Recognition of dose infiltration on pulmonary ventilation-perfusion scintigraphy

Pulmonary scintigraphy has a well-established role in the diagnosis of pulmonary embolism (PE). The diagnostic specificity is increased if the perfusion study is combined with assessment of regional ventilation. VQ scans interpreted as either normal, near-normal, or high probability are reasonably diagnostic. Misinterpretation of the VQ scan can result in failure of this simple and noninvasive modality to diagnose a PE. Dose infiltration of the perfusion tracer is one of the rare causes of the misinterpretation of the VQ scan study. We present the VQ scan images of two patients and discuss the findings when Tc99m macroaggregated serum albumin (MAA) dose infiltration was recognized and the perfusion study was repeated for optimal interpretation.