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Topic

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Arch of aorta

The arch of the aorta is the curved segment of the aorta located between the ascending aorta and the descending thoracic aorta. It begins at the level of the second sternocostal junction (T4 vertebra, sternal angle), arches superiorly, posteriorly, and to the left, and ends as the descending thoracic aorta. The arch gives rise to the brachiocephalic trunk, left common carotid artery, and left subclavian artery (classic branching pattern), although anatomical variations are common. The arch lies in close relation to the trachea, esophagus, pulmonary trunk, and recurrent laryngeal nerves, making it an important mediastinal landmark.

Synonyms

  • Aortic arch

  • Transverse aortic arch

  • Curved portion of aorta

Function

  • Conducts oxygenated blood from the left ventricle (via the ascending aorta) to the systemic circulation

  • Distributes blood to the head, neck, and upper limbs through its branches

  • Acts as a buffer for pulsatile blood flow, thanks to its elastic wall properties

  • Provides an anatomical landmark in thoracic and mediastinal imaging and surgery

MRI Appearance

T1-weighted images:

  • Blood flow in the lumen appears as a signal void (black)

  • Vessel wall appears as a thin hypointense rim

  • Useful for localization but limited for dynamic assessment

T2-weighted images:

  • Flowing blood shows signal voids

  • Vessel wall thickening or mural pathology (e.g., thrombus, dissection flap) may be visible as altered signal intensity

Cine MRI (SSFP / phase-contrast sequences):

  • Demonstrates real-time dynamic imaging of blood flow and wall motion

  • Excellent for detecting aortic stenosis, regurgitant flow, aneurysmal dilatation, or dissection

  • Phase-contrast cine quantifies flow velocity, direction, and stroke volume

  • Provides functional assessment in congenital aortic arch anomalies (coarctation, interrupted arch)

T1 Post-Contrast (Gadolinium-enhanced / MR Angiography):

  • Lumen demonstrates intense homogeneous enhancement

  • Clearly delineates the arch, its branches, and collateral circulation

  • Excellent for detecting aneurysm, dissection, stenosis, and vascular malformations

CT Appearance

Non-contrast CT:

  • Aortic arch appears as a tubular mediastinal structure with soft tissue attenuation

  • Calcified plaques, if present, appear hyperdense

  • Useful for detecting atherosclerosis or mural calcifications

Contrast-enhanced CT (CT Angiography):

  • Provides high-resolution detail of the arch lumen, wall, and branches

  • Excellent for evaluating aneurysms, dissections, congenital anomalies, stenosis, and traumatic injuries

  • Multiplanar and 3D reconstructions aid in surgical and endovascular planning

  • CTA is the gold standard for acute aortic syndromes (dissection, intramural hematoma, rupture)

MRI images

Arch of aorta anatomy MRI coronal image -img-00000-00000

CT images