If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. Thoracic Outlet Syndrome MRI Chest MRI for aTOS is performed to delineate anatomy and evaluate the pertinent anatomic spaces in both neutral and arms-abducted positions. Noncontrast MRI findings include effacement of fat adjacent to the subclavian vein. T1- weighted imaging performed in sagittal and axial planes can also demonstrate causative lesions, including cervical ribs, congenital fibromuscular anomalies, and muscular hypertrophy. Given the need to assess the subclavian artery in aTOS, noncontrast MRI would be insufficient, with contrast- enhanced MR arteriography providing optimal assessment. The combination of soft-tissue and vascular assessment provided by MRI with contrast makes it an excellent modality when compared with US and CT; however, the longer acquisition times may prove difficult for highly symptomatic patients. MRI with IV contrast may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and to assess adequate decompression. MRA Chest The primary MRA finding is narrowing of the subclavian artery; however, other findings, such as complete occlusion, collateral vessel formation, and visualization of thrombus, aid in the diagnosis of aTOS. MRA may help identify the severity of TOS and guide surgical or endovascular management [36]. If there is no evidence of compression on the abducted images, then imaging in the neutral position may be deferred. In the evaluation of TOS, if there is compression of the subclavian artery depicted on both sagittal T1-weighted and MRA, it may be denoted as aTOS. Further findings of aTOS that may be present include fixed or dynamic stenosis, aneurysm, mural thrombus, or distal emboli.
Thoracic Outlet Syndrome. If there are overlapping symptoms, review of the other Variants in this document may help with protocol optimization. Thoracic Outlet Syndrome MRI Chest MRI for aTOS is performed to delineate anatomy and evaluate the pertinent anatomic spaces in both neutral and arms-abducted positions. Noncontrast MRI findings include effacement of fat adjacent to the subclavian vein. T1- weighted imaging performed in sagittal and axial planes can also demonstrate causative lesions, including cervical ribs, congenital fibromuscular anomalies, and muscular hypertrophy. Given the need to assess the subclavian artery in aTOS, noncontrast MRI would be insufficient, with contrast- enhanced MR arteriography providing optimal assessment. The combination of soft-tissue and vascular assessment provided by MRI with contrast makes it an excellent modality when compared with US and CT; however, the longer acquisition times may prove difficult for highly symptomatic patients. MRI with IV contrast may also be performed in the postintervention setting to evaluate interval changes in the thoracic outlet and to assess adequate decompression. MRA Chest The primary MRA finding is narrowing of the subclavian artery; however, other findings, such as complete occlusion, collateral vessel formation, and visualization of thrombus, aid in the diagnosis of aTOS. MRA may help identify the severity of TOS and guide surgical or endovascular management [36]. If there is no evidence of compression on the abducted images, then imaging in the neutral position may be deferred. In the evaluation of TOS, if there is compression of the subclavian artery depicted on both sagittal T1-weighted and MRA, it may be denoted as aTOS. Further findings of aTOS that may be present include fixed or dynamic stenosis, aneurysm, mural thrombus, or distal emboli.