Background : Although transcranial Doppler ultrasound (TCD) shows oscillations in its time-series recording, its significance has not been elucidated. Some signals obtained from a biological system, such as electroencephalography or electrocardiography shows nonlinear characteristics. Objective : The purpose of this study is to characterize the temporal fluctuation of the axial blood flow velocity at the middle cerebral artery by nonlinear analysis in the normal subjects. Methods : We measured the TCD waveforms in the middle cerebral artery (MCA) for 50 seconds and analyzed the maximum blood flow velocities. From these waveforms the phase trajectories were reconstructed and presented in a three-dimensional phase portrait. Following the paradigm of nonlinear dynamical systems or “chaos” theory, complexity is best evaluated by estimating the correlation dimension (D2) and the largest Lyapunov exponent (λ1). The values of D2 and λ1 were compared between dominant and nondominant sides. Results : TCD study was performed in 26 people. The D2 values of left MCA were higher than those of right MCA while the cerebral blood flow velocities of both MCA ere not different. The λ1 value did not show any specific trend. Conclusion : The TCD waveforms are essentially nonperiodic and can be characterized by low dimensional chaos. The TCD waveforms of dominant hemisphere are more chaotic than those of nondominant hemisphere. Korean Journal of Stroke 2000;2(2): 181~185
Background : Although transcranial Doppler ultrasound (TCD) shows oscillations in its time-series recording, its significance has not been elucidated. Some signals obtained from a biological system, such as electroencephalography or electrocardiography shows nonlinear characteristics. Objective : The purpose of this study is to characterize the temporal fluctuation of the axial blood flow velocity at the middle cerebral artery by nonlinear analysis in the normal subjects. Methods : We measured the TCD waveforms in the middle cerebral artery (MCA) for 50 seconds and analyzed the maximum blood flow velocities. From these waveforms the phase trajectories were reconstructed and presented in a three-dimensional phase portrait. Following the paradigm of nonlinear dynamical systems or “chaos” theory, complexity is best evaluated by estimating the correlation dimension (D2) and the largest Lyapunov exponent (λ1). The values of D2 and λ1 were compared between dominant and nondominant sides. Results : TCD study was performed in 26 people. The D2 values of left MCA were higher than those of right MCA while the cerebral blood flow velocities of both MCA ere not different. The λ1 value did not show any specific trend. Conclusion : The TCD waveforms are essentially nonperiodic and can be characterized by low dimensional chaos. The TCD waveforms of dominant hemisphere are more chaotic than those of nondominant hemisphere. Korean Journal of Stroke 2000;2(2): 181~185
※ AI-Helper는 부적절한 답변을 할 수 있습니다.