What is the recommended imaging test to evaluate the arteries to the arm, specifically to identify blockages or stenosis?

CT Angiography (CTA) is the Recommended Imaging Test for Evaluating Arm Arteries

CTA is the most appropriate imaging modality for evaluating arterial blockages or stenosis in the arm, providing excellent visualization of vessel anatomy while being less invasive than conventional angiography. 1

Advantages of CTA for Upper Extremity Arterial Evaluation

• CTA offers volumetric (3D) imaging as opposed to planar images, enabling extensive image post-processing including multiplanar reformatted and maximum-intensity projection images to create a detailed arterial road map 1
• CTA provides simultaneous analysis of both vascular structures and surrounding anatomy, allowing for comprehensive assessment of potential causes of arterial compromise 1
• The sensitivity and specificity of CTA for detection of stenoses >50% diameter are 90% to 100% when compared with conventional angiography 1
• CTA is less invasive than conventional angiography, reducing procedural risks while maintaining diagnostic accuracy 2, 3

Technical Considerations for Upper Extremity CTA

• Multislice CT scanner should be used with collimation of 0.6 mm and reconstruction slice thickness between 0.5-1.0 mm 1
• Patient-adapted injection of non-ionic iodinated contrast agent (≥350 mg/mL) using a power injector (≥4 mL/s) 1
• Right arm injection is preferred when possible, as it produces fewer perivenous streak artifacts and less venous reflux compared to left arm injections 4
• Arterial compression should be assessed using arterial cross-sections produced by sagittal reformation of data, as axial slices alone can lead to misrepresentation of stenosis degree 1
• Reliance on axial slices alone can lead to underestimation of stenosis in 43% of cases, while sagittal reformations reduce this to only 10% 1

Comparison with Other Imaging Modalities

Conventional Angiography

• While conventional angiography has historically been considered the gold standard, it is invasive and carries risks of catheterization 1
• Conventional angiography is now primarily reserved for cases where endovascular intervention is planned rather than for diagnostic purposes alone 1
• CTA has largely replaced conventional angiography as the reference standard for arterial imaging in many institutions 1

MR Angiography (MRA)

• MRA with contrast provides excellent soft tissue contrast and vascular assessment 1
• However, MRA has longer acquisition times which may be difficult for symptomatic patients 1
• MRA is contraindicated in patients with certain implanted devices and may be limited by claustrophobia 1

Ultrasound

• Duplex ultrasound is useful for initial screening and in patients with contrast allergy or renal dysfunction 1
• However, ultrasound is operator-dependent and may have limitations in visualizing deeper vessels 1

Special Clinical Scenarios

• For suspected thoracic outlet syndrome affecting arm arteries, CTA in both neutral and elevated arm positions is recommended to assess for dynamic arterial compression 1
• In cases of trauma to the upper extremity, CTA has been shown to be reliable for detection and characterization of arterial injuries, potentially replacing conventional angiography 2, 3
• For post-intervention assessment, CTA is valuable to evaluate for vessel patency and complications such as restenosis, occlusion, or aneurysm formation 1

Potential Limitations and Pitfalls

• Heavily calcified atheromatous disease can limit the ability to interpret CT images 1
• Volume-rendered images are preferred over surface displays with 3D shading, as the latter can overestimate stenosis in 16% of cases (versus 7% with volume rendering) 1
• Timing of contrast administration is critical to avoid venous contamination or inadequate arterial opacification 1
• Dual-energy CTA can reduce blooming and beam-hardening artifact created by heavily calcified disease and metallic stents when available 1

In conclusion, CTA represents the optimal balance of diagnostic accuracy, comprehensive assessment, and minimal invasiveness for evaluating arterial blockages or stenosis in the arm, making it the preferred first-line imaging modality for this clinical scenario.