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Topic

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Pulmonary trunk

The pulmonary trunk is a large elastic artery that arises from the right ventricle of the heart and carries deoxygenated blood to the lungs for oxygenation. It begins at the level of the pulmonary valve, ascends obliquely upward, backward, and to the left, and divides into the right and left pulmonary arteries at the level of the T5–T6 vertebrae and sternal angle. The pulmonary trunk lies anterior to the ascending aorta and to the left of the midline in its proximal portion. Its wall contains elastic fibers, allowing it to accommodate stroke volume ejected from the right ventricle.

Synonyms

  • Main pulmonary artery

  • Truncus pulmonalis

  • Pulmonary arterial trunk

Function

  • Transports deoxygenated blood from the right ventricle to the lungs

  • Ensures oxygenation of blood via the pulmonary circulation

  • Plays a vital role in right ventricular afterload regulation

  • Forms part of the pulmonary arterial tree critical for systemic gas exchange

MRI Appearance

T1-weighted images:

  • Blood flow creates a signal void (black lumen) in non-contrast scans

  • Vessel wall appears as a thin low-signal rim

  • Useful for anatomical localization relative to the right ventricle and ascending aorta

T2-weighted images:

  • Flowing blood appears as a signal void, surrounding mediastinal fat is hyperintense

  • Wall abnormalities (e.g., dissection, mural thrombus) may show altered signal

  • Dilatation or aneurysm appears as enlargement with flow-related signal void

STIR (Short Tau Inversion Recovery):

  • Fat suppression improves contrast between the pulmonary trunk and surrounding mediastinal fat

  • Wall edema or inflammatory changes may appear hyperintense

  • Useful for detecting vasculitis or inflammatory conditions

T1 Post-Contrast (Gadolinium-enhanced):

  • Pulmonary trunk lumen demonstrates intense homogeneous enhancement

  • Enhances visualization of stenosis, aneurysm, thrombus, or vascular malformations

  • Essential for MR angiography of the pulmonary arteries

CT Appearance

Non-contrast CT:

  • Pulmonary trunk appears as a tubular soft tissue structure anterior to the ascending aorta

  • Lumen shows low attenuation without contrast; calcifications (rare) appear as hyperdense foci

Contrast-enhanced CT (CT Angiography):

  • Lumen opacifies with contrast, providing excellent delineation of origin, size, bifurcation, and branching

  • Best modality for detecting pulmonary embolism, aneurysm, stenosis, and congenital anomalies

  • Axial and multiplanar reconstructions allow precise measurement of pulmonary trunk diameter (important in pulmonary hypertension assessment)

MRI image

Pulmonary trunk anatomy mri coronal image -img-00000-00000

CT image

Pulmonary trunk anatomy CT axial image -img-00000-00000