Which imaging modality is definitive imaging for arterial TOS?

• A. CT and MRI
• B. X-ray
• C. Ultrasound
• D. Angiography alone

Answer: (A)

For arterial TOS, you want imaging that shows the artery in its full three‑dimensional relationship to the thoracic outlet structures and can reveal both the site of compression and any vessel injury. Cross‑sectional imaging with CT or MRI provides that comprehensive view. With contrast, CT angiography or MR angiography can visualize the arterial lumen while also detailing bones (like a cervical rib or abnormal first rib), scalene muscles, and other tissues causing compression. This combination lets you identify exactly where the artery is being squeezed and whether there are downstream changes such as stenosis, aneurysm, or thrombosis, which is essential for planning treatment.

X‑ray mainly shows bony anatomy and cannot assess the vessel itself. Ultrasound can evaluate flow but is limited by anatomic access and operator dependence, and may not reliably demonstrate the full course of the subclavian/axillary arteries behind the clavicle. Angiography alone shows the vessel lumen but lacks the surrounding anatomic context, and is invasive; it does not provide as complete a picture of the compression’s cause as cross‑sectional imaging with CT or MRI.