Question Posted 05/29/15:
There were patients whose images I downloaded because the most recent ADNI Merge Data Sheet showed me that they had both baseline scans AND two-year follow-up (24 month) scans. However, when I went back to download the follow-up images after processing the baseline images, nine of the ten patients did not have any followup scans.

Could you please inform me why the ADNI merge data sheet may say the patients have a 24 month follow-up when the data is not available for download?
Response posted 05/30/15 by Michael weiner:
There are two possible answers to your question:
1) They did have the scans, they are uploaded to LONI,and you are looking in the wrong place. You can query ADNI with the specific subject code numbers to ask if these scans are in LONI
2) They did have the scans, but they are still being QC'd by the Mayo group and thus are in quarantine. Through the ADNI website you can ask for the status of these scans