MDCT in Mediastinal Imaging

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The usefulness of MDCT in imaging vascular, tracheobronchial, lung parenchymal and chest wall lesions has been described in the recent literature by several investigators (Lawler and Fishman 2001; Ravenel et al. 2001; Remy-Jardin et al. 1998a, 1998b; Bhalla et al. 1996; Johnson et al. 1996, 1998; Calhoun et al. 1999; Kauczor et al. 1996). Very little has been written about the usefulness of MDCT in other non-vascular and non-airway mediastinal lesions as we have traditionally studied the mediastinum. In this chapter we show relevant clinical applications of MDCT in mediastinal lesions. The mediastinum is composed of the heart, vessels, airways, esophagus, fat, lymph nodes and lymphatics, thymic tissue, and nerves. These normal structures, in isolation or in consort, can be involved in a variety of disease processes which originate directly from them, metastasize to them, or invade them from adjacent structures. These disease processes can be fl uid, soft tissue, fatty material, or a combination of these. Imaging of the mediastinum, therefore, is aimed at providing relevant information regarding tissue characteristics, enhancement patterns, location of a lesion, and invasion of structures. Computed tomography (CT) has been deemed the primary modality for imaging the mediastinum (Tecce et al. 1994), particularly the anterior mediastinum; however, magnetic resonance imaging (MRI) has been used as a modality which clarifi es ambiguous fi ndings on CT (Bittner and Felix 1998; Webb and Sostman 1992) because of its multiplanar capabilities its ability to image vessels, and its ability to distinguish between different tissues. Prior to the advent of spiral CT imaging in the late 1980s, MR imaging was very comparable to CT for evaluating the mediastinum (Bittner and Felix 1998; Webb and Sostman 1992) but lost equal ground in its use once spiral CT was introduced. Multidetector CT (MDCT) has the potential to put even further distance between it and MR imaging because of its ability to perform isotropic scanning and thin-section imaging through the entire thorax in a very short space of time and the capabilities of applying postprocessing multiplanar reconstructions and three-dimensional (3D) techniques. For this reason, all of the apparent advantages of MRI have been supplanted by MDCT.