Calculate Slice ReadoutTime

  • The SliceReadoutTime is a parameter that is needed for quantification of 2D ASL acquisitions as the timing of the readout of each slice (and hence quantification) differs. For 3D, this parameter can be ignored or set to a dummy value.

  • This parameter can be obtained by calculating (minTR-PLD-labdur)/nSlices for pCASL or (minTR-TI)/nSlice for PASL. In other words, by removing the labeling part from the TR, you end up with the part taken up to readout all the slices. The minTR can differ from the actual TR as sometimes empty waiting time is included at the end of the TR.

  • The minimal TR (minTR) should be available at the scanner, in the DICOM, or in the protocol export.

  • The TI for PASL here should be the largest TI value available

  • For a consensus/white paper default ASL sequence, these parameters should be around PLD=1800 ms, labdur=1800 ms, TI = 1800 ms. As the SliceReadoutTime is around 30-50 ms usually, with e.g. 20 slices the minTR should be around 4400 ms or 2600 ms for PCASL or PASL respectively.