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SyneRBI / SIRF

Main repository for the CCP SynerBI software
http://www.ccpsynerbi.ac.uk
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MR position and table location #1023

Open KrisThielemans opened 2 years ago

KrisThielemans commented 2 years ago

We currently use the ISMRMRD header position field to find positioning https://github.com/SyneRBI/SIRF/blob/25d5c01b190b2fe02b612f88ac15c51aa712679a/src/xGadgetron/cGadgetron/gadgetron_data_containers.cpp#L1713 I recall discussions on patient_table_position. @rijobro created an issue for that https://github.com/ismrmrd/siemens_to_ismrmrd/issues/42 which now has a reply (referring to further discussions in a non-accepted PR).

I thought I'd create an issue here to make sure we don't forget about this. Or is it irrelevant @DANAJK ?

DANAJK commented 2 years ago

Position is an offset of the imaged region from the patient coordinate system origin. It’s similar to DICOM imageOrientationPatient, except I assume it refers to the location of the Fourier Transform origin in image space (roughly the middle of the image) and not the top left pixel.

patient table position relates to the position of the bed and thus to the physical gradients.

Some MR effects such as shim fields, gradient nonlinearities and concomitant fields relate to the gradient isocentre, which is not necessarily the patient origin. You would need the bed position to sort out the relation between isocentre and patient origin.

So, yes, they are both relevant.

KrisThielemans commented 2 years ago

@DANAJK do you know of any updates on this that aren't documented here yet?