A computer implemented image processing method is disclosed. The method comprises applying a selected filter to image data to identify a subset of the image data that defines a number of discrete spatial regions of the image wherein the discrete spatial regions comprise less than all of the area of the image; selecting, from a data store, a set of quantitative image metrics wherein the quantitative image metrics are selected based on descriptor data indicating tissue type, determining, for each discrete spatial region, a sample region data value for each of the set of quantitative image metrics based on the subset of image data associated with the or each discrete spatial region, using the descriptor data to select, from the data store, at least one comparator set of tissue model data values, wherein each comparator set is associated with a different corresponding comparator tissue structure and each comparator set comprises data values of the set of quantitative image metrics for the corresponding comparator tissue structure; comparing the sample region data value for each discrete region with the at least one comparator set; and in the event that the sample region data value for the or each discrete region matches the comparator set, determining based on an identity of the corresponding comparator tissue structure, whether to further analyse the or each discrete region.