SINGLE PHOTON-EMISSION COMPUTED-TOMOGRAPHY OF THE LUNG IN THE DIAGNOSIS OF PULMONARY PERFUSION DEFECTS

Single photon emission computed tomography (SPECT) of the lung was performed in addition to conventional ventilation-perfusion lung scans in 38 patients with suspected pulmonary perfusion defects. In 17 cases an additional information was gained with SPECT: 2 patients showed normal planar lung scans, but perfusion defects in SPECT. In 2 cases lung embolism was suspected by conventional scintigraphy, but SPECT developed other anatomical causes of the perfusion defects. Pulmonary embolism was unlikely after SPECT-evaluation. 13 patients showed multiple perfusion defects in conventional scintigraphy as well as in SPECT. In 8 of these patients the perfusion defects were evaluated using pulmonary angiography. Topographic identification and extent of the perfusion defects were accurate in 73% of the lung segments investigated by SPECT. SPECT increases sensitivity and specificity of conventional pulmonary scintigraphy. Additional SPECT-evaluation is indicated in cases of clinically typical symptoms of lung embolism without perfusion defects in the planar lung scan, in cases of perfusion defects in conventional scintigraphy if ventilation scintigraphy cannot be obtained and chest X-ray reveals no abnormality, and in order to evaluate the exact localization of the non or less perfused segments of the lung. This additional information is of interest in some cases of special surgery like pulmonary thromboendarterectomy.