What is the normal cardiothoracic ratio in children?: (A) 30-35%, (B) 40-45%, (C) 50-55%, (D) 60-65%
Answer is C. "The cardiac silhouette occupies 50-55% of the chest width. Cardiomegaly is present when the cardiothoracic (CT) ratio is more than 55%".The CTR is measured on a PA chest x-ray and is the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs/edge of pleura). A normal measurement should be <0.5(50%).(Refer: Nelson's Textbook of Pediatrics, SAE, 1st edition, pg no. 2170)