1. Thoracic Radiographic Anatomy
Einav Shochat MS4
Visiting Medical Student

2. PA and Lateral Chest Radiograph

3. Lobar Anatomy
There are three lobes in the right lung and two in the left
Lobes are divided into anatomic segments; each is supplied by its own bronchus and blood vessels

4. Right upper & right middle lobes
Lobar Anatomy:
Right upper & right middle lobes
RUL
RUL
RML borders the right atrium and much of the dome of the diaphragm. Indistinct borders of these areas suggest RML pathology.
RML
RML

5. Lobar Anatomy: Right lower lobe
Consolidations of the lower lobes are largely behind the diaphragm dome, hence the diaphragm border will still appear sharp on the PA film.
RLL
RLL

6. Lobar Anatomy: Left upper lobe
LUL
LUL
LUL borders the left atrium, left ventricle and much of the dome of the diaphragm. Indistinct borders of these areas suggest LUL pathology.

7. Lobar Anatomy: Left lower lobe
Most of the LLL is posterior to the left border of the heart and the dome of the diaphragm. Distinct borders of these areas with surrounding opacity is seen with LUL consolidations.
LLL
LLL

8. Can you find the source of this patient’s fever and cough?

9. Can you find the source of this patient’s fever and cough?
Left Lower
Lobe
pneumonia
Distinct borders
Note the abnormal opacification of the lower vertebrae in the lateral view. Normally there is less soft tissue around the inferior thoracic vertebrae making them appear darker than the more superior vertebrae. See next slide for comparison.

10. On the right is the same radiograph from the previous slide with a normal one for comparison.
Normally,
inferior
vertebrae
appear
darker
Note the general opacification of the lower lobe in the image on the right. Look particularly at the vertebral bodies and posterior border of the heart.

11. Lobar Anatomy
The lobes of the lungs are lined by visceral pleura, which normally is not visualized except along the interlobar fissures
Fissure anatomy may have many anatomic variations and may not be complete

12. On the right there are two fissures, the oblique (major) fissure and the horizontal (minor) fissure. The left lung contains an oblique fissure only.
minor
minor
major

13. It is uncommon to see distinct fissures
It is uncommon to see distinct fissures. If opacified there may be thickening of or fluid between the pleura.
This patient has congestive heart failure and subsequent subpleural thickening.
Can you identify the oblique fissures?

14. It is uncommon to see distinct fissures
It is uncommon to see distinct fissures. If opacified there may be thickening of or fluid between the pleura.
This patient has congestive heart failure and subsequent subpleural thickening.
Can you identify the oblique fissures?

15. Here there is fluid trapped between the pleura within the fissures.

16. Occasionally accessory fissures can be found
Occasionally accessory fissures can be found. For example, the azygos fissure, a normal variant, can form during the embryonic migration of the azygos vein through the apical pleura.

17. Knowing the normal position of the interlobar fissures helps us diagnose pulmonary volume changes. For example when a lobe collapses the fissure is displaced and seen as a sharp interface between opacified (collapsed) and aerated lung.
Can you identify the pleural lining of the collapse lung?

18. Can you identify the pleural lining of the collapse lung?
Knowing the normal position of the interlobar fissures helps us diagnose pulmonary volume changes. For example when a lobe collapses the fissure is displaced and seen as an interface between two densities (e.g., opacified/collapsed and aerated lung)
Can you identify the pleural lining of the collapse lung?
scapulae
Left pulmonary artery:
vasculature are pulled inferiorly by the collapsed LLL
Inferior vertebrae opacified by LLL atelectasis
Left hemidiaphragm becomes indistinct when adjacent to collapsed LLL
Major fissure not normally seen on the PA film because it runs parallel to the radiation beams

19. What’s happened here?

20. What’s happened here?
Right upper
lobe collapse

21. We can use the pleura to identify whether a mass is within the lung parenchyma or in the extrapleural space.
Is this mass intrapleural or extrapleural? How can you tell?

22. Is this mass intrapleural or extrapleural? How can you tell?
We can use the pleura to identify whether a mass is within the lung parenchyma or in the extrapleural space.
Is this mass intrapleural or extrapleural? How can you tell?
Extrapleural
The medial border of the mass is draped by pleura and is distinct where it is adjacent to aerated lung. The lateral border is next to bone and soft tissue of more similar density.

23. The pleura is often involved in inflammatory and traumatic insults to the chest. These may result in areas of thickening or distortion of the pleural lining, which may be appreciated in the normally sharp costophrenic & cardiophrenic angles/sulci.
Cardiophrenic angle
Posterior costophrenic angle
Lateral costophrenic angle
Lateral costophrenic angle

24. Pleural effusions can be identified by: blunting of the lateral and posterior costophrenic sulci, a meniscus sign, opacification of a hemithorax, and/or fluid in the fissures.
Small free-flowing pleural effusions are best identified on the lateral radiograph as this view captures the most dependent region of the thoracic cavity, the posterior costophrenic angles.

25. Mediastinum
Many structures can be identified within the mediastium; we will start with the heart and blood vessels…

26. How many structures can you identify?

27. SVC Aortic arch Aorta LA RA LV RV Aortic pulmonary recess
Vascular pedicle
SVC
Aortic arch
pulmonary
Right pulmonary artery
Aorta
Left
artery LA
Right pulmonary artery
(lower lobe) RA LV RV

28. How many structures
can you identify?

29. Left upper lobe bronchus
Brachiocephalic vessels
Trachea
Scapula
Manubrium
Aorta
Right upper lobe bronchus
LPA
RPA
Retrosternal space
Left upper lobe bronchus
Pulmonary outflow tract
Body of sternum LA
Confluence of pulmonary veins RV
IVC LV
Right hemidiaphragm
Gastric air bubble
Left hemidiaphragm

30. Which valve has been replaced?

31. Which valve has been replaced?
Aortic valve
Note the orientation of the valve perpendicular to the plane of the PA film.

32. Which valve has been replaced?

33. Which valve has been replaced?
Pulmonic
The pulmonary outflow tract is more superior and lateral than many people think.

34. Last one, name the valves…

35. Last one, name the valves…
Aortic
Aortic
Tricuspid
Mitral
Tricuspid
Mitral

36. The Vascular Pedicle Found in the superior mediastinum.
Right and left margins are normally formed by the superior vena cava and the descending portion of the aortic arch, respectively.
A widened vascular pedicle can have several etiologies including elevated intravascular volume, aortic trauma, or pericardial effusion.

37. Aortic arch
Vascular pedicle
Superior vena cava

38. Intravascular volume depletion vs. Intravascular volume elevation

39. Intravascular volume depletion vs. Intravascular volume elevation
Vascular pedicle
Vascular pedicle
Superior vena cava
Aorta
Superior vena cava
Aorta
Intravascular volume elevation resulting in an expanded SVC should not be mistaken for hematoma, which would have a less distinct border and more opacified appearance.

40. Trauma patient with an aortic transection
Note the vascular pedicle’s “fuzzy”, opacified right border.

41. What is happening here?

42. What is happening here? Can you follow the heart borders?
Looks pretty wide eh?
Can you follow the heart borders?

43. What is happening here?
If you look closely you can make out the superior pericardial border
The wide vascular pedicle here results from a pericardial effusion
The pacemaker wires roughly outline the right atrium border
The left heart border can be seen within the effusion
effusion
effusion
Comparing this with older films can also help make the diagnosis.

44. Pulmonary Airways & Vasculature
The lungs on the normal chest radiograph are made by pulmonary vessels, the bronchi are normally not seen.
This is because:
Pulmonary vessels are blood-filled with density similar to water.
Bronchi are filled with air and normally have thin walls that do not provide contrast to aerated lungs.

45. Pulmonary Airways & Vasculature
When lung parenchyma fill with water or inflammatory material:
Water-density vessels become less distinct.
Air-filled bronchi can be seen as “air bronchograms”.
If airways are obstructed (e.g., tumor) they may fill with fluid and no “air bronchograms” will be appreciated.

46. How do these two radiographs differ?

47. How do these two radiographs differ?
Abnormal indistinct vasculature
Normal
well-defined vessels

48. In the normal chest radiograph only airways within the mediastinum are apparent.
Trachea
Trachea
Left mainstem bronchus
Right mainstem bronchus
Left mainstem bronchus

49. What is the source of this man’s chronic cough?

50. What is the source of this man’s chronic cough?
Unilateral lung opacification with ipsilateral tracheal shift from the pressure differential helps identify RUL collapse
Obstruction
RUL
Horizontal fissure
Tented right hemidiaphragm
Inferior pulmonary ligament tethering the lobe and tenting the diaphragm
Right upper lobe collapse secondary to obstruction of the bronchus by squamous cell carcinoma.

51. What is the source of this patient’s dyspnea?

52. What is the source of this patient’s dyspnea?
Atelectasis
Seen commonly as crowded parallel air-bronchograms
(if airways are not obstructed)

53. What is abnormal here?

54. What is abnormal here? The patient has Sarcoidosis.
Lateral border of the SVC is obscured by lymphadenopathy
Bronchus lumen is obscured
Think about lymphadenopathy when opacities obscure the aortic pulmonary recess (PA) or surrounding the left distal main bronchus (on the lateral)

55. Other Mediastinal Structures
Esophagus
Thyroid
Thymus
Lymph nodes
These are generally not seen unless there is pathology

56. What could be the source of this anterior mediastinal mass?

57. What could be the source of this anterior mediastinal mass?
Ddx: Lymphoma/leukemia, germ cell tumors (e.g., teratoma), thymic mass (e.g., thymoma, cyst), enlarged thyroid, vascular (e.g., hematoma, aortic aneurysm).
This patient has a thymoma.

58. How about this one?

59. How about this one?
This patient has a an enlarged thyroid gland.

60. Extrapulmonary Structures
Diaphragm
Stomach/gastric bubble
Liver, spleen
Bones: clavicles, ribs, scapulae, spine
Other soft tissues

61. In the normal radiograph, the diaphragm is domed with the right side higher than the left (i.e., the heart lying on the left side of the diaphragm may contribute to the lower level).
Left diaphragm
Right diaphragm

62. Elevated intrathoracic pressures (e. g
Elevated intrathoracic pressures (e.g., hyperinflation from obstructive lung disease, tension pneumothorax) will flatten the diaphragm.
Flat
Flattened

63. Not many structures left, so let’s just quiz…

64. What’s abnormal in these films?

65. What’s abnormal in these films?
Notice the air around the left and right pulmonary arteries.
LLL atelectasis
The lucent stripe along the inferior heart border, crossing midline is called a “continuous diaphragm” sign and is indicative of pneumomediastinum.

66. What’s abnormal in this film?

67. What’s abnormal in this film?
Free air
Normally the only air we see under the diaphragm is in the gastric bubble and bowels. Subdiaphragmatic free air is indicative of perforated viscus.

68. What’s abnormal in this film?

69. What’s abnormal in this film?
Hiatal hernia

70. This hiatal hernia is easier to see with the gastric air bubble behind the heart.

71. What’s abnormal in this film?

72. What’s abnormal in this film?
Tracheal deviation
Gastric bubble, bad sign
Ruptured diaphragm

73. What’s abnormal in this film?

74. What’s abnormal in this film?
Splenomegaly
Gastric air bubble

75. What’s abnormal in this film?
Gastric air bubble

76. What’s abnormal in this film?
Ouch
Gastric air bubble

77. Which patient needs a chest tube?
Gastric air bubble

78. Which patient needs a chest tube?
Pneumothorax
Skin fold lateral border
Scapula medial border
To decide whether a line in the lung represents the scapula, a skin fold or a pneumothorax consider the density difference between the two sides of the line. A pneumothorax will have a sharp line with air density (equal density) on both sides. Skin or scapula will have a line with air on one side and more opaque tissue on the other.
Gastric air bubble

79. What’s abnormal in this film?

80. What’s abnormal in this film?
Nothing
The left lung appears more opacified but it is the result of uneven radiation.
The patient is rotated slightly causing the “heel effect”, the relative over exposure of one hemithorax compared to the other caused by uneven radiation. Looking at the relative exposure of the extrathoracic soft tissues can help identify the “heel effect”.

81. References:
Collins J, Stern EJ. Chest Radiology, the Essentials. Lippincott, Williams & Wilkins
Dafner RH. Clinical Radiology, the Essentials. 2nd Ed. Lippincott, Williams & Wilkins
Freindlich IM, Bragg DG. A Radiologic Approach to Diseases of the Chest. 2nd Ed. Williams & Wilkins