12/5/08 - first attempt at PET Scan.
Something happened between the Doctor's office and the insurance company, but the end result was that as of 6:45am that morning, the tracer element they inject you with had reached the end of it's viability window (the tracer element is Fluorine-18; a radioactive isotope with fairly short half-life). They either needed to start the test, or abort. To start the test I would have had to sign a waiver saying that I would pay, should the insurance decline. NOPE!
12/9/08 - successful attempt at the PET Scan. Insurance company approved the test later the previous day, and I just needed to wait for a new appointment. My health system only preforms the tests on Tuesdays and Fridays.
And on a VERY COOL side note (I'm very interested in physics and specifically quantum physics), The "P" in PET scan stands for Positron. I won't go into detail about how a PET scan works, but it requires you to be injected with material that contains Anti-Matter -- the Positron is the anti-matter counterpart to the electron in the matter side of the house. The PET scan relies on the fact that when the positron encounters an electron, they annihilate each other and emit gamma radiation as a result.
Now before you go bad mouthing insurance companies... Don't... at least not this time. More on this later.