Strong feelings of dread by any chance??

This sounds as Cheryl says like a bit of post traumatic stress. At least you have connected the dots and realised the discomfort you felt over image relates to your radiation therapy experience. I have no idea what to do about it other than echo the thoughts of Cheryl and Anne Marie but at least you have a starting point with a counsellor.

You are also not alone in your "nuttiness". Alex also suffers sort of flashbacks which can be brought on by all sorts of stuff incluging smells and sounds. This is his manifestation of PTSD.

Whilst I am 99% sure you are describing a form of stress associated with what you have been through, it wouldn't hurt to keep in mind that feelings of dread or anxiety can be hormonally driven and reflect fluctuations of hormone levels. Don't know where you are on the menopausal continuum... or maybe your rads have fried something that is causing this? Just a thought...