Medicare has a set fee schedule for every procedure, including diagnostic testing, X-ray, CT, MRI and so forth.
If you use a medical provider that accepts assignment they cannot balance bill you and your out of pocket for medically necessary testing will be limited to your Medicare deductibles and coinsurance.
Diagnostic testing is covered under Part B. You will pay 20% of the Medicare approved amount. So if the procedure costs $1000, Medicare approves $500 you would pay $100. Some states will allow an additional 15% of what is called excess charges. If you live in Ohio, you do not have to worry about that, however if you live in Florida you would have to pay. The doctor cannot balance bill you more that the 15% of the Medicare approved amount.
If you use a medical provider that accepts assignment they cannot balance bill you and your out of pocket for medically necessary testing will be limited to your Medicare deductibles and coinsurance.