Lung Perfusion Blood Volume Computed Tomographic Images of Pulmonary Embolism
Before and After Thrombolysis
A 43-year-old woman was admitted with right leg edema and pain. She had previously been prescribed low-dose oral contraceptive pills for dysmenorrhea associated with endometriosis for 2 years. Thromboses in the right superficial femoral vein were seen on venous Doppler ultrasound examination. At that time, there were no signs and symptoms of pulmonary embolism. For pulmonary embolism screening, computed tomographic (CT) study with the use of a dual-energy CT scanner (Somatom Definition scanner, Siemens Medical Systems, Forchheim, Germany) was performed in dual-energy mode. Contrast-enhanced CT images of the chest showed low-attenuation filling defects in the segmental pulmonary arteries (Figure 1). The lung perfusion blood volume (PBV) CT image showed the wedge-shaped low-attenuation areas in right middle and lower lobes (Figure 2). In the low-attenuation area of the right lower lobe, a region of interest was placed to measure parenchymal enhancement of the lung, and CT attenuation value was 36.2 Hounsfield units. In the opposite site, CT attenuation value was 73.3 Hounsfield units. The low-attenuation areas suggested reduced pulmonary perfusion. The diagnosis of pulmonary embolism was made, and the patient was empirically anticoagulated with intravenous heparin.
Follow-up contrast-enhanced CT images on the seventh day after thrombolysis showed resolution of intramural thrombi. The lung PBV CT image showed resolution of low-attenuation areas. CT attenuation values of right and left lower lobes were almost the same (Figure 3).
Pulmonary perfusion and high-resolution CT of the pulmonary artery are feasible when images are obtained from the same data set with dual-energy CT. The quantification of lung perfusion may be useful for patients with pulmonary embolism before and after thrombolysis.