Should I get a Computed Tomography Angiography (CTA) of the thorax or a CTA of the upper extremity?

CTA Thorax is the Preferred Choice for Thoracic Outlet Syndrome Imaging

For suspected thoracic outlet syndrome, CTA thorax is recommended over CTA upper extremity as it provides comprehensive evaluation of the thoracic outlet structures and central vessels while still including the subclavian and axillary vessels. 1

Rationale for CTA Thorax Selection

• CTA thorax specifically evaluates the chest and thoracic outlet, including central vessels as well as subclavian and axillary arteries and veins, which are the key structures involved in thoracic outlet syndrome 1
• CTA upper extremity protocols are designed to evaluate the entire limb peripherally to the level of the wrist, which extends beyond what's needed for thoracic outlet assessment and may miss central pathology 1
• The thoracic outlet contains critical neurovascular structures in the costoclavicular triangle and interscalene triangle that require careful evaluation to diagnose compression syndromes 2

Technical Considerations for Thoracic Outlet CTA

• CTA thorax for thoracic outlet syndrome should be performed in both neutral (arms adducted) and stressed (arms abducted) positions to demonstrate dynamic compression 1
• Scan acquisition typically uses contralateral antecubital IV injection with either empiric scan delay of 15-20 seconds or bolus tracking over the ascending aorta 1
• Some centers place the contralateral arm in abduction (with symptomatic ipsilateral arm in neutral position) to minimize streak artifact 1
• The protocol should include thin-section CT acquisition timed to coincide with peak arterial enhancement, with multiplanar reformations and 3D renderings 1

Clinical Value in Different TOS Types

For Arterial TOS (aTOS)

• CTA thorax is considered "usually appropriate" by the ACR for initial and follow-up imaging after surgery or intervention 1
• Can identify subclavian artery stenosis, aneurysms, and thrombosis that may lead to distal embolization 1
• Allows accurate measurements of vessel diameter and length for potential endograft planning 1

For Venous TOS (vTOS)

• CT with IV contrast of the chest is "usually appropriate" for initial and follow-up imaging 1
• CTV (CT venography) is obtained 120-180 seconds after IV contrast injection to evaluate venous compression 1
• Can detect thrombi in vascular lumen, stenosis, and perivascular inflammatory changes 1

For Neurogenic TOS (nTOS)

• While MRI is preferred for neurogenic TOS, CT with IV contrast can still provide valuable information about anatomical narrowing that could cause neurovascular compression 1
• CT allows quantification of changes in costoclavicular or interscalene spaces with provocative maneuvers 1
• Can identify bony abnormalities like cervical ribs that may contribute to symptoms 1

Common Pitfalls to Avoid

• Don't limit imaging to just the upper extremity, as this may miss central pathology at the thoracic outlet 1
• Be aware that calcification can interfere with CTA assessment, particularly in complex calcified plaques 1
• Recognize that segments of vessels parallel to the imaging plane may be subject to flow artifacts, creating artifactual stenosis 1
• Remember that imaging findings must be carefully correlated with clinical symptoms, as venous compression with arm abduction is often present in asymptomatic patients 3

Conclusion

CTA thorax provides comprehensive evaluation of the thoracic outlet and its neurovascular structures, making it the preferred choice over CTA upper extremity for thoracic outlet syndrome assessment. The thoracic protocol includes the critical areas where compression occurs while still capturing the proximal portions of the upper extremity vessels.