Development of non-invasive MRI methods to measure cerebral blood flow for early detection of dementia
Project Allocated in 2016-17
Arterial spin labelling (ASL) is a non-invasive, contrast-free MRI method for the measurement of cerebral blood flow (CBF). It is able to provide quantitative whole-brain CBF maps in scan times of a few minutes. However, despite its potential as an important biomarker for neurodegenerative disease, ASL has not yet found widespread use in clinical research studies due to limitations in its sensitivity, spatial resolution, and overall image quality. The aim of this project will be to improve the methods used for ASL image acquisition and reconstruction, in order to provide reliable and high quality CBF maps in patients with dementia. This will involve exploration of the relative merits of the different options available for fast MR image acquisition (echo planar imaging, single-shot and multi-shot 3D Cartesian and non-Cartesian schemes), in combination with data under-sampling techniques (parallel imaging and compressive sensing) and reconstruction/pre-processing methods designed to eliminate corruption of the images caused by patient motion during the scan (autofocus for multi-shot 3D data and optimised registration algorithms for accurate alignment of images prior to averaging). Once the optimised methods have been determined, set up and fully tested on healthy subjects, they will be applied to patients participating in research studies at the Dementia Research Centre at Queen Square. All imaging will be performed on a recently installed state-of-the-art 3T clinical MRI scanner at the National Hospital. By the end of the project, we will aim for ASL to be incorporated as a standard component of the dementia imaging protocols at Queen Square.
Non-invasive mapping of CBF abnormalities in patients with neurodegenerative disease is a long-standing goal of clinical imaging. Currently, the most widely used MRI method is dynamic susceptibility contrast (DSC) imaging, which requires a rapid bolus injection of Gd-DTPA (or other similar paramagnetic contrast agent). As well as adding extra cost and inconvenience to the scanning session, concerns have recently been raised regarding the long-term effects of Gd usage, and in some patients with deficiencies of renal function Gd injection is prohibited. Therefore, development of a completely non-invasive image acquisition method for CBF mapping is a clear methodological objective for neuroimaging applications. While the initial focus for the project will be to apply the method to investigate changes in grey matter perfusion in patients with dementia, in the future we will also look to extend the technique to measure CBF in (i) white matter; (ii) presymptomatic subjects with genetic predisposition for developing neurodegenerative disease; and (iii) patients with other neurological and psychiatric disorders (e.g. multiple sclerosis, schizophrenia).