MR imaging of the thoracic inlet

The borders of the thoracic inlet define an oblique plane that angles downward from the spine anteriorly to the first ribs. It is therefore best to consider the thoracic inlet as a region or "zone" which extends a short distance above and below this plane to include the lower portion of the infrahyoid neck and the upper portion of the superior mediastinum. MRs multiplanar imaging capability allows the thoracic inlet to be subdivided into four distinct zones; visceral, neurovascular, pulmonary, and spinal. The first section of this article reviews the normal anatomy of each zone and the sequence protocol for imaging of the brachial plexus. The second section discusses differential diagnoses relevant to each zone. Pathologic processes are also presented.