Assessment of collaterals in acute ischaemic stroke using CT imaging techniques

Guarisco, Marta (2020) Assessment of collaterals in acute ischaemic stroke using CT imaging techniques. MSc(R) thesis, University of Glasgow.

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There is growing evidence that the degree of collateral circulation in acute ischaemic stroke, and in particular of leptomeningeal collaterals, is a useful imaging marker that is correlated with various baseline and outcome clinical parameters. However, methods for assessing collaterals on acute ischaemic stroke are poorly standardized at present.
In the first part of this master thesis, an in-depth systematic review of methods for assessing collaterals published between 2009 and 2017 is presented. The review shows that although DSA is still used as gold standard, there has been a shift towards CT- and MR- based imaging modalities, which offer equal or higher sensitivity while being at the same time less invasive for the patient. In particular, CT seems to be a good candidate for replacing DSA as gold standard in the future and one scoring method proposed by Tan et al. has been widely adopted in recent studies. However, there has been zero or minimal progress towards a standardized method since previously published reviews.
In the second part of this thesis, a retrospective study conducted at the QEUH (Glasgow) to assess the reliability of collaterals on single-phase CTA is presented. CTA does not provide time-resolved information and this may lead to mislabeling of collaterals. The phase of acquisition of the scan should be taken into account when evaluating collaterals. From 4 past clinical trials, we identified paItients with confirmed ICA or MCA occlusion. Three temporal-MIP images were reconstructed from CTP for each patient, each image corresponding to one of arterial, equilibrium and venous phase of contrast enhancement. Collateral scores were measured on both the temporal-MIP images and on single-phase CTA angiography and it was found that there was substantial agreement between the scores if the CTA was acquired in the equilibrium phase but only moderate agreement if the CTA was acquired in the arterial or venous phase. This confirms that the arterial phase, despite being the preferred phase for assessing arterial occlusion and recanalization, is not the best phase for assessing collaterals and that a combination of CTA-CTP or a CTA scan employing a time-resolved protocol should be employed when evaluating collateral status in stroke patients.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Due to copyright issues this thesis cannot be made available online. Access to the printed version is available.
Keywords: Collaterals, medical imaging, CT angiography, stroke.
Subjects: R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Supervisor's Name: Muir, Prof. Keith
Date of Award: 2020
Depositing User: Ms Marta Guarisco
Unique ID: glathesis:2020-80277
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 16 Mar 2020 10:57
Last Modified: 18 Mar 2020 09:30
Thesis DOI: 10.5525/gla.thesis.80277

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