Dong Xiuzhen

High precision Multifrequency Electrical Impedance Tomography System and Preliminary imaging results on saline tank

To establish a high precision data acquisition system for multi-frequency electrical impedance tomography (EIT), a series of methods were introduced. Those methods include building a driving signal with up to four frequency components to diminish the effect of the dynamic change of tissues resistivity, extracting the impedance information by a digital demodulator that can improve the SNR by 8 times. The system that established can work at a wide range from 1.6 kHz to 380 kHz. Its CMRR is 74 dB at 100 kHz. The output impedance of current source is 2 MOmega at that frequency. And measurement precision on a 100 ohm resistor is better than -80 dB in full bandwidth. Both the quasi-static and the dynamic imaging results based on a saline tank can reflect the resistivity changes inside the phantom clearly. Therefore, the system was competent in multifrequency EIT research work

Image monitoring for an intraperitoneal bleeding model of pigs using electrical impedance tomography.

Current medical imaging techniques are not effective for timely detection of internal hemorrhage when the bleeding is slow and in small quantities. In this study, electrical impedance tomography (EIT) was applied to monitor the intraperitoneal bleeding of an animal model. Five healthy pigs three months old were used. The process of intraperitoneal bleeding was simulated with the injection of anticoagulated blood which was controlled by an electronic syringe pump. The injected rate was no more than 100 ml h(-1) and the total injection volumes ranged from 300 ml to 500 ml. Sixteen electrodes were attached to the abdomen and used for electrical current excitation and surface voltage measurement. Dynamic changes in impedance distribution within the abdomen were calculated by the back-projection algorithm and a series of EIT images were displayed in a unified range. The monitoring was performed with EIT at a rate of one frame per second and continued for at least 4 h. Intraperitoneal blood volume changes could be identified by inspection of consecutive EIT images during the progression of blood injection. 30 ml of blood in the peritoneum could be detected. EIT was shown to be a promising technique for continuous monitoring of intraperitoneal bleeding over periods of time.

Electrical impedance tomography reconstruction algorithm based on general inversion theory and finite element method.

A strict EIT reconstruction algorithm, the general inversion algorithm (GIA) is presented. To improve the noise performance, the algorithm is modified by attenuating the condition number of the forward matrixF and implemented using an improved FEM scheme, to obtain the 2D image of impedance change (dynamic image). This modified general inversion algorithm (MGIA) can be used on a larger dimension FEM model (248 elements) and is more practical than the GIA. When implementing this algorithm in computer simulation and in a physical phantom, it is found that the MGIA has a smaller reconstruction error than the currently used algorithms (equipotential-back-projection algorithm and filtered spectral expansion algorithm). With 0.1% white noise in the data, the algorithm can still reconstruct images of a complicated model. Further improvements are also discussed.

An image monitoring system for intraperitoneal bleeding using electrical impedance tomography and its preliminary results in vivo

An image monitoring system using electrical impedance tomography (EIT) for intraperitoneal bleeding was designed (FMMU V3.5). It consists of a constant current driving source with frequency of 50 KHz, a high accuracy measurement module, a driving and measuring mode program-controlled circuits, a data acquisition card, an optoelectronic isolated digital I/O board, and a custom-specified linear power supply units. The system applied equal-potential back projection algorithm to reconstruct dynamic images. The relative accuracy of the system is 0.1%, the RTI noise is 11.1 mu V (bandwidth 100 Hz). Based on physical phantom, images reconstructed by the system showed that it can image dynamically to the infused saline solution, and by infusing more solution the gray changed area of the image also enlarged accordingly. For stomach filling model in vivo, the dynamic imaging processes showed that the system can clearly and sensitively monitoring the saline solution drinking into the stomach for 50 ml each time, and by drinking more saline solution the conductivity changed area of the dynamic image also enlarged accordingly

Study of Electrical Impedance Scanning System for Breast Screening

An electrical impedance scanning (EIS) system was studied to meet the requirement of clinical breast screening. A quick examination, easy operation, safe electrical isolation and obvious diagnosis results are four main factors to a screening system. Basing on these considerations, a multi-frequency signal sampling system controlled by ARM chip was setup and the measuring data were transmitted to PC by an ethernet interface. For the measuring probe, three types of electrodes array were designed to adapt the different sizes of breast. Additionally, an imaging post-process algorithm was developed to assist the radiologist to have an obvious diagnosis results. Based on a saline-tank phantom and some satisfying results were got. The system has a character of high precision, real-time imaging and obvious results and can be used in the clinical study of EIS breast screening.

Different Approaches to the Completion of the Back-Projection Algorithm in Image Monitoring by Electrical Impedance Tomography

It is found that electrical impedance tomography(EIT) is promising in its application to the clinical image monitoring and that the back-projection algorithm of EIT can meet the preliminary requirements of the real-time monitoring through our work. In order to improve the computed speed and the imaged resolution, different ways of completing the algorithm were tried in this paper. Moreover, it is shown that the impedance change due to physiological saline with the concentration of not more than 50 milliliter 0.9% can be detected and imaged by our system. The above result is helpful for our further work of image monitoring by EIT

The Influence of Position to Phase and Magnitude Detecting in Medical Magnetic Induction Imaging

A 16-channel magnetic induction imaging system is introduced briefly. Highly precise phase and magnitude detecting method is applied to the information acquisition. The resolution of phase detecting is 0.003deg. The results of magnitude detecting also provide us with useful information. The characteristic curves are smoother than that of our previous system. One dimension results in different positions of the measurement region demonstrate the trend of variation of the detected signals. The positions of the object affect the results greatly and the trend of variation is regular

Extracting Motional Information from the PhotoPlethysmography Using Reconstruction of the Wavelet Transforms Modulus Maxima

A movement during measurements can generate motion artifacts in photoplethysmography(PPG) signals. The motion artifacts reflect some information of testers motion. If we can extract the relevant information from these interferences, it probable will be a new information collection method for portable physiological monitor. This paper first analyzes the relationship between the motion artifact and the PPG signals form the Beer-Lambert law. Then, compare the influence of PPG signals by different direction of movement. Finally, extract the information of motion through the reconstruction of wavelet transforms modulus maxima. Through compares the extracted signal and the real motional signals collected by accelerometer (ACQ), two signals have certain relativity. The extracted signal can basically reflect the testers movement. It will be a new way of community and athletes medical care.

Breast Cancer Detection Based on Multi-Frequency EIS Measurement

As a convenient, un-injurious and low cost method for women breast tumor diagnosis, Electrical Impedance Scanning (EIS) is being paid increasing attention. But EIS still has some problems. In theory the malignant tumor has higher electrical conductivity than normal tissue and benign tumor, so the cancer will be recognized in the EIS image as a bright spot. However, in practical the difference is not so obvious. In many cases it is difficult to judge whether a suspicious bright spot tells a malignant or benign tumor. This paper concerns a new method based on multi-frequency EIS measurement to solve this problem. A group of scanning results with various stimulating frequencies will be performed during an EIS measurement, which is automatically controlled by specially designed device and the location and pressure of the sensor will keep stable, so we will get a series of data at different stimulating frequencies through a measurement. Because the malignant and the benign tumor have different curves in electrical conductivity-frequency diagram, we can analyze the data at every frequency and find out the attribute of the tumor. Clinical trails have been carried out. Subjects were suspicious sufferers that were to receive histopathology examinations, and all analyses have been compared with histopathology results.

Study of influencing factors on Electrical Impedance Scanning Imaging

Electrical impedance scanning (EIS) is a new adjunctive diagnostic method for women breast cancer examination. In clinic research, we found some influencing factors which can induce a bad EIS imaging results. In order to analyze the influencing factors on EIS imaging and find the solutions, we set up an EIS workbench which can simulate the influencing factors that may happen in a clinic. We studied the influencing factors from size, depth of the target; the influence from the poor contact; the influence from the unparallel current field. The experiment results show that the detectability of EIS system is a function of the depth, the size and the area of electrodes; a good contact between the probe and the skin can decrease the artificial imaging; using the imaging algorithm can calibrate the imaging induced by unparallel current field