During an analysis technique, the locations of a polyp candidate (and, more generally, a feature) in images of the colon acquired with different orientations of an individual are compared to determine if the polyp candidate is a true positive (an actual polyp) or a false positive (an artifact). In particular, the locations are compared for images when the individual is supine and prone. During this rotation by approximately 180° (and, more generally, a symmetry operation), an actual polyp is expected to also be rotated by approximately 180°. Consequently, the location change during the symmetry operation can be used to validate whether the polyp candidate is an actual polyp. Because the colon is a non-rigid object (with degrees of freedom including rotation, compression and expansion), reference markers (such as haustral folds) are used to assist in determining the location of the polyp candidate in the images acquired in the different orientations.