I'd heard your brain was the size of a planet so I didn't like the thought of someone running down to the cellar with a handful of ten-bob bits to feed the meter because the scanner ran out of leccy.
An anxious time. Brain scans are not pleasant - some people find them very claustrophobic and request a sedative before the procedure starts. You will be given a buzzer to hold so that if things get too uncomfortable you can buzz and the procedure stops. One way of approaching this is to expect it to be unpleasant possibly noisy and to try to focus the mind on something else whilst the machine does the job -- recent football match ???
I hope it all goes well for you. You might want to buy a balaclava before you go so that the nurses can concentrate on their job instead of being distracted by your dazzling good looks