Topics

Topic

design image
Internal thoracic artery

The internal thoracic artery (ITA), historically called the internal mammary artery, is a paired branch of the first part of the subclavian artery. It arises just lateral to the origin of the vertebral artery and descends vertically within the thoracic cavity, approximately 1–2 cm lateral to the sternum, lying posterior to the costal cartilages.

The artery courses inferiorly, accompanied by paired internal thoracic veins, and is protected by the transversus thoracis muscle. At the level of the 6th intercostal space, it divides into its terminal branches: the superior epigastric artery and the musculophrenic artery. Along its course, the ITA gives off numerous anterior intercostal branches, as well as perforating branches to the breast and anterior thoracic wall.

Clinically, the internal thoracic artery is of major importance because it is the graft of choice in coronary artery bypass grafting (CABG) due to its excellent long-term patency. It also plays a role in collateral circulation between the subclavian and external iliac systems via its epigastric branches.

Synonyms

  • Internal mammary artery (IMA)

  • Arteria thoracica interna

  • ITA

Function

  • Supplies the anterior thoracic wall (sternum, intercostal muscles, overlying skin)

  • Provides arterial supply to the breast via perforating branches

  • Contributes to diaphragmatic blood supply via the musculophrenic artery

  • Provides collateral circulation between the subclavian and external iliac arteries

  • Serves as the primary graft in coronary artery bypass surgery (CABG)

Branches

  • Pericardiophrenic artery → supplies pericardium and diaphragm

  • Anterior intercostal arteries (1st–6th spaces) → supply anterior chest wall and intercostal muscles

  • Perforating branches → supply anterior thoracic wall and breast tissue

  • Terminal branches:

    • Superior epigastric artery → continues into anterior abdominal wall

    • Musculophrenic artery → supplies diaphragm and lower intercostal spaces

MRI Appearance

T1-weighted images:

  • Appears as a flow void (signal loss) in non-contrast imaging

  • Lies adjacent to sternum, running vertically within thoracic wall

  • Surrounded by hyperintense fat planes for localization

T2-weighted images:

  • Flowing blood remains a signal void

  • Wall abnormalities (e.g., dissection, aneurysm, arteritis) may appear as altered signal intensity

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, highlighting the artery within chest wall

  • Useful for detecting perivascular edema, inflammation, or neoplastic invasion

T1 Post-Contrast (Gadolinium-enhanced):

  • Lumen shows bright homogeneous enhancement

  • Excellent for evaluating branching pattern, stenosis, or surgical graft patency

MRA (Magnetic Resonance Angiography):

  • Depicts origin from subclavian and course along thoracic wall

  • Contrast-enhanced MRA demonstrates patency, branching, and collateral circulation

  • Used in preoperative planning for CABG and thoracic surgery

CT Appearance

Non-contrast CT:

  • Appears as a tubular soft tissue density parallel to sternum, often difficult to distinguish without contrast

  • Calcifications may be seen in atherosclerotic disease

CT Angiography (CTA):

  • Clearly demonstrates origin, course, and terminal bifurcation (superior epigastric and musculophrenic arteries)

  • Used in evaluating surgical graft patency, trauma, aneurysm, or tumor encasement

  • High-resolution multiplanar reconstructions aid in thoracic surgery planning and breast cancer vascular mapping

CT images

internal thoracic artery CT axial image -img-00000-00000

CT images

internal thoracic artery CT axial image -img-00000-00000_00001

MRI images

i nternal thoracic artery anatomy MRI coronal image -img-00000-00000

CT images

internal thoracic artery 1

CT images

internal thoracic artery ct axial