Annotated image - Cardiothoracic ratio
Figure 1
Figure 2
Figure 1: annotated x-ray of this same patient
Cardiothoracic ratio is measured on a PA chest x-ray, and is the ratio of:
- maximal horizontal cardiac diameter
- maximal horizontal thoracic diameter (inner edge of ribs / edge of pleura)
Figure 2: A normal measurement should be less than 0.5.