Endoscopic sinus surgery prerequisite-
(Refer: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 220 – 221)

Endoscopic surgery of inflammatory diseases of paransal 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
MRI of paraanasal sinus
CT of PNS
Mucocilliary clearing testing
Acoustic tests