BULLS-EYES AND HALOS - USEFUL MR DISCRIMINATORS OF OSSEOUS METASTASES

To evaluate the presence of (a) a focus of high signal intensity in th e center of an osseous lesion (bull's-eye) as a negative discriminator for metastasis and (b) a rim of high signal intensity around an osseo us lesion (halo) as a positive discriminator, a retrospective study wa s performed in 47 patients with osseous lesions suspect for metastatic disease who underwent magnetic resonance (MR) imaging of the pelvis. The findings in 17 patients with proved osseous metastasis were compar ed with those in 30 patients not believed to have metastatic disease; T1- and T2-weighted MR images were evaluated. The bull's-eye sign was found to be a specific indicator of normal hematopoietic marrow (sensi tivity, 95%; specificity, 99.5%). The halo sign and diffuse signal hyp erintensity were a strong indicator of metastatic disease (sensitivity , 75%; specificity, 99.5%). These results suggest that use of the bull 's-eye sign as a discriminator of benign disease and use of the halo s ign as a discriminator of metastasis help characterize suspect areas o f marrow lesions.