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.
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.
Authors: Ralf Lützkendorf; Robin M Heidemann; Thorsten Feiweier; Michael Luchtmann; Sebastian Baecke; Jörn Kaufmann; Jörg Stadler; Eike Budinger; Johannes Bernarding Journal: MAGMA Date: 2018-09-17 Impact factor: 2.310
Authors: Michael Hanke; Florian J Baumgartner; Pierre Ibe; Falko R Kaule; Stefan Pollmann; Oliver Speck; Wolf Zinke; Jörg Stadler Journal: Sci Data Date: 2014-05-27 Impact factor: 6.444
Authors: Myung-Ho In; Shinho Cho; Yunhong Shu; Hoon-Ki Min; Matt A Bernstein; Oliver Speck; Kendall H Lee; Hang Joon Jo Journal: Neuroimage Date: 2017-06-27 Impact factor: 6.556
Authors: Joana R Loureiro; Gisela E Hagberg; Thomas Ethofer; Michael Erb; Jonas Bause; Philipp Ehses; Klaus Scheffler; Marc Himmelbach Journal: Hum Brain Mapp Date: 2016-09-23 Impact factor: 5.038
Authors: Meng Li; Marie Woelfer; Lejla Colic; Adam Safron; Catie Chang; Hans-Jochen Heinze; Oliver Speck; Helen S Mayberg; Bharat B Biswal; Giacomo Salvadore; Anna Fejtova; Martin Walter Journal: Eur Arch Psychiatry Clin Neurosci Date: 2018-10-23 Impact factor: 5.270