RESUMEN
A normal lung perfusion isotope scan can exclude pulmonary emboli. However, the demonstration of lung emboli presents problems, as an abnormal lung perfusion scan can have various causes. Some of these can be excluded if the perfusion scan is assessed in combination with a chest X-ray and a ventilation scan. In this study, 21 patients with an abnormal perfusion scan were also examined using digital subtraction angiography (DSA) of the lungs. With the help of DSA it was possible to differentiate between the various causes of a lung perfusion defect on the isotope scan by having a sufficiently reliable pulmonary angiogram. From experience it appears that the quality of the pulmonary angiogram confined to the first three divisions obtained with DSA, is comparable with that from a conventional pulmonary angiogram. A perfusion isotope scan is the initial screening modality for suspected lung emboli, if this shows an abnormality, DSA seems to be indicated as the next step.