Please review this list of FAQs before contacting EndUser@nki.rfmh.org with any questions about using the NKI-RS data resource.
I’m processing resting-state functional data (1400-acquisition) from the longitudinal discovery of brain development trajectories sub-study. I wanted to ask how many volumes should be discarded as dummy scans? I’ve seen some studies discard the first 10 volumes?
Of note, we don’t typically advise end-users on how they should process our data. Since there are so many different pre-processing options, we leave these choices to the researcher. The rational for discarding the first volumes is to avoid T1w equilibrium effects on the BOLD data. On Siemens machines (we are using a Siemens Tim Trio), the scanner generates dummy scans as part of the prescan to avoid this artefact. Only after equilibrium has been achieved the scanner starts collecting data. We therefore do not need to discard any data at the beginning of the scan. This might not be the case for other scanners. But when in doubt, it’s always good to look at the data. If the signal across the brain is initially high and decreases volume-by-volume to some baseline, then you should throw away those initial volumes.
NKI-RS data can be accessed via two independent databases with the same NKI-RS DUA. See details about access to LORIS or COINS.