Clinical assessment of cardiothoracic ratio and aortic arch calcification. A) Measurement of cardiothoracic ratio (CTR). CTR is equal to the maximal cardiac width divided by thoracic width, as shown. B) Assessment of aortic calcification using chest x-ray (lateral lumbar and abdominal CT for comparison with calcification enclosed by white boxes), with examples of grade 0–3 shown. Permission pending for reproduction of this image .