Page 196 - Clinical Pearls in Cardiology

184 Clinical Pearls in Cardiology

5. Which condition classically produces the radiological
pattern described as ‘photographic negative’ of
pulmonary edema?
The ‘photographic negative’ of pulmonary edema
phenomenon is seen in chronic eosinophilic pneumonia.
Chronic eosinophilic pneumonia resembles tuberculosis
in its clinical presentation. Chest radiographs in this
condition show predominantly peripheral infiltrates.
This pattern is classically described as the photographic
negative of acute pulmonary edema.
6. How will you calculate cardiothoracic ratio on the
chest X-ray?
The cardiothoracic ratio (CTR) on the PA chest X-ray
gives an idea about the size of the heart. It is obtained
by dividing the maximum transverse cardiac silhouette
by the maximum internal thoracic diameter as shown
below (Fig. 5).

Fig. 5: Calculation of cardiothoracic ratio