1. An image data processing method comprising: registering a first set of 3D image data and a second set of 3D image data of at least partially overlapping spatial regions of a porous sample material to achieve voxel alignment, said first set of 3D image data corresponding to a dry sample of said sample material and said second set of 3D image data corresponding to a fluid saturated sample of said sample material; and processing said registered image data to obtain integrated image data by superposition of voxels of said first set of 3D image data with correspondingly registered voxels of the second set of 3D data image to obtain a quantitative estimate of the spatial distribution of a property of the sample material not available from said first set of 3D image data and said second set of 3D image data alone.