Saturday, November 1, 2008

What is CTR and how to measure CTR – cardiothoracic ratio?

This is the transverse cardiac diameter (the horizontal distance between the most rightward and leftward borders of the heart seen on a postero-anterior (PA) chest radiograph) divided by the transverse chest diameter (measured from the inside rib margin at the widest point above the costophrenic angles on a PA chest film). See attached radiograph: CTR = A/B.



A cardiothoracic ratio of more than 50% is considered abnormal in an adult; more than 66% in a neonate.
Possible causes of a ratio greater than 50% include:-cardiac failure-pericardial effusion-left or right ventricular hypertrophy

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