I had it chemically induced as well. I forget exactly what it was but is was two chemicals normally in you body. It triggers your fight or flight response so to speak. The technician will recognize the signs before you do and let you know it's about to kick in. Within a couple of minutes they will probably tell you to drink a soda. The caffeine will counteract the chemical and bring you down. About 45 minutes later they will take more photos. Relax, you do just fine.