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Biomedical subjects

D V Land

Publications and source records attributed to D V Land.

8 recordsLinked to original sources
PubMed2001

An efficient, accurate and robust radiometer configuration for microwave temperature measurement for industrial and medical applications.

The theoretical and practical design of a type of microwave radiometer particularly suited to industrial and medical temperature measurement is described. The use of sequential switching of source and reference signals with synchronous demodulation of switched signal components gives an efficient and robust instrument configuration. The radiometer measures the true, matched-impedance effective temperature of the coupled source. Changes in noise-figure, gain or frequency response of the radiometer microwave amplification do not affect the temperature measurement. Practical microwave radiometers using this configuration can be simply calibrated, and have inherently stable calibration and excellent accuracy.

Engineering↗
PubMed2001

Multiple-probe thermography for estimating the postmortem interval: I. Continuous monitoring and data analysis of brain, liver, rectal and environmental temperatures in 117 forensic cases.

One hundred seventeen forensic postmortem cases have been studied under controlled conditions. In each case, temperatures of the brain, liver, rectum, and the environment were monitored over a period beginning shortly after death and ending up to 60 h postmortem. The four temperature measurements were recorded every 5 to 10 min using the Microwave Thermography System. Rectal and environmental temperatures were measured by electrical thermocouples while brain and liver temperatures were measured using microwave probes. Data acquisition, analogue-to-digital conversion (ADC), and data processing were provided by a microcomputer. The ADC technique is described and its problems are discussed. The data were then transferred to a mainframe computer for extensive curve-fitting and statistical analysis. The microcomputer-based ADC and data logging and acquisition were found to be accurate, fast, easy to implement, and useful for the field. The postmortem rate of human body cooling was found to be adequately represented by triple-exponential equations.

Adult↗
PubMed2001

Multiple-probe thermography for estimating the postmortem interval: II. Practical versions of the Triple-Exponential Formulae (TEF) for estimating the time of death in the field.

A simple, reliable, and relatively accurate method for estimating the time since death is described. It is based on the Triple-Exponential Formulae (TEF), which are devised for the first time in this study. The postmortem cooling rate of the brain, liver, and rectum in 117 forensic cases were investigated (Part I). The method can be used in the field as a computer program, reference graph, or reference chart-ruler. The program is simple and can easily be run by any user. There are six reference graphs representing the average brain, liver, and rectal cooling curves for naked and covered body groups. The ruler is designed for the rectal cooling curves for covered and naked bodies. This method requires one temperature measurement of the chosen body site and the environment. The postmortem interval is estimated as a probable value +/- a possible range of time estimates with a built-in confidence limit.

Autopsy↗
PubMed1994

Microwave thermography as a noninvasive assessment of disease activity in inflammatory arthritis.

Microwave thermography is the technique of measuring natural thermal radiation from body tissues of clinical interest. It is safe, requires no control of environmental conditions and exposes the patient to no ionising radiation. In this study, we found that microwave thermography of the knee joints showed weak correlation with some global parameters of disease activity. Bed rest alone for three days had no significant effect on microwave thermographic index (MTI). Intra-articular steroid injection, however, was associated with a marked fall in MTI both in the injected knee and the contra-lateral knee. We conclude that microwave thermography can measure inflammatory activity in the knee joints of patients with inflammatory arthritis and can respond to clinical change brought about by major treatment intervention.

Adrenal Cortex Hormones↗
PubMed1994

A non-invasive method for postmortem temperature measurements using a microwave probe.

The use of the Microwave Thermography System in Forensic Medicine for the estimation of the post-mortem interval is explained. The Microwave Thermography System, a new device which is applied to this field for the first time, is described and its mode of operation is discussed. The main advantage of using this device for estimating the time after death is its ability to measure internal body temperatures by a non-invasive method. Using this device, it is possible now to measure temperatures of internal organs of the body by placing the sensory elements on the skin. Reliability of the system and factors affecting the accuracy of post-mortem temperature measurements have been assessed and discussed.

Adult↗
PubMed1992

A quick accurate method for measuring the microwave dielectric properties of small tissue samples.

A resonant cavity perturbation technique has been developed which provides a quick, simple and accurate method of measuring the microwave dielectric properties of small, easily prepared samples of tissues, tissue-simulating materials and biological fluids. The method gives dielectric properties averaged over the sample volume. The measurement accuracy with the apparatus used is +/- 2.2% for relative permittivity and +/- 3.5% for the loss factor for most tissue and biological material samples. With appropriate basic microwave equipment the method can be applied over the 1.5-6 GHz range of frequencies of interest for active and radiometric tissue microwave imaging.

Adipose Tissue↗
PubMed1992

Dielectric properties of female human breast tissue measured in vitro at 3.2 GHz.

Complex permittivities of in vitro diseased and undiseased human female breast tissues have been measured at 3.2 GHz using a resonant cavity technique. Ranges of dielectric properties and water contents of these tissues are presented. Experimental data are compared with models predicted from mixture equations. Measured permittivity data lie within limits set by two-phase mixture theory, but some conductivity data are in excess of those expected for a mixture of saline and protein. At any particular microwave frequency in all tissue of a given type, the relationship between permittivity and conductivity may be parametrized using the Debye relaxation equations. For each breast tissue type a characteristic relaxation frequency was calculated and found to be lower than that of physiological saline at the same temperature. It is concluded that the dielectric relaxation of tissue water is not the only dispersive process occurring at this frequency: dielectric relaxation of bound water and the tail end of a beta-dispersion may also contribute to the dielectric properties. The similarity of the dielectric properties of benign and malignant breast tumours measured in this work suggest that in vivo dielectric imaging methods will not be capable of distinguishing them.

Adipose Tissue↗