Individualized teaching mode in course of Digital Signal Processing / 医疗卫生装备

The communication between the students and the teacher was introduced from three aspects of foregone course, communication channel as well as homework and experiment. The individualized teaching mode was described involving expounding common difficulty, assigning and reading over the homework, individualized tutoring after school, on-line responding to the student's question, prompting the student to complete programming and answering questions in evening classes. It's pointed out that the individualized teaching has to take both common knowledge and student difference into considerations. Individulized mode enhances the teaching efficacy greatly.

Comparison of three dynamic algorithms of electrical impedance tomography based on simulation study / 中国医疗器械杂志

Three algorithms of electrical impedance tomography (EIT) are studied in this paper. The image resolution, anti-noise property and computation rapidity of the reconstruction algorithms are compared. As a result, it shows that back-projection algorithm has good anti-noise property, that NOSER algorithm generates images with good resolution, and that sensitivity matrix algorithm has moderate property.

3D Reconstruction for Medical Image Based on ITK and OpenGL / 医疗卫生装备

Obiective To develop a new medical image processing platform based on ITK and OpenGL. Methods This platform was designed by VC ++ 6.0 and MFC class library. ITK class library was wsed to fulfill reading, writing,segmentation of images and iso-surface extraction. OpenGL was wsed to realize 3D surface rendering. Results The new 3D-medical imaging reconstruction system was designed. Conclusion This system not only can provide graphic interface which can not be realized by using ITK class library, but also enhance the ability of three-dimension visualization by using OpenGL.

Experimental study on electrical impedance tomography for monitoring retroperitoneal inject blood model in pigs / 中华创伤杂志

Objective To apply electrical impedance tnmography that is a new evaluation ap-proach to monitor the development of retroperitoneal injury. We used retroperitoneal inject blood model in pigs to study the feasibility on monitoring retroperitoneal bleeding and to provide premise in theory and practice for clinical application. Methods Five pigs were used on the experiment. We insert a vessel into the retroperitoneal and inject blood to simulate retroperitoneal bleeding. Sixteen electrodes were atta-ched on the abdominal region circumference of pigs and used for electrical current injection and surface voltage measurement. Then the monitoring images were performed by electrical impedance tomography. Results The images of electrical impedance tomography retroperitoneal inject blood model of five pigs were clear, the minimal impedance scale was decreasing significantly as the bleeding volume increasing and the images were changed significantly too. The computerized tomography and the dissecting results confirmed the blood was limited in retroperitoneal. Conclusions The establishments of pigs retroper-itoneal inject blood model was successful. The images of electrical impedance tomography retroperitoneal inject blood model were clear with significant contrast. It's feasible to use electrical impedance tomography system to monitor the retroperitoneal bleeding. This technique may become a useful tool for monitoring ret-roperitoneal injury in intensive care patients.

Improvement in EIS diagnosis accuracy using a multi-frequency parameter analysis method: preliminary results.

In this work we assessed the validity of the multi-frequency parameter (MFP) analysis method in distinguishing EIS false positive results. We chose 15 subjects with invasive duct carcinoma as the control group in which EIS results were all positive. In the experiment, three test groups-the Contact, the Skin and the Horm groups-were set to correspond to three common types of EIS false results. In the Contact group, false positive results were induced by poor contact of the measuring probe. In the Skin group, false positive results were induced by skin ridges. In the Horm group, false positive results were induced by a high hormone level. Based on the MFP analysis method, we obtained the Cole-Cole parameters of each subject in the control group and the test groups. Statistical analyses showed there was a significant difference in G(0N), G(infinity)N) or alpha(N) between the control group and the Contact or the Skin group. A significant difference between the control group and the Horm group existed only in alpha(N). These results suggested that by means of the MFP analysis method it was possible to distinguish between a false positive result and a positive result caused by breast cancer. In conclusion, the MFP analysis method appears to be a feasible means to improve the diagnosis accuracy of EIS for breast cancer detection.

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.

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.

Antigen-antibody reaction model of solid-phase surface and active biochip system / 生物医学工程学杂志

To overcome the present limitations of passive biochip, based on the basic principle of antigen-antibody reaction, we develop an antigen-antibody reaction model of solid-phase surface and design a novel active biochip system according to this model, which introduces the negative pressure and controlling devices to control the immunoreactions on the nitrocellulose (NC) membrane. From the computer simulation results, this is a rapid, stable, robust and practicable system, which can be used to increase the efficiency of immunoreactions and improve the reproducibility and accuracy of biochip analysis.

Study on dielectric properties of human breast tissues / 国际生物医学工程杂志

Breast cancer is one of the most common malignant tumours in women. It threatens the health and life of women. The imaging technology of breast electrical impedance scanning based on the dielectric properties of breast tissues develops a new aspect of early detection and auxiliary diagnosis of the breast cancer. The dielectric properties of human breast tissues reflect the pathological and physiological state of breast tissues and the measurement of these properties serves as the basis for electrical impedance scanning(EIS) technology. In this paper, the measurements and results of dielectric properties of human breast tissues are discussed, and the problems of measurement and the application perspective of the EIS are also explored.

Study on changes of characteristic parameters of biological tissues impedance spectroscopy in vitro within 5 to 360 min after excision at the frequency range from 1Hz to 1MHz.

We constructed an impedance spectroscopy measurement system based on frequency response analyzer. Using four-terminal method, we measured impedance spectroscopy of rabbit different tissues in vitro within 5 to 360 minutes after excision at the frequency range from 1Hz to 1MHz. According to the measurement results, we analyzed the changes of characteristic parameters (Ro, Rinfin, fc and alpha) of different tissues in the time course. The results show that the Cole-Cole model characteristic parameters change notably in the time course. The value of Ro change great especially. For kidney, liver, spleen and heart, the value of Ro reached 700%, 125%, 170% and 200% respectively at the 6 hour after excision. The change of alpha is less than 30% for all tissues. The changes of fc are various remarkably for different tissues, for liver, kidney and heart, the value of fc decreased continually and the decrement reached 60%, 19%, 33% respectively at the end of the measurement. For muscle (longitudinal, transverse) and heart, the value of fc decreased firstly and then began to increase and reached 145% > 155% > 125% at 6 hour after excision. The results of our reaching show the measurement time plays a remarkable effect on the impedance spectroscopy measurement of tissue in vitro. We hypothesized that the dispersion observed in the impedance spectroscopy measurement in vitro between different researchers was partly due to the effect of measurement time.

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.

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 1.6kHz to 380kHz. Its CMRR is 74dB at 100kHz. The output impedance of current source is 2MΩ at that frequency. And measurement precision on a 100ohm resistor is better than -80dB 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.

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.

Quasi-polar drive pattern for brain electrical impedance tomography.

To seek a single source drive pattern that is more suitable for brain electrical impedance tomography (EIT), a comparison between adjacent, cross, polar and newly proposed quasi-polar drive patterns was made in aspects of boundary voltages dynamic range, independent measurement number, Total boundary voltage changes and anti-noise performance based on an equivalent circuit of the brain resistivity distribution consisting of 7300-odd resistors. The results demonstrate that quasi-polar drive pattern is optimal in all the aspects except dynamic range. Polar and cross drive patterns come next, and adjacent drive pattern is the worst. Therefore, the quasi-polar drive pattern should be chosen for brain EIT.

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.

A data acquisition system for induced current electrical impedance tomography / 生物医学工程学杂志

Induced current electrical impedance tomography (ICEIT) is a new branch of electrical impedance tomography (EIT). We have designed and set up a high accuracy ICEIT hardware system with 32 electrodes based on physical phantom, and we have brought forward a new method to reduce the additive electromotive force (EMF) in circuit of the electrode leads. By use of the technique of twisted pair wire, the additive EMF in the circuit of the electrode leads has been reduced to 10% of that before use and the precision of the system has been improved. The precision of the final results is better than 0.5% after 1000 measurement data averaged. Applying the reconstructive algorithm, we have obtained preliminary images based on physical phantom.

A bipolar optocoupler isolation amplifier with high precision and wide bandwidth / 生物医学工程学杂志

To fit the technological requirements in electrical impedance tomography system, an improved bipolar optocoupler isolation amplifier based on single analog optocoupler was realized. The experimental results illustrates that the full power -3dB bandwidth of this circuit is greater than 800 KHz, the equivalent output noise is lower than 50 uV(RMS), and the linearity at +/- 4 V inputs is lower than 0.01%. In addition to these features, the circuit also have the advantages of simple structure and no distortion caused by mismatch between analog optocouplers.

Frequency characteristic of diseased breast tissues detected by electrical impedance scanning / 生物医学工程学杂志

The rules of conductance parameters on diseased breast tissue, which change with the driven frequency, are studied by use of electrical impedance scanning. This work is intended to provide a basis for further examination of breast. We have obtained conductance parameters' frequency characteristic of three kinds of breast diseases, i.e. invasive ductal carcinoma, neoplastic hyperplasia, and mastopathia. And by comparison, we find that the frequency characteristic of the diseased breast tissues is different from that of the peripheral normal tissues, and the frequency characteristic shows differences among the three kinds of diseased breast tissues. So, we are able to identify the kind of breast disease by its frequency characteristic.

A method of building the finite-element model with the contour line of human brain / 生物医学工程学杂志

The contour line of human brain was simulated by the curve-fitting methods and then the inner area was discretized by advancing-front methods which was improved at last. The curve-fitting result was similar to the CT picture of the human brain and the discrete result of inner area could be completed quickly by improved advanced-front methods. A finite element model with the contour line of human brain was built primarily which will contribute to the next algorithm study of electrical impedance tomography in human brain.