Correct!
2. Contrast enhanced thoracic CT
Contrast-enhanced thoracic CT is the most appropriate selection among the choices listed above. The injection of intravenous contrast, as opposed to an unenhanced thoracic CT, is generally preferred when the indication for thoracic CT is for evaluation of a mediastinal mass. Intravenous contrast is essential if the mass due to vascular abnormality, and when masses do not arise from vascular structures, intravenous contrast is nevertheless still very useful because intravenous contrast administration allows for optimal assessment of the relation of the mass to surrounding vascular structures, which is important both for pre-operative assessment and determining the biologic behavior of the lesion. 18FDG – PET scan could prove useful for evaluation of the mass, but generally 18FDG – PET scan is most rewarding when obtained for further characterization of indeterminate findings at thoracic CT, rather than immediately following chest radiography. Lateral decubitus chest radiography is useful for assessment of possible pleural effusion (for evaluation of the dependent thorax), or for assessment of pneumothorax (when attention is focused on the non-dependent thorax); neither situations are relevant here. Ventilation – perfusion scintigraphy is most commonly employed for the assessment of acute or chronic thromboembolic disease, or occasionally for determination of differential pulmonary perfusion prior to thoracic surgery or for assessment of systemic shunting; none of these conditions are relevant to this outpatient with an incidentally detected, incompletely evaluated mediastinal mass. Echocardiography could potentially visualize the lesion and provide some characterization of the mediastinal mass, but it is likely that this lesion resides outside the heart and would not be the focus of an echocardiogram and probably would be incompletely visualized.
The patient subsequently underwent unenhanced thoracic CT (Figure 4).
Figure 4. Representative images from unenhanced axial (A-F) and sagittal (G-J) thoracic CT scan. Top right: video of unenhanced axial thoracic CT. Bottom right: video of unenhanced sagittal CT.
Regarding this examination, which of the following is correct? (Click on the correct answer to proceed to the fifth of nine pages)