Brendan this diagnosis was the same for me. Not a smoker - not a drinker - I mean at all - I don't touch alcohol. I am a vegetarian, no dairy, and i went to the gym daily. And I didn't even drink coffee or tea! So there you have it. It came out of nowhere though I do have my suspicions as to why!
Sorry about your CT experience - the MRI should be less troublesome though they do ask you not to swallow a lot and of course the minute hey say it it's all you can think of and it's all you want to do!!!

good luck.. Being in shape should help with your recovery!! Take care!!!