Spatial Resolution, Distortion and Magnification

What Spatial Resolution Means

Spatial resolution is the ability of an image to show small structures and sharp edges as separate, distinct details. It is measured in line pairs per millimeter (lp/mm); the more pairs per millimeter a system can separate, the finer the detail. It depends mainly on focal spot size, source-to-image distance (SID), object-to-image distance (OID) and motion. In a digital detector, the detector element (DEL) size, or pitch, sets an upper limit, because a detail smaller than one DEL cannot be shown separately, so smaller DELs allow higher spatial resolution. Likewise, pixel size equals field of view divided by matrix size, so a larger matrix gives smaller pixels. mAs and kVp control receptor exposure, image contrast and noise, but they do not change geometric sharpness.