Pulmonary scintigraphy with a triple-head camera for evaluation of acute pulmonary embolism

Ventilation-perfusion scintigraphy is a useful test for the evaluation of acute pulmonary embolism. While the sensitivity is high, there is concern from the PIOPED experience about potentially suboptimal specificity, in part reflected by a 39 % rate of intermediate probability lung scans as reported by the PIOPED investigators [7]. To help address this concern, we developed a modified procedure for ventilation scintigraphy with xenon-133 in which two serial dynamic ventilation studies offset by 180 ° were acquired with a triple-head gamma camera, yielding a six-view assessment of pulmonary ventilation. This was followed by a six-view acquisition of pulmonary perfusion with technetium-99m-macroaggregated albumin (MAA) using the same camera. A series of 100 scintigraphic assessments incorporating this procedure to evaluate possible acute pulmonary embolism were systematically reviewed to assess the potential interpretive merits of the additional ventilation views, compared to the traditional single posterior xenon-133 ventilation view. There were 36 cases identified for which the additional ventilation views were graded as either “somewhat helpful” or “essential” in formulating the scan interpretation. Of the 36 cases, 26 (72 %) were in the “low” and “high” probability categories, thereby helping to reduce the proportion of intermediate probability scan results to only 16/100, less than half the rate observed in the PIOPED experience. Thus, the use of this modified scintigraphic procedure allows multiview ventilation-perfusion assessment with xenon-133 as the ventilation tracer, improves interpretability of the scans, and helps to increase the proportion of definitive assessments for the evaluation of acute pulmonary embolism.