<prompt> What is the cardiothoracic ratio in children is -30-3540-4550-5560-65  <response>: 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 0.550. 