imaging of pulmonary embolism

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CHEST CONFERENCE 03.03.2015 THORSANG CHAYOVAN R1 CHAIYAPONGSE TANGSITTITUM R1

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CHEST CONFERENCE

03.03.2015

THORSANG CHAYOVAN R1

CHAIYAPONGSE TANGSITTITUM R1

Outline

Image findings in acute and chronic PE

PE severity index by imaging

Causes of misdiagnosis

Pulmonary embolism

The third most common acute CVS disease after myocardial infarction and stroke

Diagnostic tests for thromboembolic disease include

D-dimer assay ○ high sensitivity but poor specificity

ventilation-perfusion scintigraphy, ○ high sensitivity but very poor specificity

lower limb ultrasonography ○ high specificity but low sensitivity

CTA ○ sensitivities of 53%–100% and specificities of 83%–

100%

Pulmonary embolism

Diagnostic criteria for

Acute PE

Chronic PE

Acute PE

Diagnostic Criteria for acute PE

Complete arterial occlusion

The artery may be enlarged compared with adjacent patent vessels

Acute occlusive PE in a 32-year-old woman with chest pain. CT scan shows a PE within the posterobasal

segment of RLL. The artery is enlarged compared with adjacent patent vessels.

Diagnostic Criteria for acute PE

A partial filling defect surrounded by

contrast material

“polo mint” sign

“railway track” sign

Same pt: CT scan shows a pulmonary embolus that affects the segmental artery of the laterobasal segment of the RLL. This partial filling defect surrounded by contrast material produces the polo mint sign

Acute pulmonary embolism in a 66-year-old man .

CT scan shows an acute PE that causes a partial filling defect surrounded by contrast material (railway track sign) (arrow). Another acute pulmonary embolus affects the left main pulmonary artery (arrowhead).

Diagnostic Criteria for acute PE

A peripheral intraluminal filling defect

Acute angles with the arterial wall

Acute PE in a 58-year-old woman. CT scan demonstrates a PE that results in an eccentrically positioned partial

filling defect, which is surrounded by contrast material and forms acute angles with the arterial wall (arrows).

Diagnostic Criteria for acute PE

Ancillary findings: infarcts

Peripheral wedge-shaped areas of

hyperattenuation

Linear bands

Not specific for pulmonary embolism.

Same pt with acute PE. CT scan shows ancillary findings of a peripheral wedge-shaped area of hyperattenuation in

the lung (arrow), a finding that may represent an infarct, as well as a linear band (arrowhead).

Diagnostic Criteria for acute PE

Pulmonary arteries are indeterminate.

Lungs are clear.

To evaluate for pulmonary embolism

Ventilation-perfusion scintigraphy

Repeat CT pulmonary angiography

Chronic PE

Diagnostic Criteria for chronic PE

Complete occlusion

smaller than adjacent patent vessels

Figure 11. Chronic pulmonary embolism in a 27-year-old man with dyspnea. CT scan shows complete occlusion

of vessels in the left lung (arrowheads) that are smaller than adjacent patent vessels. Note the collateral blood supply from a branch of the right hemidiaphragmatic artery (arrow).

Diagnostic Criteria for chronic PE

Peripheral, crescent-shaped, obtuse

angles with vessel wall

Chronic PE in a 62-year-old man with dyspnea. CT scan shows an eccentrically located thrombus that forms

obtuse angles with the vessel wall (arrows). Silated collateral bronchial artery (arrowhead).

Diagnostic Criteria for chronic PE

Smaller arteries(recanalization)

Same patient . CT scan reveals a small, recanalized pulmonary artery with contrast material in the central lumen

Diagnostic Criteria for chronic PE

A web or flap within a contrast material–

filled artery

Chronic PE in a 56-year-old man with dyspnea. CT scan shows a flap (arrow) within a small right interlobar pulmonary artery. Collateral bronchial artery dilatation is also noted (arrowhead)

Diagnostic Criteria for chronic PE

Bronchial or other systemic collateral vessels

Same patient as in Figure 12. CT scan shows a large chronic PE in the main and left main pulmonary arteries (arrowhead). Arrows indicate collateral bronchial arteries.

Diagnostic Criteria for chronic PE

Calcification within eccentric vessel

thickening

Chronic pulmonary embolism in a 62-year-old man with dyspnea. CT scan shows pulmonary arterial wall calcification (arrows), a secondary sign of chronic pulmonary embolism.

Diagnostic Criteria for chronic PE

PA diameter > 30 mm, pericardial fluid

Same pt: Pulmonary arterial HTN secondary to chronic PE--PA 41 mm in diameter

Diagnostic Criteria for chronic PE

Pericardial fluid

Chronic pulmonary embolism in the same patient as in Figure 12. CT scan demonstrates pericardial fluid (arrows) associated with pulmonary arterial hypertension secondary to chronic pulmonary embolism.

Common findings

in both acute and chronic PE

Other findings of both acute and chronic PE

Mosaic perfusion pattern

Chronic PEin a 60-year-old woman. CT scan demonstrates a mosaic perfusion pattern. The dark regions of

underperfused lung are seen to contain vessels (arrows) that are smaller than the adjacent patent vessels in the normally perfused lung

Right ventricular strain or failure

Optimally monitored with echocardiography

CT pulmonary angiography

RV dilatation

○ wider RV cavity than in the short axis

○ ± contrast material reflux into the hepatic veins

Deviation of the interventricular septum toward the LV

Acute PE in a 42-year-old man. CT scan reveals that the short axis of the right ventricle (dashed line) is wider than

that of the left ventricle (solid line)

PE severity index

PE severity index by imaging

PA clot load scores

Right heart strain

Leftward bowing of the interventricular

septum

IVC contrast reflux

PA Clot Load Scores

The presence, location, and degree of

obstruction of arterial clots

Four different scoring systems by

Miller et al

Walsh et al

Qanadli et al

Mastora et al

Angiography

CTA

Miller GA, Sutton GC, Kerr IH, Gibson RV, Honey M. Comparison of streptokinase and heparin in treatment of isolated acute massive

pulmonary embolism. Br Med J 1971;2:681– 684.

Walsh PN, Greenspan RH, Simon M, et al. An angiographic severity index for pulmonary embolism. Circulation 1973;47-

48(suppl):101–108.

Qanadli SD, El Hajjam M, Vieillard-Baron A, et al. New CT index to quantify arterial obstruction in pulmonary embolism: comparison

with angiographic index and echocardiography. AJR Am J Roentgenol 2001;176:1415–1420.

Mastora I, Remy-Jardin M, Masson P, et al. Severity of acute pulmonary embolism: evaluation of a new spiral CT angiographic score

in correlation with echocardiographic data. Eur Radiol 2003;13: 29 –35.

Qanadli Score

Each lung has 10 segmental PAs 3 to the upper lobes

2 to the middle lobe or lingula

5 to the lower lobes

An embolus in a segmental PA = 1 point, and

Emboli at the most proximal arterial level = No. of segmental PAs arising distally.

Perfusion distal to the embolus weighting factor 0 no defect

1 partial occlusion

2 complete occlusion

An isolated subsegmental embolus is considered a partially occluded segmental PA and is assigned a value of 1.

The maximum CT obstruction index is 40

Mastora Score

5 mediastinal PAs PA trunk

Right and left Pas

Right and left interlobar Pas

6 lobar PAs

20 segmental PAs Three in the upper lobes

Two in the middle lobe or lingula Five in the lower lobes

based on the percentage of obstructed surface of each central and peripheral PA section and uses a 5-point scale 1 25%, 2 25%– 49%, 3 50%–74%, 4 75%–99%, 5 100%

The maximum CT obstruction score is 155

Central

Peripheral

PA Clot Load Scores

Wu et al

PA clot load score > 60% tended to succumb

Wu et al and Van der Meer et al

Qanadli score is a significant predictor of death

Wu AS, Pezzullo JA, Cronan JJ, Hou DD, MayoSmith WW. CT pulmonary angiography: quantifi-

cation of pulmonary embolus as a predictor of patient outcome—initial experience. Radiology

2004;230:831– 835.

Van der Meer RW, Pattynama PM, van Strijen MJ, et al. Right ventricular dysfunction and

pulmonary obstruction index at helical CT: prediction of clinical outcome during 3-month follow-up in

patients with acute pulmonary embolism. Radiology 2005;235:798 – 803

PA Clot Load Scores

Indicator of the severity of the current

episode of PE or treatment

effectiveness, it seems that they cannot

be used as a predictor of RV failure and

death of the patient.

Collomb D, Paramelle PJ, Calaque O, et al. Severity assessment of acute pulmonary embolism:

evaluation using helical CT. Eur Radiol 2003;13: 1508 –1514.

Ghaye B, Ghuysen A, Willems V, et al. Pulmonary embolism CT severity scores and CT

cardiovascular parameters as predictor of mortality in patients with severe pulmonary embolism.

Radiology.

Araoz PA, Gotway MB, Trowbridge RL, et al. Helical CT pulmonary angiography predictors of in-

hospital morbidity and mortality in patients with acute pulmonary embolism. J Thorac Imaging

2003;18:207–216.

PA Diameter Measurement

A PA diameter > 30 mm indicates a PA

pressure > 20 mm Hg.

Qanadli et al reported a poor correlation

between the PA clot load scores and the

mean PA pressure.

Kuriyama K, Gamsu G, Stern RG, Cann CE, Herfkens RJ, Brundage BH. CT-determined pulmonary

artery diameters in predicting pulmonary hypertension. Invest Radiol 1984;19:16 –22.

Qanadli SD, El Hajjam M, Vieillard-Baron A, et al. New CT index to quantify arterial obstruction in

pulmonary embolism: comparison with angiographic index and echocardiography. AJR Am J

Roentgenol 2001;176:1415–1420.

Leftward bowing of the

interventricular septum

Related to severe PA obstruction.

However, this sign does not seem to be

an indicator of outcome.

Oliver TB, Reid JH, Murchison JT. Interventricular septal shift due to massive pulmonary embo lism

shown by CT pulmonary angiography: an old sign revisited. Thorax 1998;53:1092–1094.

Collomb D, Paramelle PJ, Calaque O, et al. Severity assessment of acute pulmonary embolism:

evaluation using helical CT. Eur Radiol 2003;13: 1508 –1514.

Reflux of Contrast Medium into

IVC

No significant difference between

patients with severe PE and patients

with nonsevere PE in regard to this sign.

Collomb D, Paramelle PJ, Calaque O, et al. Severity assessment of acute pulmonary

embolism: evaluation using helical CT. Eur Radiol 2003;13: 1508 –1514.

Causes of Misdiagnosis of

Pulmonary Embolism

Causes of Misdiagnosis of PE:

Pathologic Factors

Mucus Plug

Causes of Misdiagnosis of PE:

Pathologic Factors

Perivascular Edema

Causes of Misdiagnosis of PE:

Pathologic Factors

Localized Increase in Vascular Resistance

Causes of Misdiagnosis of PE:

Pathologic Factors

Pulmonary Artery Stump In Situ Thrombosis

Causes of Misdiagnosis of PE:

Pathologic Factors

Primary Pulmonary Artery Sarcoma(rare)

Causes of Misdiagnosis of PE:

Pathologic Factors

Tumor Emboli

Causes of Misdiagnosis of PE:

Pathologic Factors

Idiopathic Pulmonary Hypertension

Causes of Misdiagnosis of PE:

Pathologic Factors

Takayasu Arteritis

Causes of Misdiagnosis of PE:

Pathologic Factors

Proximal Interruption of the Pulmonary Artery

Other causes of Misdiagnosis of

PE

Anatomic Factors

Partial Volume Averaging Effect in Lymph Nodes

Vascular Bifurcation

Misidentification of Veins

Technical Factors

Window Settings

Streak Artifact

Lung Algorithm Artifact

Partial Volume Artifact

Other causes of Misdiagnosis of

PE

Patient-related Factors

Respiratory Motion Artifact

Image Noise

Pulmonary Artery Catheter

Flow-related Artifact

Conclusion

Acute PE

Chronic PE

Acute Chronic

Impacted artery large small

Angle acute obtuse

Others Polomint/railway track

Mosaic

right heart strain

Recanalisation

Web/flap

Collateral arteries

Calcification

PHTN Mosaic

right heart strain

PE severity index by imaging

PA clot load scores

> 60%

Unreliable

Right heart strain

Relate with PHTN

Leftward bowing of the interventricular

septum

IVC contrast reflux

Causes of Misdiagnosis of PE

Technique-related

Patient-related

Anatomic-related

Another pathology of the lung or vessels

References

Wittram, C., M. M. Maher, A. J. Yoo, M. K. Kalra, J.-A. O. Shepard, and T. C. Mcloud. "CT Angiography of Pulmonary Embolism: Diagnostic Criteria and Causes of misdiagnosis." Radiographics 24.5 (2004): 1219-238.

Ghaye, B., A. Ghuysen, P.-J. Bruyere, V. D'orio, and R. F. Dondelinger. "Can CT Pulmonary Angiography Allow Assessment of Severity and Prognosis in Patients Presenting with Pulmonary Embolism? What the Radiologist Needs to Know." Radiographics 26.1 (2006): 23-39

References

Pena, E., Dennie, C., Veinot, J., & Muniz, S. (2012). Pulmonary Hypertension: How the Radiologist Can Help. Radiographics, 9-32

Grosse, C., & Grosse, A. (2010). CT Findings in Diseases Associated with Pulmonary Hypertension: A Current Review. Radiographics, 1753-1777.

Wijesuriya, S., Chandratreya, L., & Medford, A. (2013). Chronic Pulmonary Emboli and Radiologic Mimics on CT Pulmonary Angiography. Chest Journal, 1460-1471.