Biomedical subjects

R Bayford

Publications and source records attributed to R Bayford.

6 recordsLinked to original sources

PubMed2006

Design and calibration of a compact multi-frequency EIT system for acute stroke imaging.

A new, compact UCLH Mk 2.5 EIT system has been developed and calibrated for EIT imaging of the head. Improvements include increased input and output impedances, increased bandwidth and improved CMRR (80 dB) and linearity over frequencies and load (0.2% on a single channel, +/-0.7% on a saline tank over 20 Hz-256 kHz and 10-65 Omega). The accuracy of the system is sufficient to image severe acute stroke according to the specification from recent detailed anatomical modelling (Horesh et al 2005 3rd European Medical and Biological Engineering Conference EMBEC'05). A preliminary human study has validated the main specifications of the modelling, the range of trans-impedance from the head (8-70 Omega) using a 32 electrode, 258 combination protocol and contact impedances of 300 Omega to 2.7 kOmega over 20 Hz to 256 kHz.

Acute Disease↗

PubMed2005

Applications of GRID in clinical neurophysiology and Electrical Impedance Tomography of brain function.

The computational requirements in Neurophysiology are increasing with the development of new analysis methods. The resources the GRID has to offer are ideally suited for this complex processing. A practical implementation of the GRID, Condor, has been assessed using a local cluster of 920 PCs. The reduction in processing time was assessed in spike recognition of the Electroencephalogram (EEG) in epilepsy using wavelets and the computationally demanding task of non-linear image reconstruction with Electrical Impedance Tomography (EIT). Processing times were decreased by 25 and 40 times respectively. This represents a substantial improvement in processing time, but is still sub optimal due to factors such as shared access to resources and lack of checkpoints so that interrupted jobs had to be restarted. Future work will be to use these methods in non-linear EIT image reconstruction of brain function and methods for automated EEG analysis, if possible with further optimized GRID middleware.

Computer Systems↗

PubMed2004

The use of a European telemedicine system to examine the effects of pollutants and allergens on asthmatic respiratory health.

The experience of using a telemedicine feasibility study to integrate respiratory health response and environmental stimuli information is presented. The effects of ambient air quality, pollen and local environment conditions on asthmatic patients' lung function were investigated through the use of a novel European health telematic system. The Medical Diagnosis, Communication and Analysis Throughout Europe (MEDICATE) project developed and tested the feasibility of using a telemedicine system for chronic asthmatics in London, UK, and Barcelona, Spain. The key to this was the determination of the real time health (lung function) response to the ambient environment and allergens. Air quality, pollen and environmental lifestyle information were related to respiratory measurements for recruited asthmatic patients in the study through the design of a dedicated environmental management system (EMS) database. In total, 28 patients completed the study trial, subject to ambulatory monitoring of spirometric lung function (PEF, FEV(1) and FVC) up to four times a day over a 2-week period recorded during the year 2000. Alongside this, ambient air quality and pollen counts were used to represent local exposure to potential environmental stimuli. Personal questionnaire interviewing collected additional data about patient lifestyles, social-economic conditions and quality of life perceptions. The methods and indicative results of integrating environmental and health data in this respect are examined. Assessment tools such as GIS and object-orientated databases were designed to locate and compile environmental information about the patients' locations and lifestyles in the study areas (London and Barcelona). Socioeconomic and lifestyle factors, such as exposure to smoking, pets, personal journey lengths and modes, income, household occupancy and domestic fuel use, were found to have limited detectable effects on the patients' basic lung function levels. Patients' gender, age and predicted PEFR were significantly associated with the 2-week mean and minimum respiratory measurements. Lung function data were compared with air quality and pollen indicators to examine relationships on a daily or lagged-day basis controlling for confounding factors. The paper discusses the new methodology and the practicalities of using the telemedical system as a tool for assessing the impacts of environmental stimuli on respiratory health.

Adolescent↗

PubMed2002

A feasibility study of remote monitoring of asthmatic patients.

We assessed the feasibility of a remote monitoring system for asthmatic patients to use in their own homes. Eighty-four patients were invited to participate following discharge from hospital after an acute exacerbation of their asthma. We remotely monitored 33 patients from two hospitals for two weeks. Their mean age was 34 years (range 17-50 years). Patient compliance with monitoring was 80% (range 45-231%) and compliance with transmitting the results using a modem was 52% (range 0-100%). The average time spent teaching patients how to perform measurements was 16 min (range 2-55 min) and time spent providing asthma education was 39 min (range 5-135 min). Ninety-six per cent of patients found the equipment easy or very easy to use and 92% said they would use the equipment again in the future. Medical intervention occurred in 48% of patients during the study period, which suggests that the use of remote monitoring could be important in reducing asthma morbidity and improving treatment outcomes.

Adolescent↗

PubMed1999

Measurement of electrical current density distribution in a simple head phantom with magnetic resonance imaging.

Knowledge of the influence of the human skull on the electrical current (d.c.) distribution within the brain tissue could prove useful in measuring impedance changes inside the human head. These changes can be related to physiological functions. The studies presented in this paper examine the current density distribution in a simple phantom consisting of a saline filled tank (to simulate scalp and brain) and a ring made of dental grade plaster of Paris (to simulate the human skull). Images of the distribution of the d.c. density of the phantom with and without the plaster of Paris ring were produced using a magnetic resonance imaging technique. These images indicate that the skull is likely to produce a more uniform d.c. density within the brain.

Brain↗

PubMed1995

Experimental validation of a novel reconstruction algorithm for electrical impedance tomography based on backprojection of Lagrange multipliers.

A novel approach to image reconstruction for electrical impedance tomography (EIT) has been developed. It is based on a constrained optimization technique for the reconstruction of difference resistivity images without finite-element modelling. It solves the inverse problem by optimizing a cost function under constraints, in the form of normalized boundary potentials. Its application to the neighboring data collection method is presented here. Mathematical models are developed according to specified criteria. These express the reconstructed image in terms of one-dimensional Lagrange multiplier functions. The reconstruction problem becomes one of estimating these functions from normalized boundary potentials. This model is based on a cost criterion of the minimization of the variance between the reconstructed and the true resistivity distributions. The algorithm was tested on data collected in a cylindrical saline-filled tank. A polyacrylamide rod was placed in various positions with or without a peripheral plaster of Paris ring in place. This was intended to resemble the conditions during EIT of epileptic seizures recorded with scalp or cortical electrodes in the human head. One advantage of this approach is that compensation for non-uniform initial conditions may be made, as this is a significant problem in imaging cerebral activity through the skull.

Algorithms↗