Advanced
Technical
IVT
Nyquist ghost
MRI artifact appearing as displaced duplicate image due to phase inconsistencies in EPI sequences.
Full Definition
Nyquist ghost is a characteristic artifact in echo planar imaging sequences that appears as a faint, spatially shifted duplicate of the main image. This artifact results from phase inconsistencies between odd and even echo readouts in the rapid k-space traversal typical of EPI. Nyquist ghosts are particularly problematic in functional MRI and diffusion imaging, where they can contaminate signal measurements and compromise data quality if not properly corrected during reconstruction.
Usage
Usage note: Always capitalize Nyquist as it's named after Harry Nyquist; commonly seen in EPI-based sequences.
In Context
- "Prominent Nyquist ghost required image reconstruction with improved phase correction." — Quality control report
- "The EPI sequence showed minimal Nyquist ghosting after optimization." — Technical assessment
Also known as
EPI ghost
phase ghost
Don't confuse with
motion artifact
wrap artifact