Did not pass the stress test. Tues surgery cancelled

i have to have a two day nuclear stress test.  the doctor said it was due to my age (65).  I am really dreading this test, i read that the dye is radioactive and that you have to lay flat on  your back with your arms over your head for 30 mins after while they take pictures.  i hate lying flat on my back, i feel like my bust is choking my neck.  can anyone tell me what this procedure was like, and what i can expect.  and if i don't pass it, what then?