Purpose or Case Report: Pulmonary embolism (PE) is a potentially life-threatening condition, and accurate imaging is critical for timely diagnosis. While CT pulmonary angiography is the gold standard, MR angiography (MRA) offers a radiation-free alternative, particularly important in younger patients. However, MRA is prone to artifacts that can mimic pathology and lead to false-positive interpretations.

We present two cases of 15-year-old patients who presented to the emergency department with acute chest pain and underwent MRA as part of the diagnostic workup to avoid radiation exposure. In both cases, imaging demonstrated central dark signal voids within the pulmonary arteries, raising concern for thrombus. Closer review revealed these findings were attributable to Gibbs ringing artifact, which occurs due to undersampling and edge effects, producing alternating bright and dark bands that may simulate intraluminal filling defects. In one patient, additional challenges were posed by timing-related artifacts during k-space acquisition, where misalignment of contrast bolus and central k-space filling resulted in a “maki roll” appearance, further complicating interpretation.
Strategies to differentiate artifact from true thrombus include correlating with multiple imaging planes, and importantly, reviewing second or delayed angiographic runs to determine whether a defect persists or resolves. In both cases, the absence of persistent findings and awareness of artifact patterns prevented misdiagnosis of PE.
These cases underscore the importance of recognizing Gibbs ringing and timing-related artifacts in MRA of the pulmonary arteries. Careful image review and knowledge of common pitfalls are essential to avoid false-positive diagnoses and ensure appropriate patient management.
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