AJR 2002; 178:487-492
© American Roentgen Ray Society
Helical CT of Pulmonary Vascular Abnormalities
Himanshu Gupta1,2,
William W. Mayo-Smith1,
Martha B. Mainiero1,
Damian E. Dupuy1 and
Gerald F. Abbott1
1
Brown University School of Medicine, Department of Diagnostic Imaging, Rhode
Island Hospital, 593 Eddy St., Providence, RI 02903.
2
Present address: Department of Radiology, Salem Hospital, 81 Highland Ave.,
Salem, MA 01970.
Received March 27, 2001;
accepted after revision June 8, 2001.
Address correspondence to W. W. Mayo-Smith.
Introduction
Multidetector helical CT is revolutionizing imaging of the thoracic
vasculature. Multidetector helical CT allows high-resolution, noninvasive,
volumetric imaging that can be acquired during a single breath-hold, making it
the imaging study of choice over conventional catheter angiography. In
addition, volumetric helical imaging allows three-dimensional reconstruction
of data, which is useful in lesion detection, characterization, and surgical
planning. With multidetector helical CT, radiologists can definitively
characterize pulmonary vascular lesions. Understanding the anatomy,
physiology, and imaging appearance of pulmonary vascular lesions is essential
in making the correct diagnosis and avoiding unnecessary interventions. This
pictorial essay will illustrate multidetector helical CT manifestations of a
variety of pulmonary vascular malformations including congenital and acquired
lesions.
Technique
To characterize suspected vascular malformations, collimation, pitch,
contrast injection rate, and field of view should be tailored to the area of
interest. For a screening chest CT scan, we routinely use a 7-mm collimation,
which can be retrospectively collimated to 3.75 mm using multidetector
technology. For pulmonary embolism examinations, we use a 1.25-mm collimation.
For suspected pulmonary nodules, we use a 1.25-mm collimation reconstructed at
0.75-mm intervals with a targeted field of view. We use a pitch of 3 or 6
depending on the craniocaudal extent of the lesion and the patient's ability
to hold their breath. If required, we use 120 mL of nonionic contrast material
injected at a rate of 4-5 mL/sec. For patients with known altered cardiac
output, a timing bolus targeted to the region of interest is helpful to
optimize vascular opacification. Depending on the abnormality, arterial and
venous phase imaging can be performed through the same structure to
characterize blood supply and drainage. Volumetric imaging data can be
reconstructed using algorithms such as shaded surface display, maximum
intensity projection, or volume rendering to aid in vessel evaluation.
Congenital Anomalies
Congenital Arterial Stenosis
Pulmonary artery stenosis can occur anywhere, from the pulmonary valves to
the peripheral pulmonary arteries, and may be solitary or multiple. Pulmonary
artery stenosis may be isolated (20%), but it is often associated with cardiac
anomalies such as atrial septal defect and perivalvular pulmonic stenosis.
Pulmonary artery stenosis is associated with Williams syndrome, Down syndrome,
Ehlers-Danlos syndrome, and in utero exposure to rubella
[1]
(Fig. 1).
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Fig. 1. —38-year-old hypoxic woman with pulmonary artery stenosis.
Contrast-enhanced CT scan shows focal stenosis (arrow) of right main
pulmonary artery. Patient had history of maternal in utero exposure to
rubella.
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Congenital Arterial Aneurysms
Congenital aneurysms of the pulmonary arteries
(Fig. 2) are rare and can be
detected at birth. Pulmonary valvular stenosis can cause poststenotic
dilatation of the pulmonary artery, most commonly on the left side
[2].
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Fig. 2. —50-year-old asymptomatic man with left pulmonary artery
aneurysm. Contrast-enhanced helical CT scan shows aneurysmal dilatation
(arrow) of left pulmonary artery. Patient had no history of
associated valvular abnormality or lung disease.
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Pulmonary Venous Varices
Varicosities of the pulmonary veins are rare malformations that may be
congenital or acquired. These lesions typically occur at the confluences of
the veins adjacent to the left atrium. They are usually asymptomatic and may
manifest as a solitary pulmonary nodule on chest radiographs
[2] (Fig.
3A,3B,3C).
It is important to recognize this entity prospectively and avoid complications
of unnecessary percutaneous biopsy.
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Fig. 3A. —54-year-old woman with pulmonary venous varix who was
referred for percutaneous biopsy of nodule seen on chest radiograph. Scout
radiograph of chest shows nodular mass (arrow) in lower right
lung.
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Fig. 3B. —54-year-old woman with pulmonary venous varix who was
referred for percutaneous biopsy of nodule seen on chest radiograph. Arterial
phase multidetector helical CT scan shows no enhancement of lesion
(arrow) contiguous with left atrium.
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Fig. 3C. —54-year-old woman with pulmonary venous varix who was
referred for percutaneous biopsy of nodule seen on chest radiograph. Venous
phase CT scan obtained at same level as B shows enhancement of varicose
right inferior pulmonary vein (arrow).
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Anomalous Pulmonary Venous Return
Anomalous pulmonary venous drainage occurs when pulmonary venous blood
enters the systemic circulation or the right heart (Fig.
4A,4B,4C).
Hypogenetic lung (scimitar) syndrome is a special type of anomalous pulmonary
venous return with other anomalies, including hypoplastic right lung,
hypoplastic right pulmonary artery, and partial or complete systemic lung
arterial supply [3].
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Fig. 4B. —73-year-old woman with anomalous pulmonary venous return.
Multidetector helical CT scan shows enhancing enlarged pulmonary vein
(arrow) with anomalous drainage inferiorly into inferior vena
cava.
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Arteriovenous Malformations
Abnormal direct communication between pulmonary arteries and veins (Fig.
5A,5B)
can be an isolated lesion in 40% of patients. Approximately 60% of patients
have associated arteriovenous malformations involving the skin, mucous
membranes, and other organs known as hereditary hemorrhagic telangiectasia or
Oslar-Weber-Rendu syndrome. Small arteriovenous malformations may be
asymptomatic and incidentally found on helical CT. However, as the size and
number of lesions increase, patients are at risk for hypoxemia, cyanosis, and
paradoxical emboli [2,
4].
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Fig. 5A. —54-year-old man with arteriovenous malformation presenting
with hemoptysis. Unenhanced multidetector helical CT scan shows
well-circumscribed lobular opacity with serpentine tail (arrow)
arising from pulmonary artery.
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Fig. 5B. —54-year-old man with arteriovenous malformation presenting
with hemoptysis. Three-dimensional shaded-surface—display image confirms
lobulated arteriovenous malformation (arrow). IV contrast agent is
not required to show these lesions because of intrinsic high contrast between
vessels and lung.
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Plumonary Sequestration
Bronchopulmonary sequestration is a congenital malformation in which a
segment of nonfunctioning lung is isolated from the normal airways and
receives its blood supply from a systemic artery (Fig.
6A,6B,6C).
It is classified as intralobar (in the visceral pleura of normal lung, 75% of
patients) or extralobar (in a separate pleural envelope, 25% of patients)
[5]. Sequestrations are often
detected as inferior posteromedial masses on chest radiographs. Such
sequestrations can be accurately diagnosed on contrast-enhanced CT by seeing a
feeding vessel from the aorta.
Acquired Anomalies
Pulmonary Artery Pseudoaneurysm
Pulmonary artery pseudoaneurysm can be postinfectious or posttraumatic,
such as an injury from balloon inflation of Swan-Ganz catheters (Fig.
7A,7B,7C,7D).
Although Swan-Ganz catheter-related arterial rupture occurs in only
0.001-0.47% of patients, it is associated with a 45-65% mortality rate
[6]. If the patient survives,
false aneurysms form in 30% of patients, which carries a high risk for
recurrent hemorrhage. Pulmonary artery pseudoaneurysms can be treated by
embolization.
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Fig. 7A. —67-year-old woman with pulmonary artery pseudoaneurysm from
Swan-Ganz catheter. Chest radiograph from intensive care unit shows Swan-Ganz
catheter and air-space disease in right lower lung (arrow) from
hemorrhage. Patient was catheterized for cardiac failure and developed
hemoptysis after inflation of catheter balloon.
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Fig. 7C. —67-year-old woman with pulmonary artery pseudoaneurysm from
Swan-Ganz catheter. Contrast-enhanced multidetector helical CT scan shows
round enhancing lesion arising from pulmonary artery (arrow).
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Pulmonary Emboli
Helical CT is playing an increasing role in the evaluation of patients with
suspected pulmonary emboli (Fig.
8A,8B).
Helical CT has been shown to effectively exclude clinically significant
pulmonary embolus [7]. Thrombi
are seen as filling defects in the pulmonary arteries. Wedge-shaped peripheral
consolidation and dilated central or segmental arteries are important
secondary signs for pulmonary emboli.
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Fig. 8B. —58-year-old woman with bilateral pulmonary artery emboli.
Coronal maximum-intensity-projection CT image shows peripheral opacity at left
lower lung (arrow) consistent with infarct distal to left interlobar
artery embolus (arrowhead).
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Oncologic Imaging
In patients with known malignancy, tumor invasion of the pulmonary
vasculature can be seen with contrast-enhanced helical CT
(Fig. 9). Detection of
vascular invasion is an important finding because it changes staging and
usually means the patient is not an operative candidate.
Conclusion
With the evolution of multidetector helical CT, pulmonary vascular
abnormalities can be reliably characterized in a noninvasive manner. Tailoring
the CT examination to the suspected abnormality is essential in rendering an
accurate diagnosis.
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