As a supplement to static assessment of tissue plane transgression, dynamic MRI [45-48] during free-breathing or cinematic cardiac gating can be performed to assess movement of the mass relative to adjacent structures, confirm or exclude adherence of the mass to adjacent structures, and observe diaphragmatic motion in real time [80-84]; paradoxical motion or lack of motion can indicate phrenic nerve involvement by the mediastinal mass, without the need to perform a subsequent fluoroscopic sniff test. US Chest Unless a mediastinal mass found on chest radiography is deemed fully accessible by transthoracic US, there is little relevant literature to support its use as the next step. Transthoracic US can be used to evaluate mediastinal masses, when accessible to the sonographic window, delineating their size, location, cystic versus solid nature, relationship to important vascular structures, and vascularity, with some diagnostic potential [89]. Endoscopic US can similarly evaluate mediastinal masses when encompassed in the sonographic window [90]. The tissue characterization capability of US is inferior to MRI but not to CT. Image-Guided Transthoracic Needle Biopsy Image-guided transthoracic needle biopsy would seldom be performed without a preceding cross-sectional imaging study. Variant 3: Indeterminate mediastinal mass on CT. Next imaging study. 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. FDG-PET/CT has become the standard for staging and assessment of treatment response for lymphomas that are FDG-PET-avid at baseline or at the time recurrence [91-97].
Imaging of Mediastinal Masses. As a supplement to static assessment of tissue plane transgression, dynamic MRI [45-48] during free-breathing or cinematic cardiac gating can be performed to assess movement of the mass relative to adjacent structures, confirm or exclude adherence of the mass to adjacent structures, and observe diaphragmatic motion in real time [80-84]; paradoxical motion or lack of motion can indicate phrenic nerve involvement by the mediastinal mass, without the need to perform a subsequent fluoroscopic sniff test. US Chest Unless a mediastinal mass found on chest radiography is deemed fully accessible by transthoracic US, there is little relevant literature to support its use as the next step. Transthoracic US can be used to evaluate mediastinal masses, when accessible to the sonographic window, delineating their size, location, cystic versus solid nature, relationship to important vascular structures, and vascularity, with some diagnostic potential [89]. Endoscopic US can similarly evaluate mediastinal masses when encompassed in the sonographic window [90]. The tissue characterization capability of US is inferior to MRI but not to CT. Image-Guided Transthoracic Needle Biopsy Image-guided transthoracic needle biopsy would seldom be performed without a preceding cross-sectional imaging study. Variant 3: Indeterminate mediastinal mass on CT. Next imaging study. 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. FDG-PET/CT has become the standard for staging and assessment of treatment response for lymphomas that are FDG-PET-avid at baseline or at the time recurrence [91-97].