CTICasesRadiation Fibrosis with Comet Tail Sign
Imaging findings
CT demonstrates a focal area of volume loss and parenchymal distortion in the left lower lobe with curvilinear bronchovascular bundles and vessels converging toward it in a comet tail configuration. The airways within the fibrotic region show mild cylindrical dilatation from traction. Prior radiation treatment for a lung malignancy in 2018 explains the distribution and morphology.
Key takeaways
Late-stage radiation fibrosis produces a characteristic focal opacity with architectural distortion that may demonstrate a comet tail sign, where bronchovascular bundles curve and are drawn into the fibrous mass, analogous to rounded atelectasis. Dilated airways within the scar (traction bronchiectasis) are a hallmark. Awareness of the prior radiation field is essential to avoid mistaking chronic radiation fibrosis for a new or growing malignancy.
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