Parkes, Laura Michelle; (2003) Measuring blood perfusion in the brain using arterial spin labelled MRI. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Perfusion is a fundamental biological function, giving an indication of tissue metabolism, through the rate of blood supply. Changes in perfusion accompany almost all forms of brain disease giving a wide range of potential applications for perfusion imaging. Arterial spin labelled MRI, the subject of this thesis, is a good method of measuring brain perfusion. Issues of perfusion quantification, i.e. accuracy and precision are addressed. Current models of the perfusing system assume that water is freely diffusible across the capillary wall. Several published values show that this is not true in the brain where the blood brain barrier restricts water passage. A corrected two-compartment model is presented, with simplifications for use in vivo. Simulations show that the change to perfusion estimation is large. In vivo modelling shows an improved fit for all extremes of perfusion. Perfusion reproducibility is measured for different tissue volumes and is found to compare favourably with other perfusion techniques. A study of thirty-two normal volunteers shows that inter-subject perfusion variation is large, but perfusion within a single subject remains fairly stable over the course of a day and a week. A significant (p<0.05) negative correlation of grey matter perfusion with age is reported, giving a perfusion decrease of 0.5% per year. Female whole brain perfusion is found to be 16% higher than in males (p=0.02). Measurements of perfusion change are made in stroke, arteriovenous malformation (AVM), motor activation and multiple sclerosis. The examples in stroke and motor activation serve as important validation of the technique and the modelling. Gross perfusion abnormalities are detected in AVM showing different perfusion characteristics in different regions of AVM. More subtle changes are found in multiple sclerosis, with significant perfusion increases in the normal appearing white matter compared to normal controls.

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