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Biomedical subjects

A Ignesti

Publications and source records attributed to A Ignesti.

14 recordsLinked to original sources
PubMed1997

Hyperaemia evaluation in clinical diathermy by four-electrode impedance measurements.

The four-electrode electrical impedance measurement technique is proposed for the evaluation of the hyperaemia variation in tissues treated by diathermic therapy. An impedance meter suitable for such measurements is described, and an electrical model of the heated tissues, concerning the impedance variation during diathermy and its relation with hyperaemia, is presented. The occurrence of the substantial contribution of blood to the overall transverse impedance is demonstrated by comparing the experimental results with those arising from a 2D electrical/thermal model of the treated tissues. A two-admittance model is proposed to explain the electrical behaviour of the tissues treated by diathermy. The model allows us to separate the impedance violation due to the temperature dependence of tissue conductivity from that due to the change of tissue blood content. The results of preliminary measurements of tissue impedance on healthy volunteers treated by electromagnetic diathermy are presented and discussed, showing the feasibility of impedance detection of hyperaemia variations inside tissues.

Body Temperature↗
PubMed1993

High permittivity patch radiator for single and multi-element hyperthermia applicators.

This paper describes a compact, low-profile patch radiator which is the base element for efficient, small-size applicators suitable for superficial hyperthermia. The design criteria and the technological processes involved are presented. The electromagnetic characteristics of the patch element are outlined, and possible application of the radiator are discussed.

Ceramics↗
PubMed1988

Analysis of electric and magnetic fields leaking from induction heaters.

Results are presented of an investigation on electric and magnetic fields leaking from inductive (magnetic) heaters that are used for thermal processing of high-power electron tubes and lasers in an industrial plant. Measurements of electric and magnetic fields were done using both commercially available and laboratory-developed instrumentation. Isotropic H-field sensors were developed to allow quantitative evaluation of high-intensity magnetic fields. Ten induction heaters with nominal A.C. power ranging from 2.5 kW to 15 kW and operating at frequencies between 300 kHz and 790 kHz were surveyed. Electric field strengths up to 8 kV/m and magnetic field strengths up to 20 A/m were measured.

Environmental Exposure↗
PubMed1986

Exposure of workers to intense RF electric fields that leak from plastic sealers.

This paper presents the results of an environmental investigation in a plastic-ware industry using RF sealers. Environmental measurements have demonstrated the presence of strong electric fields the intensity of which: reaches significant levels from the health-protection point of view only in proximity to the applicators; often exceeds the maximal levels allowed by all standards (including the most permissive) for short duration exposures, especially in the region of the hands. Results of a cross-sectional study on the health of 63 female workers are related to the observed RF exposure. A statistically significant correlation was found to exist between RF exposure and some minor health effects--eye irritation, upper limb paresthesias, and vitreous body disorganization.

Equipment Safety↗
PubMed1982

A radio-frequency monitor for protection against overexposure from RF heaters.

Extensive investigation on the various potentially polluting RF sources has led to the conclusion that the largest proportion of problems arising from possible RF hazards originates from industrial heating machines (short-wave). In particular, these turn out to require checks due to their intrinsic and induced instabilities. Through the analysis of RF leakage characteristics of these machines, the problem is simplified and the solution is presented in terms of an RF hazard monitor which can be used by non-specialized personnel. The monitor is also suitable for several other types of potentially dangerous apparatus in the medium- and short-wave range.

Environmental Exposure↗
PubMed1978

Analysis of the effects of microwave energy on enzymatic activity of lactate dehydrogenase (LDH).

Interactions between microwave energy (3 GHz) and the enzyme Lactate Dehydrogenase (LDH) have been analyzed by monitoring the enzymatic activity during irradiation in steady-state or dynamic conditions, by irradiating the sample with variable power levels (up to 6 W into the sample) and, finally, by knowing accurately the true specific absorption rate. No permanent or temporary changes can be induced when the energy absorption does not cause a temperature variation. For higher energy values, effects are purely thermal in nature. Furthermore the thermal activation of the reaction velocity, caused by microwave irradiation, is in itself sufficient to give a good fit with the experimental time evolution of the enzymatic reaction.

Hot Temperature↗
PubMedDate not supplied

Phantom characterization of applicators by liquid-crystal-plate dosimetry.

A method for the determination of the SAR distribution produced by an electromagnetic applicator for localized hyperthermia is described. The procedure for SAR evaluation consists of recording the time evolution of the temperature inside a polyacrylamide phantom by means of thermochromic liquid crystal sheets inserted in it. The technique allows a complete characterization of applicators in a very broad frequency range, using power levels of the order of those needed in real treatments. Criteria for the minimum phantom size and the maximum time duration of the characterization procedure are indicated, which allow a reliable determination of the effective field size and penetration depth of the applicator.

Biophysical Phenomena↗