This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
Endoscopic sinus surgery prerequisite? 
Select and explain. 
A. MRI of paranasal sinus, B. CT of PNS, C. Mucocilliary clearing testing, D. Acoustic tests
B: CT of PNS
Answer: B: CT of PNS 
Explanation: Ans. is 'b' i.e., CT of PNS Endoscopic surgery of inflammatory diseases of paranasal sinuses (sinusitis or polyp) requires a very detailed preoperative knowledge of the individual anatomical conditions and pathological changes. CT scan are used best to visualize sinus areas. CT scan provides excellent definition of paranasal sinuses and is a prerequisite for endoscopic surgery. "CT scan limited study coronal cuts in bone window is prerequisite for endscopic sinus surgery"----Mohan Bansal