Asymmetric SE 180->90 position shift

Use Asymmetric SE 180>90 position shift with fMRI scans that are acquired with Mode: 2D, Family: Echo Planar Imaging, Pulse: Spin Echo EPI.

The Spin Echo EPI sequence is insensitive to field inhomogeneity, which means that it is also insensitive to the BOLD (blood oxygen level dependent) effect. The BOLD effect is what creates the signal intensity changes that occur during task activation on/off states.

The Gradient Echo EPI sequence is sensitive to all susceptibility induced field variations that result in signal loss when compared to a Spin Echo EPI sequence.

The Asymmetric SE 180>90 position shift CV allows shifting the position of the 180 degree refocusing pulse closer to the excitation pulse. This can provide field inhomogeneity sensitivity between Spin Echo and Gradient Echo EPI. Based on TE and the selected offset, BOLD contrast can be enhanced compared to normal SE EPI.