Description

Instead of subtracting control-Label, we want to calculate the perfusion-weighted image (pwi.nii), based on the decoding defined in the import.

Requirements

Some changes that are needed in the ASL module:
(for multiPLD case, see more info in #759 )

• Registration (ASL module - step 3)
  -> xASL_wrp_RegisterASL:
  -- Step H: There's this Pairwise subtraction that creates this PWI_Clipped image. Jan checked that this PWI_Clipped image is only used in this function and in the Realign [this Clipped_ORI can be deleted in the future because is not used anywhere else]. So, since in this function we want to obtain a single volume:

  • If Hadamard: skip this pairwise subtraction and run the decoding function instead, and then average all the PLDs
  • if multiTE: use only the first TE (will just write as a comment, since this function is only for multiPLD changes)

  And after this, the PWI_Clipped is going to work irrespectively how the Clipped was created (bRegistrationCBF loop in the step H)

• Resampling (ASL module - step 4)
  ->xASL_wrp_ResampleASL: After step6 (check header) we need to change some things
  -- Step6: We need to create PWI4D, so:

  • for Hadamard: there's a single control, so we use it (the first of the block)
  • for multiTE: discard all but the first TE (this has to be addressed later)
    -- Step8: pair-wise subtraction: (for multiPLD case, see more info in Adapting ExploreASL pipeline to multi-PLD data #759 )
  • for Hadamard: Paired subtraction is not done, we use the decoding function.
  • for multiTE: same as Hadamard, using the decoding function.
  • Hadamard & multiTE: we save them as PWI4D. But then for the PWI, we average across repetitions but not across TEs/PLDs.

How to test

Release notes

Calculates PWI image with Hadamard decoding function