Be proactive and ask ! Don't wait and the perhaps suffer from their stuff ups. What does the form say (assuming he gave you the form to take to the radiographer) ? It should say which side or the radiographer would not know what he/she is to do.
I am in the private system so perhaps things are done differently. Call the radiology department and request clarification.
My breast surgeon sees me, runs his finger along the surgery scar and says how wonderful he is then gives me the form to have the mammogram on the other side. If things need to be discussed I would be called in to see him otherwise I ring and the receptionist says all is OK.
Please, if you are uncertain, make sure you get the answers you want.