Comet Sign

Comet Sign

Imaging Blood vessels Comet tail sign A term referring to the CT appearance of a tapering, noncalcified vein, adjacent to a rounded phlebolith, which serves to differentiate it from a stone in the ureter
Imaging Gallbladder A term referring to reverberation artifacts seen by ultrasonography within a thickened wall of the gallbladder, strongly suggesting small cholesterol crystals within Rokitansky-Aschoff sinuses in adenomyomatosis, which is usually asymptomatic. Air in emphysematous cholecystitis may produce a similar picture, but in contrast to patients with cholesterol crystals, those with emphysematous cholecystitis are clinically unwell
Imaging Lung Parachute sign A focal area of collapsed lung adjacent to pleural thickening with distortion of blood vessels, which is seen as a curvilinear soft tissue density on a plain chest film, which extends from the lateral pleura to the hilum (this image is more parachute-like, given the multiple ‘tails’); the sign is due to contracted fibrous scarring and shrinking pleuritis with rounded atelectasis, and seen in the folded lung syndrome