contrast reversal

contrast reversal

An MRI term for image alteration, in which dark parts of the image become bright and vice versa; it is most prevalent in sequences utilising an extended repetition time.
References in periodicals archive ?
Besides the Flux effect, the Kinegram Colors feature on the $20 note also contains delicate fine line movements, the virtual 3D effect 'surface relief' and the hallmark Kinegram effect 'diffractive watermark', displaying a contrast reversal upon rotation of the feature by 180 degrees.
Contrast reversal: When the data page or ID card is tilted, the contrast on the surface of the central eagle motif is reversed, so that the initially light-coloured eagle now appears dark on a light hexagonal surface.
This causes spatial frequency dependent contrast reversals that prevent direct interpretation of the image.