In MRI, superimposition of a tissue image from outside the field of view on the opposite side of the desired image, usually in the phase-encode direction, due to an inadequate number of phase-encoding measurements for the size of the field of view. Inadequate sampling in the frequency-encoding direction can also cause wraparound or aliasing, but this finding is less common with modern MR equipment. SYN: wraparound artifact. [L. alias, otherwise, fr. alius, other]