conventional CT or dual-energy CT can show enhancing, cellular components of lesions [41,42]; however, the soft- tissue contrast of CT is sometimes insufficient. For example, benign hyperattenuating thymic cysts on CT can be misinterpreted as thymomas, leading to unnecessary thymectomy [24]. Not infrequently, a mediastinal lesion is indeterminate by CT and requires further workup. CT is superior to chest radiography for detection of invasion of the mass across tissue planes, secondary to its higher contrast resolution. Invasion of adjacent large blood vessels and the chest wall is important to identify, as it is associated with a higher probability of incomplete surgical resection of primary malignant mediastinal masses [43]. In addition, it can direct surgery when still planned, and in other cases, direct toward other forms of clinical management, including neoadjuvant chemotherapy and radiation therapy. As a supplement to static assessment of tissue plane transgression, which can be difficult, dynamic CT [44] during free-breathing or cinematic cardiac gating can be performed to assess movement of the mass relative to adjacent structures and to confirm or exclude adherence of the mass to adjacent structures; however, dynamic MRI during free-breathing can accomplish the same task [45- 48]. MRI remains superior to CT for detection of invasion of the mass across tissue planes, including the chest wall and diaphragm, and involvement of neurovascular structures, secondary to its higher soft-tissue contrast [49-52]. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT offers limited additional value beyond that of conventional CT in the assessment of mediastinal masses [53], with the exception of its use for primary mediastinal lymphoma staging and surveillance and detection of metastatic lymphadenopathy, the latter of which is not within the scope of this topic.
Imaging of Mediastinal Masses. conventional CT or dual-energy CT can show enhancing, cellular components of lesions [41,42]; however, the soft- tissue contrast of CT is sometimes insufficient. For example, benign hyperattenuating thymic cysts on CT can be misinterpreted as thymomas, leading to unnecessary thymectomy [24]. Not infrequently, a mediastinal lesion is indeterminate by CT and requires further workup. CT is superior to chest radiography for detection of invasion of the mass across tissue planes, secondary to its higher contrast resolution. Invasion of adjacent large blood vessels and the chest wall is important to identify, as it is associated with a higher probability of incomplete surgical resection of primary malignant mediastinal masses [43]. In addition, it can direct surgery when still planned, and in other cases, direct toward other forms of clinical management, including neoadjuvant chemotherapy and radiation therapy. As a supplement to static assessment of tissue plane transgression, which can be difficult, dynamic CT [44] during free-breathing or cinematic cardiac gating can be performed to assess movement of the mass relative to adjacent structures and to confirm or exclude adherence of the mass to adjacent structures; however, dynamic MRI during free-breathing can accomplish the same task [45- 48]. MRI remains superior to CT for detection of invasion of the mass across tissue planes, including the chest wall and diaphragm, and involvement of neurovascular structures, secondary to its higher soft-tissue contrast [49-52]. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT offers limited additional value beyond that of conventional CT in the assessment of mediastinal masses [53], with the exception of its use for primary mediastinal lymphoma staging and surveillance and detection of metastatic lymphadenopathy, the latter of which is not within the scope of this topic.