From the Guidelines
For diagnosing thoracic outlet syndrome (TOS) and subclavian stenosis, CTA of the chest with neck extension is generally recommended as the first-line imaging study. This examination should include both the chest and neck regions since the thoracic outlet spans both areas, and pathology can occur anywhere from the first rib to the axilla. The advantages of CTA include faster acquisition time, higher spatial resolution, and better visualization of bony structures that may cause compression, as noted in the study by Zurkiya et al 1.
The typical protocol involves imaging with arms in both neutral and elevated positions to identify dynamic compression, which can help assess arterial compression in TOS patients, as described in the study by Zurkiya et al 1. MRA is an excellent alternative for patients who cannot receive iodinated contrast or be exposed to radiation, and it provides superior soft tissue contrast that can better demonstrate neurogenic causes of TOS, as discussed in the study by the American College of Radiology 1.
When ordering these studies, it is essential to specify the clinical suspicion of TOS or subclavian stenosis to ensure proper positioning and imaging protocols. The choice between CTA and MRA should consider the patient's specific clinical situation, including renal function, radiation concerns, and whether arterial, venous, or neurogenic TOS is suspected. Key considerations in the decision-making process include:
- The patient's ability to tolerate iodinated contrast
- The need for radiation exposure
- The suspected type of TOS (arterial, venous, or neurogenic)
- The availability of MRA and CTA at the institution
- The patient's overall health status and ability to undergo the imaging study.
In terms of specific imaging protocols, CTA chest and CTV chest specifically denote studies tailored to evaluate the chest and thoracic outlet, including evaluation of central vessels as well as subclavian and axillary arteries and veins, respectively, as noted in the study by the American College of Radiology 1. These studies are distinct from CTA upper extremity and CTV upper-extremity protocols, which are designed to evaluate the entire limb peripherally to the level of the wrist.
From the Research
Diagnostic Tests for TOS and Subclavian Stenosis
- CTA (Computed Tomography Angiography) and MRA (Magnetic Resonance Angiography) are two diagnostic tests used to evaluate thoracic outlet syndrome (TOS) and subclavian stenosis 2, 3.
- CTA is useful in diagnosing vascular TOS, particularly in patients with symptoms of arterial ischemia 3.
- MRA is also effective in diagnosing TOS, especially in patients with neurogenic TOS, and can demonstrate the underlying cause of TOS when studies are reformatted 2.
Imaging Modalities
- 3DCE MRA (three-dimensional contrast-enhanced magnetic resonance angiography) offers extensive vessel coverage and is less prone to artifacts compared to 2D TOF (two-dimensional time of flight) sequences 2.
- Dynamic CT angiography can be used to evaluate the degree of stenosis of the subclavian artery and identify underlying anatomical predisposing factors 3.
- A novel approach using CE-MRA, T2-STIR-SPACE, and VIBE sequences can be used to assess neurovascular bundles in patients with suspected TOS 4.
Ordering Diagnostic Tests
- Diagnostic tests should be ordered based on the patient's symptoms and clinical presentation 5, 6.
- For patients with suspected arterial TOS, CTA or MRA of the chest may be ordered to evaluate the subclavian artery and identify any stenosis or aneurysms 3, 5.
- For patients with suspected neurogenic TOS, MRA of the neck may be ordered to evaluate the brachial plexus and identify any compression or scar tissue 2, 6.