Eigenimage filter application to MR imaging in patients with cerebral infarction

The authors investigate the MR appearance of cerebral infarction using Eigenimage filtering. Eigenimage filtering is a postprocessing technique that enhances desired features while suppressing those that are interfering on MR sequences in the same anatomic region. The authors have used this technique on spin-echo images of infarct sites and used signature vectors and vector analysis technique to separate various zones within the infarct region. Volumes for the differing zones are determined. Five patients with CT and clinical evidence for infarcts ranging from 48 hours to 6 months in age were analyzed by means of the Eigenimage filter technique. An outer transitional zone and an inner persistent zone were discerned in acute and subacute cases. The outer zone returned to normal signal in a patient reimaged 2 months later. Eigenimage filter application to MR imaging in stroke patients allows two distinct zones to be discussed. The outer zone may represent a penumbra of astrocyte proliferation or a region of reversible ischemia. The inner zone likely represents tissue undergoing irreversible ischemic damage