pitfalls in ct chest
TRANSCRIPT
PITFALLS IN CT CHEST
Amira El Azab
Lecturer of Diagnostic Radiology
Al Azhar University
PITFALLS IN CT CHEST
These are recognized according the
window evaluated. Also, CTPA & CT
Aortography has its own pitfalls.
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULES
Lung nodules detected by lung CT are evaluated on the base of:
Size
CT density
Ground glass
Soft tissue
CalcifiedDistribution
Clinical sitting of the patient
examined
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULES
Pitfalls in evaluation of Lung
nodules:
Evaluation of false nodules as true
nodules
Overlooking of true nodules
False interpretation of the density of a
nodule
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULESHow to preventCausePitfall
Multi-planar
images
Axial images
alone
Focal pleural
thickening or
linear atelectasis
may be mistaken
for lung nodules.
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULESHow to preventCausePitfall
Careful
assessment of
thin slices or
multiplanar
analysis
volume averaging Pseudonodule
from degenerative
changes in the
first
costochondral
junction
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULESHow to preventCausePitfall
Multiplanar images are
helpful to show that
focally dilated
bronchioles taper
distally. There is no
nidus, interconnecting
vessels, or draining
veins.
axial images aloneHigh-density mucus
plugs in focally dilated
peripheral bronchi
(bronchoceles) can
simulate a pulmonary
arteriovenous
malformation
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULESHow to preventCausePitfall
Prone images
should be
obtained
Supine position of
the patient
Nodules can
remain hidden
within dependent
densities
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULESHow to preventCausePitfall
3 mm continuous
(thicker images)
images are
evaluated.
Edge
enhancement
A soft tissue
nodule appears
calcified in HRCT
soft nodule to be
wrongly labeled
as a calcified
granuloma
CT LUNGS
PITFALLS WHEN EVALUATING LUNG NODULES
Metastatic pulmonary calcification (MPC) seen in variety
of conditions, such as chronic renal failure,
hyperparathyroidism, sarcoidosis, and multiple myeloma,
presents with bilateral upper lung ill-defined opacities.
How to preventCausePitfall
Thin1 mm images with
mediastinal or bone
window show high-
attenuation
characteristics in the
opacities.
Chest wall vessels may
demonstrate
calcification, providing a
clue to diagnosis of
underlying renal disease.
Evaluation of thick
sections in pulmonary
window alone alone
Metastatic pulmonary
calcification (MPC)
appear of ground glass
density and mistaken for
infection or edema
CT LUNGS
PITFALLS WHEN EVALUATING ROUND
ATELECTASIS Round atelectasis is an unusual pattern of chronic
atelectasis that is classically described in pleuro-
parenchymal disease associated with asbestos
exposure, which can be mistaken for a peripheral
bronchogenic neoplasm on chest radiographs as well as
CT.
CT features require presence of:
(1) a peripheral oval or wedge-shaped opacity That makes
an acute angle with the pleural surface.,
(2) a comet-tail sign which is converging connection to
hilum,
(3) associated with overlying pleural thickening or effusion,
and
(4) volume loss in the involved lobe.
CT LUNGS
PITFALLS WHEN EVALUATING CYSTIC LUNG
DISEASECavitary diseaseEmphysemaTrue cysts
Gas containing
space in the lung
having a
wall > 1 mm thick.
Centrilobular
emphysema is
identified by
multiple round
lucencies without
any walls.
True cysts are
round. With well
defined walls <
1mm thickness.
Early
They can have
thin or thick walls,
depending on the
degree of
Necrosis, .whether
the cause is
inflammatory or
neoplastic.
Becomes
confluent, pseudo-
walls formed by
interlobular septae.
Shape is polygonal,
following the shape
of a lobule.
Late-stage cystic
lung disease such
as
lymphangioleiomyo
matosis can be
difficult to
distinguish
radiologically from
confluent
emphysema. A
history of heavy
smoking for a long
duration is always
helpful.
Late
CT LUNGS
PITFALLS WHEN EVALUATING CYSTIC LUNG
DISEASE
CT LUNGS
PITFALLS WHEN EVALUATING INTERSTITIAL
LUNG DISEASE There is disagreement among even the experienced
chest radiologists about the presence or absence of
honeycombing (cluster of 3–10 mm cystic spaces in a
sub-pleural location with well defined walls).
Honeycombing is a major discriminator separating usual
interstitial pneumonia (UIP) from nonspecific interstitial
pneumonitis (NSIP), that has a significant prognostic
implication.
CT LUNGS
PITFALLS WHEN EVALUATING INTERSTITIAL
LUNG DISEASEHow to preventCausePitfall
Multiplanar
imaging (traction
bronchiectasis
spaces are
interconnected
and eventually
join the proximal
bronchioles).
Axial images
alone
Honeycombing
can be confused
with traction
cystic
bronchiectasis.
CT LUNGS
PITFALLS WHEN EVALUATING INTERSTITIAL
LUNG DISEASE
Paraseptal emphysema may coexist with honeycombing,
making it more challenging in patients with combined
pulmonary fibrosis and emphysema syndrome (CPFE).
How to preventCausePitfall
Emphysematous
spaces are
irregular with no
actual walls.
Both are dilated
sub-pleural
spaces.
Honeycombing
can be confused
with paraseptal
emphysema
CT LUNGS
PITFALLS WHEN EVALUATING INTERSTITIAL
LUNG DISEASEHow to preventCausePitfall
Prone images
taken.
Dependent
densities due to
atelectasis and
blood pooling.
•False densities in
the lower lungs
can mimic early
interstitial lung
disease (ILD).
•False densities in
the lower lungs
may hide
honeycombing.
CT LUNGS
PITFALLS WHEN EVALUATING PARAVERTEBRAL
SOFT TISSUE OPACITY
How to preventCausePitfall
•Paravertebral soft
tissue may extend to
the posterior
paravertebral muscles
and spinal canal.
•Paravertebral soft
tissue will efface the
paravertebral and
retrocrural fat. There is
blurring of the crus of
the diaphragm.
•MRI of the spine can
depict the abnormal
marrow signal of
vertebral osteomyelitis
as the etiology of the
paraspinal abscess.
•Anatomic proximity.
•Reactive pleural
effusion, may
associate
paravertebral abscess.
•No demonstrable
changes in the
vertebrae on CT of the
chest.
A paravertebral soft
tissue can be mistaken
for posterior-medial
basal segments of the
lower lobe
consolidation.
CT LUNGS
PITFALLS WHEN EVALUATING PARAVERTEBRAL
SOFT TISSUE OPACITY
CT LUNGS
PITFALLS WHEN EVALUATING CONGENITAL
ABNORMALITIES
IN ADULTS
They need to be diagnosed so that appropriate treatment
that may be surgical can be provided.
Lung anomalies that may be
undiagnosed till adulthood:
Pulmonary sequestration
Congenital bronchial atresia
(CBA)
Congenital lobar emphysema
Congenital cystic adenomatoidmalformation
(CCAM)
CT LUNGS
PITFALLS WHEN EVALUATING CONGENITAL
ABNORMALITIES
IN ADULTSHow to preventCausePitfall
The identification
of a supplying
separate branch
of aorta is
essential for
diagnosis which
should be made
on CT
angiography
Appears solid as
no
communication
with the bronchial
tree.
Pulmonary
sequestration, if
not diagnosed till
adulthood, may
present as
recurrent
pneumonia or an
indeterminate
mass.
CT LUNGS
PITFALLS WHEN EVALUATING CONGENITAL
ABNORMALITIES
IN ADULTSHow to preventCausePitfall
Define high density
mucous plug in
mediastinal window.
Obtain expiratory CT
images to detect air
trapping on lung
window.
Associated
bronchocele can be
mistaken for a mass.
The distal lung that
is supplied by an
atretic bronchus is
overinflated as the
air drifts in from the
adjacent alveoli by
collateral pathways.
Congenital bronchial
atresia can also
present in adults and
can be
misdiagnosed as a
lobar emphysema or
perihilar mass
CT LUNGS
PITFALLS WHEN EVALUATING CONGENITAL
ABNORMALITIES
IN ADULTSHow to preventCausePitfall
Follow up images
reveal characteristic
shape and lobar
distribution after
subsidence of
infection.
Unilobar CCAM
presenting in adults
is commonly missed.
Unilobar Congenital
cystic adenomatoid
malformation may
mimic cavitary
neoplasm or
infection.
CT MEDIASTINUM
PITFALLS WHEN EVALUATING PERICARDIAL
RECESSES
Pericardial recesses are known to be mistaken for a cystic
mediastinal mass or necrotic lymph node. That can result in
upstaging of malignancies. Specially if present without
pericardial effusion.
How to preventLocationPericadial recess
Familiarity with
anatomy and Multi-
planner imaging.
Right paratracheal
location, above the
aortic arch, and
posterior to right
brachiocephalic
vessels.
Superior pericardial
recess .
Characteristic
location and fluid
density.
Related to a
pulmonary vein.
Pericardial recess
accompanying the
pulmonary vein .
CT MEDIASTINUM
PITFALLS WHEN EVALUATING AZYGOS VEIN
VALVEHow to preventCausePitfall
The high-density
foci are parallel,
located within the
course of the
azygos vein and
disappear in non
enhanced
images.
Reflux of
intravenous
contrast material
in the azygos vein
from the superior
vena cava (SVC).
Contrast material
layering in cusps
of the azygos vein
valve in a direct
contrast-
enhanced CT of
the chest can be
mistaken for a
surgical clip or a
calcified lymph
node.
CT MEDIASTINUM
PITFALLS WHEN EVALUATING THROMBUS IN GREAT
VESSELSHow to preventCausePitfall
•Changing the
window settings
on the
workstation can
help in avoiding
this pitfall.
•True thrombus is
usually focal and
may be
associated with a
venous catheter.
Intra-vasculer
mixing of
opacified and
non-opacified
blood.
False filling
defects in the
SVC, IVC, and
brachiocephalic
veins must be
differentiated from
the less common
true thrombus.
CT MEDIASTINUM
PITFALLS WHEN EVALUATING CISTERNA CHYLI
How to preventCausePitfall
•Cisterna chyli is
a tubular low-
density structure
in the retrocrural
space.
•A retrocrural
node is lobular
and is of soft
tissue density.
Anatomic non
familiarity.
Dilated cisterna
chyli (as tubular
retro-crural
structure close to
the Aorta)
mimicking a
necrotic lymph
node
CT MEDIASTINUM
PITFALLS WHEN EVALUATING TRACHEOBRONCHIAL
TREEHow to preventCausePitfall
Evaluate central
airways in lung
window as well as
mediastinal
window.
The central
airways are often
evaluated in
mediastinal
window and
overlooked in
lung window.
Small tracheal
lesions, diffuse
wall thickening,
bronchial
stenosis, and
broncholiths can
be missed.
CT MEDIASTINUM
PITFALLS WHEN EVALUATING TRACHEOBRONCHIAL
TREEHow to preventCausePitfall
Dynamic
expiratory CT is
done in
suspected cases.
Routine
inspiratory phase
CT without
expiratory-phase
imaging
Tracheo-
bronchomalacia
may be
undetected by CT
of the chest which
is potentially a
non invasive
technique.
CT PULMONARY ANGIOGRAM (CTPA) AND
AORTOGRAMSUBOPTIMAL CONTRAST ENHANCEMENT
How to preventCausePitfall
Suspected
dissection should
always be
analyzed in the
phase with
greatest contrast
enhancement and
with different
window settings..
Wrong timing due
to heart failure or
bad technique.
False-positive or
false-negative
diagnosis for
aortic dissection.
CT PULMONARY ANGIOGRAM (CTPA) AND
AORTOGRAM
STREAK ARTIFACTSHow to preventCausePitfall
Scanning in the
caudal-cranial
direction and
avoiding the
metallic objects
from the scanned
area.
Beam hardening
and scatter from
dense contrast
material .
patient’s arms,
external
monitoring
devices,
pacemakers,
tubes, and lines.
Streak artifacts
can limit
evaluation of
pulmonary
arteries.
CT PULMONARY ANGIOGRAM (CTPA) AND
AORTOGRAM
STREAK ARTIFACTSHow to preventCausePitfall
Knowing that
intimal flaps are
characteristically
smooth and thin,
have a slightly
curved
appearance, and
are restricted to
the aortic
diameter.
Beam hardening
and scatter from
dense contrast
material .
patient’s arms,
external
monitoring
devices,
pacemakers,
tubes, and lines.
Streaks
resembling
dissection flaps,
leading to false
diagnosis of aortic
dissection.
CT PULMONARY ANGIOGRAM (CTPA) AND
AORTOGRAM
MOTION ARTIFACTSHow to preventCausePitfall
•Artifact is present
in one or two
slices only.
• ECG gating.
•3D software
reconstruction.
Cardiac and
aortic pulsations.
Curvilinear double
walls of the aortic
root and
ascending aorta.
CT PULMONARY ANGIOGRAM (CTPA) AND
AORTOGRAM
ADJACENT STRUCTURES
How to preventCausePitfall
Scrolling through
thin slices and
multiplanar
viewing.
Adjacent structures
with same
expected density.
•Vascular structures close to aorta can
mimic a dissection flap.
•Un opacified pulmonary veins, lymph
nodes, and mucus plugs are
commonly mistaken for pulmonary
emboli.
PITFALLS IN CT CHEST
CONCLUSION
Pitfalls in chest CT can usually be easily
avoided, if the reader is aware of them.
Technical issues, artifacts, error of
perception and error of interpretation, if
not recognized, can result in
>>>>>>>>inappropriate treatment.
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