If you need an anxiolytic, Xanax is the best for these situations. Short acting, and most imaging centers have it on hand.

At our imaging center we have an "open" magnet. Rather than a tube it's like two disks with the sides open. Most patients find this less oppressive. Just keep in mind that most open or upright MR generate images of lower quality, for the same price.

Consider scheduling a test run beforehand. Most centers will let you stop by and lay in the magnet for a minute to see how you tolerate it.

There might be other imaging options that can answer the question, such as CT or ultrasound. Your physician can consult a radiologist for advice.