Tc-99m-DTPA aerosol and radioactive gases compared as adjuncts to perfusion scintigraphy in patients with suspected pulmonary embolism.

Abstract

To evaluate the clinical utility of improved methods for radioaerosol inhalation imaging, preperfusion radioaerosol image were obtained in 107 patients (mean age = 62 yr), who were referred for evaluation of suspected pulmonary embolism (PE). For each patient, 6-view aerosol images with accompanying perfusion scans and chest radiographs and with 133Xe or 81mKr studies. Four observers at 4 different institutions independently evaluated aeorosol-perfusion and gas-perfusion pairs, classifying the probability of PE as low, high or indeterminate. The radioaerosol images were good to excellent in quality; excessive central deposition of activity was infrequent and did not interfere with image interpretation. The aerosol-perfusion studies showed 86% agreement with 133Xe perfusion interpretations (n = 299) and 80% agreement with 81mKr perfusion interpretations (n = 299). These rates of agreement were comparable with those of intraobserver agreement for gas-to-gas and aerosol-to-aerosol comparisons, and higher than intraeobserver agreement rates. In a limited number (n = 9) of angiographically documented cases, aerosol-perfusion and gas-perfusion studies provided accurate and equivalent diagnoses. Radioaerosol inhalation studies provided accurate and equivalent diagnoses. Radioaerosol inhalation studies, performed with improved nebulizers, evidently are diagnostically equivalent to ventilation imaging as an adjunct to perfusion scinitigraphy in evaluating patients with suspected PE.