X-rays show excellent bone detail, but do not show soft tissue detail, and are limited to two dimensions. X-rays do not show arteries or veins. About 1% of the population has cervical ribs, but most of these people do not have arterial TOS. Even in patients with cervical ribs and arterial TOS, they have had cervical ribs their entire life, and only developed arterial TOS when they become symptomatic. X-rays thus have quite limited value in diagnosing arterial TOS and in planning treatment.
A flexible plastic catheter is inserted by a physician directly into an artery, usually in the groin. The physician advances the catheter under live x-ray (fluoroscopy) through the aorta, the main artery of the body, until it reaches the heart. At this point, the physician injects dye into the proximal aorta, after which the dye passes through the subclavian artery. As the dye passes through the arteries, x-rays create images. Direct angiography is an invasive test with a significant radiation dose. For this reason, CT angiography or MR angiography can almost always replace direct angiography.
Ultrasound is performed without any radiation, and can demonstrate blood flow in the arteries in real time, allowing dynamic movement of the arms during the examination. However, bones create severe blind spots, limiting assessment of bony compression of arteries. Ultrasound is also quite limited for viewing fibrous bands and muscle anomalies.
CT angiography is performed by injecting contrast into a peripheral vein, without an arterial catheter. CTA is fast, and shows excellent detail of bones and arteries. CTA requires significant radiation, and is limited in the evaluation of soft tissues, including fibrous bands and muscle anomalies. In cases of pure arterial TOS, CTA is the first-line test for many vascular surgeons.
MR angiography is performed by injecting contrast into a peripheral vein, without an arterial catheter. MRA shows excellent arterial detail while eliminating most other structures, including bones. It requires no radiation. If used in conjunction with MRI, superb soft tissue detail is available. Excellent depiction of fibrous bands, muscle anomalies, bones, and the brachial plexus is possible with MRI.