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Title: The use of conventional and advanced magnetic resonance techniques in the assessment of primary brain tumours
Author: Caseiras, G. D. B.
ISNI:       0000 0004 2731 3648
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2008
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The aim of the work described in this thesis was to investigate the value of conventional, perfusion- and diffusion-weighted magnetic resonance imaging (MRI) in patients with histology-proven low-grade gliomas (LGG), and the potential role of these methods in the management of patients with these brain tumours. Thirty-six patients were studied at the National Hospital for Neurology and Neurosurgery using conventional, perfusion-weighted and diffusion-weighted MRI at study entry and 6 monthly intervals thereafter. At each visit, tumour volume, maximum rCBV and ADC histogram measures were calculated. This is a unique cohort, as patients were treatment free until malignant transformation was diagnosed, which translates the natural history of these brain tumours. It is unlikely to find such a specific cohort as most of the patients receive treatment after the initial diagnosis of low grade gliomas. Chapters 1 and 2 of this thesis describe the theoretical basis of the MRI techniques used, and summarise the natural history and imaging aspects of cerebral gliomas. Chapter 3 describes a methodological study relating to tumour perfusion measurement: since the inclusion or exclusion of intratumoural vessels may influence the quantification of relative cerebral blood volume (rCBV), a study was conducted to choose the best ROI placement technique to be used for the rCBV measurements included in this thesis. It was shown that only the approach which excluded intratumoural vessels demonstrated a significant association between rCBV values and tumour subtypes (astrocytomas, oligodendrogliomas and oligoastrocytomas) and therefore this technique was used in all subsequent rCBV measurements. In chapter 4, it was investigated whether rCBV is a useful outcome predictor in patients with low-grade gliomas. We found that in LGG susceptibility-weighted MR perfusion imaging not only allows differentiation between histological tumour subtypes but also between two different outcome groups. More importantly, rCBV at study entry can be used to predict time to transformation in these patients. To complement these studies we assessed the utility of rCBV in predicting clinical response in 2 patient groups with low-grade glioma, studied at two separate institutions. The results presented in chapter 5 suggested that glioma rCB V correlates with time to progression or death, independently of institution, despite different approaches to patient management at the two sites. Finally, in chapter 6 we analyzed which quantitative MRI measure (tumour volume, rCBV and ADC) was the best predictor of outcome (stable, progressive disease or death). We found that tumour volume at study entry, at 6 and at 12 months, and its short-term changes were stronger predictors of outcome in patients with low-grade glioma than, and independent of, rCB V, diffusion histogram parameters, age, gender, histology and treatment. Moreover tumour growth was the best predictor of time to transformation and tumour volume was the only independent predictor of time to death. Since this parameter can readily be obtained in any MRI centre and be quantified with an automated method, it may become a useful prognostic factor in clinical practice.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available