Removal of EPI Nyquist ghost artifacts with two-dimensional phase correction

Nan Kuei Chen, Alice M. Wyrwicz

Research output: Contribution to journalArticlepeer-review

71 Scopus citations


Odd-even echo inconsistencies result in Nyquist ghost artifacts in the reconstructed EPI images. The ghost artifacts reduce the image signal-to-noise ratio and make it difficult to correctly interpret the EPI data. In this article a new 2D phase mapping protocol and a postprocessing algorithm are presented for an effective Nyquist ghost artifacts removal. After an appropriate k-space data regrouping, a 2D map accurately encoding low- and high-order phase errors is derived from two phase-encoded reference scans, which were originally proposed by Hu and Le (Magn Reson Med 36:166-171;1996) for their 1D nonlinear correction method. The measured phase map can be used in the postprocessing algorithm developed to remove ghost artifacts in subsequent EPI experiments. Experimental results from phantom, animal, and human studies suggest that the new technique is more effective than previously reported methods and has a better tolerance to signal intensity differences between reference and actual EPI scans. The proposed method may potentially be applied to repeated EPI measurements without subject movements, such as functional MRI and diffusion coefficient mapping.

Original languageEnglish (US)
Pages (from-to)1247-1253
Number of pages7
JournalMagnetic Resonance in Medicine
Issue number6
StatePublished - Jun 2004
Externally publishedYes


  • EPI
  • Echo planar imaging
  • Nyquist ghost artifact

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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