High resolution Computerised Tomagraphy is a radiological procedure done to diagnose lung diseases.In this powerpoint presentation indications for HRCT,common patterns observed in HRCT to diagnose common lung diseases have been described.

1. HRCT-LUNG
BASIC INTERPRETATION
Dr Dileep MD
Assistant Professor
Dept. of Pulmonary Medicine
MIMS

2. Introduction
• HRCT uses very thin slices (1mm vs 3-10mm standard CT) to
achieve better spatial resolution and precision
• Narrow X-ray beam collimation :1-1.3mm vs Conventional 3-
10mm
• Cross sections are further apart :10mm
• High definition images of lung parenchyma : vessels, airspaces,
airway and interstitium

3. Indications
• Suspected Emphysema and other obstructive
diseases
• Bronchiectasis
• Suspected Fibrotic or Restrictive Disease, or
Unknown Lung Disease
• Hemoptysis evaluation
• Suspected Pulmonary Vascular Disease

4. Secondary pulmonary lobule
• Smallest functional unit
• Size -1 to 2.5 cm and is made up of 5-15
pulmonary acini, that contain the alveoli for gas
exchange.
• Supplied by a terminal bronchiole and a
centrilobular artery –centrilobular area
• Pulm.veins and lymphatics –perilymphatic area
• It is surrounded by connective tissue septa

5. Secondary lobule

6. Pulmonary anatomy
Secondary pulmonary lobule

7. • 1.Axial fiber system:
 peribronchovascular
interstitium : connective
tissue sheath that
surrounds large bronchi
and arteries.
 centrilobular interstitium:
peripheral continuum of
peribronchovascular
interstitium, which is
associated with small
centrilobular bronchioles
and arteries
• 2.Peripheral fiber
system
 subpleural interstitium is
located beneath the
visceral pleura; it envelops
the lung in a fibrous sac
from which connective
tissue septa penetrate into
the lung parenchyma
3.Septal fiber system
 Intralobular septa
INTERSTITIUM

8. Basic interpretation
• Pattern- Increased or decreased lung attenuation.
• Location in the secondary lobule
• Upper Vs lower zones
• Peripheral Vs central

9. High Attenuation pattern

10. Increased lung opacity
• Nodules
• Reticulation
• Ground glass opacity
• Consolidation

11. Nodules
• Sharply defined, discrete, nearly circular opacity
in the lung.
• Size-2 to 30 mm.

12. Nodular pattern

13. Centrilobular nodules
• Hypersensitivity
pneumonitis
• RB-ILD in smokers
• Infectious airways
diseases (TB and
Br.pneumonia)

14. ‘Tree in bud’
• Dilated and impacted
(mucus or pus-filled)
centrilobular bronchioles.
• Endobronchial spread of
infection; TB or any
bacterial
bronchopneumonia and
bronchiectasis)

15. ‘Tree in bud

17. Perilymphatic nodules
• Sarcoidosis
• Lymphangitic carcinomatosis
• Silicosis & coal worker’s pneumoconiosis.

18. sarcoidosis

19. Random nodules
• Due to hematogenous spread of the infection.
• Hematogenous metastases.
• Miliary tuberculosis
• Fungal infections
• Langerhans cell histiocytosis (early nodular
stage)

20. Miliary tuberculosis

21. Langerhans cell histiocytosis
Early nodular phase before typical cysts appear

22. Reticular pattern
• Thickening of the interstitium by fluid, fibrosis or
infiltration by cells.
• Smooth –pulmonary edema
• Nodular or irregular –lymphatic spread of
carcinoma, sarcoidosis.

23. Focal septal thickening in lymphangitis carcinomatosis

24. Cardiogenic pulmonary
edema
• A combination of septal
thickening and ground-
glass opacity

25. Ground glass opacity
• Hazy increased attenuation but not obscuring the
underlying vessels.
• Interstitial (fibrosis) as well as alveolar abnormality(air
space filling).
• Eg:
• Acute-pulmonary oedema, haemorrhage, pneumonia.
• Chronic-hypersensitivity pneumonitis, organising
pneumonia,NSIP and bronchoalveolar carcinoma.

26. Bronchoalveolar cell carcinoma with GGO and consolidation

27. Consolidation
• Air-space disease.
• Filled by blood, pus, fluid or cells.
• Air-bronchogram.

29. Low Attenuation Patterns

30. • Emphysema
• Lung cysts
• Bronchiectasis
• Honeycombing

31. Decreased lung opacity

32. Emphysema
• Permanent, abnormal enlargement of air
spaces.
• Destruction of air space walls.

33. • Centrilobular emphysema due to smoking.
• The periphery of the lung is spared.
• Centrilobular artery (yellow arrows) is seen in the
center of the hypo dense area.

34. Paraseptal emphysema
• Localized near fissures and pleura.
• Bullae formation.
• May lead to spontaneous pneumothorax.

35. Panlobular emphysema
• Complete destruction of sec. lobules.
• More severe in lower lobes.

36. Cysts
• Lung cysts are defined as radiolucent areas with
a wall thickness of less than 4mm.

37. • Langerhans cell histiocytosis

38. Bronchiectasis
• Localised, irreversible dilation of the bronchial
tree.
• A bronchus is considered to be dilated if the
bronchoarterial ratio (its internal diameter
divided by the diameter of its accompanying
artery)exceeds 1
• Signet ring sign.
• Lack of bronchial tapering.
• Visualisation of peripheral airways.

39. Cylindrical bronchiectasis
• Thick-walled bronchi
that extend into the lung
periphery and fail to
show normal tapering.
• On HRCT, bronchi are
not normally visible in
the peripheral 1 cm of
lung
• But in patients with
bronchiectasis,
bronchial wall
thickening, peribronchial
fibrosis, and dilatation of
the bronchial lumen,
can be seen in the lung
periphery

40. Varicose bronchiectasis
• Similar in
appearance to
cylindrical
bronchiectasis;
however the
bronchial walls are
more irregular and
can assume a
beaded appearance .
• The term string of
pearls has been
used to describe
varicose
bronchiectasis.

41. Cystic bronchiectasis
• It appears as a
group or cluster of
air-filled cysts giving
the appearance of a
cluster of grapes
• Cystic
bronchiectasis is
often patchy in
distribution

42. Honey comb lung
• Honeycombing is defined by the presence of small cystic
spaces with irregularly thickened walls composed of fibrous
tissue
• Honeycomb cysts often predominate in the peripheral and
subpleural lung regions regardless of their cause
• Subpleural honeycomb cysts typically occur in several
contiguous layers

43. • Honeycombing
• .

44. UIP

45. Upper Vs Lower zones
Upper zone
• Sarcoid/Silicosis
• Pneumoconiosis
• Langerhans cell
histiocytosis
• Centrilobular
emphysema
Lower zone
• Edema
• Panlobular
emphysema
• Aspiration
• UIP

46. Central Vs Peripheral zone
• Central Peripheral
Sarcoid -COP
Bronchitis -Chronic
eosinophilic pneumonia
-Hematogenous
metastases
-UIP

47. Summary
• Assessment of diffuse parenchymal lung disease(DPLD)
• Pulmonary anatomy is a prerequisite for interpretation
• Systematic approach to the patterns of abnormalities on
HRCT is essential for a good diagnosis
• Always integrate clinical findings with HRCT images for
better diagnosis
• Go for biopsy/ HPE when in doubt

48. THANK YOU