ABSTRACT
Piglets having each a body weight of 20-30 kg and an abdominal perimeter like human's were used in the experiment. Being guided by ultrasound, we stabbed the piglet's abdomen, placed a catheter on the liver's lower margin, then injected the anticoagulated blood through the catheter by electrical infusion pump with constant speed respectively, and monitored the whole process by EIT. We observed the image change, using Ultrasound and CT to examine the area of blood injection after the end of monitoring,and we dissected to check the result of observations. The results reveal: (1) Ultrasound, CT and dissection are all able to find out a large amount of blood in piglet's abdominal cavity; (2) The pixel value of EIT target area decreases with the increase of blood, and the change in impedance image can be obviously observed. Therefore, this animal model is suitable for simulating intraperitoneal bleeding, and the speed of bleeding therein can be controlled. We can get a limpid image when EIT is used for monitoring the intraperitoneal bleeding simulated by this animal model.
Subject(s)
Animals , Female , Male , Electric Impedance , Hemorrhage , Diagnosis , Image Interpretation, Computer-Assisted , Methods , Monitoring, Physiologic , Methods , Peritoneal Diseases , Diagnosis , Plethysmography, Impedance , Methods , Swine , Tomography , MethodsABSTRACT
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.
ABSTRACT
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.
Subject(s)
Algorithms , Amplifiers, Electronic , Electric Impedance , Electrodes , Electromagnetic Phenomena , Equipment Design , Models, Theoretical , Signal Processing, Computer-Assisted , Tomography , MethodsABSTRACT
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.
Subject(s)
Humans , Amplifiers, Electronic , Electric Impedance , Equipment Design , TomographyABSTRACT
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.
Subject(s)
Female , Humans , Breast Diseases , Diagnosis , Pathology , Breast Neoplasms , Diagnosis , Carcinoma, Ductal, Breast , Diagnosis , Electric Impedance , Electronics, Medical , Methods , Hyperplasia , DiagnosisABSTRACT
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.
Subject(s)
Humans , Algorithms , Brain , Finite Element Analysis , Models, Anatomic , Models, NeurologicalABSTRACT
Induced-current electrical impedance tomography (ICEIT) is a newly hot research field in electrical impedance tomography (EIT) because of its advantages of contactless exciting. A preliminary ICEIT system with 3 excitation coils has been accomplished. It includes the constant current source (CCS), power amplifiers, excitation coils,physical phantom, measurement-mode setting circuit, signal measuring block, DAC and digital I/O card. The CCS is accomplished with Direct Digital Synthesis (DDS) technique. Its frequency is 46.875 KHz. Its output current is divided into 16 steps from 0.16 mA to 2.56 mA which can be set by computer. The three driving coils have the same diameter of 50 cm, each coil's inductance is 193.5 microH. The power amplifier can provide 800 mA driving current (f = 46.875 KHz) to the coil under +/- 25 V power supplying. The signal from measurement electrodes is switched to measurement channel which includes IA, BP filter and synchronized demodulator, then the analog signal is converted to digital signal by a 12b A/D Card and the data is acquired by DMA mode. Our experiments show that a distinguish change of signal from the surface electrodes can be acquired by the experimental system when different objects are placed in the physical phantom. And 3 x 31 signals for preliminary imaging have been acquired.
Subject(s)
Humans , Algorithms , Amplifiers, Electronic , Electric Impedance , Electrodes , Electromagnetic Fields , Electromagnetic Phenomena , Image Processing, Computer-Assisted , Phantoms, Imaging , Tomography , MethodsABSTRACT
Objective To compare the performance of novel Ag/AgCl pulverized electrodes with conventional Ag/AgCl coating electrodes in cerebral application of Electrical Impedance Tomography(EIT).Methods Based on the EIT system developed by our group,raw data were measured on a phantom and an adult volunteer,with Ag/AgCl coating electrodes and pulverized electrodes,respectively.The performances of electrode systems were evaluated in contact impedance and two other figures(the high-frequency SNR,HFSNR;the low-frequency SNR,LFSNR).Results Ag/AgCl pulverized electrode plays a better performance in resisting noise and keeping stabilization.Conclusion Ag/AgCl pulverized electrode develops the needs of imaging and monitoring human brains in EIT more availably.
ABSTRACT
Objective To study the image processing methods of electrical impedance tomography(EIT) in order to improve the display quality.Methods Evaluate the conductivity of the nodes using the conductivity of the adjacent triangle elements.The conductivity of any point in one triangle element was calculated according to the conductivity of 3 vertexes of the element by 2D linear interpolation method.Results The original blocky images of electrical impedance tomography by the triangle elements can be transformed into smoothing images.Conclusion The visual quality of the images is improved greatly.The image processing method is adaptive to all kinds of images of electrical impedance tomography based on triangle element.
ABSTRACT
The complex impedance measurements of human brain tissue in vitro are made by using four-electrode measurement methods in the frequency range from 0.1 Hz to 1 MHz. The Solartron 1255 B frequency response analyzer is used. The frequency response curves of the imaginary part of human brain's complex impedance do not appear as a single peak curve which other bio-tissues show, and the Cole-Cole diagram of human brain is different from the others as well. The construction of the equivalent circuit model obtained is more complex. However, these characteristics of human brain are all the same as rabbit brain's. The equivalent circuit model obtained will be helpful to constructing the equivalent circuit model of human head in the EIT researches.
Subject(s)
Adult , Humans , Male , Brain , Physiology , Electric Impedance , Electrodes , In Vitro Techniques , Models, BiologicalABSTRACT
The in vivo measurements of rabbit brain tissue impedance were taken under both normal and ischemic conditions by using two-electrode measurement method in the frequency range from 0.1 Hz to 1 MHz. The dynamic images about the resistivity of cerebral ischemia were reconstructed based on a 16-electrode system. The results of in vivo measurement showed that the ratio of impedance increased can be as high as 75% at frequencies lower than 10 Hz. In the range from 1 KHz to 1 MHz, the ratio showed a constant value of 15%. The electrical impedance tomography (EIT) images obtained suggested that the regions of impedance changes highly correspond to the position of ischemia. It is confirmed that the brain function changes caused by local deficiency of blood can be detected and imaged by EIT method.
Subject(s)
Animals , Female , Male , Rabbits , Brain , Physiology , Brain Ischemia , Electric Impedance , Tomography , MethodsABSTRACT
It is the intent of this paper to develop better reconstruction algorithm for electrical impedance tomography (EIT). Simulation study of the reconstruction algorithm based on the sensitivity theorem is made and the reconstruction algorithm is compared with other normal algorithms. The results indicate that sensitivity method as a kind of static reconstruction algorithm has higher accuracy and speed of iteration, so it is worth researching for laboratory modality work.
Subject(s)
Algorithms , Computer Simulation , Electric Impedance , Tomography , MethodsABSTRACT
The human skull impedance was quantitatively measured by means of Frequency Response Analyzer and its software. The impedance-frequency response curves of human skull were obtained. By analyzing the curves, we found that the characteristic frequency of human skull should be around 10 KHz.