@aykut The answer as to whether an MRI or X-ray can be used instead of a CT for your sinus is "probably not" - neither provides and adequate image of the cyst or growth you describe.

The concern about radiation is a separate issue. A head CT exposes you to about 2 mSV of radiation - equivalent to perhaps 10-20 x-rays - so it is wise to be cautious.

However, think about whether you want to treat the problem permanently...right now you are putting steroids in your body every day, which are not particularly healthy to use for a lifetime. Perhaps after surgery and healing you will be able to reduce or eliminate those, so you could view it as a tradeoff. For example, I have a chronic lung condition, including a low-grade infection. I have 2 choices - keep it at bay with careful airway hygiene and have it checked by CT every 12-18 months to be sure it is not worsening, or stay on a course of 3 antibiotics (that wreak havoc with my body) indefinitely, I have opted for airway hygiene and periodic CT as the safer of the two.

What do you think of looking at the issue in this different way?
Sue