If the interview determined it was unsafe for a participant to go through some or all of the imaging stations (MRI and DXA) then they indicated the reasons using the boxes that appear when they flag a station as unsafe.

This resource can be downloaded or viewed using the link: scr_unsafe.png

If you have wget available (typically on linux systems), then you can also obtain a copy using the command

 wget  -nd  biobank.ctsu.ox.ac.uk/ukb/ukb/images/scr_unsafe.png