imaging of pulmonary embolism
TRANSCRIPT
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%
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
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).
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).
Same patient . CT scan reveals a small, recanalized pulmonary artery with contrast material in the central lumen
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)
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.
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.
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.
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 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.
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.