Accurately controlling resistivity of 3D printing materials for establishing human-head volume conductor model / 医疗卫生装备

Objective To propose a method for accurately controlling the resistivity of 3D printing materials to facilitate to establish a human-head volume conductor model.Methods Two kinds of ABS/CB composite conductive printing materials covering the resistivity ranges of parenchymal and skull were selected through resistivity measurement and analysis. The correlation between the proportions and resistivities of the two kinds of ABS/CB materials and the empirical formula on the correlation between the resistivity and proportion was obtained through exponential function fitting. Results The selected ABS/CB composite material behaved well in frequency stability and time stability,and the obtained empirical formula had high-correlation coefficient.Conclusion Accurate control of 3D printing model resistivity is realized,and it's facilitated to gain 3D printing material with the same resistivity as those of skull and parenchymal.

Novel human-head phantom with realistic skull anatomy and resistivity distribution / 医疗卫生装备

Objective To establish a human-head phantom with realistic skull anatomy and resistivity distribution in order to provide an accurate experimental platform for brain electrical impedance tomography(EIT).Methods Firstly a skull model with 3-layer structure was constructed with double-nozzle 3D printer,and every layer had its specific resistivity verified on the accuracy. Then brain parenchyma with its resistivity was modelled using 3D printer and cerebrospinal fluid and scalp were mimicked using NaCl solution;after the whole phantom was assembled,imaging test using EIT was performed.Results The skull model was similar to the realistic one in terms of anatomy and resistivity distribution;the EIT experiment on the new phantom showed similar results to simulation.Conclusion The proposed phantom has realistic skull anatomy,resistivity distribution and multi-layer anatomical structure, which reflects the features of skull resistivity and thus is suitable for experiments on brain EIT.

Evaluation by damped least-square algorithm on target identification ability of intracranial focal bidirectional electrical impedance perturbation / 医疗卫生装备

Objective To evaluate the effect of damped least-square algorithm on the identification of focal bidirectional electrical impedance perturbation in the intracranial area, and to analyze the influence of this kind of perturbation on the reconstruction quality of electrical impedance tomography. Methods Focal bidirectional electrical impedance perturbation was built based on the three-dimensional model and damped least-square algorithm was introduced into imaging. The position error and resolution were used to evaluate the imaging performance.Results When the focal electrical impedance perturbation existed,the target whose conductivity varied greatly or volume was large was more likely to be identified in the images while the target with smaller volume or variable conductivity presented in the reconstruction image was not obvious. It's pointed out that it may cause reconstruction images in some cases could not truly reflect the location and change information of the object of primary cerebral hemorrhage.At the same time,it affected the reconstruction precision,causing the position error and resolution with large fluctuation. Conclusion In reconstruction algorithm linearity correct matrix introduced for bidirectional electrical impedance perturbation contributes to enhancing the recognition of bidirectional perturbation, so that the characterization of the electrical impedance imaging can be augmented for clinical intracerebral hemorrhage.

Method for synchronous measurement of multichannel electrode-scalp contact impedances in brain EIT / 医疗卫生装备

Objective To study a method for monitoring multichannel electrode-scalp contact impedances in electrical impedance tomography (EIT), and to provide support for exploring the impact of contact impedances on imaging and the suppression method.Methods A reference electrode was introduced for the system,placed on the back of the neck or the top of the head. In the spare time of boundary voltage signal acquisition phase, the method of two electrodes was adopted to measure the electrical impedance between each imaging electrode and reference electrode, which was used to analyze the characteristics of multichannel contact impedances.Based on the existing EIT hardware system,the module for monitoring multichannel contact impedance was implemented.Results The calibration board test showed that the measurement error of this method was less than 1‰,and the maximum relative fluctuation of the measurement result within 10 hours was less than 1‰. Preliminary human test indicated that this method had the ability to obtain two kinds of information about spatial consistency and temporal stability of 16-channel contact impedances. Conclusion This method has high accuracy and stability,so it meets the requirements of monitoring multichannel contact impedances in brain EIT.

Electrical impedance scanning in breast tumor imaging: correlation with the growth pattern of lesion / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>This study researched the electric impedance properties of breast tissue and demonstrated the different characteristic of electrical impedance scanning (EIS) images.</p><p><b>METHODS</b>The impedance character of 40 malignant tumors, 34 benign tumors and some normal breast tissue from 69 patients undergoing breast surgery was examined by EIS in vivo measurement and mammography screening, with a series of frequencies set between 100 Hz - 100 kHz in the ex vivo spectroscopy measurement.</p><p><b>RESULTS</b>Of the 39 patients with 40 malignant tumors, 24 showed bright spots, 11 showed dark areas in EIS and 5 showed no specific image. Of the 30 patients with 34 benign tumors there were almost no specific abnormality shown in the EIS results. Primary ex vivo spectroscopy experiments showed that the resistivity of various breast tissue take the following pattern: adipose tissue > cancerous tissue > mammary gland and benign tumor tissue.</p><p><b>CONCLUSIONS</b>There are significant differences in the electrical impedance properties between cancerous tissue and healthy tissue. The impedivity of benign tumor is lower, and is at the same level with that of the mammary glandular tissue. The distinct growth pattern of breast lesions determined the different electrical impedance characteristics in the EIS results.</p>

Simulation study of electrical impedance tomography based on approaching real finite-element model of brain / 医疗卫生装备

This paper is to build a finite element model of brain with a real brain shapeon which simulation studies of electrical impedance tomography EIT in the brain is based. A curve of a real brain shape is simulated with the curve-fitting methods and EIT in the brain is finished with finite-element methods and Equipotential Lines Back-Projection algorithm.The locationarea and amplitude of the change of the resistivity are reconstructed accurately. But the image quality has to be further improved.This paper provides a basis for clinical applications of EIT in brain.