The borders of the mediastinum on the CXR are defined by the contrast produced by adjacent air filled lung.
Postero-Anterior View
Fig indicate the structures that form the mediastinal contours. The right ventricle is the only chamber that does not contribute to the cardiac silhouette on the PA view.
Fig indicate the structures that form the mediastinal contours. The right ventricle is the only chamber that does not contribute to the cardiac silhouette on the PA view.
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| Cardiac contours: Lateral view - CXR: Lateral view |
Mediastinal Borders
1 = Right brachiocephalic vessels
2 = Superior vena cava
3 = Right atrium
4 = Inferior vena cava
5 = Left subclavian artery and brachiocephalic vein
6 = Aortic knuckle
7 = Pulmonary trunk/conus
8 = Left atrial appendage
9 = Left ventricle
Lateral View
The lateral view is always used in combination with the PA view. In addition to defining specific chamber enlargement, it is particularly useful in the following situations:
i)Demonstrates lesions in the retrosternal and costophrenic regions.
ii) Localizes lung pathology to its lobe and assesses lobar volume loss.
iii) Defines interlobar or small pleural effusions.
iv) Separates diaphragmatic variants from adjacent lung or subdiaphragmatic pathology.
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| Cardiac contours: Lateral view-CXR: Lateral view |
Fig. illustrates the structures that are border forming on the lateral view. The right ventricle and pulmonary trunk form the anterior margins of the cardiac contour. The posterior border is formed by the left atrium and the left ventricle. There is a small contribution from the inferior vena cava (IVC).
Right Anterior Oblique View
Because the long axis of the heart lies at about 45° to the sagittal plane, patient rotation such that the right shoulder is closer to the cassette (RAO) enlarges the cardiac image. Fig demonstrate the cardiac borders defined by this view.
Right Anterior Oblique View
Because the long axis of the heart lies at about 45° to the sagittal plane, patient rotation such that the right shoulder is closer to the cassette (RAO) enlarges the cardiac image. Fig demonstrate the cardiac borders defined by this view.
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| RAO view: Cardiac contours - CXR: LAO view |
Left Anterior Oblique View
As the long axis of the heart lies at about 45° to the sagittal plane, patient rotation with the left shoulder forward (LAO) reduces the cardiac size. Fig. show the cardiac borders defined by this view. The aorta is better seen.
As the long axis of the heart lies at about 45° to the sagittal plane, patient rotation with the left shoulder forward (LAO) reduces the cardiac size. Fig. show the cardiac borders defined by this view. The aorta is better seen.
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| LAO view: Cardiac contours - CXR: LAO view |
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