This document provides an overview of lung imaging using CT scans. It begins with the history of tomography and CT scans. It then discusses the different types of CT chest scans and their indications. Next, it covers CT chest anatomy including lung segments and windows. The document outlines patterns of abnormalities seen on CT scans like nodules, ground glass opacities, and consolidation. It also discusses specific lung diseases and their CT findings such as bronchiectasis, ABPA, and pleural effusions. In summary, the document is a guide to interpreting CT chest scans by covering scan types, anatomy, and patterns of lung abnormalities.

1. LUNG IMAGING CT SCAN
MODERATOR:-
Dr. AMAAN LATIF
(Assistant Professor)
M.D RESPIRATORY MEDICINE
Dr. MURARI LAL CHEST HOSPITAL
G.S.V.M MEDICAL COLLEGE, KANPUR
PRESENTED BY:-
Dr. Kranti Kumar
SEMINAR

2. TOMOGRAPHY
TOMO:-SLICE
GRAPHIC:-TO WRITE
DEFINITION:-IMAGING OF AN OBJECT BY
ANALYSING ITS SLICES

3. H/O TOMOGRAPHY
• 1924:-MATHEMATIC THEORY OF TOMOGRAPHIC
IMAGES RECONSTRUCTION(JOHANN RADON)
• 1930:-CONVENTIONAL
TOMOGRAPHY(A.VALLEBONE)
• 1963:-THEORETICAL BASIS OF CT (A MACLOED
CORMACK)
• 1971:-FIRST COMMERCIAL CT(SIR GODFREY
HOUNSFEILD)

4. CT Chest:-
1. CT Chest Type:-
2. CT Chest Anatomy
3. CT Chest Abnormalities

5. CT Chest Type:-
1. Standard or Conventional CT:- •Slice thickness: 3-10 mm
•scans a large volume,
very quickly
•Covers the full lung
•+/- contrast

6. 2. High-Resolution Computed tomography (HRCT)
•Narrow x-ray beam
collimation: 1-1.3mm vs.
conventional 3-10mm
•Cross sections are further
apart: 10 mm
•High definition images of
lung parenchyma: vessels,
airspaces, airway and
interstitium
•No contrast

7. 3. Low Dose CT
• Uses:
• Screening of lung cancer
•F/U: Infection, post lung
transplant, metastasis
•Premise: lower dose
radiation will not reduce
the diagnostic
functionality of the scan
(eg. 250 mAs 50 mAs)
•Detail is decreased

8. 4. CT Angiography
Indications:-
• Pulmonary embolism
• Aortic aneurysm
• Aortic dissection
Risk :-
• HSR
• Contrast induced
nephropathy (CIN)
•Contrast injected into peripheral vein
•Injection timing/rate controlled automatically
•Dye is where you want it during scan
•Replaced conventional catheter angiogram

9. Indications
Std CT Chest:
• Chest x-ray (CXR)
abnormality
• Lung cancer staging
• F/U metastases
• Pleural and
mediastinal
abnormalities
• Empyema
HRCT
• ILD:
• Bronchiectasis
• Emphysema
• Normal or
equivocal CXR:
suspected lung
diseases and pattern
clarification
• Normal CXR with
abnormal PFT
• Evaluation of
hemoptysis
CECT
• Evaluation of the
mediastinum
(lymph nodes,
infection)
• Infection of the
chest wall
• Pleural thickening,
nodules, empyema
and evaluation of
metastatic or
primary malignancy
of the pleura.
• Pulmonary Lobar
Collapse
• Lung abscess,

10. CHEST CT :
GENERAL PRINCIPLES
• Scan levels : Lung apices to posterior costophrenic
angles.
• Patients position : Supine.
• Lung volume : Full inspiration ,single breath hold.
• Gantry rotation time : Approximately 0.5s in most
instances.
• Scan duration : Approximately 2.5s for the thorax
using MDCT and fast scanning.
• Detector width : The thinnest detector are typically
used for image acquisition

11. CT Chest Anatomy – Hounsfield
unit

12. CT Chest Anatomy - Views

15. CT Chest Anatomy – Window
setting
• Three windows :-
1. Mediastinal window
2. Lung window
3. Bone window

16. CT Chest Anatomy – Mediastinum
a) Supra-aortic mediastinum

17. Supra-aortic mediastinum

18. Supra-aortic mediastinum

19. b) Aortic arch

20. Azygos & aorto-pulmonary window

21. c) Main pulmonary artery :-

22. Right pulmonary artery

23. d) Heart and paracardiac mediastinum

24. Heart

25. CT Chest Anatomy – Lung segments
a) At level of trachea (Upper Lobe)

26. • At level of trachea (Upper Lobe)

27. b) At level of main stem bronchi (Carina)

28. At level of main stem bronchi (Carina)

29. c) At the level of the heart.

30. • At the level of the heart.

31. SECONDARY LOBULE:-
Basic Anatomic Unit
Of Pulmonary
Structure And
Function

32. THE SECONDARY PULMONARY LOBULES
HAS THREE PRINCIPAL COMPONENTS :
1. The Interlobular Septa.
2. The Centrilobular Region.
3. The Lobular Lung Parenchyma.

34. INTERPRETATION OF CT SCAN
The three pillars on which the diagnosis of lung disease
on a chest CT is based:
1. The Appearance Pattern,
2. The Location And Distribution Pattern Of The
Abnormalities
3. Patient Data

40. APPEARANCE PATTERN OF DISEASE
• Abnormalities associated with an increase in
lung density, i.e. increased lung attenuation
• Abnormalities associated with a decrease in
lung density, i.e. decreased lung attenuation
• Abnormalities presenting as nodular opacities
• Abnormalities presenting as linear opacities

41. WHAT IS ATTENUATION ?

42. NODULAR PATTERN
•A nodule with a diameter less than 1 cm (small
nodule),larger than 1 cm (large nodule).
•The term “micronodule” smaller than 3 mm in
diameter.
•The term “miliary pattern” indicates the presence of
multiple small (1–3 mm) micronodules with sharp
contours distributed in a major part of the lungs.

43. The Nodular Pattern: Diagnostic Algorithm

49. Tree-in-bud
• In centrilobular nodules the recognition of 'tree-
in-bud' is of value for narrowing the differential
diagnosis.
• Tree-in-bud describes the appearance of an
irregular and often nodular branching structure,
most easily identified in the lung periphery.
• It represents dilated and impacted (mucus or pus-
filled) cen- trilobular bronchioles.

50. • Tree-in-bud almost always indicates the presence
of:
• Endobronchial spread of infection (TB, MAC, any
bacterial bronchopneumonia)
• Airway disease associated with infection (cystic
fibrosis, bronchiectasis)
• less often, an airway disease associated primarily
with mucus retention (allergic bronchopulmonary
aspergillosis, asthma).

52. INCREASED ATTENUATION
PATTERN
Increase in density of the lung parenchyma

54. • Increased Lung Attenuation Is Called As Ground
Glass Opacity - If There Is A Hazy Increase In Lung
Opacity Without Obscuration Of Underlying Vessels
And
• Consolidation If The Increase In Lung Opacity
Obscures The Vessels
• In Both Ground Glass And Consolidation The
Increase In Lung Density Is The Replacement Of Air
In The Alveoli By Fluid, cells or Fibrosis.

55. • Ground Glass Opacity:-density Of Intrabronchial Air
Appears Darker As The Air In The Surrounding
Alveoli(called As Dark Bronchus Sign)
• Consolidation:-exclusively Air Left In Intrabronchial
Called As Air Bronchus Sign
• The location of the abnormalities in ground glass
pattern can be helpfull:
• Upper zone predominance: Respiratory bronchiolitis,
PCP.
• Lower zone predominance: UIP, NSIP, DIP.
• Centrilobular distribution: Hypersensitivity
pneumonitis, Respiratory bronchiolitis

58. Fibrosis

59. Consolidation

60. DECREASED
ATTENUATION PATTERN
Generally four causes of decreased lung
attenuation can be found:
• Hypoperfusion
• Air trapping
• Cystic and cyst-like lesions
• Pulmonary emphysema

63. • Cysts are low-density thin-walled areas that
are well defined and circumscribed and that
have a cellular wall (usually less than 3 mm
thick)
• Most frequent causes of cystic lung changes is
advanced fibrosis giving rise to honeycombing
or honeycomb cysts

65. RETICULAR/LINEAR PATTERN:-
• TOO MANY LINES EITHER AS ARESULT OF
THICKENING OF LUNG INTERLOBULAR
SEPTA OR INTRALOBULAR SEPTA.
• THICKENING OF LUNG INTERSTITIUM BY
FLUID ,FIBROUS TISSUE OR INFILTRATION BY
CELLS RESULTS IN PATTERN OF RETICULAR
OPACITY DUE TO THICKENING OF SEPTA.

66. Linear opacities can develop:
• When the interstitium is thickened
• When lymphatics are involved
• When peripheral acinar alveoli are
filled or collapsed
• When blood vessels and airways are
involved
• When lung atelectasis or fibrosis occurs

67. RETICULAR
LINEAR

68. PARENCHYMAL SIGN
• Air Crescent Sign
• Monod Sign
• Halo Sign
• Atoll Sign
• Cheerio Sign
• Comet Tail Sign
• Mosaic Sign
• Head Cheese Sign

73. AIRWAY SIGN
• TREE IN BUD
• AIR BRONCHOGRAM SIGN
• TRAM TRACK SIGN
• BRONCHUS SIGN
• SINGNET RING SIGN

77. VASCULAR SIGN
• FEEDING VESSEL SIGN
• CT ANGIOGRAM SIGN

79. PLEURAL-BASED SIGNS

80. ABPA
• Allergic bronchopulmonary aspergillosis (ABPA) is
an idiopathic inflammatory disease of the lung,
characterized by an allergic inflammatory response
to colonization of the airways by Aspergillus
fumigatus or other fungi.

81. HRCT Finding :-
• Bronchiectasis is classically cylindric and proximal
(central),occurring within the proximal two-thirds of the
lung.
• Widespread proximal cylindrical bronchiectasis (mostly of
upper lobes)
• Bronchial wall thickening
• Mucous plugging
• Atelectasis
• Peripheral airspace consolidation
• Ground-glass attenuation
• Mosaic perfusion
• Air trapping

83. Central bronchiectasis and mucoid impaction
(finger-inglove sign), characteristic of ABPA.

84. Bronchiectasis
• Bronchiectasis is an entity characterized
pathologically by airway inflammation, and
permanent bronchial dilatation, and clinically by
cough, sputum production, and exacerbations with
recurrent respiratory tract infections.

85. CT signs of bronchiectasis
• Signet ring appearance on CT: normally, the vessel is larger
than the corresponding bronchus in bronchiectasis, the
bronchus is larger than the corresponding vessel.
• Bronchial dilation, the cardinal sign of bronchiectasis, is
characterised on HRCT by a bronchoarterial ratio (BAR) of .1,
lack of bronchial tapering, and visibility of airways within 1
cm of the pleural surface or abutting the mediastinal pleural
surface.
• "Tramlines" or "honeycombing represents dilated,
thickened bronchial walls.

86. Signet-ring sign.
Tram-track sign.
Characteristic radiologic findings of bronchiectasis: airway
dilation and bronchial wall thickening.

87. Types of Bronchiectasis
 Cylindrical (tram
track sign)
• This description applies to dilated
airways seen in a horizontal
orientation.

88. • Varicose
• Implies non uniform bronchial
dilatation. Cystic or saccular A
cluster of thin walled cystic
spaces

89. • Sacculer or Cystics
• A cluster of thin walled cystic spaces

90. Pleural Effusion
• Pleural effusion, a collection of fluid in the pleural
space, is rarely a primary disease process but is
usually secondary to other diseases.
• The pleural space normally contains only about 10-20
ml of serous fluid.
• Pleural fluid normally seeps continually into the
pleural space from the capillaries lining the parietal
pleura and is reabsorbed by the visceral pleural
capillaries and lymphatic system.

91. CT Finding :-
• Contrast-enhanced computed tomography: split
pleural sign .
• Split pleural sign refers to thickening & increased
contrast enhancement of the visceral & parietal pleura
separated by empyema or an exudative effusion.

92. Pneumothorax
• abnormal presence of
air in the pleural
cavity, separating
the visceral from the
parietal pleura, is
known as
pneumothorax.

93. COPD
• Chronic obstructive Pulmonary Disease (COPD) is a
Heterogeneous Lung condition characterized by
chronic respiratory symptoms (dyspnea, cough,
sputum production and/or exacerbation) due to
abnormalities of airways (bronchitis, bronchiolitis)
and/or alveoli (emphysema) that cause persistent,
often progressive, airflow obstruction.

94. CT Finding
•Emphysema ( Hypodense area) Enlarged Alveolar duct and Alveoli.
•Bronchitis Shows bronchial wall thickning.

95. Tuberculosis
• HRCT findings in TB :-
• Consolidation anywhere, lymphadenopathy and
pleural effusion. Usually regresses to calcified lung
nodule.
• Cavitation
• (Endobronchial spread) Tree in bud appearance)
• Miliary TB: 2-3 mm nodules with random
distribution.

98. Pulmonary Artery Hypertension
 Findings in CT:
• Extra cardiac vascular signs:
• Enlarged pulmonary trunk >29 mm diameter is often
used as a general predictive cut-off
• Enlarged pulmonary arteries
• Mural calcification in central pulmonary arteries
• Evidence of previous pulmonary emboli

99. • Cardiac signs:
• Right ventricular hypertrophy: defined as wall
thickness of more than 4 mm.
• Straightening or bowing (towards the left ventricle)
of the interventricular septum
• Right ventricular dilatation
• Decreased right ventricular ejection fraction
• Dilatation of the inferior vena cava and hepatic veins
• Pericardial effusion

100. • Parenchymal signs:
• Centrilobular ground-glass nodules (Cholesterol
granuloma).
• Neovascularity: tiny serpiginous intrapulmonary
vessels that often emerge from centrilobular
arterioles.

103. ILD (INTERSTITIAL LUNG
DISEASES)
• ILD refers to a heterogeneous collections of lung
disorder that are grouped together because they
share clinical radiographic and pathological
features , ILD also refers to as Diffuse
parenchymal lung Diseases.
• ILD involved the Parenchyma of Lung, Alveoli,
The Alveolar Epithelium, the capillary
endothelium, and the spaces between these
structure as well as perivascular and lymphatic
tissue.

104. Distribution of ILD

105. Pattern of ILD

106. Radiographic Signs in ILD

107. Anterior upper Lobe sign.
Concentration of fibrosis within the anterior aspect of upper lobe and
concomitant lower lobe involvement.

108. Exuberant honeycombing
Honeycomb cyst formation within the lung constituting greater than 70%
fibrotic person of Lung.

109. Straight edge sign
Isolation of fibrosis to the lung bases with sharp
demarcation in the craniocaudal plane without substantial
extension along the lateral margins

110. Three-density sign/
headcheese
CT imaging shows patchy ground-glass attenuation in the anterior left
upper lobe (blue circle). Other lobules are of preserved (normal)
attenuation (yellow circle), and there is lobular decreased attenuation in
the posterior left lung (red circle). No signs of fibrosis are present

111. Atoll sign/reverse halo
Central ground glass opacity surrounded by denser
consolidation in the shape of a crescent or ring.

112. Galaxy sign
CT images demonstrate perilymphatic irregular nodular thickening in an
upper/mid lung distribution with some areas of mass-like coalescing nodules,
more concentrated in the center than at the periphery the “galaxy sign.”

113. Sarcoidosis
• Sarcoidosis is a systemic disorder of unknown
origin.
• It is characterized by non-caseating granulomas in
multiple organs, that may resolve spontaneously
or progress to fibrosis.
• Pulmonary manifestations are present in 90% of
patients.
• Less than 5% of patients die from sarcoidosis
usually as a result of pulmonary fibrosis.

114. HRCT findings in Sarcoidosis
• Common findings:
-Small nodules in a per lymphatic distribution
(i.e. along subpleural surface and fissures, along
interlobular septa and the peribronchovascular
bundle).
-Upper and middle zone predominance.
-Lymphadenopathy in left hilus, right hilus and
paratracheal (1-2- 3 sign). Often with
calcifications.

115. • Uncommon findings:
-Conglomerate masses in a perihilar location.
-Larger nodules (> 1cm in diameter, in < 20%)
-Grouped nodules or coalescent nodules
surrounded by multiple satellite nodules (Galaxi
sign)
-Nodules so small and dense that they appear as
ground glass or even as consolidations (alveolar
sarcoidosis)

116. Typical presentation of sarcoidosis with mediastinal lymphadenopathy and
small nodules in a perilymphatic distribution along bronchovascular bundles
and along fissures (yellow arrows).
Always look for small nodules along the fissures, because this is a very specific
and typical sign of sarcoidosis.

117. Silicosis / Coal worker
pneumoconiosis
• Silicosis and Coal worker pneumoconiosis (CWP) are
pathologically distinct entities with differing
histology, resulting from the inhalation of different
inorganic dusts.
• The radiographic and HRCT appearances of these
diseases, however, may not be distinguishable from
each other and may be similar to sarcoidosis.
• Silicosis and CWP occur in a specific patient group
(construction workers, mining workers, workers
exposed to sandblasting, glass blowing and pottery).

118. HRCT findings in Silicosis/CWP
• Small well-defined nodules of 2 to 5mm in diameter
in both lungs.
• Upper lobe predominance
• Nodules may be calcified
• Centrilobular and subpleural distribution
• Sometimes random distribution
• Irregular conglomerate masses, known as progressive
massive fibrosis
• Masses may cavitate due to ischemic necrosis.
• Often hilar and mediastinal lymphnodes.

119. A case of silicosis showing nodules of varying sizes with a random and
subpleural distribution. One nodule contains calcification (arrow).
Note the absence of a lymphatic distribution pattern (peribronchovascular and
along fissures), which would be suggestive of sarcoidosis.

120. Hypersensitivity Pneumonitis
• Hypersensitivity pneumonitis (HP) is also known as
extrinsic allergic alveolitis (EAA).
HP is an allergic lung disease caused by the inhalation
of a variety of antigens (farmer's lung, bird fancier's
lung, 'hot tub' lung, humidifier lung).
• The radiographic and pathologic abnormalities in
patients can be classified into acute, subacute, and
chronic stages.
• Mostly HRCT is performed in the subacute stage of
HP, weeks to months following the first exposure to the
antigen or in the chronic phase.

121. Three-density pattern
• Ground glass opacification
• Mosaic attenuation with zonesof diminished
attenuation/hypoperfusion.
• Areas of normal-appearing parenchyma.

122. CT imaging shows patchy ground-glass attenuation in the anterior left
upper lobe (blue circle). Other lobules are of preserved (normal)
attenuation (yellow circle), and there is lobular decreased attenuation in
the posterior left lung (red circle). No signs of fibrosis are present

123. Usual interstitial pneumonia (UIP)
Computed tomography scan illustrates the “classic”
features of idiopathic pulmonary fibrosis (IPF), the usual interstitial
pneumonia (UIP) pattern. Bilateral, peripheral, and subpleural reticular
infiltrates are evident. The presence of advanced fibrosis is indicated by
honeycomb changes (arrowheads) and traction bronchiectasis (arrow).

124. Nonspecific interstitial pneumonia
(NSIP).
• Nonspecific interstitial pneumonia (NSIP). High-resolution CT
images through the upper (A) and lower (B) thorax
demonstrate peripheral and lower lobe–predominant ground-
glass opacities with mild reticular markings and minimal
traction bronchiectasis (arrows).

125. Central Tumor

126. Peripheral Tumor

127. Solitary Pulmonary Nodules
Corona radiata or the "sunburst appearance" - Presence of
spiculation associated with a nodule or a mass- Feature of
malignant lesion.

129. Pulmonary Metastasis
Lung metastases from non seminomatous germ cell tumour of testis. Seen as
multiple opacities in both the lung fields. ( Canon Ball appearance)

130. THANKYOU