A 30 year old man presents with 6 month history of nasal discharge, facial pain and fever. On antibiotic therapy, fever subsided. After 1 month again had symptoms of mucopurulent discharge from the middle meatus and the mucosa of the meatus appeared congested and oedematous. Next best investigation would be:
MRI of the sinuses Non-Contrast CT of the nose and para-nasal sinuses Plain x-ray of the para-nasal sinuses Inferior meatus puncture