Improved detection of skull metastasis with diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE Metastasis to the skull is clinically important, but routine MR imaging offers moderate sensitivity for skull-metastasis detection in our experience. We sought to determine if diffusion-weighted MR imaging (DWI) could improve the detection of skull metastasis in patients with primary carcinomas that metastasized to bone compared with conventional MR imaging. MATERIALS AND METHODS Seventy-five patients from the tumor registry of our institution with extracranial primary malignancy who had brain MR imaging with DWI and radionuclide bone scanning (RNBS, gold standard) within a 6-week interval were evaluated. Thirty-eight patients demonstrated increased radiopharmaceutical uptake on RNBS, consistent with skull metastasis of any size, and the remaining 37 were control subjects. Two readers correlated the DWI and conventional MR imaging with RNBS. RESULTS The overall sensitivity of DWI for detection of skull metastases was 68.4%-71.1% (kappa=0.68) versus 42.1%-55.3% (kappa=0.65) for conventional MR imaging. Breast cancer (n=20) was detected with greatest sensitivity of 86.7%-93.3% (kappa=0.80) for DWI versus 60%-80% (kappa=0.5) for conventional MR imaging. Lung cancer (n=32) was detected with 63.6%-72.7% sensitivity (kappa=0.56), and prostate cancer (n=8) with 14.3% sensitivity (kappa=0.5) for DWI versus 27.3%-36.4% (kappa=0.81) and 14.3-42.9% (kappa=0), respectively, for conventional MR imaging. CONCLUSIONS DWI is a useful sequence for identifying focal skull metastases for breast and lung malignancies and, compared with conventional MR imaging, provides improved detection of these lesions. DWI is insensitive for detecting skull metastases from prostate carcinoma.