Pulmonary strain and end-expiratory lung volume during apnea test: a comparative analysis using electrical impedance tomography / Stress pulmonar y volumen pulmonar de fin de es piración durante el test de apnea: estudio compara tivo utilizando tomografía por impedancia eléctrica

Abstract The apnea test, employed for brain death assessment, aims to demonstrate the absence of respiratory drive due to hypercapnia. The tracheal oxygen insufflation apnea test mode (I-AT) involves disconnecting the pa tient from invasive mechanical ventilation (iMV) for ap proximately 8 minutes while maintaining oxygenation. This test supports the diagnosis of brain death based on a specified increase in PaCO2. Common complications include hypoxemia and hemodynamic instability, and lung collapse-induced reduction in end-expiratory lung volume (EELV). In our case series utilizing electrical impedance to mography (EIT), we observed that continuous positive airway pressure during the apnea test (CPAP-AT) effec tively mitigated lung collapse. This resulted in improved pulmonary strain compared to the disconnection of iMV. These findings suggest the potential benefits of routine CPAP-AT, particularly for potential lung donors, emphasizing the relevance of our study in providing quantitative insights into EELV loss and its association with pulmonary strain and potential lung injury.

Resumen La prueba de apnea es una técnica diagnóstica am pliamente utilizada para la evaluación de la muerte cerebral, con el objetivo de demostrar la ausencia de impulso respiratorio debido a la hipercapnia. La variante de la prueba de apnea con insuflación de oxígeno traqueal (I-AT) implica desconectar al pacien te de la ventilación mecánica invasiva (iVM) durante aproximadamente 8 minutos, manteniendo la oxigena ción mediante un catéter de insuflación. Esta prueba respalda el diagnóstico de muerte cerebral cuando se determina un aumento de la PaCO2 superior a 20 mmHg en comparación con el valor inicial o un nivel de PaCO2 superior a 60 mmHg al final de la prueba. En nuestra serie de casos, la implementación de la tomografía de impedancia eléctrica (EIT) reveló que la prueba de apnea con presión positiva continua (CPAP-AT) mitiga eficazmente el colapso pulmonar. Este enfo que resulta en una mejora en la tensión pulmonar en comparación con la desconexión de iMV, demostrando su relevancia en el contexto de potenciales donantes de pulmones.

A Sensor for Detection of Breast Tumor with Three-dimensional Electrical Impedance Tomography / 分析化学

An intensive breast array sensor was designed based on three-dimensional electrical impedance tomography in this work.Firstly,an electrical impedance sensor for detection of breast cancer was developed.The sensor adopted the integrated design of excitation electrode array and ground electrode to achieve structural simplification.It realized electric field densification through conical matrix and double-layer circumferentially arranged electrode array and improved the detection accuracy of target object through taper optimization.Secondly,the imaging system was designed,and the sensor was optimized by numerical simulation.The simulation results showed that halving the number of electrodes did not affect imaging accuracy of the sensor,but could improve the imaging speed.Finally,the performance of the sensor was verified by experiment.The signal-to-noise ratio and channel consistency of the system were at a good level.The sensor was used to reconstruct three-dimensional image of the experimental model with relative volume of the detection field of 0.4%.The image correlation coefficient of the single target imaging was above 0.6 and the position of the double target object could be clearly identified,and thus the visual detection of breast cancer was realized.

Research progress of electrical impedance tomography in positive end-expiratory pressure titration / 临床麻醉学杂志

Appropriate positive end-expiratory pressure(PEEP)level is an important component of protective lung ventilation strategy.PEEP can maintain the openness of alveoli and reduce lung collapse in-jury.Although individualized PEEP application has been increasingly recognized by clinical physicians,the optimal PEEP titration method is still controversial.Electrical impedance tomography(EIT)is a non-inva-sive and radiation-free imaging technique that can be used to dynamically assess lung function at the bedside.EIT presents changes in impedance during ventilation as dynamic images,which can reflect altera-tions in ventilation and gas distribution before and after PEEP adjustments.Therefore,EIT can be utilized to tailor individualized PEEP.This article provides a brief overview of the basic principles and monitoring pa-rameters of EIT.It elucidates the PEEP titration method under the guidance of EIT in clinical applications(PEEPEIT),aiming at enhancing the understanding of the advantages and limitations of EIT and providing reference for the setting of individualized PEEP.

Evaluation of Clinical Efficacy of Modified Houpo Dahuangtang in Moderate and Severe ARDS Patients Based on Electrical Impedance Tomography / 中国实验方剂学杂志

ObjectiveTo evaluate the clinical efficacy of modified Houpo Dahuangtang in moderate and severe acute respiratory distress syndrome （ARDS） patients with phlegm-heat accumulation，and monitor the pulmonary ventilation changes of patients before and after treatment by electrical impedance tomography（EIT）. MethodThe 62 cases of moderate and severe ARDS patients with phlegm-heat accumulation who required mechanical ventilation in the department of intensive care unit （ICU） in Chongqing Hospital of Traditional Chinese Medicine from September 2021 to June 2022 were selected，and divided into an experimental group（31 cases）and a control group（31 cases）using a random number table. On the basis of regular Western medicine treatment，the experimental group received modified Houpo Dahuangtang and the control group received warm water by a nasogastric tube for seven days. The changes in the clinical efficacy of traditional Chinese medicine（TCM），the oxygenation index［arterial oxygen partial pressure （PaO2）/fractional inspired oxygen（FiO2），P/F］，lactic acid（Lac），acute physiology and chronic health evaluation Ⅱ（APACHE Ⅱ） score，compliance，plateau pressure，gas distribution parameters monitored by EIT（Z1，Z2，Z3 and Z4），inflammatory factors［interleukin-6 （IL-6），IL-10， tumor necrosis factor-α （TNF-α） and C-reactive protein （CRP）］ of both groups before and after treatment were recorded. Besides， the mechanical ventilation time， length of stay in ICU， 28-day mortality and incidence of adverse reactions（delirium，abdominal pain and diarrhea）in the two groups were also observed. ResultThere was no significant difference in the baseline indexes of patients in the two groups，and thus the two groups were comparable. After treatment for one week， the total effective rate for TCM syndromes in the experimental group was 90.30%（28/31）， higher than the 67.74%（21/31）in the control group（Z=-2.415，P<0.05）.Compared with the same group before treatment， the plateau pressure and Lac decreased （P<0.01）and the compliance and P/F increased （P<0.01） in experimental group， while the Lac decreased （P<0.05）and the P/F increased （P<0.05）， and the compliance and plateau pressure did not change significantly in the control group. After treatment，the plateau pressure and inflammatory factors in the experimental group were lower than those in the control group（P<0.05）， but the compliance and P/F in the experimental group were higher than those in the control group（P<0.05）， and the gas distribution parameters Z1，Z2，Z3，Z4，Z1+Z2，and Z3+Z4 monitored by EIT in the experimental group were all higher than those in the control group （P<0.05）. There was no significant difference in mechanical ventilation time， ICU hospitalization time， 28-day mortality， delirium， abdominal pain， diarrhea and other adverse reactions between the two groups. ConclusionModified Houpo Dahuangtang can significantly improve the P/F，pulmonary ventilation in gravity-dependent regions and pulmonary compliance，reduce the release of inflammatory factors in moderate and severe ARDS patients. Compared with conventional methods，EIT can timely monitor the pulmonary ventilation changes in ARDS patients，which suggests its clinical feasibility.

Physiological effect of high flow oxygen therapy measured by electrical impedance tomography in single-lung transplantation / Efectos fisiológicos del alto flujo de oxígeno medido por tomografía de impedancia eléctrica en trasplante unipulmonar

Abstract In patients with chronic obstructive pulmonary dis ease (COPD), single lung transplantation (SLT) is some times performed as an alternative to bilateral lung trans plantation due to limited organ availability. However, the postoperative management of SLT presents challenges, including complications related to the distinct compli ance of each lung. This case report presents the case of a 65-year-old male patient who underwent SLT and was in the weaning period from mechanical ventilation. High-flow oxygen therapy (HFOT) was administered, and the physiological effects were measured using electrical impedance tomography (EIT). The results demonstrated that the application of HFOT increased air trapping and overdistention in the native lung without benefiting the transplanted lung. HFOT through a tracheostomy tube or nasal cannula resulted in a more heterogeneous distri bution of ventilation, with increased end expiratory lung impedance, prolonged expiratory time constants, and an increase in silent spaces. The drop in tidal impedance after applying HFOT did not indicate hypoventilation but rather overdistention and air trapping in the native lung, while the transplanted lung showed evidence of hypoventilation. These findings suggest that HFOT may not be beneficial for SLT patients and could potentially worsen outcomes. However, due to the limited scope of this case report, further prospective studies with larger patient cohorts are needed to confirm these results.

Resumen En pacientes con enfermedad pulmonar obstructiva crónica (EPOC), el trasplante pulmonar unilateral (SLT, por sus siglas en inglés) se realiza como alternativa a la disponibilidad limitada de donantes para el trasplante pulmonar bilateral. Sin embargo, el manejo postoperato rio del SLT presenta desafíos, incluyendo complicaciones relacionadas con la distinta complacencia de cada pul món. Este reporte presenta el caso de un paciente varón de 65 años que fue sometido a un SLT y se encontraba en el proceso de destete de la ventilación mecánica. Se administró terapia de oxígeno de alto flujo (HFOT, por sus siglas en inglés) y se midieron los efectos fisiológicos utilizando la tomografía de impedancia eléctrica (EIT, por sus siglas en inglés). Los resultados demostraron que la aplicación de HFOT aumentó la retención de aire y la hiperinflación en el pulmón nativo sin beneficiar al pulmón trasplantado. Tanto la HFOT a través de un tubo de traqueostomía como a través de cánula nasal resultaron en una distribución más heterogénea de la ventilación, con un aumento en la impedancia pulmonar al final de la espiración, prolongación de las constantes de tiempo espiratorias y un aumento en los espacios silentes. La disminución de la impedancia tidal después de aplicar HFOT no indicó hipoventilación, sino más bien hiperinsuflación y retención de gas en el pulmón nativo, mientras que el pulmón trasplantado mostró evidencia de hipoventilación. Estos hallazgos sugieren que el HFOT puede no ser beneficioso para los pacientes con SLT y podría empeorar los resultados. Sin embargo, debido al alcance limitado de este informe de caso, se necesitan estudios prospectivos con cohortes de pacientes más amplias para confirmar estos resultados.

Prediction method for weaning outcomes based on machine learning and electrical impedance tomography / 医疗卫生装备

Objective To propose a method for predicting weaning outcomes based on machine learning and electrical impedance tomography(EIT).Methods Firstly,EIT image features were extracted from a total of 84 samples from 30 patients,and the important features screened with the extreme gradient boosting(XGBoost)algorithm were used as inputs to the model.Secondly,the prediction model was built with six machine learning methods,namely random forest(RF),support vector machines(SVM),XGBoost,gradient boosting decision tree(GBDT),logistic regression(LR)and decision tree(tree).Then the prediction model had its prediction performance evaluated by AUC,accuracy,sensitivity and specificity under imbalanced dataset,over-sampling balanced dataset and random under-sampling balanced dataset.Results In terms of AUC,accuracy and specificity,the model under the over-sampling balanced dataset and the random under-sampling balanced dataset behaved better than that under the imbalanced dataset(P＜0.05);in terms of sensitivity,the difference in model performance between the over-sampling balanced dataset and the imbalanced dataset was not statistically significant(P＞0.05),and the model performance under the random under-sampling balanced dataset decreased when compared with that under the imbalanced dataset(P＜0.05).There were no significant differences between the model performance under the over-sampling balanced dataset and that under the random under-sampling balanced dataset(P＞0.05).The model based on XGBoost behaved the best under the over-sampling balanced dataset,with an AUC of 0.769,an accuracy of 0.808,a sensitivity of 0.938 and a specificity of 0.600.Conclusion The method based on machine learning and EIT predicts weaning outcomes of patients with prolonged mechanical ventilation,and thus can be used for auxiliary decision support for clinicians to determine the appropriate timing of weaning.[Chinese Medical Equipment Journal,2023,44(10):1-6]

Research progress on electrical impedance tomography in pulmonary perfusion / 生物医学工程学杂志

Electrical impedance tomography (EIT) is an emerging technology for real-time monitoring based on the impedance differences of different tissues and organs in the human body. It has been initially applied in clinical research as well as disease diagnosis and treatment. Lung perfusion refers to the blood flow perfusion function of lung tissue, and the occurrence and development of many diseases are closely related to lung perfusion. Therefore, real-time monitoring of lung perfusion is particularly important. The application and development of EIT further promote the monitoring of lung perfusion, and related research has made great progress. This article reviews the principles of EIT imaging, lung perfusion imaging methods, and their clinical applications in recent years, with the aim of providing assistance to clinical and scientific researchers.

Electrical Impedance Tomography to Measure Spirometry Parameters in Chronic Obstructive Pulmonary Disease Patients / Tomografía por Impedancia Eléctrica para Medir Parámetros de Espirometría en Pacientes con Enfermedad Pulmonar Obstructiva Crónica

ABSTRACT Spirometry is a test for the diagnosis of chronic obstructive pulmonary disease. It is a technique that can be intolerant due to the essential use of a mouthpiece and a clamp. This study proposes the use of electrical impedance tomogra phy to measure respiratory parameters. Patients underwent spirometry and three respiratory exercises. The imped ance signals were convolved, and the resultant was analyzed by fast Fourier transform. The frequency spectrum was divided into seven segments (R1 to R7). Each segment was represented in terms of quartiles (Q25%, Q50%, Q75%). Each quartile of each segment was correlated with the spirometric parameters to obtain a fitting equation. FVC was correlated 70% with the 3 quartiles of R7, 3 equations were obtained with a fit of 60%. FEV1 correlated 70% with the Q50% of R7, obtaining an equation with a fit of 40%. FEV1/FVC correlated 69% with Q75% of R2, obtaining an equation with a fit of 60%. Spirometric parameters can be estimated from the implied carrier frequency components of the ventilatory impedance signal.

RESUMEN La espirometría es una prueba para el diagnóstico de enfermedad pulmonar obstructiva crónica. Es una técnica que puede resultar intolerante debido al uso imprescindible de una boquilla y una de pinza. Este estudio propone el uso de la tomografía de impedancia eléctrica para medir los parámetros respiratorios. Los pacientes realizaron una espi rometría y tres ejercicios respiratorios. Las señales de impedancia fueron convolucionadas, y la resultante se analizó mediante una transformada rápida de Fourier. El espectro en frecuencias se dividió en siete segmentos (R1 a R7). Cada segmento se representó en términos de cuartiles (Q25%, Q50%, Q75%). Cada cuartil de cada segmento se co rrelacionó con los parámetros espirométricos para obtener una ecuación de ajuste. La FVC se correlacionó en un 70% con los 3 cuartiles de R7, se obtuvieron 3 ecuaciones con un ajuste del 60%. El FEV1 se correlacionó en un 70% con el Q50% de R7, obteniéndose una ecuación con un ajuste del 40%. El FEV1/FVC se correlacionó en un 69% con el Q75% de R2, obteniéndose una ecuación con un ajuste del 60%. Los parámetros espirométricos pueden ser estimados a partir de los componentes de frecuencia portadora implícitos de la señal de impedancia ventilatoria.

Pendelluft volume during double-triggered asynchronous breaths under pressure support ventilation: a prospective physiological study / 中华危重病急救医学

Objective:To investigate the relationship between double-triggering and abnormal movement of air in the lungs (pendelluft phenomenon) under pressure support ventilation (PSV).Methods:A prospective observational study was conducted, postoperative patients admitted to department of critical care medicine of Beijing Tiantan Hospital, Capital Medical University from April 1, 2019 to August 31, 2020 and received invasive mechanical ventilation with PSV mode were enrolled. Electrical impedance tomography (EIT) monitoring was performed. Airway pressure-time, flow-time, global and regional impedance-time curves were synchronously collected and analyzed offline. The volume of abnormal movement of air in the lungs at the beginning of inspiration was measured and defined as pendelluft volume. Double-triggered breaths were identified by trained researchers. Pendelluft volume during double-triggering was measured including the first triggered breath, the double-triggered breath, and the breath immediately following the double-triggered breath. Pendelluft volume was also measured for normal breath during the study. According to the frequency of double-triggering, patients were divided into severe (≥1 time/min) and non-severe double-triggering group. Pendelluft volume, parameters of respiratory mechanics, and clinical outcomes between the two groups were compared.Results:In 40 enrolled patients, a total of 9 711 breaths [(243±63) breaths/patient] were collected and analyzed, among which 222 breaths (2.3%) were identified as double-triggering. The Kappa of interobserver reliability to detect double-triggering was 0.964 [95% confidence interval (95% CI) was 0.946-0.982]. In 222 double-triggered breaths, pendelluft volume could not be measured in 7 breaths (3.2%), but the pendelluft phenomenon did exist as shown by opposite regional impedance change at the beginning of double-triggered inspiration. Finally, pendelluft volume was measured in 215 double-triggered breaths. Meanwhile, 400 normal breaths (10 normal breaths randomly selected for each patient) were identified as control. Compared with normal breath, pendelluft volume significantly increased in the first breath, the double-triggered breath, and the following normal breath [mL: 3.0 (1.4, 6.4), 8.3 (3.6, 13.2), 4.3 (1.9, 9.1) vs. 1.4 (0.7, 2.8), all P < 0.05]. Patients in severe double-triggering, pendelluft volume of normal breath and double-triggered breath were significantly higher than those in non-severe double-triggering group [mL: 1.8 (0.9, 3.2) vs. 1.1 (0.5, 2.1), P < 0.001; 8.5 (3.9, 13.4) vs. 2.0 (0.6, 9.1), P = 0.008]. Patients in severe double-triggering group had significantly higher respiratory rate than that in the non-severe double-triggering group (breaths/min: 20.9±3.5 vs. 15.2±3.7, P < 0.001). There were no significant differences in other respiratory mechanics parameters and main clinical outcomes between the two groups. Conclusions:During PSV, the abnormal movement of air in the lungs (pendelluft phenomenon) was more likely to occur in double-triggering especially in double-triggered breath. The more frequent the double-triggering occurred, the more serious the pendelluft phenomenon was. A higher pendelluft volume of normal breath and a higher respiratory rate were related to severity of double-triggering.

A multifrequency time-difference electrical impedance tomography algorithm using spectral constraints / 生物医学工程学杂志

This study aims to propose a multifrequency time-difference algorithm using spectral constraints. Based on the knowledge of tissue spectrum in the imaging domain, the fraction model was used in conjunction with the finite element method (FEM) to approximate a conductivity distribution. Then a frequency independent parameter (volume or area fraction change) was reconstructed which made it possible to simultaneously employ multifrequency time-difference boundary voltage data and then reduce the degrees of freedom of the reconstruction problem. Furthermore, this will alleviate the illness of the EIT inverse problem and lead to a better reconstruction result. The numerical validation results suggested that the proposed time-difference fraction reconstruction algorithm behaved better than traditional damped least squares algorithm (DLS) especially in the noise suppression capability. Moreover, under the condition of low signal-to-noise ratio, the proposed algorithm had a more obvious advantage in reconstructions of targets shape and position. This algorithm provides an efficient way to simultaneously utilize multifrequency measurement data for time-difference EIT, and leads to a more accurate reconstruction result. It may show us a new direction for the development of time-difference EIT algorithms in the case that the tissue spectrums are known.

Research progress of weaning from mechanical ventilation guided by electrical impedance tomography / 中华危重病急救医学

Weaning?failure?from?mechanical?ventilation?is?an?important?clinical?problem,?the?traditional?methods?of?assessing?whether?patients?can?be?weaned?from?mechanical?ventilation?or?not?cannot?meet?the?clinical?needs.?Finding?more?effective?weaning?indicators?to?determine?the?optimal?timing?of?weaning?has?important?clinical?value?for?improving?the?outcome?of?weaning?and?reducing?the?mortality?of?patients.?As?a?new?method?of?assessing?respiratory?function?of?patients,?electrical?impedance?tomography?(EIT)?is?gradually?applied?to?the?clinic,?and?its?guided?assessment?of?respiratory?function?may?open?a?new?way?for?directing?successful?weaning.?This?article?reviews?the?progress?of?EIT?in?ventilation?weaning,?in?order?to?provide?a?new?judgment?method?and?theoretical?basis?for?the?successful?weaning.

Application of electrical impedance tomography for postoperative lung recruitment in patients undergoing off pump coronary artery bypass grafting surgery / 上海交通大学学报（医学版）

Objective • To find out the optimal positive end expiratory pressure (PEEP) by electrical impedance tomography (EIT) for better lung recruitment and ventilation distribution in patients undergoing off pump coronary artery bypass grafting surgery (OPCAB). Methods • 105 patients underwent OPCAB from Jan. 2017 to Dec. 2017 were analysed. Patients were randomly divided into two groups, i.e. experiment group (54 cases) and control group (51 cases). Four regions of interest (ROI) were recorded by EIT. PEEP were 3 cmH2O in control group while PEEP were increased stepwise by 2 cmH2O from 0 cmH2O to 14 cmH2O in experiment group. The optimal PEEP for lung recruitment was applied in experiment group. Postoperative oxygenation index (PaO2/FiO2) and pulmonary complication were compared between two groups. Results • The overall mortality was 2 (1.90%). The incidence of postoperative pulmonary complication, pulmonary infection, atelectasis, pleural effusion were 18.10%, 2.86%, 18.10%, 18.10%, respectively. The optimal PEEP zone was 6-9 cmH2O. PaO2/FiO2 was significantly increased with the optimal PEEP in experiment group (P=0.00). There were significant differences in postoperative pulmonary complication between two groups (P=0.02). Conclusion • EIT can directly monitor ventilation distribution and titrate suitable PEEP for better lung recruitment in patients undergoing OPCAB. It can significantly reduce postoperative pulmonary complication, improve oxygenation, and decrease ICU stay and ventilation duration.

Application of electrical impedance tomography for postoperative lung recruitment in patients undergoing off pump coronary artery bypass grafting surgery / 上海交通大学学报（医学版）

Objective·To find out the optimal positive end expiratory pressure (PEEP) by electrical impedance tomography (EIT) for better lung recruitment and ventilation distribution in patients undergoing off pump coronary artery bypass grafting surgery (OPCAB). Methods?·?105 patients underwent OPCAB from Jan. 2017 to Dec. 2017 were analysed. Patients were randomly divided into two groups, i.e. experiment group (54 cases) and control group (51 cases). Four regions of interest (ROI) were recorded by EIT. PEEP were 3?cmH2O in control group while PEEP were increased stepwise by 2?cmH2O from 0?cmH2O to 14?cmH2O in experiment group. The optimal PEEP for lung recruitment was applied in experiment group. Postoperative oxygenation index (PaO2/FiO2) and pulmonary complication were compared between two groups. Results?·?The overall mortality was 2 (1.90%). The incidence of postoperative pulmonary complication, pulmonary infection, atelectasis, pleural effusion were 18.10%, 2.86%, 18.10%, 18.10%, respectively. The optimal PEEP zone was 6-9?cmH2O. PaO2/FiO2was significantly increased with the optimal PEEP in experiment group (P=0.00). There were significant differences in postoperative pulmonary complication between two groups (P=0.02). Conclusion?·?EIT can directly monitor ventilation distribution and titrate suitable PEEP for better lung recruitment in patients undergoing OPCAB. It can significantly reduce postoperative pulmonary complication, improve oxygenation, and decrease ICU stay and ventilation duration.

Experimental study on effect of body position on lung ventilation determined by electrical impedance tomography / 医疗卫生装备

Objective To monitor and compare the effects of body position on the regional lung volume and FEV1/FVC with electrical impedance tomography(EIT).Methods Twelve healthy young subjects[(26.6±2.5)yr]were detected by EIT during FVC maneuver in 3 body positions (sitting,supine and prone).Functional EIT images of FVC and FEV1/FVC were obtained;the proportion of regional ventilation volume and the mean of regional FEV1/FVC were calculated.Results The ventral and dorsal proportion of ventilation volume was 37.65% : 62.35% in sitting position and 37.59% : 62.41% in supine position, respectively.While in the prone position,the value was 48.56%:51.44%,which was close to 1:1.The mean of regional FEV1/FVC in the dependent lung region was 0.84 in supine position and 0.81 in prone position,while in sitting position,the corresponding value was 0.90 and 0.94, respectively. Conclusion The results shows that the ventilation transfers to the gravity dependent region obviously, while the flow rate decreases. The result provides direct evidences for mechanical ventilation patients using prone position to improve oxygenation,as well as a research foundation for EIT monitoring regional lung ventilation in the clinical setting.

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.

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.

Study on the inverse problem of electrical impedance tomography based on self-diagnosis regularization / 生物医学工程学杂志

The inverse problem of electrical impedance tomography (EIT) is seriously ill-posed, which restricts the clinical application of EIT. Regularization is an important numerical method to improve the stability of the EIT inverse problem as well as the resolution of the imaging. This paper proposes a self-diagnosis regularization method based on Tikhonov regularization and diagonal weight regularization method (DWRM). Firstly, the ill-posedness of the inverse problem is analyzed by sensitivity. Then, the performance of the self-diagnosis regularization is analyzed through the singular value theory. Finally, some simulated experiments including simulations and flume experiment are carried out and verify that the self-diagnosis regularization has better image quality and anti-noise ability than those of traditional regularization methods. The self-diagnosis regularization method weakens the ill-posedness of inverse problem of EIT and can prompt the practical application of EIT.

Método para medir densidad ósea a partir de conductividad eléctrica calculada por Tomografía de Impedancia Eléctrica / Method for measuring bone density through the electrical conductivity calculated by Electrical Impedance Tomography

RESUMEN: En este trabajo se presenta un método para medir densidad ósea. El método consiste en la medición de conductividad eléctrica de material óseo por medio de Tomografía de Impedancia Eléctrica (TIE). Se hace uso de una celda de prueba con valores simulados de hueso aplicando corrientes y registrando voltajes, para después usar una reconstrucción por retroproyección y generar mapas de conductividad por medio de gráficas. Los datos obtenidos son analizados y a partir de ellos se obtiene una distribución de la medida de conductividad eléctrica del material óseo, que varía dependiendo del grado de porosidad que presenta en cada región. La ventaja de utilizar el método de tomografía de impedancia es que permite medir la conductividad efectiva del hueso porque se mide en todas las direcciones. Por lo tanto es posible determinar porosidad en material óseo usando mediciones de conductividad eléctrica por medio del método TIE propuesto, lo cual permite calcular un valor numérico de densidad ósea.

ABSTRACT: In this paper a method to measure bone density was developed. The method consists in the measurement of electrical conductivity of bone by Electrical Impedance Tomography (EIT). A phantom with simulated data of bone is used, applying currents and recording voltages; then a backprojection reconstruction is used to generate maps with graphic conductivity values. The data obtained were analyzed and was obtained a distribution of electrical conduc tivity of bone, wich varies according to the bone porosity level in each region. A significant advantage of using this method is that is possible to measure electrical conductivity in several directions of the bone, obtaining an effective conductivity. Therefore it is possible to determine the porosity in the bone with measurements of electrical conductivity using the proposed EIT method, this allows to calculate a numerical value for bone density.

3D electrical impedance finite element joint modeling and simulation using COMSOL and Visual C++ / 医疗卫生装备

Objective To put forward a method for 3D electrical impedance finite element joint modeling and simulation using COMSOL for visual modeling and Visual C++ for programming.Methods A model was established with COMSOL,and then transformed into a.stl file and introduced into Visual C++ simulation platform.Delaunay tetrahedral mesh generation algorithm was used for finite element meshing,calculation and simulation,and joint modeling and simulation were realized finally.Results Simulation result showed that the method could be used to introduce COMSOL model and complete 3D finite element simulation.Conclusion The method proves its compatibility with the models generated by multi software and practicability for joint modeling and simulation.

Research on regularization matrix construction in electrical impedance tomography / 医疗卫生装备

Objective To improve the image quality of the electrical impedance tomography (EIT) by introducing the prior information into the regularization matrix.Methods The linear combination of the conductivity was established by background conductivity of dynamic variation,the covariance matrix was used here to remove the correlation between the background conductivity,and this prior information was introduced to construct the regularization matrix.Resnlts Compared with the traditional regularization matrix,the one involving in the prior information on the dynamic background gained more stable and better images.Conclusion Trials prove the efficacy of the regularization matrix on EIT imaging in 1 respiratory cycles (or heart beat),and following related researches may find theoretical references and support for feasibility.