Generalize AcquisitionDuration to any MR scan

[effigies]

Via @jcohenadad @ https://neurostars.org/t/why-should-acquisitionduration-and-repetitiontime-be-mutually-exclusive/21153

In the context of anatomical data (T2starw), we need to access the total acquisition time (a.k.a. “TA”) in order to compute SNR per unit time measures.

Our current definition of AcquisitionDuration is:

Duration (in seconds) of volume acquisition. Corresponds to DICOM Tag 0018,9073 Acquisition Duration. This field is mutually exclusive with RepetitionTime.

This could be made applicable to all MR scans by updating the term to:

Duration (in seconds) of volume acquisition. Corresponds to DICOM Tag 0018,9073 Acquisition Duration.

In the BOLD context, we can add the additional note "This field is mutually exclusive with RepetitionTime.".

Thoughts?

[jcohenadad]

This might get trickier. I looked at the DICOM metadata from a few sequences (Siemens T1w MPRAGE, Siemens GRE), and the Tag 0018,9073 is not present. However, another one is (under 'private') and it does correspond to the volume acquisition duration (the infamous "TA"):

Given that this is under a private field, I fear there is no standardization across vendors about how total acquisition time is encoded in DICOM data. Feedback would be appreciated here.

[jcohenadad]

FWIW, I looked at an enhanced Dicom from a Philips MPRAGE, and the 0018,9073 is there:

[effigies]

This file by @dangom shows 0051,100a as TotalAcqTime, so that's at least a vote of confidence. I can't find any declarations of this field in a DICOM conformance statement... in fact, they claim they support 0018,9073, but it's only under MR spectroscopy in some older statements. We would probably need to check both.

Looks like GE has its own "Acquisition Duration" and 0051,100a tags (via https://www.gehealthcare.com/-/media/1150764f8c7b41a79c134e1e87e03204.pdf?la=en-us; also attached in case that URL goes dead):

Attribute Name	Tag	VR	VM
Store level of Functional Image	0051,100A	SL	1
Acquisition Duration	(0019,105A)	FL	1