Abstract
Object
To further improve the quality and robustness of the point-spread function (PSF) mapping method for fully automatic and accurate correction of geometric distortions in EPI at ultra high field such as 7 Tesla with high fidelity.
Materials and methods
Conventional gradient-echo EPI and corresponding PSF reference data in phantoms and in in vivo measurements of the human brain were acquired at 7 Tesla. To accurately determine and correct geometric distortions, i.e., in peripheral areas, the method calculates the local shift in the distorted phase-encoding dimension instead of the non-distorted spin-wrap encoding dimension. The results of the proposed method are compared with those originally demonstrated (Zaitsev et al. Magn Reson Med (2004) 52:1156–1166).
Results
The results show that the proposed method allows measurement and correction of the geometric distortions in EPI with high accuracy, and reduction of residual blurring. In addition, this method prevents errors in the shift map induced by PSF-ghost artifacts.
Conclusion
More precise mapping and correction of pixel shifts and blurring is accomplished with the proposed improvements. Errors in the shift map that are caused by PSF-ghost artifacts in the multi-shot PSF acquisition, e.g., from small motion during the reference scan, do not affect the improved shift estimation method.
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References
Mansfield P (1977) Multi-planar image formation using NMR spin-echoes. J Phys C 10: L5–L58
Weisskoff RM, Davis TL (1992) Correcting gross distortion on echo-planar images. In: Proceedings of the SMRM 11th annual meeting, Berlin, (abstract 4515)
Jezzard P, Balaban RS (1995) Correction for geometric distortion in echo planar images from B0 field variations. Magn Reson Med 34(1): 65–73
Reber PJ, Wong EC, Buxton RB, Frank LR (1998) Correction of off resonance related distortion in echo-planar imaging using EPI-based field maps. Magn Reson Med 39(2): 328–330
Hutton C, Bork A, Josephs O, Deichmann R, Ashburner J, Turner R (2002) Image distortion correction in fMRI: a quantitative evaluation. Neuroimage 16(1): 217–240
Wan X, Gullberg GT, Parker DL, Zeng GL (1997) Reduction of geometric and intensity distortions in echo-planar imaging using a multi reference scan. Magn Reson Med 37(6): 932–942
Chen NK, Wyrwicz AM (1999) Correction for EPI distortions using multi-echo gradient-echo imaging. Magn Reson Med 41(6): 1206–1213
Chen NK, Wyrwicz AM (2001) Optimized distortion correction technique for echo planar imaging. Magn Reson Med 45(3): 525–528
Zeng H, Gatenby JC, Zhao Y, Gore JC (2004) New approach for correcting distortions in echo planner imaging. Magn Reson Med 52: 1373–1378
Robson MD, Gore JC, Constable RT (1997) Measurement of the point spread function in MRI using constant time imaging. Magn Reson Med 38(5): 733–740
Zeng H, Constable RT (2002) Image distortion correction in EPI: comparison of field mapping with point spread function mapping. Magn Reson Med 48(1): 137–146
Zaitsev M, Hennig J, Speck O (2004) Point spread function mapping with parallel imaging techniques and high acceleration factors: fast, robust, and flexible method for echo-planar imaging distortion correction. Magn Reson Med 52: 1156–1166
Stevick JW, Harding SG, Paquet U, Ansorge RE, Carpenter TA, Williams GB (2008) Gaussian process modeling for image distortion correction in echo planar imaging. Magn Reson Med 59: 598–606
Edelstein WA, Hutchison JMS, Johnson G, Redpath TW (1980) Spin wrap NMR imaging and applications to human whole-body imaging. Phys Med Biol 25: 751–756
Ahn CB, Cho ZH (1987) A new phase correction method in NMR imaging based on autocorrelation and histogram analysis. IEEE Trans Med Imag MI 6: 32–36
Ashburner J, Friston K (1997) Multimodal image coregistration and partitioning—A unified framework. NeuroImage 6: 209–217
Brett M, Johnsrude IS, Owen AM (2002) The problem of functional localization in the human brain. Nat Rev Neurosci 3: 243–249
Toga AW, Thompson PM, Mori S, Amunts K, Zilles K (2006) multimodal atlases of the human brain. Nat Rev Neurosci 7: 952–966
Deichmann R, Gottfried JA, Hutton C, Turner R (2003) Optimized EPI for fMRI studies of the orbitofrontal cortex. Neuroimage 19: 430–441
Speck O, Stadler J, Zaitsev M (2008) High resolution single-shot EPI at 7T. Magn Reson Mater Phy 21(1): 73–86
Weiskopf N, Hutton C, Josephs O, Turner R, Deichmann R (2007) Optimized EPI for fMRI studies of the orbitofrontal cortex: compensation of susceptibility-induced gradients in the readout direction. Magn Reson Mater Phy 20(1): 39–49
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J.-Y. Chung and M.-H. In contributed equally to this work.
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Chung, JY., In, MH., Oh, SH. et al. An improved PSF mapping method for EPI distortion correction in human brain at ultra high field (7T). Magn Reson Mater Phy 24, 179–190 (2011). https://doi.org/10.1007/s10334-011-0251-1
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DOI: https://doi.org/10.1007/s10334-011-0251-1