I was a Nuclear Med Tech many moon's ago... I did lots of Cardiac scans. There are several ways that they do them, but basically they are all the same... 2 sets of pictures- one is a base line, and one is after the "stress". Usually they start with the baseline picutures. If they are puting you on a treadmill, they will have you on it until you reach peak stress, they will inject the radioactive material, and then shortly after that, let you off. Then the second set of pictures...
The sequence is a little different for Thallium.
The only thing you have to really prepare for is the effect of the exercise on your blood sugar. Depending on what kind of shape you are in, the treadmill experience could go long (10 minutes) or short (less than 5 minutes). Adjust your insulin and food accordingly. Each set of pictures takes about 1/2 hour a piece, so you may want to check your blood sugar before each scan to make sure you'll be ok- because you have to hold VERY still during the whole scan.
Good luck. I hope everything turns out good for you.
I'm sure you won't be like many of my previous patients, and ask to go outside for a cigarette break in between scans...
Melissa