A computer-implemented method, comprising: generating (1102, 1202, 1302), with an imaging system, spectral projection data of a subject, including at least first spectral projection data corresponding to a first energy range and second spectral projection data corresponding to a second energy range, wherein the first and the second energy range are different; constructing an image from a combination of the spectral projection data; constructing (1104, 1204, 1304) a set of basis images for the energy ranges and from the spectral projection data; constructing (1106, 1206, 1306) a multi-dimensional histogram from the set of basis images, wherein the multi-dimensional histogram includes at least two axes, a first corresponding to a first basis component and a second corresponding to a second basis component, and the multi-dimensional histogram includes a set of clusters, including one cluster for each material represented in the spectral projection data; visually displaying, concurrently, the image and the multi-dimensional histogram; and comparing (1108, 1112, 1208, 1308) the displayed multi-dimensional histogram with a multi-dimensional histogram for known normal tissue and/or with a multi-dimensional histogram for known abnormal tissue, and: determining (1110, 1210, 1310) a presence of an abnormality in the displayed multi-dimensional histogram based on a cluster in the displayed multi-dimensional histogram being absent in the multi-dimensional histogram for known normal tissue; and/or determining (1110, 1210, 1310) a presence of the abnormality in the displayed multi-dimensional histogram based on a cluster in the displayed multi-dimensional histogram present in the multi-dimensional histogram for the known abnormal tissue. generating (1102, 1202, 1302), with an imaging system, spectral projection data of a subject, including at least first spectral projection data corresponding to a first energy range and second spectral projection data corresponding to a second energy range, wherein the first and the second energy range are different; constructing an image from a combination of the spectral projection data; constructing (1104, 1204, 1304) a set of basis images for the energy ranges and from the spectral projection data; constructing (1106, 1206, 1306) a multi-dimensional histogram from the set of basis images, wherein the multi-dimensional histogram includes at least two axes, a first corresponding to a first basis component and a second corresponding to a second basis component, and the multi-dimensional histogram includes a set of clusters, including one cluster for each material represented in the spectral projection data; visually displaying, concurrently, the image and the multi-dimensional histogram; and comparing (1108, 1112, 1208, 1308) the displayed multi-dimensional histogram with a multi-dimensional histogram for known normal tissue and/or with a multi-dimensional histogram for known abnormal tissue, and: determining (1110, 1210, 1310) a presence of an abnormality in the displayed multi-dimensional histogram based on a cluster in the displayed multi-dimensional histogram being absent in the multi-dimensional histogram for known normal tissue; and/or determining (1110, 1210, 1310) a presence of the abnormality in the displayed multi-dimensional histogram based on a cluster in the displayed multi-dimensional histogram present in the multi-dimensional histogram for the known abnormal tissue. determining (1110, 1210, 1310) a presence of an abnormality in the displayed multi-dimensional histogram based on a cluster in the displayed multi-dimensional histogram being absent in the multi-dimensional histogram for known normal tissue; and/or determining (1110, 1210, 1310) a presence of the abnormality in the displayed multi-dimensional histogram based on a cluster in the displayed multi-dimensional histogram present in the multi-dimensional histogram for the known abnormal tissue.