RESUMO
Ex vivo bioimpedance data measured on normal and cancerous female breast tissues are reported. They clearly show that the electrical properties of normal tissues, surrounding tissues, and carcinoma are different. These differences lie in the conductivity, in the characteristic frequency (frequency of the maximum of the imaginary part of the bioimpedance), and also in the shape of the Bode plots. Modeling using an R-S-Zcpe model is reported as well as indexes extracted from the real and imaginary parts of the bioimpedance. Even if a classification of the different types of tissues remains a difficult task and leads to much less precise diagnosis than microscopic examination, the electrical behavior of mammary tissue could be used to develop a noninvasive technique for early breast cancer detection.
Assuntos
Neoplasias da Mama/diagnóstico , Mama/patologia , Carcinoma Ductal de Mama/diagnóstico , Impedância Elétrica , Biópsia , Mama/anatomia & histologia , Condutividade Elétrica , Eletrodos , Técnicas Histológicas , Humanos , Modelos EstatísticosRESUMO
A multifrequency (1 kHz-1 MHz) serial electrical impedance tomography (EIT) system has been developed. It is based on 16 active electrodes and can be extended up to 32. Each active electrode can be programmed for current driving and for measuring either the injected current or the voltage difference between adjacent electrodes, and includes calibration facilities. Real and imaginary parts of the impedance are obtained by applying a parametric identification method (extended Prony), but other techniques are easily adaptable. Image reconstruction is carried out using the Sheffield filtered back-projection algorithm. Characteristic frequency images are under development and should be of great interest to distinguish between normal and tumorous tissues.
Assuntos
Impedância Elétrica , Tomografia/instrumentação , Algoritmos , Eletrodos , Eletrônica Médica/instrumentação , Eletrônica Médica/estatística & dados numéricos , Desenho de Equipamento , Humanos , Processamento de Imagem Assistida por Computador , Neoplasias/diagnóstico , Imagens de Fantasmas , Tomografia/estatística & dados numéricosRESUMO
Electrical impedance spectrometry is an important application field of bioimpedance measurements. After introducing the electrical properties of biological tissues, this part presents instrumental aspects and applications of electrical impedance spectrometry. The main instrumental constraints encountered in spectrometric electrical impedance measurements are reviewed, focusing on low-frequency applications. Examples of impedance cells and probes are presented and several instrumental setups operating in the frequency and time domain are described. Some examples of applications are presented, including in vitro characterization and modeling of normal tissues, in vitro and in vivo characterization of cancerous tissues, and assessment of tissue perfusion/ischemia levels.
Assuntos
Impedância Elétrica , Eletrofisiologia/métodos , Neoplasias/fisiopatologia , Neoplasias da Mama/fisiopatologia , Fenômenos Fisiológicos Celulares , Condutividade Elétrica , Eletrodos , Eletrofisiologia/instrumentação , Humanos , Isquemia , Modelos Biológicos , PerfusãoRESUMO
An accurate and easy to use test circuit has been developed for the performance evaluation of the heat exchangers used in cardiac surgery during extracorporeal circulation. The water part of the heat exchanger is fixed at a flow rate of 15 l/min and at a temperature of 40 degrees C. In the blood side, the flow rate is varied from 1 to 6 l/min and the temperature is 30 degrees C. The use of a precise thermometer (precision 0.01 degrees C) and of a microcomputer permits efficiency with a good reproducibility. The results obtained show a real improvement in the efficiency of the new extracorporeal blood heat exchangers devices.