Radiation-Induced Lung Disease
Acute Changes = Radiation Pneumonitis:
Ill-defined parenchymal air-space disease often results as an inflammatory response to radiation therapy, and can be intensely FDG-avid. It typically occurs between 4 and 12 weeks after therapy and can persist for many months.
The CT appearance classically demonstrates air-space disease, often with air bronchograms. This radiation pneumonitis frequently demonstrates linear borders, corresponding to the margins of the radiation field.
It can be extremely difficult to exclude underlying malignancy within these acute radiation changes, as the air-space disease can have a mass-like appearance. Follow-up is often required.
Chronic Changes = Radiation Fibrosis (Post-Therapeutic Scarring):
As the acute parenchymal changes of radiation pneumonitis resolve, ill-defined areas of soft tissue density remain, sometimes with associated traction bronchiectasis. Mild residual metabolic activity can persist for years.
These areas of fibrosis usually develop within 6 months, but can progress for up to two years.
Case 1
Case 1 (Image 2)
MIP image 8-weeks post radiation therapy now demonstrates a very large region of intense metabolic activity in the location of the patient’s lung cancer, markedly increased in size from the initial study.
Case 1 (Image 3)
The post-radiation therapy scan now demonstrates a large and intensely avid parenchymal consolidation, containing air bronchograms. This is a typical appearance of acute radiation pneumonitis after treatment of a lung cancer.
Case 1 (Image 4)
Acute radiation pneumonitis after treatment of a lung cancer typically presents as intensely avid air-space disease, containing air bronchograms. These changes often obscure the original mass, requiring follow up.
Case 2
Case 2 (Image 2)
The post-radiation therapy scan now demonstrates a large and intensely avid parenchymal consolidation, containing air bronchograms, a typical appearance of acute radiation pneumonitis after treatment of a lung cancer.
Case 2 (Image 3)
Acute radiation pneumonitis after lung cancer treatment typically presents as intensely avid air-space disease, containing air bronchograms. These changes often obscure the original mass, requiring follow up.
Case 3
Case 4
Case 4 (Image 2)
8-weeks post radiation treatment of the patient’s metastatic latissimus dorsi lesion demonstrates patchy FDG-avid air-space disease in the subjacent right lung parenchyma, consistent with acute radiation pneumonitis.
Case 5
Case 5 (Image 1)
1-year post radiation treatment of the right lung cancer. MIP is now unremarkable. Axial images demonstrate prominent, ill-defined soft tissue density in the right paramediastinal region, not significantly FDG-avid. This is a typical appearance of radiation fibrosis (“post-therapeutic scarring”), the late/chronic sequela of radiation therapy. Note the linear lateral margin of these changes (box), corresponding to the margin of the radiation field.
Case 5 (Image 3)
Pre & post-therapy axial fused images demonstrate the evolution of hypermetabolic mass to ill-defined post-therapeutic scarring, not significantly avid (its metabolic activity is not greater than mediastinal blood pool uptake).
Case 5 (Image 4)
MIP images are a useful tool for assessing metabolic activity relative to liver or blood pool uptake. Here, the post-treatment MIP illustrates that any residual soft tissue in the region of the prior mass does not demonstrate activity above mediastinal blood pool uptake.
Case 6
Case 6 (Image 2)
Residual ill-defined soft tissue density in the left lung, not significantly avid, 12-months after radiation treatment of an intensely avid lung cancer, most consistent with post-therapeutic scarring.
Case 6 (Image 3)
Residual ill-defined soft tissue density in the left lung 15-months after radiation therapy of an intensely avid lung cancer, non-avid. The appearance is typical of post-therapeutic scarring.
Case 6 (Image 4)
Residual ill-defined soft tissue density in the left lung 12-months after radiation treatment of an intensely avid lung cancer. This tissue is non-avid and has the typical appearance post-therapeutic scarring.
Case 7
Case 7 (Image 2)
Both the sagittal and coronal images demonstrate the ill-defined density to be linear in configuration, confirming our diagnosis of post-therapeutic scarring. Such fibrosis is commonly seen in breast cancer patients treated with radiation.
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