13. Extra Pleural Sign
Cancer Lung
Density in periphery
Sharp inner margin
Indistinct outer margin
Angle of contact with chest wall
Expanding destructive rib lesion
Paratracheal widening
This is an example of an RUL lesion
17. Lateral Chest
There is valuable information that can be obtained by a chest
lateral view. A few of them are listed below:
Sternum
Vertebral column
Retrosternal space
Localization of lung lesions
Lobes of lungs
Oblique fissures
Pulmonary artery
Heart
Aorta
Mediastinal masses
Diaphragm
Volume measurements
SPN
Radiologic TLC
Tracheoesophageal stripe
18. Tuberculosis of Spine
Loss of intervertebral space
Vertebral collapse
Cold abscess is not present in this case. PA view is not diagnostic.
20. RML Atelectasis
Vague density in right lower lung field, almost normal
RML atelectasis in lateral view, not evident in PA view
21. Atelectasis Left Upper
Lobe
Hazy density over left
upper lung field
Loss of left heart
silhouette
Tracheal shift to left
A: Forward movement of oblique
fissure
C: Atelectatic LUL
B: Herniated right lung
22. Localization
When a lesion is not contiguous to a
silhouette, it is not possible to localize it
without a lateral view. This is a case of a
solitary pulmonary nodule with popcorn
calcification: Hamartoma.
23.
24.
25.
26.
27. Air Bronchogram
• In a normal chest x-ray, the tracheobronchial tree is not
visible beyond the 4th order. As the bronchial tree
branches, the cartilaginous rings become thinner, and
eventually disappear in respiratory bronchioles. The
lumen of the bronchus contains air and the surrounding
alveoli contain air. Thus, there is no contrast to visualize
the bronchi.
• The air column in the bronchi beyond the 4th order
becomes recognizable if the surrounding alveoli is filled,
providing a contrast or if the bronchi get thickened
• The term air bronchogram is used for the former state
and signifies alveolar disease.
28.
29. Silhouette Sign
Adjacent Lobe/SegmentSilhouette
RLL/Basal segmentsRight diaphragm
RML/Medial segmentRight heart margin
RUL/Anterior segmentAscending aorta
LUL/Posterior segmentAortic knob
Lingula/Inferior segmentLeft heart margin
LLL/Superior and basal segmentsDescending aorta
LLL/Basal segmentsLeft diaphragm
Cardiac margins are clearly seen because there is contrast between the fluid
density of the heart and the adjacent air filled alveoli. Both being of fluid density,
you cannot visualize the partition of the right and left ventricle because there is no
contrast between them. If the adjacent lung is devoid of air, the clarity of the
silhouette will be lost. The silhouette sign is extremely useful in localizing lung
lesions.
30.
31. Atelectasis Right Lung
Homogenous density right hemithorax
Mediastinal shift to right
Right hemithorax smaller
Right heart and diaphragmatic silhouette are not identifiable
32. Atelectasis Left Lung
Homogenous density left hemithorax
Mediastinal shift to left
Left hemithorax smaller
Diaphragm and heart silhouette are not identifiable
33. Lateral
Movement of oblique and transverse
fissures
Atelectasis Right Upper Lobe
Homogenous density right upper lung
field
Mediastinal shift to right
Loss of silhouette of ascending aorta
34. Atelectasis Left Upper
Lobe
Hazy density over left
upper lung field
Loss of left heart
silhouette
Tracheal shift to left
Lateral
A: Forward movement of
oblique fissure
B: Herniated right lung
C: Atelectatic LUL
35. Consolidation Right
Upper Lobe /
Density in right upper lung
field
Lobar density
Loss of ascending aorta
silhouette
No shift of mediastinum
Transverse fissure not
significantly shifted
Air bronchogram
36. Consolidation Left Lower Lobe
Density in left lower lung field
Left heart silhouette intact
Loss of diaphragmatic silhouette
No shift of mediastinum
Pneumatocele
One diaphragm only visible
Lobar density
Oblique fissure not significantly
shifted
37. Left Upper Lobe Consolidation
Density in the left upper lung field
Loss of silhouette of left heart margin
Density in the projection of LUL in lateral view
Air bronchogram in PA view
No significant loss of lung volume
38. Vague density right lower lung field
Indistinct right cardiac silhouette
Intact diaphragmatic silhouette
Density corresponding to RML
No loss of lung volume
RML pneumonia
39. S Curve of Golden
When there is a mass
adjacent to a fissure, the
fissure takes the shape
of an "S". The proximal
convexity is due to a mass,
and the distal concavity is
due to atelectasis. Note the
shape of the transverse
fissure.
This example represents a
RUL mass with atelectasis
40. Tracheal Shift
Trachea is index of upper mediastinal position. The pleural pressures on either
side determine the position of the mediastinum. The mediastinum will shift
towards the side with relatively higher negative pressure compared to the
opposite side. Tracheal deviation can occur under the following conditions:
• Deviated towards diseased side
– Atelectasis
– Agenesis of lung
– Pneumonectomy
– Pleural fibrosis
• Deviated away from diseased side
– Pneumothorax
– Pleural effusion
– Large mass
• Mediastinal masses
• Tracheal masses
• Kyphoscoliosis
41. Atelectasis Right Lung
• Homogenous density
right hemithorax
• Mediastinal shift to right
• Right hemithorax smaller
• Right heart and
diaphragmatic silhouette
are not identifiable
•
42. Pleural Effusion Massive
• Unilateral homogenous
density
• Mediastinal shift to right
• Left diaphragmatic and
left heart silhouettes lost
• Left hemithorax larger
45. Air Bronchogram
• In a normal chest x-ray, the tracheobronchial tree is not
visible beyond the 4th order. As the bronchial tree
branches, the cartilaginous rings become thinner, and
eventually disappear in respiratory bronchioles. The
lumen of the bronchus contains air and the surrounding
alveoli contain air. Thus, there is no contrast to visualize
the bronchi.
• The air column in the bronchi beyond the 4th order
becomes recognizable if the surrounding alveoli is filled,
providing a contrast or if the bronchi get thickened
• The term air bronchogram is used for the former state
and signifies alveolar disease.
46.
47. Bowing Sign
• In LUL atelectasis or
following resection, as in
this case, the oblique
fissure bows forwards
(lateral view). Bowing
sign refers to this feature.
The arrow points to the
forward movement of the
left oblique fissure.
48. Doubling Time
• Time to double in volume (not diameter)
• Useful in determining the etiology of solitary
pulmonary nodule
• Utility
– Less than 30 days: Inflammatory process
– Greater than 450 days: Benign tumor
– Malignancy falls in between
49. Eccentric Location of Cavity in a
Mass
• Thick wall and irregular lumen can be
seen in both malignancy and
inflammatory lesions.
• However eccentric location of cavity is
diagnostic of malignancy.
50. • This is an example of
squamous cell
carcinoma lung.
• LUL mass
• Thick walled cavity
• Eccentric location of
cavity
• Fluid level
• This is diagnostic of
malignancy.
51. Cortical Distribution
• Mirror image of pulmonary edema
• Alveolar disease of outer portion of lung
• Encountered in:
– Eosinophilic pneumonia
– Bronchiolitis obliterans with pneumonia
52. Medullary Distribution
• It is also called "butterfly pattern"
• Note the sparing of lung periphery both in
the CT, PA and lateral views
• This is one of the radiologic signs
indicative of diffuse alveolar disease
• This is an example of alveolar proteinosis.
53. Note the sparing of lung periphery both in the CT, and PA view
This is one of the radiologic signs indicative of diffuse alveolar disease
This is an example of alveolar proteinosis.
54. Diffuse Alveolar Disease
Radiological Signs
• Butterfly distribution / Medullary distribution
• Lobar or segmental distribution
• Air bronchogram
• Alveologram
• Confluent shadows
• Soft fluffy edges
• Acinar nodules
• Rapid changes
• No significant loss of lung volume
• Ground glass appearance on HRCT
58. Acinar Nodules
InterstitialAcinar
Same size
Sharp edges
smaller
Varying in size
Indistinct edges
Larger than interstitial nodules
Acinar nodules are difficult to distinguish from interstitial
nodules. Some distinguishing characteristics are as follows:
59.
60. Cut Off Sign
• When you see an abrupt ending of visualized
bronchus, it is called a "cut off sign". It indicates
an intrabronchial lesion. This is useful to identify
the etiology of atelectasis . Be careful as the
tracheobronchial tree is three dimensional and
the finding need to be confirmed with tomogram.
In the modern era, a CT scan will take care of
this.
62. Wedge Shaped Density
The wedge's base is pleural
and the apex is towards the
hilum, giving a triangular
shape. You can encounter
either of the following:
Vascular wedges :
Infarct
Invasive aspergillosis
Bronchial wedges :
Consolidation
Atelectasis
63. Polycyclic Margin
The wavy shape of
the mediastinal mass
margin indicates that
it is made up of
multiple masses,
usually lymph nodes.
This is a case of
lymphoma.
64. Open Bronchus Sign / Alveolar Atelectasis
The right lung is atelectatic. You can see air bronchogram, which indicates
that the airways are patent .This case is an example of adhesive alveolar
atelectasis.
65. Pulmonary Artery Overlay
Sign
This is the same concept as
a silhouette sign. If you can
recognize the interlobar
pulmonary artery, it means
that the mass seen is either
in front of or behind it.
This is an example of a
dissecting aneurysm.
66. S Curve of Golden
When there is a mass
adjacent to a fissure, the
fissure takes the shape
of an "S". The proximal
convexity is due to a mass,
and the distal concavity is
due to atelectasis. Note the
shape of the transverse
fissure.
This example represents a
RUL mass with atelectasis
67. Tracheoesophageal Stripe
The posterior wall of the trachea (T)
and the anterior wall of the esophagus
(E) are in close contact and form the
tracheoesophageal stripe in the lateral
view (arrow).
It is considered abnormal when it is
wider than __ mm.
Common causes for thickening of
tracheoesophageal stripe are:
Esophageal disease
Nodal enlargement
70. The definition of atelectasis is loss of air in the alveoli;
alveoli devoid of air (not replaced).
A diagnosis of atelectasis requires the following:
1-A density, representing lung devoid of air
2-Signs indicating loss of lung volume
Atelectasis
71. 1-Absorption Atelectasis
When airways are obstructed there is no further
ventilation to the lungs and beyond. In the early
stages, blood flow continues and gradually the
oxygen and nitrogen get absorbed, resulting in
atelectasis.
Types of Atelectasis:
72. 2-Relaxation Atelectasis
The lung is held close to the chest wall because of the
negative pressure in the pleural space. Once the
negative pressure is lost the lung tends to recoil due
to elastic properties and becomes atelectatic. This
occurs in patients with pneumothorax and pleural
effusion. In this instance, the loss of negative
pressure in the pleura permits the lung to relax, due
to elastic recoil. There is common misconception that
atelectasis is due to compression.
Types of Atelectasis:
73. 3-Adhesive Atelectasis :
Surfactant reduces surface tension and keeps the
alveoli open. In conditions where there is loss of
surfactant, the alveoli collapse and become
atelectatic. In ARDS this occurs diffusely to both
lungs. In pulmonary embolism due to loss of blood
flow and lack of CO2, the integrity of surfactant
gets impaired.
Types of Atelectasis:
75. .
5-Round Atelectasis
An instance where the lung gets trapped by
pleural disease and is devoid of air.
Classically encountered in asbestosis.
Types of Atelectasis:
76. Generalized
1-Shift of mediastinum: The trachea and heart gets shifted
towards the atelectatic lung.
2-Elevation of diaphragm: The diaphragm moves up and
the normal relationship between left and right side gets
altered.
3-Drooping of shoulder.
4-Crowding of ribs: The interspace between the ribs is
narrower compared to the opposite side.
Signs of Loss of Lung Volume:
77. Movement of Fissures
You need a lateral view to appreciate the movement of
oblique fissures. Forward movement of oblique fissure in
LUL atelectasis. Backward movement in lower lobe
atelectasis.
Movement of transverse fissure can be recognized in the
PA film.
Signs of Loss of Lung Volume:
78. Movement of Hilum
The right hilum is normally slightly lower than the left.
This relationship will change with lobar atelectasis.
Signs of Loss of Lung Volume:
80. Alterations in Proportion of Left and
Right Lung
The right lung is approximately 55% and left lung 45%. In
atelectasis this apportionment will change and can be a
clue to recognition of atelectasis. .
Signs of Loss of Lung Volume:
81. Hemithorax Asymmetry
In normals, the right and left hemithorax are equal in size.
The size of the hemithorax will be asymmetrical and
smaller on the side of atelectasis
Signs of Loss of Lung Volume:
82. Signs of Loss of Lung Volume:
Generalized
Shift of mediastinum: The trachea and heart gets shifted towards the atelectatic lung.
Elevation of diaphragm: The diaphragm moves up and the normal relationship between left
and right side gets altered.
Drooping of shoulder.
Crowding of ribs: The interspace between the ribs is narrower compared to the opposite side.
Movement of Fissures
You need a lateral view to appreciate the movement of oblique fissures. Forward movement of
oblique fissure in LUL atelectasis. Backward movement in lower lobe atelectasis.
Movement of transverse fissure can be recognized in the PA film.
Movement of Hilum
The right hilum is normally slightly lower than the left. This relationship will change with lobar
atelectasis.
Compensatory Hyperinflation
Compensatory hyperinflation as evidenced by increased radiolucency and splaying of vessels
can be seen with the normal lobe or opposite lung.
Alterations in Proportion of Left and Right Lung
The right lung is approximately 55% and left lung 45%. In atelectasis this apportionment will
change and can be a clue to recognition of atelectasis.
Hemithorax Asymmetry
In normals, the right and left hemithorax are equal in size. The size of the hemithorax will be
asymmetrical and smaller on the side of atelectasis
83. Atelectasis Right Lung
Homogenous density right hemithorax
Mediastinal shift to right
Right hemithorax smaller
Right heart and diaphragmatic silhouette are not identifiable
84. Atelectasis Left Lung
Homogenous density left hemithorax
Mediastinal shift to left
Left hemithorax smaller
Diaphragm and heart silhouette are not identifiable
85. Left Lower Lobe Atelectasis
• Inhomogeneous cardiac density
• Left hilum pulled down
• Non-visualization of left diaphragm
• Triangular retrocardiac atelectatic LLL
86. Atelectasis Left Lower Lobe
Double density over heart
Inhomogenous cardiac density
Triangular retrocardiac density
Left hilum pulled down
Other findings include:
Pneumomediastinum
87. Atelectasis Left
Upper Lobe
Mediastinal shift to left
Density left upper lung field
Loss of aortic knob and left hilar
silhouettes
Herniation of right lung
Atelectatic left upper lobe
Forward movement of left
oblique fissure "Bowing sign"
88. Atelectasis Left Upper
Lobe
Hazy density over left
upper lung field
Loss of left heart
silhouette
Tracheal shift to left
Lateral
A: Forward movement of
oblique fissure
B: Herniated right lung
C: Atelectatic LUL
89. Lateral
Movement of oblique and transverse
fissures
Atelectasis Right Upper Lobe
Homogenous density right upper lung
field
Mediastinal shift to right
Loss of silhouette of ascending aorta
90. Lateral
Movement of oblique and transverse
fissures
Atelectasis Right Upper Lobe
Homogenous density right upper lung field
Mediastinal shift to right
Loss of silhouette of ascending aorta
91. RML Atelectasis
Vague density in right lower lung field, almost normal
RML atelectasis in lateral view, not evident in PA view
92. Vague density in right lower lung field (almost a normal film).
Dramatic RML atelectasis in lateral view, not evident in PA view. Movement of
transverse fissure.
Other findings include: Azygous lobe
93. Atelectasis Right Lower Lobe
Density in right lower lung field
Indistinct right diaphragm
Right heart silhouette retained
Transverse fissure moved down
Right hilum moved down
94. Adhesive Atelectasis
Alveoli are kept open by the integrity of surfactant. When there is loss
of surfactant, alveoli collapse. ARDS is an example of diffuse alveolar
atelectasis.
Plate-like atelectasis is an example of focal loss of surfactant.
95. Relaxation Atelectasis
The lung is held in apposition to the chest wall because of negative pressure
in the pleura. When the negative pressure is lost, as in pneumothorax or
pleural effusion, the lung relaxes to its atelectatic position. The atelectasis is
a secondary event. The pleural problem is primary and dictates other
radiological findings.
96. Round Atelectasis
Mass like density
Pleural based
Base of lungs
Blunting of costophrenic angle
Pleural thickening
Pulmonary vasculature curving
into the density
Esophageal surgical clips
97. Round Atelectasis
Mass like density
Pleural based
Base of lungs
Blunting of costophrenic angle, pleural thickening
Pulmonary vasculature curving into the density
106. Bronchiectasis
Left lung atelectasis due to mucus plugging
Mucus plugs suctioned with bronchoscopy
Bronchogram done after bronchoscopy
Saccular bronchiectasis in bronchogram below
107. Bronchogram
Bronchograms are rarely done nowadays. The need for it
disappeared with the invention of the fiberoptic
bronchoscopy and high resolution CT scan. View these
images to get a greater understanding of a three
dimensional view of a bronchial tree..
108. Bronchogram
Bronchograms are rarely done nowadays. The need for it disappeared with the
invention of the fiberoptic bronchoscopy and high resolution CT scan.
122. Number:
Multiple bilateral cavities would raise
suspicion for either bronchiogenous or
hematogenous process. You should consider:
Aspiration lung abscess
Septic emboli
Metastatic lesions
Vasculitis (Wegener's)
Coccidioidomycosis, tuberculosis
123. Location:
• Classical locations for aspiration lung abscess
are superior segment of the lower lobes
posterior segments of upper lobes.
• Tuberculous cavities are common in superior
segments of upper and lower lobes or posterior
segments of upper lobes.
• When a cavity in anterior segment is
encountered, a strong suspicion for lung cancer
should be raised. TB and aspiration lung
abscess are rare in anterior segments. Cancer
lung can occur in any segment.
124. Wall Thickness:
• Thick walls are seen in:
– Lung abscess
– Necrotizing squamous cell lung cancer
– Wegener's granulomatosis
– Blastomycosis
125. Wall Thickness:
• Thin walled cavities are seen in:
• Coccidioidomycosis
• Metastatic cavitating squamous cell
carcinoma from the cervix
• M. Kansasii infection
• Congenital or acquired bullae
• Post-traumatic cysts
• Open negative TB
126. Contents:
• The most common cause for air fluid level is
lung abscess. Air fluid levels can rarely be
seen in malignancy and in tuberculous
cavities from rupture of Rasmussen's
aneurysm.
• A fungous ball should make you consider
aspergillosis. A blood clot and fibrin ball will
have the same appearance.
• Floating Water Lily: The collapsed membrane
of a ruptured echinococcal cyst, floats giving
this appearance.
127. Lining of Wall:
The wall lining is irregular and nodular in
lung cancer or shaggy in lung abscess
128. Evolution of Lesion:
Many times review of old films to assess the
evolution of the radiological appearance of
the lesion extremely helpful. Examples
• Infected bullae
• Aspergilloma
• Sub acute necrotizing aspergillosis
• Bleeding from Rasmussen's aneurysm in a
tuberculous cavity
131. Bulla
Definition
•Thin-walled–less than 1 mm
•Air-filled space
•In the lung> 1 cm in size and up to 75% of lung
•Walls may be formed by pleura, septa,
or compressed lung tissue.
•Results from destruction, dilatation and
confluence of airspaces distal to terminal
bronchioles.
132. •Bullous disease may be primary or associated
with emphysema or interstitial lung disease.
• Primary bullous lung disease may be familial
and has been associated with Marfan's, Ehler's
Danlos, IV drug users, HIV infection, and
vanishing lung syndrome.
•Bullae may occasionally become very large
and compromise respiratory function. Thus
has been referred as vanishing lung syndrome,
and may be seen in young men.
137. Pneumatocele is a benign air containing cyst of lung, with
thin wall < 1mm as bulla but with different mechanism
Infection with staph aureus is the commonest cause ( less
common causes are, trauma, barotrauma) lead to necrosis
and liquefaction followed by air leak and subpleural
dissection forming a thin walled cyst.
138. •Honeycombing is defined as multiple cysts < 1cm in diameter,with
well defined walls, in a background of fibrosis, tend to form
clusters and is considered as end stage lung .
•It is formed by extensive interstitial fibrosis of lung with residual
cystic areas.
139.
140. A cyst is a ring
shadow > 1 cm in
diameter and up to
10 cm with wall
thickness from 1-3
mm.
143. A cavity is > 1cm
in diameter, and its
wall thickness is
more than 3 mm.
144. •A central portion necrosis and communicate to bronchus.
•The draining bronchus is visible (arrow). CT (2 mm slice thickness)
shows discrete air bronchograms in the consolidated area.
Mechanism
167. Consolidation Right
Upper Lobe /
Density in right upper lung
field
Lobar density
Loss of ascending aorta
silhouette
No shift of mediastinum
Transverse fissure not
significantly shifted
Air bronchogram
169. Radiation Pneumonia
Post Mediastinal Radiation
Air space disease (air bronchogram)
Over radiation port (vertical and paramediastinal)
Bilateral
Progression to fibrosis
173. Consolidation / Lingula
Density in left lower lung field
Loss of left heart silhouette
Diaphragmatic silhouette intact
No shift of mediastinum
Blunting of costophrenic angle
Lateral
Lobar density
Oblique fissure not
significantly shifted
Air bronchogram
174. Consolidation Left Lower Lobe
Density in left lower lung field
Left heart silhouette intact
Loss of diaphragmatic silhouette
No shift of mediastinum
Pneumatocele
One diaphragm only visible
Lobar density
Oblique fissure not significantly
shifted
175. Left Upper Lobe Consolidation
Density in the left upper lung field
Loss of silhouette of left heart margin
Density in the projection of LUL in lateral view
Air bronchogram in PA view
No significant loss of lung volume
176. Vague density right lower lung field
Indistinct right cardiac silhouette
Intact diaphragmatic silhouette
Density corresponding to RML
No loss of lung volume
RML pneumonia
177. Consolidation Right Upper Lobe /
Air Bronchogram
Density in right upper lung field
Lobar density
Loss of ascending aorta silhouette
No shift of mediastinum
Transverse fissure not significantly shifted
Air bronchogram
180. Alveolar Cell Carcinoma - Progression
Old film on left
Solitary pulmonary nodule resected
Onset of diaphragmatic paralysis
Progression to multicentric acinar nodules
181. Hyperlucent Lung
Factors
Vasculature: Decrease
Air: Excess
Tissue : Decrease
Bilateral diffuse
Emphysema
Asthma
Unilateral
Swyer James syndrome
Agenesis of pulmonary artery
Absent breast or pectoral muscle
Partial airway obstruction
Compensatory hyperinflation
Localized
Bullae
Westermark's sign : Pulmonary embolus
182. Agenesis of Left Pulmonary Artery
Missing vascular markings in left lung
Left hilum not seen
Entire cardiac output to right lung
195. Achalasia of
esophagus
• Inhomogeneous
cardiac density:
Right half more
dense than left
• Density crossing
midline (right black
arrow)
• Right sided inlet to
outlet shadow
• Right para spinal line
(left black arrow)
• Barium swallow
below: Dilated
esophagus
200. Dissecting Aneurysm
Mediastinal widening
Inlet to outlet shadow
on left side
Retrocardiac: Intact
silhouette of left heart
margin
Pulmonary artery
overlay sign: Density
behind left lower lobe
Wavy margin
228. of PE Diagnostic Algorithm
1. Patients with normal chest radiographic findings
are evaluated with a perfusion scan and, if
necessary, an aerosol ventilation scan. Patients
with normal or very low probability scintigraphic
findings are presumed not to have pulmonary
emboli .
2-Patients with a high-probability scan usually
undergo anticoagulation therapy. All other patients
should be evaluated with helical CT pulmonary
angiography, conventional pulmonary
angiography, or lower-extremity US, depending on
the clinical situation
229. of PE Diagnostic Algorithm
3-Patients with abnormal chest radiographic findings, are
unlikely to have definitive scintigraphic findings. These
patients undergo helical CT pulmonary angiography as well
as axial CT of the inferior vena cava and the iliac, femoral,
and popliteal veins. If the findings at helical CT pulmonary
angiography are equivocal or technically inadequate (5%–
10% of cases) or clinical suspicion remains high despite
negative findings, additional imaging is required.
4-Patients who have symptoms of deep venous thrombosis
but not of pulmonary embolism initially undergo US, which
is a less expensive alternative. If the findings are negative,
imaging is usually discontinued; if they are positive, the
patient is evaluated for pulmonary embolism at the
discretion of the referring physician.
249. Potential Sources of Mediastinal Air
Intrathoracic
Trachea and major bronchi
Esophagus
Lung
Pleural space
Extrathoracic
Head and neck
Intraperitoneum and retroperitoneum
250.
251.
252.
253. Radiographic Signs of Pneumomediastinum
Subcutaneous emphysema
Thymic sail sign
Pneumoprecardium
Ring around the artery sign
Tubular artery sign
Double bronchial wall sign
Continuous diaphragm sign
Extrapleural sign
Air in the pulmonary ligament
265. The CT features of benign
mediastinal cyst are
(a) a smooth, oval or tubular mass with a well-
defined thin wall that usually enhances after
intravascular administration of contrast
material,
(b) homogeneous attenuation, usually in the
range of water attenuation (0–20 HU),
(c) no enhancement of cyst contents, and
(d) no infiltration of adjacent mediastinal
structures.
266. Cysts that contain serous fluid typically have
long T1 and T2 relaxation values, which
produce low signal intensity on T1-weighted
MR images and high signal intensity on T2-
weighted images.
267.
268. Because cysts containing nonserous
fluid can have high attenuation at CT,
they may be mistaken for solid
lesions. MR imaging can be useful in
showing the cystic nature of these
masses because these cysts continue
to have characteristically high signal
intensity when imaged with T2-
weighted sequences regardless of the
nature of the cyst contents
269. Radionuclide imaging can be helpful in
detecting functioning thyroid tissue
(iodine-123 or I-131) or parathyroid
tissue (technetium-99m sestamibi) in
the mediastinal cystic mass . gallium-
67 scintigraphy may show increased
radiotracer uptake in the cystic
malignancy owing to necrosis such as
lymphoma or metastatic carcinoma.
270. Ultrasonography (US) can be useful in
evaluating a mass adjacent to the
pleural surface or cardiophrenic angle.
At US, the benign cysts typically
appear as anechoic thin-walled
masses with increased through
transmission
