Continuing Education Ventilation Scintigraphy

Ventilation scintigraphy is a well-established adjunct to perfusion lung imaging in the diagnosis of pulmonary thromboembolus (PE). Although PE may be diagnosed with a standard chest radiograph and perfusion scintigraphy, the findings may be largely nonspecific due to the many types oflung pathology that result in perfusion defects. The specificity of the perfusion (Q) study may be substantially increased with the addition of ventilation (V) scintigraphy, which allows one to differentiate perfusion defects due toPE (VQ mismatch) from those resulting from obstructive lung disease (VQ match). Ventilation scintigraphy is performed at most institutions with a radioactive gas, usually xenon-133 (1 33Xe), xenon-127 (1 27Xe), or krypton-81m (81mKr). More recently, however, radiolabeled aerosols have evolved as an accepted alternative to gas tracer techniques to evaluate regional ventilation. This article reviews the clinical uses, advantages, and disadvantages of gas and aerosol ventilation agents. A more in-depth discussion of aerosols is given due in part to the increasing use of this particular tracer to evaluate regional ventilation.