In this article, we are going to describe the cross-sectional anatomy of thorax which is essential in understanding cross-sectional imaging.
Cross-Sectional Anatomy of Thorax Level T3:
- It is the level of superior mediastinum.
- The trachea lies in the midline with the right brachiocephalic artery, left common carotid artery and left subclavian artery anteriorly.
- The esophagus is seen behind the trachea and anterior to the vertebra.
- The brachiocephalic veins are anterior and lateral to the arteries and unite to form the superior vena cava.
- The left brachiocephalic vein is seen passing anterior to the branches of the aortic arch.
Cross-Sectional Anatomy of Thorax Level T4:
- This plane passes through the lower board of T4 and the sternal angle.
- This plane demarcates the superior and the inferior mediastinum.
- The lower part of the aortic arch is seen to the left of the trachea.
- The arch of an azygous vein crosses the right hilum to drain into the posterior aspect of superior vena cava at this level.
- The oblique fissure can be seen at the level on CT.
Cross-Sectional Anatomy of Thorax Level T5:
- This plane is at or just below the tracheal bifurcation.
- The main pulmonary artery divides into right pulmonary artery and the left pulmonary artery
- The right pulmonary artery runs anteriorly to its bronchus.
- The left pulmonary artery arches superiorly out of the plane to pass over the left bronchus.
- The superior pulmonary veins are seen anteriorly.
- The right superior pulmonary vein is anterior to the interlobar artery.
- The left superior pulmonary artery is separated from lower lobe artery by the left bronchus.
- The ascending aorta is seen lying to the right of the main pulmonary artery.
- Most anteriorly is the anterior junctional line that is the junction of the anterior pleurae of the lungs
- The esophagus, azygous vein, and the descending aorta are seen in the posterior mediastinum.
- The azygo-oesophageal recess may be seen.
Cross-Sectional Anatomy of Thorax Level T6:
- This level passes through the upper part of the heart.
- The right atrial appendage is seen overlapping the origin of the aorta.
- The coronary artery arises from the at this level.
- The right ventricular outflow tract is seen anterior to the origin of the aorta.
- The esophagus is seen left to the left atrium.
Cross-Sectional Anatomy of Thorax Level T8:
- At this level, we can see the relationship of heart chambers to each other.
- The left ventricular inflow and outflow tracts are separated from each other by the anterior leaflet of the mitral valve.
- The aortic sinuses are seen at this level.
- The right border of the heart is formed by the right atrium.
- The left ventricle forms the left border of the heart.
- The right ventricle forms the anterior border of the heart.
Cross-Sectional Anatomy of Thorax Level T10:
- Part of the abdominal cavity is seen at this level because the domes of the diaphragm reach the level of T9.
- The esophagus traverses the diaphragm at the level of T10 through the esophageal opening.
- The fundus of the stomach, part of liver and spleen are seen.
- The inferior vena cava (IVC) is situated slightly anteriorly.
- The descending aorta is seen posteriorly.
- The azygous and hemizygous veins are on the right and left of the descending aorta respectively.