Correct!
4. Thoracic CT

The persistent and worsening clinical symptoms, particularly with the development of blood-streaked sputum, raise the possibility of thromboembolic disease, so 99mTc-MAA ventilation-perfusion scintigraphy is not an incorrect step. However, anatomic imaging would probably be more efficacious in this setting as the patient is complaining primarily of worsening cough. Therefore, thoracic CT is the best choice, and could be performed as CT pulmonary angiography if desired to simultaneously exclude thromboembolic disease. Again, thoracic MRI does not play a role for the evaluation of patients with new-onset respiratory symptoms, such as cough, particularly in the acute setting. Thoracic MRI may have some role in the staging of lung malignancies and assessment of mediastinal masses, and perhaps in the pre-operative staging of malignant pleural mesothelioma, but offers little value in the assessment of pulmonary disorders that cannot otherwise be gleaned from chest radiography or CT. 18FDG-PET plays an important role in the evaluation of solitary pulmonary nodules and lung cancer staging, but focal opacities suspicious for pneumonia are not readily assessed with this technique because tracer avidity can occur with either inflammatory or neoplastic lesions, whereas the lack of tracer utilization in a focal pulmonary opacity, in a symptomatic patient, provides little management-altering information. Catheter pulmonary angiography has a very limited role in modern medical practice, and is used primarily for treatment of arteriovenous malformations or interventions related to pulmonary embolism, or, even less commonly, pre-operative embolization of congenital / developmental lesions, such as sequestrations, but has no role in the evaluation of this patient).

Further clinical course: The patient underwent unenhanced thoracic CT (Figure 3), with a thoracic CT performed over one year previously (Figure 4) presented for comparison.

Figure 3. Panels A-I: Axial unenhanced thoracic CT displayed in soft tissue windows. Panels J-O: Axial unenhanced thoracic CT displayed in lung windows. Panels P-S: Coronal unenhanced thoracic CT displayed in a wide window width.

Figure 4. Axial unenhanced thoracic CT displayed in lung windows performed 1 year prior to Figure 3.

Which of the following statements regarding the thoracic CT is most accurate? (Click on the correct answer to proceed to the sixth of nine panels)

1. The thoracic CT shows abnormal findings, but these abnormalities were also present on the comparison CT over one year earlier
2. The thoracic CT shows findings less extensive than those seen at chest radiography, suggesting the process is already resolving
3. The thoracic CT shows findings not readily appreciated at the presentation chest radiograph
4. The thoracic CT shows the same findings seen at chest radiography but discloses no new or management-altering information
5. The unenhanced nature of the CT examination renders it too limited to be of diagnostic value

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