Measurement of <a href="https://en.wikipedia.org/wiki/Cardiothoracic_ratio" class="extiw" title="en:Cardiothoracic ratio">cardiothoracic ratio</a>. This ratio equals (MRD + MLD)/ID where,
<ul><li>MRD = greatest perpendicular diameter from midline to right heart border</li>
<li>MLD = greatest perpendicular diameter from midline to left heart border</li>
<li>ID = internal diameter of chest at level of right hemidiaphragm</li></ul>
<a href="//commons.wikimedia.org/wiki/User:Mikael_H%C3%A4ggstr%C3%B6m" title="User:Mikael Häggström">Mikael Häggström</a>
<p><a href="//commons.wikimedia.org/wiki/File:Chest_X-ray_2346.jpg" title="File:Chest X-ray 2346.jpg">File:Chest_X-ray_2346.jpg</a> (Public Domain)
</p>
<ul><li>Measurement: <a rel="nofollow" class="external text" href="http://www.ohsu.edu/xd/education/schools/school-of-medicine/departments/clinical-departments/diagnostic-radiology/pediatric-radiology-normal-measurements/chest-measurements.cfm">Chest Measurements</a>. <i><a href="//commons.wikimedia.org/w/index.php?title=Oregon_Health_%26_Science_University&amp;action=edit&amp;redlink=1" class="new" title="Oregon Health &amp; Science University (page does not exist)">Oregon Health &amp; Science University</a></i>. Retrieved on <span class="mw-formatted-date" title="2017-01-13">2017-01-13</span>.</li></ul>