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bids-standard / bids-2-devel

Discussions and suggestions of backwards incompatible changes to BIDS
https://bids.neuroimaging.io/
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Remove RepetitionTime metadata field #4

Open tsalo opened 4 years ago

tsalo commented 4 years ago

This information is already stored in the NIfTI header (as the current field description seems informed of). Apparently this field isn't intended to override the header either (which would have been a bad idea anyway), so it's basically useless data duplication, with all the potential inconsistency issues that brings. I would recommend entirely removing this field in order to minimize ambiguity.

Original authors: Unknown

tsalo commented 4 years ago

@marcelzwiers wrote:

This information is already stored in the NIfTI header

You mean in pixdim4? True but kind of cumbersome to read, and the standard tools and libraries can't do it

tsalo commented 4 years ago

@effigies wrote:

I would recommend entirely removing this field in order to minimize ambiguity.

I would oppose this on the grounds that TR may not be constant (see VolumeTiming), in which case pixdim4 is insufficient metadata.

effigies commented 4 years ago

RepetitionTime is mutually exclusive with VolumeTiming, so I don't see that as problematic.

Also, what tools have problems with pixdim4?

neurolabusc commented 4 years ago

In general, the NIfTI and BIDS headers store mutually independent information, which prevents issues of precedence for conflicting information.For most MR sequences, RepetitionTime and pixdim4 are the same. I also commented on this during the development of BIDS. One major reason for storing this is that SPM would not retain pixdim4. Therefore, if SPM was used at any time to modify a NIfTI image, the resulting image would no longer include pixdim4. Therefore, the inclusion of RepetitionTime for BIDS had strong pragmatic motivation.