Chapter 1 maximum velocity envelope can often be recorded as analog output signal from the TCD device. Transcranial Doppler ultrasonography depends on an acoustic window, i.e. a region of the skull with better penetration of the ultrasound beam. The tran- stemporal window is most relevant for studying cerebral autoregulation, since through this window the middle cerebral artery (MCA) can be insonated as well as the anterior (ACA) and posterior cerebral arteries (PCA). Mostly cerebral blood flow velocity measurements in the MCA are used for studying dCA 19. Figure 3Sonogram showing the distribution of transcranial Doppler ultrasound shift frequencies in the middle cerebral artery. The top white envelope curve indicates the maximum velocity estimate. Aims Combining noninvasive finger blood pressure recording with TCD recording of cerebral blood velocity in the intracranial vessels allows studying of cerebral hemodynamics at time resolutions faster than normal heart rate. To learn more about the physiology and working mechanisms of dCA and to develop clinical applications of evaluating dCA, it is necessary to develop a reliable method to measure and quantify dCA. Being able to reliably estimate parameters of dynamic cerebral autoregulation with sufficient reproducibility by non-invasive means could improve patient diagnostics and management for several conditions. This thesis aims to improve clinical applicability of testing dynamic cerebral autoregu- lation. The first aim of this thesis is to evaluate the use of transfer function analy- 14
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