بسم هللا الرحمن الرحيم

Dr AHMED ESAWY

An Article By

Dr. Ahmed Eisawy

MBBS M.Sc MD

Dr AHMED ESAWY

PULMONARY EMBOLISM

IMAGING

Dr AHMED ESAWY

• Pathology Of Pulmonary Embolism

• Imaging Of Pulmonary Embolism

• Pitfalls in Diagnosis of Pulmonary Embolism with Helical CT Angiography

• Nonthrombotic Pulmonary Embolism

• Other modalities

Dr AHMED ESAWY

Dr AHMED ESAWY

Dr AHMED ESAWY

Dr AHMED ESAWY

Dr AHMED ESAWY

• Multidetector spiral CT image shows anterior

segmental artery of the right upper lobe (arrow)

Dr AHMED ESAWY

• Multidetector spiral CT image shows the medial segmental artery of the right middle lobe (white arrow) and the right lower lobe artery (black arrow)

Dr AHMED ESAWY

• Multidetector spiral CT image shows left lower lobe

pulmonary artery (arrow)

Dr AHMED ESAWY

Cross-sectional antomy of central vessels . Dr AHMED ESAWY

Right Upper Lobe Segmental Vessels .

Right Lower Lobe Segmental Vessels . Dr AHMED ESAWY

Left Upper Lobe (Upper division) Segmental vessels Dr AHMED ESAWY

Left Upper Lobe (Lower division) Segmental vessels Dr AHMED ESAWY

Left Lower Lobe Segmental vessels Dr AHMED ESAWY

Pathology Of Pulmonary Embolism

Dr AHMED ESAWY

Pathogenesis of

pulmonary

thromboembolis

m

Dr AHMED ESAWY

Pathological findings of pulmonary thromboembolism are often considered in two categories: those in which the embolic episode

is acute and those in which the emboli are chronic are/or repeated (Weigs and Jaff,

2004).

Dr AHMED ESAWY

Pathological Findings in

Acute Pulmonary Thrombo

Embolism: Emboli were considered acute if they are partially or

completely occluded the arterial lumen and the arterial diameter was not reduced: In most instances

the lung parenchyma distal PE eighther normal or shows only mild atelectasis and minimal intraolvealar

hemorrhage or edema. (Müller et al., 2002).

Dr AHMED ESAWY

Chronic Pulmonary

Thrombo Embolism: Lung emboli were considered chronic if at least two of the

following features were present: 1-An eccentric location contiguous to the vessel wall. 2-Evidence of recanaliazation within the intraluminal filling

defect (circumferential filling defect with central or eccentric patent lumen).

3-Arterial stenosis or webs. 4-Reduction of more than 50% of the arterial diameter. 5-Complete occlusion at the level of stenosed arteries. (Müller et al., 2002).

Dr AHMED ESAWY

Pulmonary Embolism

thrombotic

non-thrombotic

Dr AHMED ESAWY

Imaging For PE Includes

- Chest radiography.

- Ventilation-perfusion (V/Q) lung scintigraphy.

- Pulmonary angiography.

- Computed tomography (CT, spiral or MDCT

- Magnetic resonance imaging (MRI).

-Echocardiography and transthoracic ultrasound.

- Imaging studies to search for thrombosis (DVT).

Dr AHMED ESAWY

Embolism without Infarction

• Most PEs (90%)

• Frequently normal chest x-ray

• Pleural effusion

• Westermark’s sign

• “Knuckle” sign abrupt tapering of an occluded vessel

distally

• Elevated hemidiaphragm

Dr AHMED ESAWY

Embolism with Infarction

• Consolidation

• Cavitation

• Pleural effusion

(bloody in 65%)

• No air bronchograms

• “Melting” sign of

healing (Heals with

linear scar)

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ray-Chest XPlain film radiography

• Initial CxR always

NORMAL.

Dr AHMED ESAWY

CXR

• Hampton’s Hump

– consists of a

pleura based

shallow wedge-

shaped

consolidation in

the lung periphery

with the base

against the

pleural surface.

Dr AHMED ESAWY

Watermarks sign. Chest radiograph demonstrates pulmonary oligemia in

the right mid-lung secondary to central right pulmonary embolus

Chest radiograph showing calcified pulmonary embolism

Dr AHMED ESAWY

Radiographic Eponyms Hampton’s Hump, Westermark’s Sign

Westermark’s

Sign

Hampton’s Hump

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Chest radiograph showing pulmonary infarct in right lower lobe

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V/Q

Scanning

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VQ Scan results 2

Perfusion Ventilation Mismatch Dr AHMED ESAWY

advantages of V/Q

• the arteries from the lingula remain the most

difficult to interpret by spiral CT due to their

small caliber

• unlike spiral CT, it has no absolute

contraindications

Dr AHMED ESAWY

Drawback of V/Q

• non conclusive results of intermediate probability category of the test.

• interobserver variability.

• False-negative lung scan interpretations tend to have nonocclusive subsegmental

• thrombi

Dr AHMED ESAWY

Other causes of V/Q mismatch in the absence of

positive V/Q study) include-(falsePE

• (1) who do not have acute PE is related to chronic or unresolved PE .

• (2) compression of the pulmonary vasculature (mass lesions, adenopathy, and mediastinal fibrosis);

• (3) vessel wall abnormalities (e.g. pulmonary artery tumors, vasculitis);

• (4) non-thromboembolic intraluminal obstruction (tumor emboli, foreign body emboli);

• (5) congenital vascular abnormalities (e.g. pulmonary artery agenesis or hypoplasia)

Dr AHMED ESAWY

Spiral / MDCT

Dr AHMED ESAWY

CT

• Contraindicated in cases of renal disease.

• Sensitive for PE in the proximal pulmonary

arteries, but less so in the distal segments.

Dr AHMED ESAWY

CT

• Quickly becoming the test of choice for initial

evaluation of a suspected PE.

• CT detect extraluminal non vascular abnormality

Dr AHMED ESAWY

• Accurate for segmental or larger PE

• Sensitivity 85 - 95% (Overall 50-60%)

• Specificity 90 - 100%

• Accuracy depends on interpreter

• Large Inter-interpreter variability

• Reduced accuracy with less experience

• Can identify other pulmonary etiologies

Pulmonary Embolism Diagnosis - Chest CT

Dr AHMED ESAWY

The diagnostic performance of

CT angiography for detecting

Subsegmental thrombi is lower

Dr AHMED ESAWY

technique

• A high-volume (100–150-mL) bolus

• 3-4ml / second

• 15–17-second scan delay

• 2-5 mm thickness

Dr AHMED ESAWY

CT Features OF PE

The cardinal sign of acute PE on CTPA is an

intravascular filling defect in a pulmonary artery

that partially or completely occluded the vessel

and is often associated with increased diameter

of the affected vessel.

Dr AHMED ESAWY

Helical CT Findings in Acute PTE

Vascular abnormalities

intraluminal filling defects

acute angles with the vessel wall

total cutoff of vascular enhancement

enlargement of an occluded vessel

Dr AHMED ESAWY

Ancillary signs of PE although non specific by themselves, can be helpful in case of subtle thrombus (Kazereoni and Gross, 2004).

Ancillary findings suggestive of acute PE include : - Pleural based wedge shaped areas of increased attenuation With no contrast enhancement - Linear atelectasis - An expanded, unopacified vessel. - Eccentric filling defects. - Peripheral wedge shaped consolidation - Oligemia. - Peripheral effusion.

Dr AHMED ESAWY

CT Findings in Chronic PTE

Cardiac abnormalities

right ventricular enlargement

right atrial enlargement

thrombi in the right atrium or ventricle

Vascular abnormalities

eccentric filling defect at angle with vessel wall

irregular or nodular arterial wall

abrupt narrowing of the vessel diameter

abrupt cut off distal lobar or segmental artery

recanalization of the thrombosed vessel

webs or bands (less frequent)

pulmonary abnormalities

bronchial artery dilatation

bronchiectasis

areas of decreased attenuation in the lung

(mosaic perfusion pattern) Dr AHMED ESAWY

extensive pulmonary embolism

Acute pulmonary embolism (PE) in

longitudinal section: the 'railroad track' sign.

the anterior segment right

upper lobe pulmonary

artery

the left

pulmonar

y artery

(curved

arrow)

right

pulmonary

artery

(black

arrowhead)

interlobar

artery

(white

arrowhead)

Dr AHMED ESAWY

extensive intraluminal filling

defects in both pulmonary

arteries (arrows),

thrombus extending into

segmental and subsegmental

branches (arrows).

Dr AHMED ESAWY

Acute pulmonary embolism (PE):

Pulmonary infarct.

Acute

lobar

segmental

right

lower

lobe

pulmona

ry artery

left lower

lobe

segmental

vessels

Dr AHMED ESAWY

calcification in the left pulmonary artery,

compatible with calcified thrombus (arrow) Chronic pulmonary embolism with

recanalization of thrombus.

right

descending

pulmonary

artery

Dr AHMED ESAWY

excellent degree of vascular enhancement

MDCT 80 ml contrast/ bolus triggering

Dr AHMED ESAWY

• Acute PE.

• partial filling defect in the anterior segmental

artery of the right upper lobe (arrow) Dr AHMED ESAWY

Acute PE.

medial segmental artery of

the right middle lobe

partial filling

defect in the

right lower lobe

artery

Dr AHMED ESAWY

Acute PE.

left lower lobe

pulmonary artery

Dr AHMED ESAWY

single-slice CT

Isolated filling defect in a

subsegmental pulmonary

artery of the external

segment of the right middle

lobe (arrow) Dr AHMED ESAWY

Massive acute, subacute and

chronic pulmonary embolism

Dr AHMED ESAWY

Right lower lobe segmental filling defect

with irregular edges

Left upper lobe posterior segment defect

occupying about 70% of the artery

Dr AHMED ESAWY

left main pulmonary artery

left upper, and lower lobe pulmonary

arteries. Another filling defect is seen in the

right interlobar pulmonary artery

Dr AHMED ESAWY

segmental branches of the left lower lobe pulmonary artery

Right lower segmental artery filling defects

Dr AHMED ESAWY

the right and the left lower lobe pulmonary

arteries

bifurcation of the left lower

lobe pulmonary artery

Dr AHMED ESAWY

Bilateral and extensive pulmonary embolism.

both right and left main pulmonary arteries

right upper lobe pulmonary artery.

A thrombus is also seen in the left lower

lobe pulmonary artery

left lower lobe, right middle and lower lobe

pulmonary arteries

Dr AHMED ESAWY

Multiple bilateral pulmonary embolisms.

right main pulmonary artery right lower lobe pulmonary artery

right and the left lower lobe pulmonary arteries Dr AHMED ESAWY

Pulmonary embolism An embolus is seen in the right lower lobe pulmonary artery

near just distal to its origin from the right interlobar pulmonary artery.

Dr AHMED ESAWY

pulmonary embolus in the right upper lobe pulmonary artery

Dr AHMED ESAWY

right lower lobe pulmonary artery (arrow).

Bilateral pleural effusion is also present.

Dr AHMED ESAWY

Pitfalls in Diagnosis of

Pulmonary Embolism with

Helical CT Angiography

Dr AHMED ESAWY

Causes of Misdiagnosis of

Pulmonary Embolism Patient-related Factors

• Respiratory Motion Artifact.—

• Image Noise.—

• Pulmonary Artery Catheter.—

Flow-related Artifact

Technical Factors Window Settings.—

• Streak Artifact.—

• Lung Algorithm Artifact.—

• Partial Volume Artifact.—

• Stair Step Artifact.—

Dr AHMED ESAWY

Anatomic Factors

Partial Volume Averaging Effect in Lymph Nodes.—

• Vascular Bifurcation.—

Pathologic Factors Mucus Plug.—

• Perivascular Edema.—

Dr AHMED ESAWY

Pitfalls of CT Angiography

Dr AHMED ESAWY

pseudo-filling defects.

Technique-related pitfalls include

• inadequate selection of injection parameters, such as

• flow rate,

• concentration

• scan delay,

• improper selection of the duration of the apnea,

Dr AHMED ESAWY

40-year-oldwoman with pulmonary embolism at level of left upper lobe parallelism and proximity of arteries and bronchi conversely to veins (straight arrows). Note pulmonary embolism at level of Subsegmental artery of apicoposteior segment (curved arrow).

Dr AHMED ESAWY

posterior and medial location of

venous return of apical segment of

inferior lobe(arrow).

confluence of vessel into inferior

pulmonary vein (arrow).

normal anatomy Dr AHMED ESAWY

pseudofilling defect

within pulmonary vein.

right inferior segmental arteries 60-year

intravascular area of low attenuation in

pulmonary vein(arrow).Medial

topography of vessel is well see in

B.Note respiratory artifacts. Dr AHMED ESAWY

variant anatomy of

lingular artery.

60-year

culminal artery(curved arrow)with anterior segmental artery at same level (straight arrow).

lingular artery (arrow) originating from culminal artery instead of left interlobar artery. Parallelism with lingular bronchus is well seen in B.

Dr AHMED ESAWY

Hilar Lymph Nodes and Perivascular Tissue

• 45-year-old woman with normal

• right hilar lymph located between intermediate Bronchus and right interlobar coulds simulate mural thrombus.

Dr AHMED ESAWY

enlarged lymph nodes

(arrows) in left hilum.

60-yearM

enlarged lymph nodes medial in relation to left

interlobar pulmonary artery with nodular shape

perivascular

nature of

hypodense

tissue

Dr AHMED ESAWY

Intersegmental lymph nodes

mimicking pulmonary embolism

a partially calcified lymph node mimicking a filling defect (arrow). Non-calcified lymph node is also demonstrated (arrowhead). A7 paracardiac segmental artery; A8 antero-basal segmental artery; A9+10 common trunk of latero-basal and postero-basal segmental arteries

The calcified lymph node (arrow) is well differentiated

from contrast-enhanced pulmonary arteries

Dr AHMED ESAWY

enlarged lymph nodes at culminal level.

50-year M

hypodensities lateral to

culminal artery (arrow) that

could correspond to lymph

nodes or marginal clot

perivascular nature of hypodensities (arrow, B) between artery and Bronchus (arrow, C).

Dr AHMED ESAWY

60-year-M

unilateral lymphangitis carcinomatosa.

areas of low attenuation (straight arrow) simulating pulmonary embolism.Visualization of vessel in transverse section (curved arrow) confirms perivascular topography of hypodensities.Note associated pleural effusion.

Dr AHMED ESAWY

area of low attenuation (arrow) projecting on anterior segmental artery of left upper lobe

because of partial volume deffect from lung parenchyma.This is well seen in B.

Pitfalls Related to Vessel Orientation

Dr AHMED ESAWY

hypodensities are related to vessel wall.

tortuosity of right main pulmonary artery

Simulating endoluminal abnormality.

70-year M

Dr AHMED ESAWY

Kinetic Artifacts

pseudofilling defect caused by motion artifacts.

pseudofilling defectat level of posterior segmental artery of right lower lobe (arrows)

on only one axial image.Respiratory motion artifacts are better shown on B

complete opacification of vessel (arrow) without any motion artifacts Dr AHMED ESAWY

pseudofilling defect caused by car diac and respiratory kinetic artifacts

generate intraarterial hypodense area simulating pulmonary embolism (arrow, A). These artifacts are well Seen in B.Note pleural effusion

Dr AHMED ESAWY

streak artifacts

flow-related artifacts from superior vena cava gener ating hypo- and hyperattenuated radiating images over right main and upper lobar pulmonary arteries.

65-year M

Dr AHMED ESAWY

under estimated pulmonary

embolism obscured by dense

surrounding contrast material

56-year M smal area of low attenuation (arrow) inri htinter lobar artery partially obscured by dense surrounding contrast material.

intraluminal clot (arrow)

Dr AHMED ESAWY

Insufficient Enhancement

• inadequate delay of injection

• too long a delay

• Delayed enhancement of the pulmonary

arteries can also be related to factors intrinsic to

the patient

• Insufficient contrast

Dr AHMED ESAWY

Nonthrombotic

pulmonary embolism

Dr AHMED ESAWY

Nonthrombotic pulmonary

embolism

• Septic Pulmonary Embolism

• Hydatid Embolism

• Fat Embolism

• Amniotic Fluid Embolism

• Tumor Embolism

• Air Embolism

• Talc Embolism

Dr AHMED ESAWY

Septic pulmonary embolism in a 28-year M

intravenous drug abuser with human

immunodeficiency viral infection

multiple cavitary nodules throughout both

lungs

the feeding vessel sign (vessel leading directly to

the nodule) in several nodules (arrows) Dr AHMED ESAWY

Septic emboli: metastatic lung abscesses

scattered thin-walled cavities

throughout both lungs, associated

with ill-defined areas of

consolidation in peripheral portions

of both lower lobes

Scattered nodules can be identified, both solid

and in various stages of cavitation /subpleural

feeding vessels are associated with many of

them (arrows), compatible with hematogenous

seeding in a patient with documented tricuspid

vegetations

Dr AHMED ESAWY

• pulmonary transplantation

• enlarged or engorged branches of the pulmonary arteries in the bilateral lower lung zones (arrows).

Pulmonary hydatid embolism caused by rupture of a mediastinal hydatid cyst into the right pulmonary artery 22-year-old F

Dr AHMED ESAWY

Fat embolism in a 58-year F

intramuscular injection of some fatty

materials into the buttock several

days earlier

bilateral ground-glass areas of increased opacity

widespread patchy ground-glass attenuation and

consolidation. A follow-up radiograph obtained 10 days

later (not shown) revealed complete resolution of the

ground-glass patterns Dr AHMED ESAWY

• left basal trunk shows multifocal tree-in-bud appearances

(arrows) caused by tumor emboli.

Pulmonary tumor thrombotic microangiopathy caused by metastatic gastric carcinoma in

a 57-year-old man

Dr AHMED ESAWY

• Talc embolism in a 37-year-old male drug abuser.

• left interlobar artery shows diffuse pulmonary involvement with ill-defined centrilobular small nodules (arrows). Note also the nodular branching structures (tree-in-bud appearance). Dr AHMED ESAWY

• widespread small pulmonary nodules with increased opacity, a finding that represents Cement embolism

Cement embolism in a 29-year-old F The patient had recently undergone cyanoacrylate embolization for intracerebral arteriovenous malformation

Dr AHMED ESAWY

Polymethylmethacrylate embolism

following percutaneous vertebroplasty in

a 64-year-old woman.

inferior portion of the left atrium shows radiopaque emboli in the segmental and subsegmental levels of the pulmonary arteries (arrows).

pelvic inlet shows tortuous paravertebral veins filled with polymethylmethacrylate (arrows). The vertebral body has been reinforced with this material.

Dr AHMED ESAWY

Other modalities

Dr AHMED ESAWY

Pulmonary Angiographic

• Angiography is the most definitive

technique for the diagnosis of PTE

However, because angiography is an

invasive technique, it is seldom performed,

even in major academic centers.

Dr AHMED ESAWY

Pulmonary angiogram

Dr AHMED ESAWY

Pulmonary Embolism Diagnosis - Pulmonary Arteriogram

Lobar Defect Normal Segmental Defect

Dr AHMED ESAWY

Acute pulmonary embolism on pulmonary

angiogram. A. Right and (B) left pulmonary

artery selective injections demonstrating

multiple filling defects (arrows) and vessel

cutoff sign (arrowheads)

Chronic pulmonary

embolism with stenosis.

Selective right pulmonary

angiogram demonstrating

segmental stenosis of the

right upper lobe pulmonary

artery (arrow) Dr AHMED ESAWY

101

MRA with contrast

Dr AHMED ESAWY

102

MRA Real Time

Dr AHMED ESAWY

MRI MR Angiogram

• Very good to visualize the blood flow.

• Almost similar to angiogram

3D Pulmonary MRA

Dr AHMED ESAWY

A B

Acute pulmonary embolism. Magnetic resonance

angiography demonstrates filling defect (arrow)

compatible with pulmonary embolism in the (A) right

and (B) left main pulmonary arteries

Dr AHMED ESAWY

Magnetic

resonance

angiography (MRA)

• relatively higher signal in the right pulmonary artery (arrows).

• (B) Close-up of contrast-enhanced fast gradient-echo image showing embolus in distal right pulmonary artery

Dr AHMED ESAWY

Ultrasound

• Duplex scanning with compression will

aid to detect any thrombus.

Highly sensitive and specific for

diagnosing DVT.

Look for loss of flow signal,

intravascular defects or non collapsing

vessels in the venous system

Dr AHMED ESAWY

D-Dimer Assays.

• Gainfully employed to select patients for further

radiological imaging.

• It is a cross linked fibrin degradation product and

a plasma marker of fibrin lysis.

• Serum level less than 500ng/L excludes PE with

90-95% accuracy.

• Unfortunately a positive test is non specific

(specificity only 25 – 67% and occurs in about

40 – 69% of the patients).

Dr AHMED ESAWY

Unreliable in presence of

• Malignancy.

• Sepsis.

• Recent Surgery.

• Recent Trauma

Dr AHMED ESAWY

THANK YOU

Dr AHMED ESAWY