Chronic pulmonary thromboembolism: detection of regional hypoperfusion with CT.

PURPOSE

To study the relationship of regional hypoperfusion and areas of decreased lung attenuation on computed tomographic (CT) scans of patients with chronic pulmonary thromboembolism.

MATERIALS AND METHODS

Preoperative CT scans of five patients (four men and one woman, aged 29-72 years) with chronic pulmonary thromboembolism were reviewed and compared with axial single photon emission CT (SPECT) perfusion scans obtained at similar levels. Regions of varying attenuation and perfusion were scored on a three-point scale.

RESULTS

In the five patients, 198 regions were identified. Of 176 abnormal regions at SPECT, 133 were abnormal at CT (sensitivity, 75.6%). Eleven of 22 regions interpreted as normal at SPECT were judged to have normal attenuation at CT (specificity, 50%). The overall accuracy of CT for detecting areas of hypoperfusion was 72.7% (P = .011).

CONCLUSION

A mosaic pattern of lung attenuation at CT is a sign of variable regional perfusion and may suggest chronic pulmonary thromboembolism as a cause for pulmonary hypertension.