MR Imaging of the Thoracic Inlet

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The thoracic inlet serves as the junction between the neck and the chest. As such, it is sometimes considered a sort of “no-man's-land” between the well-defined and comfortable territories of the thoracic radiologist and that of the head and neck radiologist. Crucial digestive, respiratory, vascular, lymphatic, and neural structures traverse the thoracic inlet. Endocrine structures also are in close proximity to, and sometimes extend into, the thoracic inlet. Familiarity with the normal anatomy of the thoracic inlet on routine chest or neck imaging, and on dedicated high-resolution examinations of such areas as the brachial plexus, is critical for detection and characterization of pathologic conditions.

Section snippets

Anatomic boundaries and definitions

The thoracic inlet is best described as a thin axial plane of tissue best defined by its osseous boundaries: the body of the first thoracic vertebra posteriorly and superiorly, the first pair of ribs and their costal cartilages bilaterally, and the superior border of the manubrium anteriorly and inferiorly.1 The inlet slopes anteroinferiorly, paralleling the obliquity of the first pair of ribs, so that the lung apices are located at the posterior aspect of the inlet, whereas the major

Fascial spaces of the infrahyoid neck and thoracic inlet

The spaces of the infrahyoid neck are anatomically demarcated by layers of the deep cervical fascia.2 Many of these spaces traverse the thoracic inlet into the mediastinum. Figs. 1A and 1B are axial diagrams of the lower neck (at the level of C7) and the thoracic inlet (at the level of T1). The boundaries and contents of spaces associated with the thoracic inlet are also summarized in Table 1. At the level of the thoracic inlet, the visceral space is divided into the pretracheal space

Structures traversing the thoracic inlet

Multiple structures traverse the thoracic inlet within these fascially defined spaces and are best described by organ system.

Summary

  • The thoracic inlet is really best considered as a plane connecting the neck and chest but through which traverses crucial digestive, respiratory, vascular, lymphatic, and neural structures. Endocrine tissues located in the lower neck (the thyroid and parathyroid glands) may also extend into the thoracic inlet.

  • Knowledge of the fascial spaces of the infrahyoid neck is helpful for understanding and predicting patterns of spread of tumor or infection through the thoracic inlet and into the

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