Radial Artery: Anatomy, Course, Branches, Function, MRA & CTA Imaging

Topic

Radial artery

The radial artery is one of the terminal branches of the brachial artery, arising in the cubital fossa at the level of the neck of the radius. It is the principal artery of the lateral aspect of the forearm, running distally to the wrist and hand. The radial artery provides a major contribution to the deep palmar arch, supplying the thumb, index finger, and lateral half of the hand.

Clinically, it is the most accessible site for arterial pulse palpation and a common vessel used in coronary angiography access and arterial grafting. Its superficial position in the distal forearm makes it highly relevant for both clinical and imaging evaluation.

Synonyms

Arteria radialis
Lateral terminal branch of brachial artery

Origin, Course, and Termination

Origin: Arises in the cubital fossa as the smaller terminal branch of the brachial artery, opposite the neck of the radius.
Course:
- Descends laterally in the forearm under the cover of the brachioradialis muscle.
- Becomes superficial in the distal third of the forearm, just lateral to the flexor carpi radialis tendon.
- Winds dorsally around the lateral aspect of the wrist, through the anatomical snuffbox, and enters the palm between the heads of the first dorsal interosseous muscle.
Termination: Joins the deep branch of the ulnar artery to form the deep palmar arch.

Relations

Proximally: Lies beneath the brachioradialis, lateral to the pronator teres.
Distally: Lies between the tendons of the brachioradialis and flexor carpi radialis, then superficial in the wrist region.
Posteriorly: In the anatomical snuffbox, lies on the scaphoid and trapezium.
Accompanied by: Radial artery is accompanied by two venae comitantes throughout the forearm.

Branches

In the forearm:
- Radial recurrent artery (to elbow joint and brachioradialis)
- Muscular branches to lateral forearm muscles
- Palmar carpal branch (joins palmar carpal network)
- Superficial palmar branch (contributes to superficial palmar arch)
In the hand:
- Dorsal carpal branch (to dorsal carpal network)
- First dorsal metacarpal artery
- Princeps pollicis artery (main artery to the thumb)
- Radialis indicis artery (to lateral side of index finger)
- Deep palmar arch (terminal branch)

Function

Major blood supply to the lateral forearm and hand
Contributes to both palmar arterial arches, ensuring collateral circulation
Supplies thumb and index finger, critical for prehension and grip function
Pulse palpation site: At the wrist, lateral to the flexor carpi radialis tendon
Preferred access site for percutaneous coronary procedures and arterial blood sampling

Clinical Significance

Radial pulse: Easily palpable and a key vital sign
Allen test: Assesses patency of the radial and ulnar arteries before cannulation or grafting
Arterial cannulation: Preferred for monitoring and sampling due to collateral supply
Trauma and thrombosis: Can lead to hand ischemia if ulnar collateral flow is insufficient
Aneurysm and pseudoaneurysm: Rare but may occur post-catheterization
Surgical relevance: Commonly harvested for coronary artery bypass grafts (CABG)

MRI Appearance

T1-weighted images:
- Arterial lumen: Low signal (dark) due to flowing blood
- Wall: Thin, slightly higher signal relative to lumen
- Perivascular fat: Bright, providing contrast for vessel identification
- Thrombosis: May appear as intermediate-to-high signal intensity in the lumen
T2-weighted images:
- Lumen: Flow void (dark) in normal patency
- Wall: Intermediate-to-high signal if thickened or inflamed (vasculitis)
- Thrombus: Hyperintense signal compared to flow void
- Surrounding soft tissue: Displays normal intermediate muscle signal
STIR:
- Normal artery: Low-to-intermediate signal (flow void maintained)
- Pathology: Bright hyperintensity in perivascular edema, inflammation, or hematoma
Proton Density Fat-Saturated (PD FS):
- Normal vessel: Low signal lumen; clear wall outline
- Abnormal: Bright perivascular edema or thrombus signal enhancement
T1 Fat-Sat Post-Contrast (MR Angiography sequences):
- Artery: Bright signal representing contrast-filled lumen
- Aneurysm or dissection: Focal dilation or intimal flap visible
- Thrombosed segments: Absent enhancement
- Vasculitis: Irregular mural thickening with patchy enhancement

MRA (Magnetic Resonance Angiography) Appearance

Normal MRA:
- Radial artery visualized as a bright continuous contrast-filled tubular structure from the cubital fossa to the hand.
- Clearly delineated course through forearm and anatomical snuffbox.
Pathology:
- Stenosis: Focal or segmental narrowing with reduced signal intensity.
- Aneurysm: Focal saccular or fusiform enlargement with bright contrast filling.
- Occlusion: Absence of flow signal distal to obstruction.
- Dissection: Intimal flap or dual-lumen appearance.
3D MRA reconstructions provide excellent visualization for surgical or interventional planning.

CT Appearance

Non-Contrast CT:

Arterial wall: Soft-tissue density tubular structure, poorly defined without contrast.
Calcifications: High-density foci along wall (arteriosclerosis).
Surrounding fat planes: Clear and symmetric unless inflamed or compressed.

Post-Contrast CT (Standard Angiographic Phase):

Artery enhances brightly with contrast, outlining course and branches.
Wall calcifications visible as non-enhancing dense rims.
Pathology:
- Stenosis or occlusion: Abrupt or tapered luminal narrowing.
- Aneurysm: Focal contrast-filled dilation.
- Thrombosis: Filling defect within lumen.
- Dissection: Intimal flap separating true and false lumens.

CTA (Computed Tomography Angiography) Appearance

Normal CTA:
- Radial artery appears as a bright contrast-opacified vessel with smooth walls and uniform caliber.
- Excellent visualization from its origin to the palmar arch.
Pathology:
- Stenosis: Focal luminal narrowing or irregular wall thickening.
- Occlusion: Segmental absence of contrast opacification.
- Aneurysm: Saccular or fusiform dilation with full contrast filling.
- Atherosclerosis: Calcified or non-calcified plaques along arterial wall.
- Post-surgical changes: Patent or occluded grafts, stents, or cannulation sites.
3D CTA reconstructions allow high-resolution mapping of forearm and hand arterial anatomy, especially before interventions or graft harvest.