Although the approval of recombinant tissue plasminogen activator (rtPA) for the treatment of acute ischaemic stroke has been based on the primary imaging technique of conventional cerebral computerised tomography (CT),¹ newer and more refined magnetic resonance (MR) techniques are unrelentlessly extending into this particular field of emergency medicine, stimulated by the important hope that these new techniques could help to prolong the therapeutic time window beyond the 3 hour limit in selected patients. Several recent papers have clearly demonstrated that the mismatch concept,² though leading to diagnostic pitfalls in a small number of cases as well, seems to be helpful in …