An existing MR sequence, TRUST (T2-relaxation-under-spin-tagging), is adapted in order to obtain spatially localised T2 measurements for venous blood. T2-encoding, and hence determination of venous oxygenation, is achieved via localised encoding of the longitudinal magnetisation, that is then decoded in the sagittal sinus. Saturation pulses enable spatial localisation by removing signal from unwanted brain regions. Thus, hemispheric and global T2 measurements are acquired and compared. The delay between labelling and arrival of tagged venous blood in the sagittal sinus is evaluated and shown to increase in the presence of saturation pulses.