Streamlined-qBOLD¹ is a recently proposed refinement of the qBOLD methodology² that provides a simplified approach to mapping baseline brain oxygen metabolism. We demonstrate its potential to observe the evolution of oxygen metabolism in the ischaemic penumbra in serially imaged patients with acute stroke.The original concept of the ischaemic penumbra suggested that concurrent imaging of regional cerebral blood flow (CBF) and metabolism would be required to identify tissue at risk that may benefit from intervention³. qBOLD is a non-invasive MR technique that describes the transverse MR signal decay in the presence of a blood vessel network by exploiting the sensitivity of the reversible-transverse-relaxation-rate (R₂′) to Oxygen Extraction Fraction (OEF) and Deoxygenated Blood Volume (DBV)². Streamlined-qBOLD uses a novel acquisition protocol to minimise confounding effects (CSF contamination, magnetic field inhomogeneities and R₂-weighting) from the measurement of R₂′ and improve the robustness of the resultant parametric maps. Streamlined-qBOLD provides an approach to mapping baseline brain oxygenation with good brain coverage in a clinically feasible acquisition time and a non-invasive, patient friendly manner. As such, this technique is ideally suited to clinical studies requiring repeated imaging sessions to track the progression of baseline brain oxygenation and metabolism.Patients with acute ischaemic stroke were recruited and scanned at 3T under a National Ethic Committee approved protocol, which included possible repeat scanning at 2 hours, 24 hours, 1 week and 1 month after initial scan. Nine patients were scanned on presentation with a minimum of one follow-up scan. Imaging sequences included streamlined-qBOLD (FOV=220mm², 96x96 matrix, nine 5mm slabs, 1mm gap, TR/TE=3s/74ms, BW=2004Hz/px, TI_FLAIR=1210ms, ASE-sampling scheme 𝜏_start:Δ𝜏:𝜏_finish=-16:8:64ms, scan duration 4.5mins), alongside T₁-, T₂- and diffusion (DWI) weighted imaging with apparent diffusion coefficient (ADC) calculation. R₂′ was calculated using a log-linear fit to the mono-exponential regime (𝜏>15ms)⁴ of the ASE data. The intercept of this fit and the spin-echo signal (𝜏=0ms) were subtracted to measure DBV. OEF was then calculated using, $$OEF=\frac{R_2^\prime}{DBV\;\gamma\frac{4}{3}\pi\;\Delta\chi_0\;Hct\;B_0}\tag{1}$$ where parameters are known or assumed constants (Δ𝜒0=0.264x10^-6, Hct=0.34)².Figures 1-3 show T₁-weighted, T₂-weighted, DWI (b-1000 and ADC) and baseline brain oxygen weighted (Spin Echo, R₂′, OEF and DBV) maps over multiple imaging time-points from example patients chosen to demonstrate the potential and limitations of streamlined-qBOLD. Patient characteristics are reported in figure captions, including National Institutes of Health Stroke Scores (NIHSS). It should also be noted that OEF and DBV are physiological measurements, whereas R₂′ is sensitive to the product of these parameters.Streamlined-qBOLD imaging of acute stroke patients in this exploratory cohort appears to deliver similar information on the evolution of oxygen metabolism in the ischaemic penumbra to previous studies using Positron Emission Tomography (PET) imaging⁵. In Figure 1 there is a region of elevated R₂′ on presentation, not within the presenting DWI lesion. This region is later recruited to the 24 hour DWI lesion. This supports the potential of using brain oxygenation imaging to identify tissue at risk of infarction. Figure 2 shows an area of elevated R₂′ which corresponds with the lesion as identified on DWI. This appears to repeat the PET observation of ongoing metabolism within a DWI lesion⁶. Motion artefact can also be seen in the R₂′ image at presentation where CSF suppression was not effective (high signal in the ventricles). Despite this artefact the area of ischemia is still visible in the presenting R₂′ map. Figure 3 shows a lesion in deep grey matter. The R₂′-map demonstrates elevated R₂′ bilaterally due to the high iron content of these structures. Despite this the OEF maps discriminate ischemic from normal tissue and are elevated on the affected side. Further work involving the use of imaging based regional definitions of ischaemia⁷ could help clarify the role of R₂′ and OEF in defining regions of metabolic stress and the relevance of these regions to final infarct outcome. Future methodological developments will concentrate on improving robustness to subject motion (a particular problem in this patient cohort) and improving the quantification of OEF and DBV.Streamlined-qBOLD offers metabolic information in an acute patient population which is complimentary to the current methodologies. Resting brain oxygenation characteristics are demonstrated to vary between regions with different tissue outcomes. This imaging approach has the potential to refine the identification of the ischemic penumbra.