Cardiothoracic ratio
Updates to Article Attributes
The cardiothoracic ratio (CTR) aids in the detection of enlargement of the cardiac silhouette, which is most commonly from cardiomegaly but can be due to other processes such as a pericardial effusion.
Terminology
Some report CTR as a percentage, however this is incorrect, as it is a ratio.
Radiographic features
The 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 less than 0.5.
The CTR should not be measured on an AP chest x-ray. Objects nearer the Xx-ray tube appear artificially enlarged due to divergence of the Xx-ray beam, this resultsresulting in the heart appearing artificially large on AP radiographs.
Related pathology
It should be noted that this measurement is a crude marker of disease 4. If the patient is symptomatic then echocardiography is required but the yield of echocardiography is low if performed just for an increased CTR 3.
In the following situations, cardiothoracic ratio is more than 0.5 on a PA chest radiograph, but heart and pericardium are normal:
- a prominent epicardial fat pad
- due to expiration
-<p>The <strong>cardiothoracic ratio</strong> (<strong>CTR</strong>) aids in the detection of <a href="/articles/enlargement-of-the-cardiac-silhouette">enlargement of the cardiac silhouette</a>, which is most commonly from <a href="/articles/cardiomegaly">cardiomegaly</a> but can be due to other processes such as a <a href="/articles/pericardial-effusion">pericardial effusion</a>. </p><h4>Terminology</h4><p>Some report CTR as a percentage, however this is incorrect, as it is a ratio.</p><h4>Radiographic features</h4><p>The CTR is measured on a PA <a href="/articles/chest-radiograph">chest x-ray</a>, 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 less than 0.5.</p><p>The CTR should not be measured on an AP chest x-ray. Objects nearer the X-ray tube appear artificially enlarged due to divergence of the X-ray beam, this results in the heart appearing artificially large on AP radiographs.</p><h4>Related pathology</h4><p>It should be noted that this measurement is a crude marker of disease <sup>4</sup>. If the patient is symptomatic then echocardiography is required but the yield of echocardiography is low if performed just for an increased CTR <sup>3</sup>.</p><p>In the following situations, cardiothoracic ratio is more than 0.5 on a PA chest radiograph, but heart and pericardium are normal:</p><ul>- +<p>The <strong>cardiothoracic ratio</strong> (<strong>CTR</strong>) aids in the detection of <a href="/articles/enlargement-of-the-cardiac-silhouette">enlargement of the cardiac silhouette</a>, which is most commonly from <a href="/articles/cardiomegaly">cardiomegaly</a> but can be due to other processes such as a <a href="/articles/pericardial-effusion">pericardial effusion</a>. </p><h4>Terminology</h4><p>Some report CTR as a percentage, however this is incorrect, as it is a ratio.</p><h4>Radiographic features</h4><p>The CTR is measured on a PA <a href="/articles/chest-radiograph">chest x-ray</a>, 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 less than 0.5.</p><p>The CTR should not be measured on an AP chest x-ray. Objects nearer the x-ray tube appear artificially enlarged due to divergence of the x-ray beam, resulting in the heart appearing artificially large on AP radiographs.</p><h4>Related pathology</h4><p>It should be noted that this measurement is a crude marker of disease <sup>4</sup>. If the patient is symptomatic then echocardiography is required but the yield of echocardiography is low if performed just for an increased CTR <sup>3</sup>.</p><p>In the following situations, cardiothoracic ratio is more than 0.5 on a PA chest radiograph, but heart and pericardium are normal:</p><ul>
Image 5 X-ray (Frontal) ( create )
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