[Nuclear medical diagnosis of pulmonary embolism]

Lung perfusion scintigraphy can make arterial embolic obstruction visible because the uptake of microspheres labelled with 99mTc is lower than normal in the corresponding lobes, segments or subsegments. The sensitivity for pulmonary embolism is high (up to 98%). The specificity of a positive finding increases with additional investigations: infiltrative and space occupying lesions can be seen on the chest X-ray, and broncho-obstructive diseases with concomitant perfusion defects can be identified with the help of ventilation scintigraphy using 133Xe. In view of its high sensitivity and specificity, its low cost, low risk with practically no discomfort for the patient, and standardized techniques not dependent on the skill of the examiner, lung scintigraphy can replace pulmonary angiography in nearly all circumstances. It should be noted, however, that late sequelae--after thrombolysis and recanalization have taken place and when atelectases or pneumonia may dominate--may blur the scintigraphy findings. Thus, patients must be sent for lung scintigraphy as soon as suspicion of pulmonary embolism arises.