To assess the therapeutic effect of Novalis radiosurgery for metastatic spinal tumors and evaluate the changes after treatment using MR imaging.

Between November 2003 and June 2005, 21 patients with metastatic spinal tumors underwent Novalis radiosurgery. Of these patients, the 7 with 13 metastatic spinal tumors who had undergone follow-up MR imaging were included in this study. The tumor locations were cervical spine in three, thoracic spine in four, lumbar spine in five and sacrum in one. During the first three months after Novalis radiosurgery, follow-up MRI was performed monthly and subsequently at 3-6-month intervals. On MR imaging, the volume of the tumors, the changes of their signal intensities and any changes in adjacent spinal cord were evaluated.

Among the 13 lesions, 9 were decreased in volume (69.2%), 2 were stable (15.4%) and 2 were slightly increased. Seven of 9 lesions showed decreased signal intensity on T2 weighted images and 4 had compressive deformity. Two of 9 lesions had increased T2 signal intensity and tumor necrosis were detected on contrast-enhanced MR imaging. No changes in spinal cord were noted in any of the lesions. Those changes were detected on MRI obtained 1 month after Novalis surgery and the lesion sizes were gradually changed up to 3 months.

Novalis radiosurgery was effective for the treatment of metastatic spinal tumor and the suppression of tumor growth. The estimation of therapeutic effect and detecting complication were precisely evaluated on MR imaging.