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Anterior segmental artery of left lung

The anterior segmental artery of the left lung (A3) is a segmental branch of the left superior lobar artery, which arises from the left pulmonary artery. It supplies the anterior segment (S3) of the left upper lobe, one of the five bronchopulmonary segments of the left upper lobe.

The A3 artery typically arises anteriorly from the left superior lobar artery, running parallel and anterior to the segmental bronchus (B3) and its associated vein (V3). It courses anteroinferiorly within the upper lobe parenchyma toward the anterior lung surface. Its venous drainage is via the anterior segmental vein (V3), which empties into the superior pulmonary vein, while the bronchial supply is via the anterior segmental bronchus (B3).

The artery is of clinical significance in segmentectomy of the left upper lobe, pulmonary embolism affecting segmental branches, and in CT pulmonary angiography interpretation, where segmental arteries must be carefully traced for embolic occlusion.

Synonyms

  • A3 artery

  • Left upper lobe anterior segmental artery

  • Arteria segmentalis anterior (pulmonis sinistri)

Function

  • Provides oxygen-depleted blood from the pulmonary trunk to the anterior segment (S3) of the left upper lobe

  • Supports gas exchange by perfusing the anterior alveolar parenchyma

  • Serves as a surgical and imaging landmark for segmental resections

Branches

  • Intrapulmonary branches supplying the anterior segment (S3) of the left upper lobe

MRI Appearance

T1-weighted images:

  • Appears as a signal void (black lumen) running with the anterior segmental bronchus

  • Wall is hypointense; perihilar fat provides background contrast

T2-weighted images:

  • Lumen shows a signal void

  • Filling defect may represent embolus or thrombus

T2 TRUFISP (cardiac/respiratory-gated):

  • Demonstrates the A3 artery as a bright vascular channel coursing to the anterior upper lobe

  • Provides cine-like assessment of pulmonary arterial patency and flow

STIR:

  • Suppresses fat, enhancing visualization of vessel against hilar fat

  • Perivascular edema or inflammation appears hyperintense

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • A3 enhances homogeneously

  • Filling defects correspond to segmental pulmonary embolism

  • Useful for angiographic mapping of upper lobe segmental branches

MRI Non-Contrast Cardiac-Gated 3D Imaging:

  • Depicts A3 in 3D course from left superior lobar artery to anterior segment

  • Especially valuable in patients with renal insufficiency or contrast contraindications

  • Useful for preoperative pulmonary venous/arterial mapping

MRA (Magnetic Resonance Angiography):

  • Contrast-enhanced MRA visualizes A3 origin and course, especially in research and advanced thoracic vascular imaging

CT Appearance

CT Pulmonary Angiography (CTPA):

  • Best modality for direct visualization of A3

  • Opacifies brightly with contrast, showing its origin from the left superior lobar artery and course with B3 bronchus

  • Detects segmental pulmonary embolism, stenosis, anomalous branching, or extrinsic compression

  • Multiplanar and 3D reconstructions are essential for thoracic surgical planning and segmentectomy

CT image

Anterior segmental artery of left lung anatomy ct axial image -img-00000-00000

MRI image

Anterior segmental artery of left lung mri image