Nyquist ghost elimination for diffusion MRI by dual-polarity readout at low b-values

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Abstract
Dual-polarity readout is a simple and robust way to mitigate Nyquist ghosting in diffusion-weighted echo-planar imaging but imposes doubled scan time. We here propose how dual-polarity readout can be implemented with little or no increase in scan time by exploiting an observed b-value dependence and signal averaging. The b-value dependence was confirmed in healthy volunteers with distinct ghosting at low b-values but of negligible magnitude at b = 1000 s/mm2. The usefulness of the suggested strategy was exemplified with a scan using tensor-valued diffusion encoding for estimation of parameter maps of mean diffusivity, and anisotropic and isotropic mean kurtosis, showing that ghosting propagated into all three parameter maps unless dual-polarity readout was applied. Results thus imply that extending the use of dual-polarity readout to low non-zero b-values provides effective ghost elimination and can be used without increased scan time for any diffusion MRI scan containing signal averaging at low b-values.
Funding Information
  • Gustav V Jubilee Clinic Cancer Research Foundation (2020:316)
  • Lion’s Cancer Research Fund of Western Sweden (2021:11)
  • the Sahlgrenska University Hospital Research Funds (SU-984679)
  • Stiftelsen Assar Gabrielssons Fond (FB22-29)
  • The Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (ALFGBG-942659)
  • Cancerfonden (CAN 2018/628)

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