Value of MR inaging in assessment of the response to therapy of skeletal metastases

This report evaluates the utility of MR imagining in assessing the response to therapy of skeletal metastases. Twenty-four patients with metastasis to the spine were evaluated before and at various times (1--31 months) after therapy (irradiation, chemotherapy, or hormonal therapy). T1-(250--500/12-25) and T2-(2,000/80--100) weighted spin-echo (SE short inversion recovery (STIR) (1,5000--2,000/100) images were obtained at 0.5 T. The signal intensities of the lesions were measured and compared with the intensities of the marrow of the adjacent normal vertebral bodies. Prior to therapy, the signal intensities of the metastatic foci were, on average, 50% less than that of the normal vertebral bodies on the T1-weighted SE images and 71% and 92% greater than normal on the T2-weighted SE and STIR images, respectively. After therapy, patients fell into two distinct groups: 10 responders and 14 nonresponders. In the responders, the signal intensities of the metastasis approached that of the normal marrow; on average the differences in signal intensities between metastasis and normal marrow diminished to 10% on the T1-weighted, 7% on the T2-weighted, and 9% on the STIR images