Collecting tilted spin echo field map scans correctly

Software: Siemens VE11 Skyra and product spin echo sequence

Typically with straight transverse slices, we collect an A–>P SE scan and then set the second SE scan to P–>A by setting it to -180 degrees. However, when using autoalign, our A–>P scans don’t start at 0, but usually some slight rotation (e.g. -2.5 deg). In those cases, should we set our P–>A scan to -180 still or should we set it in this example to -177.5 to account for that rotation?


Hi @mrribbits , welcome to NeuroStars!
In your example, there should be indeed a 180 degrees difference between both directions, so you should write + 177.5 for you PA scan.

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Thank you! Am I correct to assume that in the above example, if I had used 180 instead of 177.5, the distortion correction would still do a pretty decent job?

Well, I guess so, but this should be better checked by acquiring two images, one with 180 and another with 177.5 and see how much the distorsions differ between them.

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