Detection And Analysis Of Limb Venous Thrombosis Based On Impedance Plethysmography

Venous thrombosis has become one of the most important causes of death in the world.In the diagnosis of cardiovascular diseases,the increasing proportion of venous thrombosis indicates that Chinese government departments and clinics need to change their thinking to focus on prevention,supplemented by a treatment,and strengthen screening and diagnosis.Impedance plethysmography is an important method for the diagnosis of cardiovascular diseases,which is sensitive to cardiovascular diseases.In order to reduce false-negative diagnosis,capillary filtration rate and venous wave velocity were introduced to improve the thrombus detection model;The venous thrombosis detection method and venous thrombosis detection system were designed according to the improved model;The corresponding data processing was carried out according to the signal characteristics of venous impedance plethysmography;The characteristics of basic impedance,ascending impedance change rate,descending impedance change rate,vascular volume change,capillary filtration rate and venous blood flow velocity were automatically extracted;Finally,the improved model was used to detect thrombus.The paper’s principal work is divided into the design of the data acquisition platform,the design of data processing for venous impedance plethysmography,and the verification of the venous thrombosis detection system.The data acquisition platform comprises an air pump control module,constant current source module,voltage acquisition module,basic impedance acquisition module,signal modulation,demodulation module,and signal acquisition module.The constant current source module generates a constant current excitation signal,and the excitation signal forms an electric field inside the limb to be measured through the excitation electrode.The potential signal collected by the receiving electrode is processed by the voltage acquisition module,the basic impedance acquisition module,and the signal demodulation module and then converted into basic impedance and impedance signal.For problems of impedance plethysmography signal,which is weak,sensitive,and has low signal-to-noise ratio,this paper designs a signal acquisition module for obtaining venous impedance plethysmography,general impedance plethysmography,and impedance differential plethysmography signals.Simultaneously,simulation verification,actual verification and adjustment of each module circuit were carried out to ensure the data acquisition platform’s feasibility.The design of data processing is divided into the design of signal processing and feature extraction and the thrombus detection model design.Aiming at the problems of information loss and signal interference in the acquisition process,the digital signal processes of the venous impedance plethysmography signal were performed,such as digital filtering,interpolation resampling,capillary filtering correction and validity judgment.These processes improved the signal-to-noise ratio,smoothed the signal waveform,improved the quality of the venous impedance plethysmography signal,and made feature extraction more convenient.Finally,aiming at the problem of the false-negative judgment,based on the theory of the blood circulation system,the thrombus detection model was improved by introducing capillary filtration rate and venous fluctuation speed.And logistic regression was used to establish a thrombus detection model,which improved the ability of positive judgment.After completing the venous thrombosis detection system,the system function verification was carried out,the signal was calibrated,and many people were tested.Since there were no thrombus samples in the experiment,a hemostatic bandage was used to simulate thrombus.From experiment’s preliminary results,the improved model of thrombus detection system has limited improvement in the positive judgment ability,and more experimental accumulation and design improvement are needed.However,venous impedance plethysmography’s ability to assist judgment of thrombus is still worthy of recognition.