<prompt> Active pulmonary TB can be diagnosed on CT-scan by following finding ?Tree in bud appearanceHoney comb appearanceGround glass appearanceSignet ring sign  <response>: Ans. is a i.e., Tree in bud appearanceRef Chapman 4ne p.142,143; Fundamentals of radiology Tree-in-bud sign or pattern describes the CT appearance of multiple areas of centrilobular nodules with a linear branching pattern.This is a characteristic sign of active pulmonary TB.Other impoant sign of pulmonary TB on CT is lymph nodes showing peripheral rim enhancement because of necrosis. 