Dielectric Properties of Ex Vivo Porcine Liver Tissue Characterized at Frequencies Between 5 and 500 kHz When Heated at Different Rates.

OBJECTIVE: The released energy during radio frequency thermal ablation therapy changes the dielectric properties of biological tissues. Understanding changes of dielectric properties of biological tissues during heating is fundamental to suitably model the medical procedure. The aim of this work is to obtain the thermal dependences of conductivity and permittivity of ex vivo porcine liver tissue at six frequencies from 5 to 500 kHz, during heating from 37 °C to 100 °C at three heating rates of approximately 0.1, 3, and 10 °C/min. METHODS: Two experimental setups using different heating sources and a four-needle electrode connected to an impedance analyzer were developed to evaluate the thermal dependencies. RESULTS: The results at a body temperature of 37 °C show a good agreement with the data reported in the literature. The conductivity initially shows an increase followed by a decrease, whereas the permittivity increases before a subsequent sharp decrease. Above 60 °C, different trends are observed for the three heating rates studied. CONCLUSION: The electric conductivity and permittivity show a similar behavior at all evaluated frequencies and heating rates. The observed abrupt change of the slope near 45 °C at a slow heating rate may be used to identify the region of reversible changes in the tissue. SIGNIFICANCE: These results confirm the connection among tissue dielectric properties, working frequency, and exposure time with thermal damage during heating.

Evaluación del ambiente electromagnético en salas de rehabilitación / Evaluation of the electromagnetic environment in rehabilitation wards

Se realizó un estudio del ambiente electromagnético en 2 departamentos de electroterapia del municipio Palma Soriano de Santiago de Cuba, a fin de obtener el patrón de distribución para diferentes modos de operatividad y explotación del equipamiento médico-terapéutico. Para la caracterización electromagnética de los ambientes evaluados se elaboró un protocolo de medición a partir del análisis de normas internacionales y se empleó un medidor isotrópico que mostró los resultados a través de mapas de contorno. El equipo electromédico Magnetomed, modelo 7200 fue el que más aportó, aunque el valor máximo de la inducción magnética obtenido (19,7 µT) estuvo por debajo del límite de exposición establecido y por encima del límite de exposición sugerido por el Grupo de Trabajo Bioiniciativa. Se recomienda limitar la permanencia de personas en sus proximidades mientras está en funcionamiento.

A study of the electromagnetic environment was carried out in 2 electrotherapy departments of Palma Soriano in Santiago de Cuba, in order to obtain the distribution pattern for different operability ways and exploitation of the medical-therapeutic equipment. For the electromagnetic characterization of the evaluated environments a measurement protocol was elaborated starting from the analysis of international standards and an isotropic measure was used that showed the results through contour maps. The electro-medical device Magnetomed, model 7200 was the one that contributed the most, although the maximum value of the obtained magnetic induction (19.7 µT) was below the established exhibition limit and above the exhibition limit suggested by the Bioiniciativa Work Group. It is recommended to limit the permanency of people around, while it is in operation.

Evaluación del ambiente electromagnético en salas de rehabilitación / Evaluation of the electromagnetic environment in rehabilitation wards

Se realizó un estudio del ambiente electromagnético en 2 departamentos de electroterapia del municipio Palma Soriano de Santiago de Cuba, a fin de obtener el patrón de distribución para diferentes modos de operatividad y explotación del equipamiento médico-terapéutico. Para la caracterización electromagnética de los ambientes evaluados se elaboró un protocolo de medición a partir del análisis de normas internacionales y se empleó un medidor isotrópico que mostró los resultados a través de mapas de contorno. El equipo electromédico Magnetomed, modelo 7200 fue el que más aportó, aunque el valor máximo de la inducción magnética obtenido (19,7 µT) estuvo por debajo del límite de exposición establecido y por encima del límite de exposición sugerido por el Grupo de Trabajo Bioiniciativa. Se recomienda limitar la permanencia de personas en sus proximidades mientras está en funcionamiento(AU)

A study of the electromagnetic environment was carried out in 2 electrotherapy departments of Palma Soriano in Santiago de Cuba, in order to obtain the distribution pattern for different operability ways and exploitation of the medical-therapeutic equipment. For the electromagnetic characterization of the evaluated environments a measurement protocol was elaborated starting from the analysis of international standards and an isotropic measure was used that showed the results through contour maps. The electro-medical device Magnetomed, model 7200 was the one that contributed the most, although the maximum value of the obtained magnetic induction (19.7 µT) was below the established exhibition limit and above the exhibition limit suggested by the Bioiniciativa Work Group. It is recommended to limit the permanency of people around, while it is in operation.(AU)

Caracterización de los niveles de exposición a campos electromagnéticos durante el tratamiento con diatermia / Characterization of the exposure levels to electromagnetic fields during the diathermy treatment

Se realizó un estudio del campo electromagnético generado por distintos electrodos de tipo capacitivo, empleados en el equipo de fisioterapia por diatermia de onda corta YB4-66, considerando su interacción con el medio ambiente que le rodea. Se realizaron las mediciones de campo eléctrico para diferentes configuraciones de tratamiento y se utilizó un medidor de campo eléctrico de sonda isotrópica. Se diseñó, mediante un software profesional de simulación, un modelo electromagnético paramétrico bidimensional con simetría axial, para obtener detalladamente en cada configuración de los electrodos evaluados la interacción del campo electromagnético con el tejido biológico y el ambiente exterior. Se halló una buena correspondencia entre los resultados obtenidos de forma experimental y las simulaciones, lo cual permitió identificar los niveles de exposición y tomar decisiones para lograr un tratamiento más efectivo y con el menor daño posible a los seres humanos.

A study of the electromagnetic field generated by different electrodes of capacitive type, used by the physiotherapy device for short wave diathermy (YB4-66), was carried out considering their interaction with the surrounding environment. The measurements of the electric field for different treatment configurations were carried out and a meter with electric isotropic field probe was used. By means of a professional software of simulation, a two-dimensional parametric electromagnetic model with axial symmetry was designed, to obtain detailedly in each configuration of the evaluated electrodes the interaction of the electromagnetic field with the biological tissue and the external environment. A good correspondence was found between the obtained results in an experimental way and the simulations, which allowed to identify the exposure levels and to make decisions to achieve a more effective treatment and with the shortest possible damage for the human beings.