Sinus CAT scan or CT is used to evaluate patients with recurrent or chronic sinus symptoms who are not responding to medical treatment. These symptoms may include nasal congestion, sinus drainage, facial pain or pressure, and headaches. Your doctor may also order a sinus CT if an abnormality is identified in physical examination. A sinus CT provides detailed information about sources of nasal obstruction, sinus drainage pathways, and the presence of infection. Specific anatomic abnormalities, which may be causing sinus symptoms, can be easily identified.