Signet ring sign – a CT feature of bronchiectasis. As a general rule a bronchus should be no larger than its accompanying pulmonary artery, and if a bronchus is more than 50% larger then this is diagnostic of bronchiectasis. When a dilated bronchiectatic bronchus is viewed in cross-section next to its smaller accompanying pulmonary artery this simulates the appearance of a signet ring, a type of ring once worn by nobles who used them to apply wax seals to their correspondences.
from our tumblr blog: http://radiologysigns.tumblr.com/post/25330514278
http://radiologysigns.tumblr.com/
