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HRCT
Low attenuation pattern
DR SAKHER-ALKHADERI
CONSULTANT RADIOLOGIST AMC
Low Attenuation pattern
Emphysema
Lung cysts (LAM, LIP, Langerhans cell
histiocytosis)
Bronchiectasis
Honeycombing
Emphysema
Emphysema typically presents as
areas of low attenuation without
visible walls as a result of
parenchymal destru...
EMPHYSEMA
Permanent, abnormal enlargement of air
spaces distal to the terminal bronchiole
and accompanied by the destructi...
Most common type
Irreversible destruction of alveolar
walls in the centrilobular portion of
the lobule
Upper lobe predo...
Centrilobular (proximal
or centriacinar)
emphysemaFound most commonly in the upper lobes
Manifests as multiple small areas...
Centrilobular emphysema due to smoking. The
periphery of the lung is spared (blue arrows).
Centrilobular artery (yellow ar...
PANLOBULAR EMPHYSEMA
Affects the whole secondary lobule
Lower lobe predominance
In alpha-1-antitrypsin deficiency, but
...
PANLOBULAR
EMPHYSEMA
Affects the entire secondary pulmonary
lobule and is more pronounced in the lower
zones
Complete dest...
PANLOBULAR
EMPHYSEMA
13
Panlobular emphysema
Paraseptal (distal
acinar) emphysema
Affects the peripheral parts of
the secondary pulmonary lobule
Produces subpleural lu...
Paraseptal emphysema
Cystic lung disease
Lung cysts are defined as radiolucent areas with a
wall thickness of less than 4mm.
There is proliferation of Langerhans cells in the bronchiolar and
bronchial epithelium, forming granulomas. It is postulat...
Cysts : more pronounced later in the disease
usually less than 10 mm in diameter
may measure up to 2-3 centimetres in size...
The disease is characterised by the persistence of dilated lymphatics and
interstitial proliferation of abnormal smooth mu...
Lymphangiomyomatosis complicated by pneumothorax
Lymphocytic interstitial pneumonia is a benign
lymphoproliferative disorder characterized by a
diffuse and exquisitely int...
Bronchiectasis
Bronchiectasis is defined as localized irreversible
bronchial dilatation.
bronchial wall thickening
lack of...
Subtypes
According to macroscopic morphology, three types have been described, which
also represet a spectrum of severity ...
ABPA: glove-finger shadow due to mucoid impaction in central
bronchiectasis in a patient with asthma.
Signet-Ring Sign
A signet-ring sign represents an axial cut of a dilated
bronchus (ring) with its accompanying small artery
Tram Tracks
Bronchial dilation with lack of
tapering .Cystic bronchiectasis
HONEYCOMBING
Defined as - small cystic spaces with
irregularly thickened walls composed of
fibrous tissue.
Predominate in ...
Honeycombing
Honeycombing is defined by the presence of small cystic
spaces with irregularly thickened walls composed of
f...
Causes
Lower lobe predominance :
1. UIP or interstitial fibrosis
2. Connective tissue disorders
3. Hypersensitivity pneumo...
Honeycombing
HRCT
showing
honeycobing
Honeycombing and traction bronchiectasis in
UIP.
Typical UIP with honeycombing and traction
bronchiectasis in a patient with idiopathic
pulmonary fibrosis (IPF)
THE END
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
HRCT Low attenuation pattern
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HRCT Low attenuation pattern

Describes the differential diagnosis of low attenuation pattern of diffuse lung disease and how to approach HRCT findings .

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HRCT Low attenuation pattern

  1. 1. HRCT Low attenuation pattern DR SAKHER-ALKHADERI CONSULTANT RADIOLOGIST AMC
  2. 2. Low Attenuation pattern Emphysema Lung cysts (LAM, LIP, Langerhans cell histiocytosis) Bronchiectasis Honeycombing
  3. 3. Emphysema Emphysema typically presents as areas of low attenuation without visible walls as a result of parenchymal destruction.
  4. 4. EMPHYSEMA Permanent, abnormal enlargement of air spaces distal to the terminal bronchiole and accompanied by the destruction of the walls of the involved air spaces. 7
  5. 5. Most common type Irreversible destruction of alveolar walls in the centrilobular portion of the lobule Upper lobe predominance and uneven distribution Strongly associated with smoking. Centrilobular (proximal or centriacinar) emphysema
  6. 6. Centrilobular (proximal or centriacinar) emphysemaFound most commonly in the upper lobes Manifests as multiple small areas of low attenuation without a perceptible wall, producing a punched-out appearance. Often the centrilobular artery is visible within the centre of these lucencies. 9
  7. 7. Centrilobular emphysema due to smoking. The periphery of the lung is spared (blue arrows). Centrilobular artery (yellow arrows) is seen in the center of the hypodense area.
  8. 8. PANLOBULAR EMPHYSEMA Affects the whole secondary lobule Lower lobe predominance In alpha-1-antitrypsin deficiency, but also seen in smokers with advanced emphysema
  9. 9. PANLOBULAR EMPHYSEMA Affects the entire secondary pulmonary lobule and is more pronounced in the lower zones Complete destruction of the entire pulmonary lobule. Results in an overall decrease in lung attenuation and a reduction in size of pulmonary vessels 12
  10. 10. PANLOBULAR EMPHYSEMA 13
  11. 11. Panlobular emphysema
  12. 12. Paraseptal (distal acinar) emphysema Affects the peripheral parts of the secondary pulmonary lobule Produces subpleural lucencies. 15
  13. 13. Paraseptal emphysema
  14. 14. Cystic lung disease Lung cysts are defined as radiolucent areas with a wall thickness of less than 4mm.
  15. 15. There is proliferation of Langerhans cells in the bronchiolar and bronchial epithelium, forming granulomas. It is postulated that as these cellular granulomas evolve, peripheral fibrosis forms resulting in traction on the central bronchiole which becomes cyst-like 3 . This explains the presumed evolution from nodule, through cavitating nodule and thick walled cysts, to the 'stable' thin-walled cysts 3 CT : nodules:more pronounced early in the disease may range in number from a few to innumerable 1-10 mm in diameter (typically 1-5 mm 4 ) centrilobular distribution usually irregular margin surrounding lung parenchyma appears normal may cavitate and become cysts
  16. 16. Cysts : more pronounced later in the disease usually less than 10 mm in diameter may measure up to 2-3 centimetres in size the extreme bases may be preserved usually thin-walled, but on occasion may be up to a few millimetres thick Other common findings include 1,3 : ground-glass opacities: emphysema mosaic attenuation Differential diagnoses -granulomatous disease Wegener granulomatosis sarcoidosis -metastases -miliary tuberculosis-lymphangiomyomatosis (LAM)
  17. 17. The disease is characterised by the persistence of dilated lymphatics and interstitial proliferation of abnormal smooth muscle that in turn can obstruct venules, lymphatics, and small airways. HRCT thin walled cysts of variable sizes surrounded by normal lung parenchyma can be seen throughout the lung interlobular septal thickening may show a dilated thoracic duct haemorrhages may be seen as areas of increased attenuation Differential diagnosis For pulmonary manifestations, the primary differential to be considered is Langerhans cell histiocytosis (LCH) which tends to happen in children and young adults with history of heavy cigarette smoking. It has a mid to upper lobe distribution with preservation of costophrenic angles. In addition, the cysts in LCH tend to be more irregular in contour. LCH has much more favourable prognosis compared with LAM.
  18. 18. Lymphangiomyomatosis complicated by pneumothorax
  19. 19. Lymphocytic interstitial pneumonia is a benign lymphoproliferative disorder characterized by a diffuse and exquisitely interstitial proliferation of small lymphocytes and plasma cells (1). Lymphocytic interstitial pneumonia occurs most commonly in patients who have Sjögren syndrome, autoimmune thyroid disease, acquired immunodeficiency syndrome (AIDS), or Castleman disease LIP Radiology findings : ground-glass attenuation, airspace consolidation, parenchymal nodules, interlobular septal Radiology findings : ground-glass attenuation, airspace consolidation, parenchymal nodules, interlobular septal
  20. 20. Bronchiectasis Bronchiectasis is defined as localized irreversible bronchial dilatation. bronchial wall thickening lack of normal tapering with visibility of airways in the peripheral lung mucus retention in the bronchial lumen associated atelectasis and sometimes air trapping
  21. 21. Subtypes According to macroscopic morphology, three types have been described, which also represet a spectrum of severity 8 : cylindrical bronchiectasis bronchi have a uniform calibre, do not taper and have parallel walls (tram track sign and signet ring sign) commonest form 14 varicose bronchiectasis relatively uncommon beaded appearances where dilated bronchi have interspersed sites of relative narrowing cystic bronchiectasis severe form with cyst-like bronchi that extend to the pleural surface air-fluid levels are commonly present
  22. 22. ABPA: glove-finger shadow due to mucoid impaction in central bronchiectasis in a patient with asthma.
  23. 23. Signet-Ring Sign A signet-ring sign represents an axial cut of a dilated bronchus (ring) with its accompanying small artery
  24. 24. Tram Tracks
  25. 25. Bronchial dilation with lack of tapering .Cystic bronchiectasis
  26. 26. HONEYCOMBING Defined as - small cystic spaces with irregularly thickened walls composed of fibrous tissue. Predominate in the peripheral and subpleural lung regions Subpleural honeycomb cysts typically occur in several contiguous layers. D/D- paraseptal emphysema in which subpleural cysts 40
  27. 27. Honeycombing Honeycombing is defined by the presence of small cystic spaces with irregularly thickened walls composed of fibrous tissue.
  28. 28. Causes Lower lobe predominance : 1. UIP or interstitial fibrosis 2. Connective tissue disorders 3. Hypersensitivity pneumonitis 4. Asbestosis 5. NSIP (rare) Upper lobe predominance : 1. End stage sarcodosis 2. Radiation 3. Hypersensitivity Pneumonitis 4. End stage ARDS 42
  29. 29. Honeycombing HRCT showing honeycobing
  30. 30. Honeycombing and traction bronchiectasis in UIP.
  31. 31. Typical UIP with honeycombing and traction bronchiectasis in a patient with idiopathic pulmonary fibrosis (IPF)
  32. 32. THE END

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