Thoracic vertebral photopenia may predict fatty changes of the corresponding bone marrow following irradiation

We present a patient with unresectable bronchogenic carcinoma who underwent irradiation, then had four consecutive bone imaging studies in a 26-month period. Apparent photopenia of the upper thoracic vertebrae developed within six months after irradiation and became more apparent in the images thereafter. At autopsy a section of the corresponding bone marrow showed extensive fatty changes with very few residual blood vessels. Radiation damage of the vascular networks may significantly reduce the blood supply, when integrity of the blood supply is essential for delivery of a normal bone image by the bone-imaging agent. Interruption of blood supply may cause photopenia, and this interruption plus irradiation to marrow elements may also affect the hematopoietic activity of the corresponding bone marrow. The occurrence of radiation-induced photopenia on a bone-imaging study may indicate fatty changes of the corresponding marrow.