Due to changes necessitated by the COVID-19 pandemic, recruitment for the first repeat imaging appointments (i.e. data having ins_index=3 using instancing 2) was subject to different selection criteria over different "phases". This document details the selection criteria and timing of the different recruitment phases of these first repeat imaging appointments. If researchers are interested in selecting participants associated with a particular phase, they can do so by restricting the data by assessment date (Field 53) using the non-overlapping time periods detailed herein.

This resource can be downloaded or viewed using the link: first_repeat_imaging_selection.pdf

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/docs/first_repeat_imaging_selection.pdf