CTICasesInterrupted Contrast Bolus Artifact Mimicking Pulmonary Embolism
Imaging findings
A large patient in the emergency department with chest pain and shortness of breath had a suboptimal-bolus CT pulmonary angiogram showing an apparent branching filling defect with straight edges within a pulmonary artery, but with a relatively low mean pulmonary artery attenuation (around 27-28 HU) and surrounding flow-related artifact ("smoke") elsewhere, raising uncertainty about whether this represented true clot. A subsequent MR angiogram of the same area was negative, and the apparent filling defect was attributed to interrupted/suboptimal contrast bolus timing rather than true pulmonary embolism.
Key takeaways
An apparent filling defect with straight edges on a CT pulmonary angiogram obtained with a poor contrast bolus and low overall pulmonary artery attenuation should raise suspicion for an interrupted-bolus flow artifact rather than true thrombus, and confirmatory imaging (VQ scan or MR angiography) should be pursued when bolus quality is suboptimal rather than accepting an equivocal filling defect at face value.
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