Sokolska, MJ; (2017) Optimisation of Arterial Spin Labelling MRI for the assessment of perinatal brain injury. Doctoral thesis , UCL (University College London).

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Abstract

Perinatal brain injury is a consequence of insufficient blood and oxygen supply to the brain during labour or delivery and can lead to impaired neurodevelopment or mortality. Hypoxicischemia triggers a chain of physiological reactions of the vasculature and measuring cerebral blood flow (CBF) has the potential to improve our knowledge of injury location and progression, as well as to deepen our understanding of the therapeutic processes involved in treatments. Quantitative regional CBF can be measured non-invasively with a magnetic resonance imaging technique called pseudo-continuous ASL (pCASL). However, the use of pCASL for neonatal CBF assessment in research or clinical practice is still uncommon due to several challenges specific to this patient group. This thesis addressed some of the acquisition and quantification challenges and established a clinically feasible ASL protocol and processing pipeline for neonates with presumed hypoxicischemic encephalopathy (HIE). Specifically, a Bloch equation simulator was implemented to estimate the labelling efficiency of pCASL in neonates. The robustness of pCASL efficiency was investigated theoretically using the simulator and in vivo in a group of healthy adult volunteers. A high robustness of the pCASL efficiency against the angulation of the labelling plane was determined. Additionally, a problem of acoustic noise was studied theoretically and a method was proposed which resulted in a 6dB reduction of the acoustic noise. This thesis also developed an image analysis framework for robust motion correction and exclusion of corrupted datasets. The framework enabled the inclusion of all the acquired datasets (compared to seven out of twelve if no motion correction was used). Finally, the proposed developments and imaging framework was applied in a clinical study of neonates with presumed HIE. The new information provided by CBF was investigated separately and in combination with magnetic resonance spectroscopy (MRS), which is used routinely in HIE outcome prediction. In neonates at high risk of adverse outcome, lentiform nuclei and cingulate cortex were found to have elevated CBF values compared to neonates at low risk.

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