Stefan Skare1,2, Roland Bammer1
1Radiology, Stanford University,
Stanford, CA, United States; 2MR Center, Clinical Neuroscience,
Karolinska Institute, Stockholm, Sweden
By
acquiring EPI data both with positive and negative phase encoding blips one
obtains two oppositely distorted images.
The reversed gradient polarity (RGPM) method can be used to correct
these images by searching for a displacement field that explains their
difference. However, even if the estimated displacement field is adequate,
the two corrected EPI images have a very low resolution in anatomical regions
that have been too compressed. In this work, we use a Jacobian weighting
scheme to make an informative choice about the combination of the two images
that avoids the inclusion of signals from very compressed regions.