Post-Radiation Therapy Skeletal Changes

Radiation causes a decrease in FDG uptake within bone marrow included in the radiation field. This effect is most dramatic in the spine, where multiple vertebral bodies will appear nearly photopenic on the PET images, best appreciated on the sagittal views.

This effect is most apparent after chemotherapy and CSF administration, when the normal non-radiated spine will demonstrate intense reactive marrow uptake, while the irradiated spine will remain non-avid.

This is most frequently encountered in cases where radiation therapy was performed to the chest (e.g. lung cancer, lymphoma and esophageal cancer) or pelvis (prostate, colorectal or gynecologic cancers).