Me too. It was a mobile mammogram unit and apparently if another patient arrives when you are 'being done' their steps can wobble the machine and cause a shadow.
Don't forget that you can ring the hospital and ask why you have been referred. If you don't know the name of the consultant, your GP should be able to tell you, and you can ask for their secretary. If not, a call to the department should be enough. There will be some sort of note on your file, and if not, ask for a message to go to the consultant and for someone to call you back.
I agree with the others that it sounds straightforward, but wish you luck
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