DTPA AEROSOL IN VENTILATION PERFUSION SCINTIGRAPHY FOR DIAGNOSING PULMONARY-EMBOLISM/

The use of lung scintigraphy in evaluating suspected pulmonary embolis m (PE) is controversial. Several diagnostic methods have been describe d for lung scans, of which the most widely applied uses Tc-99m-MAA for perfusion, Xe-133 for Ventilation and PIOPED diagnostic criteria. Thi s study evaluates the accuracy of lung scintigraphy using an alternati ve ventilation agent, Tc-99m-diethylenetriamine pentacetic acid (DTPA) aerosol, and specific criteria. Methods: Diagnostic criteria for DTPA aerosol ventilation were prospectively applied to 5017 patients over a 9-yr period. Lung scan interpretations were analyzed for frequency o f occurrence, and results were compared to those of angiography in 455 patients. Results: Scans were interpreted as normal, low or high prob ability in 79% of patients and as either indeterminate or medium proba bility in 21% of patients. Three patients had normal scans and negativ e angiography. In patients with low-probability scans, 111 angiograms were performed: 103 (93%) were negative, and 8 (7%) were positive. In patients with indeterminate scans, 114 angiograms were performed: 85 ( 75%) were negative, and 29 (25%) were positive. In patients with mediu m-probability scans, 149 angiograms were performed: 86 (58%) were nega tive, and 63 (42%) were positive. In patients with high-probability sc ans, 78 angiograms were performed: 6 (8%) were negative, and 72 (92%) were positive. Conclusion: These results indicate that lung scintigrap hy using DTPA aerosol and our criteria is accurate in diagnosing and s tratifying risk of pulmonary embolic disease. Compared with Xe-133 and PIOPED criteria, DTPA ventilation and our criteria reduced the false- negative rate in low-probability scans (7% Versus 16%, p < 0.005) and decreased the fraction of intermediate-probability scans (21% versus 3 9%, p < 0.01).