(mahk), the appearance of a light or dark line on a radiograph where there is a concave or convex interface in the subject, a physiologic optical form of edge enhancement. See also: Mach band.
Mach ef·fect
(mahk e-fekt') The appearance of a light or dark line on a radiograph where there is a concave or convex interface in the subject, a physiologic optic form of edge enhancement.