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1. 133Xe-ventilation – 99mTc-perfusion scintigraphy
133Xe-ventilation – 99mTc-perfusion scintigraphy would be the best choice among the various tests listed. High-resolution chest CT (HRCT) is a reasonable choice as well and may play a role in the evaluation of this patient, but the chest radiographic findings do not suggest diffuse lung disease, which is the typical indication for HRCT. Furthermore, the clinical symptoms of shortness of breath out of proportion to the pulmonary function testing results, and the decreased diffusion capacity for carbon monoxide, in the context of mild chest radiographic abnormalities, raise the possibility of pulmonary embolism, and pulmonary embolism cannot be assessed using unenhanced HRCT technique. Additionally, while HRCT could provide some information regarding the hilar enlargement apparent at chest radiography, this finding would be better assessed with dedicated enhanced thoracic CT. Clearly catheter pulmonary angiography could be employed to diagnose or exclude pulmonary embolism, but this test is needlessly invasive at this point and the possibility of pulmonary embolism could be non-invasively addressed with contrast-enhanced pulmonary CT angiography, but this option was not provided above. 68Ga-citrate scintigraphy is rarely employed for the assessment of diffuse lung disease, particularly acute diffuse infections in immunocompromised patients, but this situation does not apply to this patient. Thoracic MRA, if conducted in a fashion to address the possibility of pulmonary embolism, could prove useful for this patient, but commonly thoracic MRA for pulmonary embolism is employed when contraindications to CT pulmonary angiography exist, which is not the situation for this patient. Furthermore, thoracic MRA would provide little information regarding the lung parenchymal abnormalities.
The patient underwent 133Xe-ventilation – 99mTc-perfusion scintigraphy (Figure 3).
Figure 3. 133 Xe-Ventilation (top two rows) – 99m Tc-perfusion (bottom two rows) scintigraphy.
Which of the following statements regarding the 133Xe-ventilation – 99mTc-perfusion scintigraphy is most accurate? (Click on the correct answer to proceed to the fifth of nine pages)