Describe your problem in detail.

Prompted by work happening in #1831, but is actually a consequence of #1725.

Having acquired data with all scanner-generated derivatives enabled, I can confirm that the "*_TRACEW" image produced by the Siemens product DWI sequence is not the trace of the diffusion tensor, as the specification currently states; rather, it is a "trace-weighted image", being the mean intensity of b>0 data.

(Unfortunately I did not think to obtain multi-shell data to find out whether the sequence does what one would naturally expect for multi-shell data, being a 4D series with a trace-weighted image volume per unique b-value. It's possible that whether or not it does this will depend on the scanner base software version / sequence used.)

Describe what you expected.

No response

BIDS specification section

https://bids-specification.readthedocs.io/en/latest/modality-specific-files/magnetic-resonance-imaging-data.html#diffusion-imaging-data