Correct!
4. Unenhanced thoracic CT
Typically, unenhanced thoracic CT is the study of choice for the characterization of indeterminate pulmonary nodules when prior imaging is lacking or unavailable. CT may be performed with intravenous iodinated contrast for nodule characterization, typically when a specific “nodule enhancement study” is desired, usually for nodules at least 1 cm in size. This examination measures the degree of enhancement of a nodule, compared to an unenhanced baseline, at each of 4, 1-minute intervals, assessing for degree of contrast enhancement. If the nodule attenuation does not increase 15 HU or greater compared with the baseline unenhanced images, the nodule is very likely benign; enhancement greater than 15 HU at any of the 4 post-contrast time points suggests possible malignancy, but is non-specific, as some benign nodules may show enhancement. Such nodule enhancement CT protocols are not typically performed when more than one nodule is present. Enhanced thoracic MRI is not typically employed for nodule characterization. Some data regarding the ability of MRI to characterize nodules has recently emerged, but the utility of MRI in this regard is still speculative and far less well understood than the role of CT for nodule characterization. Lateral decubitus chest radiography is typically employed to assess for laying pleural effusion or pneumothorax, but neither is a consideration here. 131Xe ventilation – 99mTc-MAA perfusion scanning is used to assess pulmonary blood flow, typically for thromboembolic disease assessment or in the context of pre-operative testing for differential pulmonary blood flow assessment, but neither consideration is particularly applicable to a patient with indeterminate pulmonary nodules. Finally, 68Ga-Dotatate PET/CT is a somatostatin analogue and is most commonly employed for assessment of neuroendocrine malignancies, and therefore is not applicable to this patient’s evaluation at this point.
The patient underwent unenhanced CT of the thorax (Figure 2).
Figure 2. Axial enhanced thoracic CT through the level of the aortic arch (A) displayed in lung windows and slightly more caudally, at the level of the left pulmonary artery (B), the latter displayed in soft tissue windows.
Which of the following is correct regarding the description of the thoracic CT findings? (Click on the correct answer to proceed to the fith of nine pages)