IntendedFor Specification

To initiate field map or pepolar distortion correction, BIDS apps like fMRIprep and QSIprep depend on fields in the JSON sidecars. In particular, the IntendedFor field should be added to the JSON sidecar of the appropriate field map. The IntendedFor field is a key-value pair that tells a compliant BIDS app what target image to correct with that particular field map.

The Problem

Unfortunately, DICOM-to-BIDS conversion tools do not always generate and populate the optional IntendedFor field, despite the fact that the field and its values may be necessary for some apps to implement optimal susceptibility distortion correction. In addition, it is entirely possible to only discover after the fact that you should have added an IntendedFor field!

Comparison of ezBIDS and HeuDiConv

In the ezBIDS lesson, you provided an IntendedFor value, and that key-value pair was created in the accompanying JSON sidecar for the field map. In the HeuDiConv lesson, the IntendedFor field was not created in the JSON sidecar at all! You can verify this by opening the field map JSON files from each dataset with a code editor, like VScode, and searching for IntendedFor.

For example, in the ezBIDS dataset my fmap/sub-188_phasediff.json contains this entry:

and the fmap/sub-188_dir-PA_epi.json created by ezBIDS also contains the IntendedFor entry:

IntendedFor fields are NOT present in the corresponding Heudiconv sidecars!

Note

It should be possible to generate and populate the Intendedfor filed in the HeuDiConv heuristic. I have just never managed it.

SDC 2 (15)