Cross sectional anatomy of chest by Dr. Milan

Cross sectional anatomy of chest

1. CROSS SECTIONAL ANATOMY OF CHEST Dr. Milan Silwal Resident, 1 st year, MD Radiodiagnosis NAMS

2. BOUNDARIES OF THORAX Superior aperture/Thoracic Inlet : Oblique plane covered incompletely by Suprapleural membrane /Sibson’s fascia. Ant: upper border of manubrium sterni Post: Superior surface of body of 1 st thoracic vertebra On each Side: first rib with its cartilage Thoracic cage: Ant: Sternum Post:12 Thoracic vertebrae Sides: 12 ribs +cartilage Inferior aperture/ Thoracic outlet : is closed by large musculocutaneous partition, the diaphragm. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

3. MEDIASTINUM m iddle space in thoracic cavity in between the lungs. Boundries - Anteriorly: Sternum Posteriorly: Vertebral column Superiorly: Thoracic inlet Inferiorly: Diaphragm Laterarly : Mediastinal pleura. Divisions: Superior Mediastinum Inferior: Anterior Mediastinum Middle Mediastinum Posterior Mediastinum Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

4. Superior Mediastinum is the space between the thoracic inlet and the superior aspect of the aortic arch Boundries : Anteriorly: Manubrium sterni Posteriorly: upper four thoracic vertebrae Superiorly: plane of thoracic inlet Inferiorly: An imaginary line passing through sternal angle in front and lower border of body of fourth thoracic vertebrae behind On each side: Mesdiastinal pleura Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

5. Contents: Trachea and oesophagus Muscles: origin of sternohyoid , sternothyroid , lower end of longus coli Arteries: Arch of aorta, Brachiocephalic artery,left common carotid artery,left subclavian artery Veins: Right and left brachiocephalic vein, upper half of superior vena cava, left superior intercostal vein Nerves: Vagus , Phrenic, cardiac nerve of both side, left recurrrnt laryngeal nerve Thymus: Thoracic duct Lymph nodes : Paratracheal , brachiocephalic and tracheobronchial Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

6. Anterior mediastinum: is a very narrow space in front of pericardium. Boundries : Anteriorly: Body of sternum posteriorly : Pericardium Contents: thymus, branches of the internal mammary artery and vein, lymph nodes, and fat. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

7. Middle Mediastinum Boundries : Anteriorly: anterior border of the pericardium and Posteriorly: an imaginary line drawn 1 cm posterior to the anterior border of the vertebral bodies on the lateral radiograph Contents: heart, aorta, superior and inferior vena cavae , brachiocephalic arteries and veins, pulmonary arteries and veins, thoracic duct, azygos and hemiazygos veins, phrenic and vagus nerves , mediastinal fat, and lymph nodes Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

8. Posterior mediastinum Boundries : Anteriorly: line drawn 1 cm posterior to the anterior border of the vertebral bodies Posteriorly: the posterior paravertebral gutters. Contents: nerves, fat, vertebral column, and lymph nodes. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

9. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

10. Mediastinal levels: Interpretation of mediastinal anatomy can be assisted by analyzing CT images at specific levels within the chest that are easily identifiable because of their characteristic anatomic landmarks and appearance. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

11. 1. Thoracic Inlet Level At the junction of the neck and the thorax, most of the mediastinal structures are vascular. The two brachiocephalic veins are formed as the internal jugular veins join the subclavian veins and are located posterior to the clavicular heads. These veins are the most anterior and lateral of the six major vessels at this level . More medial are the two common carotid arteries , and just posterior to these are the subclavian arteries . The esophagus is posterior or posterolateral to the trachea. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

12. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

13. 2. Left Brachiocephalic Vein Level The left brachiocephalic vein crosses the midline anterior to the arterial branches of the aorta and joins the more vertically orientated right brachiocephalic vein to form the superior vena cava . The innominate, left common carotid, and left subclavian arteries are located posterior to the left brachiocephalic vein and anterior to the trachea. The innominate artery is the more centrally located artery; the left common carotid artery and the left subclavian artery are located to the left of the midline in a more lateral and posterior position. The esophagus maintains its position posterior or posterolateral to the trachea and anterior to the spine. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

14. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

15. 3. Aortic Arch Level The transverse arch crosses the mediastinum anterior to the trachea , coursing obliquely from right to left and from anterior to posterior. The superior vena cava is located adjacent to the anterior aspect of the transverse aorta to the right of the trachea. The fat-filled region posterior to the superior vena cava, anterior to the trachea, and lateral to the aorta is the pretracheal or anterior paratracheal space . Anterior to the transverse aorta is the fat-filled prevascular space,. If present, the thymus gland is located in this space. T hese spaces often contain a few small lymph nodes . Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

16. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

17. 4. Azygos Arch– Aortopulmonary Window Level The azygos vein, located anterior and slightly to the right of the spine, arches anteriorly and joins the superior vena cava at this level. The azygos arch may not be seen in its entirety on one slice and may be confused with lymphadenopathy. The aortopulmonary window is a space located between the inferior aspect of the aortic arch and the superior aspect of the left main pulmonary artery. The space is fat filled and contains a few small lymph nodes, the left recurrent laryngeal nerve, and the ligamentum arteriosum . Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

18. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

19. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

20. 5. Left Pulmonary Artery Level The main pulmonary artery is anterior and to the left of the ascending aorta. The left pulmonary artery curves posteriorly from its origin from the main pulmonary artery and is located anterolateral to the left main bronchus at the level of the carina. The left superior pulmonary veins are located lateral to the posterior portion of the left pulmonary artery. On the right, at the level of the carina, is the origin of the right upper lobe bronchus. Anterior to the right upper lobe bronchus lies the right upper lobe pulmonary artery, the truncus anterior . The right superior pulmonary veins are located anterior and lateral to the truncus anterior. The azygos vein is located posterior and to the right of the esophagus, while the hemiazygos vein parallels the course of the azygos but is to the left of the spine. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

21. The superior pericardial recess , a crescent-shaped extension of the pericardial space, is contiguous to the posterior aspect of the ascending aorta. The space often contains a small amount of fluid and may occasionally be confused with a lymph node. However, its characteristic location, shape, and low attenuation allow confident identification. Occasionally , the superior pericardial recess extends more cephalad , to the level of the brachiocephalic vessels, and may be mistaken for a mass or mediastinal cyst. The use of thin sections can be helpful to distinguish this so-called high-riding pericardial recess from pathologic conditions by showing that the “mass” is of water attenuation and by demonstrating continuity with the superior pericardial recess at the level of the ascending aorta. The concave extension of the right lung into the mediastinum anterior to the spine is the azygoesophageal recess, which extends inferiorly from the subcarinal region to the level of the diaphragm . Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

22. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

23. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

24. 6. Right Pulmonary Artery Level The main pulmonary artery is anterior and to the left of the ascending aorta. The right pulmonary artery extends posteriorly and to the right from the main pulmonary artery, passing anterior to the bronchus intermedius and posterior to the superior vena cava. The right superior pulmonary vein is to the right of and lateral to the intrapulmonary portion of the right pulmonary artery. Anterior to the left main and upper lobe bronchi is the left superior pulmonary vein, and posterior to the left upper lobe bronchus is the left lower lobe pulmonary artery. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

25. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

26. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

27. 7. Left Atrial Level Anterior to the superior vena cava is the right atrial appendage, curving around the ascending aorta. The aorta is located centrally within the mediastinum, and anterior and to the left of the aorta is the pulmonary outflow tract. Posterolateral and to the left of the pulmonary outflow tract is the left atrial appendage. Within the fat between the left atrial appendage and the aortic root is the left main coronary artery. The left superior pulmonary vein enters the left atrium immediately posterior to the left atrial appendage. The right superior pulmonary veins enter the left atrium just posterior to the superior vena cava. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

28. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

29. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

30. 8. Four-Chamber Level The posteriorly located left atrium is the most cranial of all the chambers. The right and left inferior pulmonary veins enter the posterolateral aspect of the left atrium . Anterior and to the right is right atrium. To the left and anterior to the right atrium is the right ventricle, located behind the sternum. The left ventricle is to the left and posterior to the right ventricle . The coronary arteries can be detected if they are calcified or if there is fat surrounding the heart. The right coronary artery lies in the right atrioventricular groove. The circumflex coronary artery lies in the left atrioventricular groove, and the left anterior descending coronary artery lies in the interventricular groove between the left and right ventricles. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

31. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

32. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

33. 9. Three-Chamber Level The ventricles and right atrium are identified at this level; the left atrium, because of its more cranial position, is not visible. The right atrium is located to the right. To the left and anteriorly, the thin-walled right ventricle is located just beneath the sternum. The thick-walled left ventricle makes up the posterolateral left portion of the mediastinum. Between the left ventricle and the inferior vena cava's opening into the right atrium is the coronary sinus. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

34. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

35. LUNGS Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

36. Lungs Lungs are a pair of respiratory organs situated in a thoracic cavity. Right and left lung are separated by the mediastinum. Right lung: 2 fissures: oblique and horizontal; 3 lobes: superior, middle & inferior Left lung: 1 fissure: Oblique 2 lobes: Superior & Inferior Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

37. Bronchopulmonary segments Bronchopulmonary segments of lungs are well defined sectors of lung,each of which is aerated by a tertiary or segmental bronchus.Each segment is pyramidal in shape with its apex directed towards the root of the lung . No. of bronchopulmonary segments: Right lung: 10 Left lung: 8 Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

38. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

39. Intersegmental planes Each segment is surrounded by connective tissue which is continuous on the surface with visceral pleura.Thus the brochopulmonary segments are independent respiratory units. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

40. Relation to pulmonary artery Branches of pulmonary artery accompany the bronchi. The artery lies dorsolateral to bronchus. Thus each segment has its own separate artery. Relation to pulmonary vein Pulmonary vein do not accompany bronchi or pulmonary artery. They run in intersegmental planes. Thus each segment has more than one veins &each vein drains more than one segment. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

41. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

42. Bronchopulmonary segments at four representative levels: Aortic Arch level Left Pulmonary Artery level Right Pulmonary Artery level Four chamber level Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

43. 1. Section till trachea is visible Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

44. Till trachea is visible Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

45. 2. At level of tracheal bifurcation Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

46. Left and right pulmonary artery level Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

47. 3 . Cardiac ventricular level Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

48. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

49. Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

50. Case 1. 56 yr male with chronic SOB, cough and cachexia Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

51. Case 2. 5 day history of fever and cough Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

52. Case 3. 45 male with chronic cough and hemoptysis Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

53. Case 4. Case of pulmonary embolism Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS

54. Case 5. Case of bronchiectasis and cavitatory lesion Dr. Milan Silwal, 1st year Resident, MD Radiodiagnosis, NAMS