(With apologies to Burleyshirley for going off topic):
No, Barry. Being zapped with radiation doesn't make one radioactive. (There is a different type of radiotherapy, where they insert a radioactive source into one's body next to the cancer, that requires the patient to stay in hospital for a few days because the radiation might be dangerous to others but the 'external beam' radiotherapy I'm having isn't like that)
I did have a scan several months ago where I was injected with a radioactive liquid four hours beforehand though. I was allowed to go shopping in the period between the injection and the scan but I was given strict instructions to keep my distance from other people, especially young children and pregnant women.