A correction method for streak artifacts in gradient-echo EPI using spin-echo EPI reference data

• Published in: Magma (New York, N.Y.) Vol. 25; no. 3; pp. 205 - 213
• Main Authors: Chung, Jun-Young, Han, Yeji, Cho, Zang-Hee, Park, HyunWook
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2012
• Subjects: Algorithms; Biomedical Engineering and Bioengineering; Computer Appl. in Life Sciences; Echo-Planar Imaging - methods; Echo-Planar Imaging - standards; Health Informatics; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Imaging; Medicine; Medicine & Public Health; Radiology; Reference Values; Reproducibility of Results; Research Article; Sensitivity and Specificity; Solid State Physics; Subtraction Technique; Streak artifacts; Field inhomogeneity in high field MRI; Gradient-echo EPI; Spin-echo EPI reference scan; Nyquist ghost artifact; Echo planar imaging (EPI)
• ISSN: 0968-5243; 1352-8661
• DOI: 10.1007/s10334-011-0289-0

Objective To analyze the streak artifacts in a gradient-echo echo planar imaging (GE-EPI) sequence and to propose a correction method for the Nyquist ghost artifacts that does not cause streak artifacts in the GE-EPI imaging. Materials and methods Several GE-EPI imaging experiments with various reference scans, using both GE-EPI and SE-EPI scan data, were performed to analyze the streak artifacts and to investigate the spin dephasing phenomena of the GE-EPI reference scan. In addition, the analysis based on the spin dephasing was undertaken in order to demonstrate that the SE-EPI reference data can be used for the correction of the GE-EPI main scan data. Results The experimental results confirmed that the improvement of the reference data using either signal averaging or a large flip angle cannot guarantee perfect correction of the streak artifact if the noise is not completely removed. Due to the main field inhomogeneity, the spins of the GE-EPI reference data were dephased in multiple echo signals. The proposed correction method, which uses a SE-EPI reference scan for the GE-EPI images, eliminates the N/2 ghost artifacts without producing streak artifacts. Conclusion It is believed that the proposed phase error correction scheme can improve the EPI performance in high field MRIs with higher magnetic field inhomogeneities.