Not easy at first but you will get the hang of it, drink lots of water the day before, they should have given you the list of food to eat and start that diet before the scan. The list they gave me was the opposite of what I thought was going to be. The nurses also said an enema would not be advised for treatments but would be ok for initial CT scan. For your mapping scan it would not be good I was told.
I had 39 radiation treatments and it took 2 or 3 to figure it out.