Thrombus Detection System Of The Artificial Heartbased On Ultrasonic Doppler

Thrombus formation is a serious complication in the development of artificial heart.When the artificial heart is implemented in the patients with heart diseases, once the thrombus produced by the artificial heart enters the patients'cardiovascular system, the patients may have a stroke or coronary cardiopathy, which will further deteriorate the patients'condition.In recent years, researchers try many methods in the field of thrombus detection within artificial heart, such as optimizing the structure design, adopting the anti-clotting technique and biocompatible material, and etc. However, thrombus formation still cannot be efficiently prevented. Thus, it calls for the need to detect and quantify the thrombi, which paves the path for improvement of device structure and effectiveness of control mechanism. The aim of this research is to prevent thrombus and facilitate R & D of aritificial hearts.This thesis presents the design of the thrombus detection system used in artificial heart, based on the principle of Transonic Doppler. Below are several achievements made so far:1. According to Ultrasonic Doppler Effect, different phenomena are presented when ultrasonic wave encounters thrombi and blood corpuscles. Hence, it is feasible to adopt the method of Ultrasonic Doppler for thrombus detection.2. Based on the characteristics of ultrasonic wave propogation, an ultrasonic probe is designed and self-made; based on the resonance feature of piezoelectric ceramics as well as the properties of ultrasonic signals, the transmitter/receive circuit as well as the data processing and collecting circuit are realized and successfully tested in lab.3. In accordance with the requirement of the thrombus detection system, a series of software programs on the FPGA platform are written and debugged, such as FIFO and SRAM processing, RS232 Serial Port communications, and etc.4. On the basis of experiements in the mock system, the mimicking thrombus is successfully detected through careful analysis of power fluctuation of thrombus signals by short-time Fourier analysis (STFT). In this way, the hemodynamic performances under heart assistance can be evaluated in vitro.This thesis explores into the application of thrombus detection in artificial heart, which provides a useful tool for improvement of assist device structure and effectiveness of control mechanism.