Numerous MRA techniques have been described including noncontrast MRA, including inversion recovery methods for patients unable or unwilling to have contrast [42], simultaneous bilateral MRA [34], and dual-gadolinium injection protocols [35]. Ancillary findings include possible etiologies of aTOS, frequently cervical or anomalous first rib, scalene muscle, fibromuscular bands, or pectoralis minor tendon, and anomalous course of the subclavian artery within the scalene muscle. MRA may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and confirm arterial patency. MRV Chest MRV is not needed in patients with aTOS. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. Radiography Chest Because of the importance of identifying osseous structures that may impinge on the spaces of the thoracic outlet, chest radiography is useful in performing a robust evaluation for all types of TOS. As opposed to directly evaluating vascular structures, osseous abnormalities associated with TOS are frequently easily diagnosed by chest radiographs. These include first rib anomalies [20], cervical ribs [23], congenital osseous malformations [24,25], and focal bone lesions [26]. In the postoperative setting, radiographs may be useful to confirm osseous changes and evaluate for postoperative complications such as pneumothorax. US Duplex Doppler Subclavian Artery and Vein As with vTOS, US is an excellent initial study in the evaluation of aTOS. The subclavian and axillary arteries can be directly visualized and assessed for aneurysmal change, arterial stenosis, and thrombosis. Dynamic arterial blood flow can be assessed during abduction. Findings include decrease in arterial diameter, changes in peak velocity, or reproducible symptoms considered to be diagnostic of aTOS. Evaluation of the cross-sectional area of the costocervical space may also be performed [28].
Thoracic Outlet Syndrome. Numerous MRA techniques have been described including noncontrast MRA, including inversion recovery methods for patients unable or unwilling to have contrast [42], simultaneous bilateral MRA [34], and dual-gadolinium injection protocols [35]. Ancillary findings include possible etiologies of aTOS, frequently cervical or anomalous first rib, scalene muscle, fibromuscular bands, or pectoralis minor tendon, and anomalous course of the subclavian artery within the scalene muscle. MRA may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet, assess adequate decompression, and confirm arterial patency. MRV Chest MRV is not needed in patients with aTOS. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. Radiography Chest Because of the importance of identifying osseous structures that may impinge on the spaces of the thoracic outlet, chest radiography is useful in performing a robust evaluation for all types of TOS. As opposed to directly evaluating vascular structures, osseous abnormalities associated with TOS are frequently easily diagnosed by chest radiographs. These include first rib anomalies [20], cervical ribs [23], congenital osseous malformations [24,25], and focal bone lesions [26]. In the postoperative setting, radiographs may be useful to confirm osseous changes and evaluate for postoperative complications such as pneumothorax. US Duplex Doppler Subclavian Artery and Vein As with vTOS, US is an excellent initial study in the evaluation of aTOS. The subclavian and axillary arteries can be directly visualized and assessed for aneurysmal change, arterial stenosis, and thrombosis. Dynamic arterial blood flow can be assessed during abduction. Findings include decrease in arterial diameter, changes in peak velocity, or reproducible symptoms considered to be diagnostic of aTOS. Evaluation of the cross-sectional area of the costocervical space may also be performed [28].