I remember heated debate over whether the protocol and a couple other advancements in radiology could be applied retrospectively or not. I think Reefrad thought this particular protocol might be used prospectively, but it could not be used retrospectively. I may be wrong.
Looking at your cite, I think this is a key sentence.
I think the interpretation part might be possible retrospectively, but the actual scans could not be conducted retrospectively after the relevant time period or window has passed. Just my .02 cents.
Senti: Thanks for sharing that post, I hadn't been aware of it. Timing is quite interesting, and I hadn't even considered calibration and consistency issues before.