COMPARISON OF RADIONUCLIDE BONE SCANS AND MAGNETIC-RESONANCE-IMAGING IN DETECTING SPINAL METASTASES

A retrospective comparison was made between Tc-99m-MDP bone scans and corresponding spine MR images in 35 patients who had complementary stu dies within 2 mo. Bone scans were performed with planar imaging of the entire body and MRI was performed with a 1.5 tests signal scanner usi ng standard techniques with T1- and T2-weighted images. There were 18 male and 17 female patients diagnosed with cancer prior to these studi es. Cancer diagnoses included 14 prostate, 12 breast, 1 bladder, 2 ren al, 2 lung, 1 each of esophagus, melanoma, myeloma and adenocarcinoma of unknown primary cancer. Of the regions compared, 69 were positive f or bony metastases by MRI and 63 regions by bone scans. Thirty-eight r egions were concordantly positive and 56 regions concordantly negative . No patients with entirely positive bone scans were negative by MRI, but one patient was entirely positive by MRI but negative by a bone sc an. At least one region was discordantly read in 21 patients. Distribu tion of positive regions was similar on bone scan and MRI. The greates t number and proportion of discordant readings occurred in the lumbar regions and more frequently in patients with prostate cancer. Consider ing its widespread availability and the ease of performing a whole-bod y survey for metastasis, radionuclide bone scanning remains the study of choice for initial evaluation of patients with cancer. However, MRI is an excellent complementary technique when bone scan findings are i nadequate for answering clinical questions. MRI appears to be quite se nsitive and probably more specific for metastasis in certain locations of the spine.