| 摘要 |
<p>An ultrasonic non-invasive technique is described for deriving the time dependencies of characteristics of certain regions in the intracranium medium. Precise measurements of the transit travel times of acoustic pulses are made and processed to extract variable portions indicative of, for example, the pulsatility due to cardiac pulses of a basal artery or a cerebroventricle or the variation in the pressure of brain tissue, as well as changes in the cross-sectional dimension of the basal artery and ventricle. In one technique, the transit time variations attributable to cardiac pulses are extracted by processing higher harmonics in the frequency domain. Frequency and phase detection techniques are described.</p> |
