What is the cardiothoracic ratio in children is -

“The cardiac silhouette occupies 50-55% of the chest width. Cardiomegaly is present when the cardiothoracic (CT) ratio is more than 55%” he 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%).