Abstract
Metabolic markers of baseline brain oxygenation and tissue perfusion have an important role to play in the early identification of ischaemic tissue in acute stroke. Although well established MRI techniques exist for mapping brain perfusion, quantitative imaging of brain oxygenation is poorly served. Streamlined‐qBOLD (sqBOLD) is a recently developed technique for mapping oxygenation that is well suited to the challenge of investigating acute stroke. In this study a noninvasive serial imaging protocol was implemented, incorporating sqBOLD and arterial spin labelling to map blood oxygenation and perfusion, respectively. The utility of these parameters was investigated using imaging based definitions of tissue outcome (ischaemic core, infarct growth and contralateral tissue). Voxel wise analysis revealed significant differences between all tissue outcomes using pairwise comparisons for the transverse reversible relaxation rate (R 2 ′), deoxygenated blood volume (DBV) and deoxyghaemoglobin concentration ([dHb]; p < 0.01 in all cases). At the patient level (n = 9), a significant difference was observed for [dHb] between ischaemic core and contralateral tissue. Furthermore, serial analysis at the patient level (n = 6) revealed significant changes in R 2 ′ between the presentation and 1 week scans for both ischaemic core (p < 0.01) and infarct growth (p < 0.05). In conclusion, this study presents evidence supporting the potential of sqBOLD for imaging oxygenation in stroke.
Highlights
Ischaemic stroke is characterised by restricted blood supply to regions of tissue that may result in infarction
Magnetic resonance imaging (MRI) is already widely used in the assessment of patients with acute stroke and has the potential to be a viable alternative to Positron Emission Tomography (PET) in measuring oxygen metabolism
For the MRI data acquired during presentation and follow-up scanning, voxel values of R20, deoxygenated blood volume (DBV), [dHb], and cerebral blood flow (CBF) were extracted from the native space of the acquired parameter maps using the ROI definitions of ischaemic core, infarct growth and contralateral tissue
Summary
Ischaemic stroke is characterised by restricted blood supply to regions of tissue that may result in infarction. Magnetic resonance imaging (MRI) is already widely used in the assessment of patients with acute stroke and has the potential to be a viable alternative to PET in measuring oxygen metabolism Such measurements are made possible by the inherent sensitivity of the transverse MR relaxation rate (R2*) to deoxyhaemoglobin. Dynamic susceptibility contrast (DSC) MRI has been used to improve the physiological interpretation of R20 by providing cerebral blood volume (CBV) and cerebral blood flow (CBF) information allowing [dHb] to be estimated (Christen, Schmiedeskamp, Straka, Bammer, & Zaharchuk, 2012) These methods have previously been employed to investigate acute stroke (Gersing et al, 2015; Seiler et al, 2017a; Seiler et al, 2017b). The aim of this study is to investigate the potential of sqBOLD to monitor regional changes in brain oxygenation following ischaemic stroke, and its relation to tissue outcome over time in a cohort of patients undergoing serial non-contrast multi-modal MR imaging, including ASL perfusion imaging
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