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Topic

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Right internal thoracic artery

The right internal thoracic artery (RITA), also known as the right internal mammary artery, is a paired branch of the subclavian artery. It arises from the inferior surface of the first part of the right subclavian artery, descending vertically along the inner chest wall, parallel to the sternum, and posterior to the costal cartilages.

The artery runs about 1 cm lateral to the sternum, enclosed between the transversus thoracis muscle and costal cartilages. Along its course, it gives rise to anterior intercostal branches, perforating branches, and the pericardiophrenic artery. It terminates at the sixth intercostal space, dividing into the superior epigastric artery and musculophrenic artery.

Clinically, the RITA (along with the LITA) is of paramount importance in coronary artery bypass grafting (CABG), due to its long-term patency when used as a graft for the right or left coronary circulation. It also plays a role in supplying the thoracic wall, breast, diaphragm, and anterior mediastinum.

Synonyms

  • Right internal mammary artery

  • Arteria thoracica interna dextra

Function

  • Supplies the anterior thoracic wall, intercostal spaces, sternum, and breast

  • Contributes to collateral circulation between the subclavian and external iliac arteries via superior epigastric and musculophrenic branches

  • Provides blood supply to pericardium, thymus, and diaphragm

  • Acts as a graft vessel in coronary artery bypass surgery

Branches

  • Pericardiophrenic artery (to pericardium and diaphragm)

  • Anterior intercostal arteries (upper six intercostal spaces)

  • Perforating branches (to thoracic wall and breast)

  • Terminal branches: musculophrenic artery and superior epigastric artery

MRI Appearance

T1-weighted images:

  • RITA lumen appears as a flow void (dark signal) along the parasternal region

  • Adjacent mediastinal fat provides contrast

T2-weighted images:

  • Lumen appears as a signal void; vessel walls are better delineated with high-resolution sequences

STIR:

  • Suppresses fat, improving conspicuity of the artery along the thoracic wall

  • Useful for identifying perivascular edema or inflammatory changes

T1 Fat-Saturated (Pre-contrast):

  • Arterial lumen typically shows intermediate signal, standing out against suppressed fat background

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • RITA enhances brightly and homogeneously

  • Highlights course and branching pattern

  • Useful for detecting aneurysms, stenosis, or post-surgical graft patency

MR Angiography (MRA):

  • Provides 3D mapping of RITA from its subclavian origin to terminal bifurcation

  • Useful in CABG graft assessment and thoracic vascular planning

CT Appearance

CT Pre-Contrast:

  • Artery seen as a soft-tissue tubular structure along parasternal line, often subtle without contrast

CT Post-Contrast:

  • Enhances brightly during arterial phase

  • Defines origin, parasternal course, and terminal branches

CT Angiography (CTA):

  • Gold standard for detailed evaluation

  • Demonstrates origin, entire course, and branching of RITA

  • Critical in pre-CABG planning, post-graft patency evaluation, and thoracic vascular mapping

  • Multiplanar and 3D reconstructions highlight relationship to sternum and adjacent structures

CT image

internal thoracic artery right