Well, I think they "have" to give you a copy if you request it (the imaging place you had the MRI done at). You did pay for an MRI, after all. My ENT told me to have it done where ever my insurance would cover it, then pick up the films and carry them to my appointment. Later, months later in fact, I called the imaging place and told them I wanted a CD. It was ready for me the next day. There were no further costs involved either.
I can see how small tumors would be easier to miss without contrast, although mine was only 1.3 cm at the time of the image. Certainly some of those 2 to 5 mm ones would be tricky, perhaps even with contrast as there are other things that get picked up with contrasts.
Then, there's the obvious, it certainly "stands out" better to me with contrast, but I think a "trained" eye would have no trouble with AN's that exceed a certain size.