1. High-Resolution Lung CT: Key Findings and What They Mean W
High-Resolution Lung CT: Key Findings and What They Mean W. Richard Webb MD

2. Key HRCT Findings of Lung Disease
interlobular septal thickening
honeycombing
irregular reticular opacities
traction bronchiectasis
nodules (3 patterns)
“tree-in-bud”
consolidation
ground-glass opacity
emphysema
lung cysts
mosaic perfusion and air trapping

3. High-Resolution Lung CT: Technique
thin collimation (1 mm)
spaced scans (1-2 cm)
prone scans (1-2 cm)
inspiration
expiratory scans (3-5 levels)
MDRCT: volumetric (spiral) scans

4. Secondary Pulmonary Lobule
1-2 cm in diameter
interlobular septa (a few visible in nls)
centrilobular artery (normally visible) and bronchiole (normally invisible)

5. Pulmonary Lobule .
courtesy H. Itoh

6. interlobular septa: pulmonary lobules

7. Interlobular Septal Thickening
lines outline lobules of characteristic size and shape
centrilobular artery
septal veins .

8. Interlobular Septal Thickening: significance
ignore IST unless it is a predominant finding
smooth - interstitial infiltration
» lymphangitic spread of neoplasm
» pulmonary edema
» rare diseases
nodular - “perilymphatic pattern”
» sarcoidosis
irregular (lung distortion) - fibrosis
» other findings of fibrosis present

9. smooth septal thickening.

10. Lung carcinoma: lymphangitic spread.

11. Lung carcinoma: lymphangitic spread.

12. interstitial pulmonary edema.

13. Erdheim-Chester Disease.

14. Erdheim-Chester Disease.

15. nodular septal thickening
sarcoidosis
neoplasm .

16. UIP/IPF .

17. asbestosis .

18. Honeycombing cystic lucencies air containing 3-10 mm in diameter
subpleural
early: isolated cysts
late: several layers
cysts share walls when numerous

19. UIP
(IPF) .

20. Honeycombing: differential diagnosis
usual interstitial pneumonia (UIP)
idiopathic pulmonary fibrosis (IPF)
rheumatoid arthritis, scleroderma, other CVD
drugs
chronic hypersensitivity pneumonitis
asbestosis (uncommon)
end-stage sarcoidosis (uncommon)
fibrotic NSIP

21. Rheumatoid lung disease.

22. Honeycombing: significance
a very important finding in practice
fibrosis is present
UIP is likely the histologic pattern
in the absence of a known disease, IPF very likely
lung biopsy is uncommonly performed if significant honeycombing is visible

23. UIP (IPF) .

24. honeycombing?
UIP (IPF) .

25. paraseptal emphysema .
honeycombing?

26. UIP
(IPF) .

27. honeycombing?
UIP (IPF) .

28. honeycombing?
UIP (IPF) .

29. UIP (IPF)
honeycombing? .

30. ?
honeycombing? .

31. Honeycombing and window settings.

32. Irregular reticular opacities
reticular opacities not representing interlobular septal thickening or honeycombing
nonspecific
fibrosis or interstitial infiltration
ground-glass opacity: likely infiltration
honeycombing also present: likely fibrosis
traction bronchiectasis: likely fibrosis

33. Nonspecific interstitial pnuemonia (NSIP)
inflammation
fibrosis .

34. Cellular NSIP with infiltration.

35. NSIP:
fibrosis .

36. Traction Bronchiectasis
bronchiectasis resulting from fibrosis
corkscrew appearance
mucous plugging absent
bronchioles may be involved
associated with other findings of fibrosis (e.g. reticulation or honeycombing) .

37. traction bronchiectasis traction bronchiolectasis.

38. UIP (IPF) .

39. fibrotic
NSIP .

40. NSIP
fibrosis .

41. Traction Bronchiectasis: significance
fibrosis is very likely present
useful in diagnosis when a reticular abnormality is unassociated with honeycombing
UIP and IPF are common causes
other causes of fibrosis (i.e. sarcoidosis, HP, NSIP) are more likely than when honeycombing present
biopsy often indicated unless the patient has a C-V disease

42. Nodules - anatomic distribution (Colby)
lymphatic distribution - along lymphatics
random distribution - random relative to lung structures
bronchiolocentric - centrilobular airways
angiocentric - in relation to small vessels

43. Nodules - anatomic distribution (HRCT)
perilymphatic distribution
random distribution
centrilobular distribution

44. Perilymphatic nodules
nodules in relation to lymphatics
subpleural nodules
peribronchovascular nodules
septal nodules
patchy distribution

45. Perilymphatic Nodules: differential diagnosis
sarcoidosis
lymphangitic spread of tumor
silicosis and CWP (uncommon)
amyloidosis (rare)
LIP (rare)

46. Sarcoidosis

47. Sarcoidosis

48. Sarcoidosis .

49. Sarcoidosis .

50. Sarcoidosis .

51. lymphangitic spread of carcinoma.
lymphangitic spread of carcinoma

52. Lymphangitic spread: breast cancer
55 year-old woman
with
dyspnea .

53. Simple Silicosis

54. Perilymphatic Nodules: significance
sarcoidosis or lymphangitic carcinoma very likely
clinical history may be sufficient for diagnosis
bronchoscopy will likely provide diagnostic material

55. Random nodules
random distribution relative to lung structures
subpleural nodules
uniform distribution

56. Random Nodules: differential diagnosis
miliary TB
miliary fungal infections
hematogenous metastases
sarcoidosis (uncommon)

57. Miliary TB

58. Miliary TB
65 year-old with cough .

59. .

60. Miliary Coccidioidomycosis in AIDS.

61. Miliary cocci in AIDS .

63. .

64. Random Nodules: significance
metastases or TB very likely, depending on history
bronchoscopy will likely provide diagnostic material

65. Centrilobular nodules
occur in relation to centrilobular bronchiole or artery
centered 5-10 mm from pleura
evenly spaced
diffuse or patchy

66. Multiple Nodules subpleural nodules no pleural nodules patchy or
nonuniform
diffuse and
uniform
perilymphatic
distribution
random
distribution
centrilobular
distribution
sarcoidosis
silicosis
lymphangitic carc
miliary TB
hematogenous met
diseases involving
small airways
or vessels

67. Hypersensitivity Pneumonitis.

68. Hypersensitivity pneumonitis.

69. Summer-type hypersensitivity pneumonitis.

70. Centrilobular Nodules: differential diagnosis
bronchiolitis, e.g. infectious, inflammatory
endobronchial spread of TB, MAC
bronchopneumonia (any cause)
hypersensitivity pneumonitis
endobronchial spread of tumor (BAC)
pneumoconiosis (e.g. silicosis)
organizing pneumonia, i.e. BOOP (rare)
histiocytosis (rare)
edema or vasculitis (uncommon)

71. Bronchiolitis .

72. 27 year old with cough, SOB, and fever

74. TB

75. Viral pneumonia .

76. bronchopneumonia
SOB and fever .

77. aspiration .

78. BAC

79. Pulmonary hypertension
Pulmonary capillary hemangiomatosis
centrilobular nodules

80. Centrilobular branching opacities in talcosis.

81. metastatic calcification

82. Centrilobular Nodules: significance
small airways disease (e.g. bronchiolitis) most likely
consider infection
with appropriate history, may be diagnostic of hypersensitivity pneumonitis
remember BAC
because of relation of nodules to airways, transbronchoscopic biopsy often diagnostic in patients with infection or tumor

83. Tree in bud: diagnosis
dilatation and impaction of centrilobular airways
resembles a budding tree
centered mm from the pleural surface
more conspicuous than normal branching vessels
often associated with centrilobular nodules

84. “tree-in-bud” dilated, impacted centrilobular bronchioles
clustered centrilobular nodules or rosettes .

85. “Tree-in-bud”
courtesy J-G Im .

86. Tree-in-bud 27 cases all had infection
Aquino et al. JCAT 1996; 20:
27 cases
all had infection
common in bronchiectasis and bronchopneumonia
uncommon in other airway diseases (e.g. BO, BOOP, HP) .

87. AIDS-related airways disease.

88. Tree-in-bud: differential diagnosis
endobronchial spread of TB, MAC
bronchopneumonia (any cause)
bronchiectasis or bronchitis
cystic fibrosis
panbronchiolitis (rare)
aspiration (rare)
ABPA or asthma (rare)
BAC (rare)

89. pseudomonas bronchopneumonia.

90. active TB .

91. Tree-in-bud: significance
a very characteristic appearance
almost always infection
the diagnosis is in the sputum
if not, bronchoscopy should be diagnostic