Follow-up CT and MR findings of osteoblastic spinal metastatic lesions after stereotactic radiotherapy

Abstract

We retrospectively analyzed pre and post-stereotactic radiotherapy CT and MRI findings and volume changes for osteoblastic spinal metastatic lesions. Of 114 lesions in 72 patients, 11 were osteoblastic. CT and MR images were reviewed to determine tumor volume, CT attenuation, T2 signal intensities, and contrast enhancement. Tumor volume did not change for 10 lesions and increased for 1 lesion. CT attenuation increased for 8 lesions with heterogeneous T2 signal intensities. Of these 8 lesions, 4 had patterns of dark signal foci and the other 4 had patterns of both dark and bright signal foci. T2 signal intensity became heterogenous, with dark and bright foci, for 2 of 3 lesions for which CT attenuation decreased, and normalized for the third lesion. The degree of contrast enhancement decreased for 6 lesions and did not change for 5 lesions. There were no changes in volume except for one case. On CT images, sclerotic changes were more common than loss of sclerotic foci. On T2-weighted images, dark signal intensities with or without bright signal foci developed and the degree of enhancement decreased for more than half of the cases.