PDT2 Multiecho Images BIDS Specs

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#1

Hello All,
I am working with PDT2 images, which dcm2niix converts into two echos.

I found a discussion about naming multiecho PDT2 images here. https://github.com/bids-standard/bids-specification/issues/223
However couldnt figure out what was agreed to under BIDS spec.

Can someone share more information on this?
I have PDT2 sequence converted into two nifti files(echo1 and echo2). Per the current specs i found the modality label as PDT2map but how to encode echos?

#2

Hi Suyash,

BEP-001 is in review stage, so it has a PR here and is rendered here.

According to Conventional MRI suffixes, it looks like PDT2 is a valid suffix and, accord to Anatomical template the echo- entity will be valid for general anatomical images.

Obviously things are subject to change until BEP-001 is merged, but these seem uncontroversial…

1 Like
#3

This came up again recently, and it seems that there are three use-cases that are supported by the BIDS specification (as of 1.7.1).

  1. A single, 4D series, intended to be viewed as a group by switching between volumes: *_PDT2.nii.gz, and the EchoTime metadata should be an array.
    • Tools expecting to work with PDw or T2w images may not be prepared to extract these volumes.
  2. 2 3D volumes intended to be viewed by tools/users independently: *_PDw.nii.gz and *_T2w.nii.gz, each with their own scalar EchoTime value.
    • Note that there is no way in BIDS to declare that these two volumes are already in register.
  3. 2 3D volumes intended to be used for quantitative estimates of physical parameters: *_echo-1_{MESE,MEGRE}.nii.gz and *_echo-2_{MESE,MEGRE}.nii.gz, each with their own scalar EchoTime value.
    • These may not be recognized by tooling as being PDw or T2w.