Korean J Radiol.  2010 Apr;11(2):222-230. 10.3348/kjr.2010.11.2.222.

Multislice CT Virtual Intravascular Endoscopy for Assessing Pulmonary Embolisms: a Pictorial Review

• Sun Z
• Dosari SA
• Ng C
• al-Muntashari A
• Almaliky S

• KMID: 1783199
• DOI: http://doi.org/10.3348/kjr.2010.11.2.222

Abstract

Multislice CT has been widely used in clinical practice for diagnosing cardiovascular disease due to its reduced invasiveness and its high spatial and temporal resolution. As a reliable alternative to conventional pulmonary angiography, multislice CT angiography has been recognized as the first line technique for detecting and diagnosing pulmonary embolism. A pulmonary embolism located in the main pulmonary artery, as well as being located in the segmental branches, can be accurately detected with multislice CT imaging, and especially with the use of 16- and 64-slice CT scanners. Visualization of pulmonary embolisms has traditionally been limited to 2D, multiplanar reformation and the 3D external surface visualizations. In this pictorial review, we present our experience of using 3D virtual intravascular endoscopy to characterize and evaluate the intraluminal appearance of pulmonary embolisms in a group of patients who were suspected of having pulmonary embolism and who were undergoing multislice CT angiography. We expect that the research findings from this study will provide insight into the extent of disease and the luminal changes to the pulmonary arteries that are due to the presence of thrombus, and so monitoring of the progress of disease and predicting the treatment outcome can well be achieved.

Keyword

Multislice CT; Pulmonary embolism; 3D visualization; Virtual intravascular endoscopy

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Contrast Media/diagnostic use
Endoscopy/*methods
Female
Humans
Imaging, Three-Dimensional/methods
Iohexol/diagnostic use
Male
Middle Aged
Pulmonary Artery/radiography
Pulmonary Embolism/*radiography
Radiographic Image Enhancement/methods
Radiographic Image Interpretation, Computer-Assisted/*methods
Tomography, X-Ray Computed/*methods
User-Computer Interface
Young Adult

Figure

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  Fig. 1 Measurement of signal to noise ratio. Circular region of interest with minimum area of 50 mm2 is placed at bilateral main pulmonary arteries to measure mean CT attenuation and image noise, and latter is described as standard deviation. Signal to noise ratio is calculated by dividing CT attenuation by standard deviation.

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  Fig. 2 Normal main pulmonary arteries visualized on virtual intravascular endoscopy. Measured signal to noise ratios were 19 and 24 at right and left pulmonary arteries, respectively. LPA = left pulmonary artery, RPA = right pulmonary artery

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  Fig. 3 Virtual intravascular endoscopy visualization of pulmonary embolism in right pulmonary artery is affected by high density contrast in superior vena cava. Measured signal to noise ratio was 8.9 at right pulmonary artery. Beam-hardening streak artifact (arrows in A) causes irregular appearance of right pulmonary artery visualized on virtual intravascular endoscopy (B). Corresponding orthogonal views confirm that irregular luminal change (C) is caused by artifact. Arrows in B and C indicate irregular wall changes that are due to artifact. RLA = right lower lobar artery, RUA = right upper lobar artery.

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  Fig. 4 Virtual intravascular endoscopy visualization of pulmonary embolism in right main pulmonary artery. CT attenuation of thrombus is measured to be 35.87 HU (A), and it appears as protruding sign (arrows in B) inside pulmonary artery after applying upper CT threshold of 250 HU to remove contrast-enhanced blood. Arrowhead refers to artifacts caused by high density in superior vena cava.

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  Fig. 5 Pulmonary embolism involving bilateral pulmonary artery branches. Large thrombus is present in left main pulmonary artery and it extends to right side (A). Orthogonal views show that viewing position is located in pulmonary trunk (B). C and D demonstrate continuous extension of thrombus from proximal part of main pulmonary artery to distal segment with lumen narrowing, as well as protruding sign in lumen.

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  Fig. 6 Virtual intravascular endoscopy visualization of multiple emboli in left lobar arteries (A). Multiplanar views help to confirm that location of thrombus corresponds to involved lobar artery (B). Blue box indicates viewing position placed at left upper lobar thrombus. LLA = lower lobar artery, MLA = middle (lingular) lobar artery, ULA = upper lobar artery

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  Fig. 7 Virtual intravascular endoscopy views of left lower lobar embolism from proximal to distal segments of lobar artery (A, B). Accurate position of thrombus is confirmed with using multiplanar views (C).

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  Fig. 8 Virtual intravascular endoscopy views of right posterobasal segmental embolism. Thrombus extends from right lower lobar artery (A) to posterobasal segmental arteries (B, C). Corresponding orthogonal view confirms that position of thrombus is located in right posterobasal segmental artery with compressing corresponding posterobasal segmental artery (D). ASA = anteromedial basal segmental artery, PSA = posterobasal segmental artery

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  Fig. 9 Virtual intravascular endoscopy views of left lower pulmonary segmental embolism involving two arterial branches. Left lateral basal and anteromedial basal segmental arteries become narrowed due to presence of thrombus (A), while left posterobasal segmental artery is normal. Corresponding orthogonal views (B) confirm relationship between thrombus and segmental artery branches. ASA = anteromedial basal segmental artery, LSA = lateral basal segmental artery, PSA = posterobasal segmental artery

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