MPM B1 map -- cannot extract flip angle

We are trying to put data from MPM acquisition into BIDS. Fortunately, the data actually come from the same scanner that the example dataset available at OSF , which made the job easier than we thought. However, for the B1 map images, we are unable to extract FlipAngle using various dicom converters. We initially tried dcm2niix, it produces a 4D volume that is consistent with the number of 3D images that we expect, but no FlipAngle is extracted. The example dataset has a set of 3D images, and is extracted using SPM12. We next tried that – although 3D volumes were output, FlipAngle is reported as 0 in all of them.

The BIDS field FlipAngle corresponds to DICOM tag 0018,1314. This suggests that the tag 0018,1314 is missing from your DICOM data. Perhaps your DICOMs were corrupted by an anonymization step. Try converting the DICOM images direct from the scanner prior to being tampered with.

As Chris noted, the tag should be there at 0018,1314. In AFNI there is a small utility for DICOM tag viewing:

dicom_hdr somedicomfile.dcm | grep -i “ACQ Flip Angle”
0018 1314 10 [1674 ] // ACQ Flip Angle//90.00000

While I am not sure it is always correct, it does seem to always be there, at least in a quick review of about 5000 DICOM files.

dicom_hdr produces this:
0018 1314 2 [1708 ] // ACQ Flip Angle//0

The only number that varies between individual .ima files is the one within brackets (1708 here).