which makes implementation of thermal lesion control easier, giving the scheme a high potential for application to current ultrasound thermal therapy systems. [ABSTRACT FROM AUTHOR]

The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterise in vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined from in vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (alpha). This approach was applied with ten scoliotic patients undergoing spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38 < or = alpha < or = 10.0) and four of the ten right thoracic segments (1.74 < or = alpha < or = 5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4 degrees +/- 3 degrees). The in vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres. [ABSTRACT FROM AUTHOR]

Several recent studies have quantified abnormalities in Parkinsonian gait. However, few studies have attempted to quantify the regularity of body motion during walking in patients with Parkinson's disease. The aim of the paper was to characterise body motion patterns in healthy, elderly subjects and patients with Parkinson's disease during walking. Body motion was recorded during walking for 16 patients with Parkinson's disease and ten healthy, elderly subjects using a tri-axial accelerometer device. To characterise the body motion patterns, time-frequency patterns of the body acceleration signal were estimated using a matching pursuit algorithm. Data from the study showed that the healthy, elderly subjects and patients with Parkinson's disease had different time-frequency patterns. The time-frequency patterns were classified into four distinct patterns based on their time durations: vertical (<0.15 s), circular (0.15-0.5 s), short horizontal (0.5-2.0 s) and long horizontal (>2.0 s). The data showed that the energy of the long horizontal patterns, representing long-term smooth and regular (rhythmic) activities, significantly decreased, but the energy of the circular patterns, representing irregular activities, increased in the patients with mild Parkinson's disease, compared with those of the healthy, elderly subjects (p< 0.01). Futhermore, these features were seen more clearly in the body motions of severe case patients than is that of mild case patients. It was concluded that these differences are probably due to a lack of ability to control normal and smooth movement is Parkinson's disease. [ABSTRACT FROM AUTHOR]

It is still unclear what fundamental criteria influence the ability of alternating current (AC) to induce ventricular fibrillation (VF) in vivo. As the VF threshold has a bowl-shaped relationship with frequency (showing a minimum threshold at some frequency), similar to the nervous system, one proposed model has assumed that the mechanisms underlying AC stimulation of nerves are at work for VF induction. More recent work has suggested a second approach, whereby a simple RC-like model is sufficient to understand the cardiac AC stimulation threshold's frequency dependence, suggesting that some unarticulated mechanism is at work for VF. The paper directly tests these two models. In 12 intact dogs and 20 intact guinea pigs, DC pulses were used to stimulate AC square and AC sine waves at 10, 20, 40, 80 and 160 Hz. All electrodes were endocardial, with the return electrode being on a paw or thorax. It was found that, for square and sine wave stimulation in both dogs and guinea pigs, the stimulation threshold increased monotonically with frequency from 10Hz up to 160Hz (p < 0.01 for dogs and guinea pigs). Between 80 and 160Hz, the AC stimulation threshold doubled, exactly as predicted by an RC model. It was concluded that the AC stimulation threshold is not bowl-shaped and is best understood with an RC model. As the VF threshold does exhibit a bowl-shape with frequency, as opposed to the stimulation threshold which does not, the VF induction frequency dependence must have different origins. [ABSTRACT FROM AUTHOR]

This paper describes a portable heart simulator for the study of electromagnetic interference with active implantable devices. The simulator consists of plexiglas box divided into three chambers simulating the left atrium and the ventricles, plus a lateral compartment for the implantable device. The box is linked to a laptop computer by an analogue-to-digital convertor board, and the three chambers are monitored and driven by dedicated hardware and software interfaces. Synthetic endocardial atrial and ventricle signals for 13 cardiac rhythms are stored in the computer. They are applied to the cardiac chambers by AgCl plates. Sensing electrodes are in the form of AgCl needles inserted in saline. The simulator was able to demonstrate the behaviour of three pacemakers tested in the absence and presence of electromagnetic interference, generated by mobile phones (European GSM 900 and 1800 MHz) that emitted up to 2W (1 W at 1800 MHz). Pacemakers can be programmed with sensitivity from 0.1 mV to 5 mV, pulse width from 0.1 ms to 1.5 ms and pulse amplitude from 0.5 V to 5 V. The structural separation in three cardiac chambers (plus the one for the device) allowed a fast analysis procedure for dual- and tri-chamber implantable devices. [ABSTRACT FROM AUTHOR]

Over a period of some years, the components of a system for discerning erosion on children's teeth have been progressively developed, for use in an extensive project seeking correlations between erosion and various perceived risk factors. The aim was the detection of minute levels of erosion, based on mappings of the palatal surfaces of the maxillary central incisors in children. Significant challenges were encountered, the primary problem being the impracticality of placing control marks that would aid the realignment of successive measurements. The paper describes the erosion detection system and initial experiences based on the results of the first 100 subjects measured after 9 months. The procedures detected the occurrence of erosion of 50 microm magnitude on about one-quarter of the teeth over the 9 month period, at a precision estimated to be +/- 15 microm. The occurrence of some anomalous incidents prevented the procedure from being fully automatic, and it necessitated human examination of a graphical diagram derived from the surface matching program, but it was nevertheless superior to current practices of examining impressions or replicas entirely by eye. [ABSTRACT FROM AUTHOR]

Surface auditory evoked potentials are generally recorded using a headset of 32, 64 or 128 electrodes, but the quality of the responses is quite heterogeneous on the scalp surface. In some contexts, such as the analysis of auditory evoked potentials recorded in radio-frequency fields, the signal quality is essential, and it appears pertinent to consider only a limited number of electrodes. Therefore, before analysing signals influenced by radio-frequency fields, it is necessary to consider the preliminary step of selecting the channels where auditory activity is strong. This step is often realised by human visual selection and can take a considerable time. In this paper, a simple k-means clustering method is proposed, to select automatically the important channels, and the results are compared with traditional methods of selection. The method detected channels that showed a concordance rate of 86.5% with the visual selection (performed by five individuals) and gave the same final selection (only two extra electrodes in the automatic case). Moreover, the time needed for this automatic selection was 100 times less than that for the visual selection, and also human variability was avoided. [ABSTRACT FROM AUTHOR]

Radiofrequency (RF) ablation has become an important means of treatment of non-resectable primary and metastatic liver tumours. Recurrence of treated tumours is associated with cancer cell survival next to blood vessels. The paper examines the performance of classical monopolar, and two configurations of bipolar, RF ablation using a LeVeen ten-prong catheter. Finite element method models of monopolar and bipolar configurations were created at 5 mm distance from a vessel of the size of a typical portal vein (10 mm diameter). In one bipolar configuration, the probes were oriented in the same axial direction (asymmetric configuration); in the second bipolar configuration, the two probes were facing each other (symmetric configuration). The distribution of temperature and current density was analysed for three different flow conditions: normal flow, reduced flow due to portal hypertension and high flow. For normal flow, the distance between the formed coagulation zone and the blood vessel was 1.8 mm for monopolar, 1 mm for asymmetric bipolar, and 0.2 mm for symmetric bipolar, configurations. Symmetric bipolar RF ablation creates coagulation zones significantly closer to blood vessels compared with monopolar RF ablation. This may reduce tumour cell survival next to blood vessels and reduce recurrence rates. [ABSTRACT FROM AUTHOR]

The paper presents an evaluation of the possibility of using fetal magnetocardiogram (FMCG) signals to estimate and classify the accessory pathway in fetal Wolff-Parkinson-White (WPW) syndrome. The FMCG signals of two fetuses with WPW syndrome (type A) were detected using a 64-channel superconducting quantum-interference device system. An average across the cycles of these signals was taken to obtain clear WPW signals. To determine the direction and position of the accessory pathway in a fetal heart accurately, the accessory pathway and activated pathway at the peak of the QRS complex thus obtained were estimated for each fetus, using a single-dipole model. The phase angle (about 90 degrees) between the equivalent current dipoles (ECDs) was the same for both fetuses. This angle suggested that the accessory pathway is in the left side of the heart, i.e. that the pathway exists in the left ventricle, which indicates type A WPW syndrome. Identification of the position of the accessory pathway in a fetus with WPW syndrome from the angle between the ECD of the accessory pathway and the ECD of the peak in the QRS complex was thus demonstrated. [ABSTRACT FROM AUTHOR]

This study focused on the application of real-time Kalman filters to biomechanical data and, in particular, the simulation environment used to compare the performance of modified and standard two-state Kalman filters when estimating displacement and velocity from noisy displacement data. The modification proposed in this paper was the numerical tachometer, augmented by a median smoother. The numerical tachometer integrated the derivative estimates from finite differences of noisy sampled data into the Kalman filter structure; the median smoother acted before differentiation, to protect from grossly erroneous measurements. The numerical tachometer allowed better fits to the simulated data than can be achieved without it: the root mean square errors decreased by 10% in the displacement domain and by 54% in the velocity domain, for sampling frequencies and signal contamination levels that were typical in human movement sciences. The sensitivity to errors in the modelling of the signal and noise characteristics was less than in the standard filter implementation. The use of the median smoother improved the robustness of the filtering algorithm against additive white Gaussian measurement noise and allowed the cancellation of isolated noise spikes. [ABSTRACT FROM AUTHOR]

The paper describes an application of a new, non-linear dimensionality reduction method, named Isomap, for mining the structural knowledge from high-dimensional medical data. The algorithm was evaluated on two publicly available medical datasets: the pathological dataset of breast cancer (241 malignant samples) and the gene expression dataset from the lung (186 tumours). It was found by Isomap that the approximate intrinsic dimensionalities of these two datasets were as low as three. The spatial structures of both datasets were presented in low-dimensional space. Isomap, as a general tool for dimensionality reduction analysis, is helpful in revealing the nonlinear structural knowledge of high-dimensional medical data. [ABSTRACT FROM AUTHOR]