Radiation-induced changes in bone.

Radiation therapy has important applications in curative, adjuvant, and palliative therapy for a wide range of malignant conditions. Evidence of radiation therapy may be seen on radiologic images obtained subsequent to therapy. Bone growth disturbances may be observed in the immature axial or appendicular skeleton. Complications in the mature skeleton include osteoradionecrosis, pathologic fracture, and radiation-induced neoplasms. Radiologic features of mandibular osteoradionecrosis include ill-defined cortical destruction without sequestration. In osteoradionecrosis of the ribs, clavicle, scapula, and humerus, radiography may demonstrate osteopenia, disorganization and coarsening of trabecular architecture, and cortical irregularity; computed tomography more clearly depicts subtle fractures, alterations in bone architecture, and dystrophic soft-tissue calcification. In osteoradionecrosis of the spine, hematopoietic cellular elements of the spinal marrow are replaced with fat, which has high signal intensity on T1-weighted magnetic resonance images and intermediate signal intensity on T2-weighted images. Radiation-induced changes in the pelvis include osteopenia, increased bone density, and widening and irregularity of the sacroiliac joints. Radiation-induced osteochondromas are radiographically identical to those that arise spontaneously. Radiographic findings in radiation-induced sarcoma demonstrate an aggressive pattern of bone destruction. Awareness of the varied radiographic manifestations of radiation-induced changes in bone and correlation with clinical features and the radiation field will usually allow distinction of these changes from those associated with other pathologic conditions.