Abstract: A method and apparatus for visualization of tissue areas insufficiently supplied with blood, in particular in the event of an acute stroke, by evaluation of local fluctuations of a BOLD signal produced and recorded by an apparatus; passed to a data detection device; pre-processed in a first evaluation device for image recognition; subjected to a time delay analysis applied to the BOLD signal data of at least one voxel in a second evaluation device in order to calculate a time dependent positive and negative phase shift of the BOLD signal data; and assigned a reference value which is an estimated time delay between the BOLD signal data of at least one voxel and the entire average time course of a selected region during the recording of the BOLD data in order to estimate modified BOLD signal data which are used to determine at least one area of the hypoperfused tissue.