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Incorrect slice times for Siemens Vida XA11 #303
This reflects a error in some Siemens XA11 DICOM multi-band images. Perhaps future versions of dcm2niix can include a kludge to work around this. For the moment, Vida users should carefully inspect the slice times recorded in BIDS JSON files.
Consider a diffusion EPI sequence with multi-band acceleration factor 2, 80 slices per volume and a TR of 5.8sec. The FrameAcquisitionDateTime (0018,9074) values are correct, with a range of 5.7sec with forty unique values. However, TimeAfterStart (0021,1104) is incorrect, with 80 unique values evenly spaced from 0..9.15sec (perhaps times if acquisition had been single band).
The current version of dcm2niix ignores the correct 0018,9074 and instead relies on the incorrect 0021,1104. The reason for this is that 0018,9074 was scrambled by XA10 if the user selected de-identification (as 0018,9074 includes the time of time, while 0021,1104 is only relative to the start of the sequence).
I will attempt to get a shareable dataset. Note that the user reported this problem for diffusion multi-band images, but fMRI data from the same system included the correct 0021,1104.