A nonlinear autoregressive (NAR) model is built to model the heartbeat interval time series and the optimum model degree is proposed to be taken to evaluate the nonlinearity degree of heart rate variability (HRV). A g...A nonlinear autoregressive (NAR) model is built to model the heartbeat interval time series and the optimum model degree is proposed to be taken to evaluate the nonlinearity degree of heart rate variability (HRV). A group of healthy persons are studied and the results indicate that this method can effectively get nonlinear information from short (6—7 min) heartbeat series and consequently reflect the degree of heart rate variability, which supplies convenience in clinical application. Finally, a comparison with the traditional time domain method shows that the NAR model method can reflect the complexity of the whole signal and lessen the influence of noise and instability, in the signal.展开更多
Recently with the rapid development of the high-intensity focused ultrasound (HIFU) in biomedical ul- trasound, much attention has been paid to the noninvasive temperature estimation in biological tissue in order to d...Recently with the rapid development of the high-intensity focused ultrasound (HIFU) in biomedical ul- trasound, much attention has been paid to the noninvasive temperature estimation in biological tissue in order to de- termine the region and degree of the ultrasound-induced lesions. In ultrasound hyperthermal therapy it is highly de- sirable to study the real-time noninvasive monitoring of temperature distribution in biological tissue. In this paper, the relationship between the nonlinearity parameter B/A and the temperature in biological tissue is studied and compared with the theoretical model as well as the experimental results from the thermocouple. Results indicated that B/A could be used as an effective tool to monitor the temperature distribu- tion in biological media.展开更多
文摘A nonlinear autoregressive (NAR) model is built to model the heartbeat interval time series and the optimum model degree is proposed to be taken to evaluate the nonlinearity degree of heart rate variability (HRV). A group of healthy persons are studied and the results indicate that this method can effectively get nonlinear information from short (6—7 min) heartbeat series and consequently reflect the degree of heart rate variability, which supplies convenience in clinical application. Finally, a comparison with the traditional time domain method shows that the NAR model method can reflect the complexity of the whole signal and lessen the influence of noise and instability, in the signal.
文摘Recently with the rapid development of the high-intensity focused ultrasound (HIFU) in biomedical ul- trasound, much attention has been paid to the noninvasive temperature estimation in biological tissue in order to de- termine the region and degree of the ultrasound-induced lesions. In ultrasound hyperthermal therapy it is highly de- sirable to study the real-time noninvasive monitoring of temperature distribution in biological tissue. In this paper, the relationship between the nonlinearity parameter B/A and the temperature in biological tissue is studied and compared with the theoretical model as well as the experimental results from the thermocouple. Results indicated that B/A could be used as an effective tool to monitor the temperature distribu- tion in biological media.
