Analysis of doppler waveforms of the cerebral circulation
Author(s)
Raynor, Sheila M.
Type
Thesis
Abstract
Development of the technique of Transcranial Doppler ultrasound (TCD) could have important clinical and cost-saving benefits. This thesis describes the development and testing of a novel method for acquiring and analysing TCD blood flow velocity waveforms, in conjunction with other physiological data. Custom-designed waveform analysis software allows for a range of waveform shape parameters and indices (in addition to those in current use) to be measured. This software allows for tracking of changes in the cerebral circulation over time, during physiological or pharmaceutical interventions, or between subjects. Data can be reviewed in numerical format, 2-D (waveform shape) or 3-D rendering. We present the repeatability and reproducibility results for the waveform shape parameters.Additionally, we establish a set of 'normal values' obtained from a group of 35 healthy subjects (17 males/18 females), mean age 35.8 ± 11.3 (range 22.63 years). Doppler waveform shape changes are further evaluated during vasoreactivity testing using 6% CO2 and during controlled hyperventilation. Our results show that Doppler waveforms are encoded with physiological information, and that each individual has a distinctive cerebral waveform shape. During changes in cerebral resistance (vasoreactivity testing), Doppler waveforms undergo measurable and reproducible shape changes. We identify the parameters of the waveform shape, which are indicative of both cerebral vasodilation and of vasoconstriction. We examine the relationship of blood flow velocity to cerebral resistance. We also introduce cerebrovascular set-point theory. This thesis builds on the technical, practical and theoretical foundations of Doppler ultrasound for the cerebral circulation, and demonstrates how innovative, yet inexpensive techniques have the potential to be utilised to provide clinically significant information.
Version
Open Access
Date Awarded
2007
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Parker, Kim
Publisher Department
Department of Medicine
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)