Pitfalls in ct chest

PITFALLS IN CT CHEST

Amira El Azab

Lecturer of Diagnostic Radiology

Al Azhar University


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 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


Careful

assessment of

thin slices or

multiplanar

analysis

volume averaging Pseudonodule

from degenerative

changes in the

first

costochondral

junction

CT LUNGS


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


Prone images

should be

obtained

Supine position of

the patient

Nodules can

remain hidden

within dependent

densities

CT LUNGS


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


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


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


LUNG DISEASE

Paraseptal emphysema may coexist with honeycombing,

making it more challenging in patients with combined

pulmonary fibrosis and emphysema syndrome (CPFE).


Emphysematous

spaces are

irregular with no

actual walls.

Both are dilated

sub-pleural

spaces.

Honeycombing

can be confused

with paraseptal

emphysema

CT LUNGS


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


•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


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


ABNORMALITIES


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


ABNORMALITIES


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


•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


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.


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.


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.


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.


AORTOGRAM

ADJACENT STRUCTURES


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.


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.

THANK YOU

Pitfalls in ct chest

Health & Medicine

Transcript of Pitfalls in ct chest