Benefit of 3T Diffusion-weighted Imaging in Comparison to Contrast-enhanced MR Imaging for the Evaluation of Disseminated Lesions in Primary Malignant Brain Tumors

Purpose: We aimed to determine whether 3T diffusion-weighted imaging (DWI) has an additive value relative to contrast-enhanced MR imaging for the detection of disseminated lesions in patients with primary malignant brain tumors. Methods: We included consecutive 12 patients with nodular disseminated lesions of primary malignant brain tumors that were confirmed by surgery or follow-up MR imaging. All underwent conventional MR imaging, DWI at b = 1000 and 3000 s/mm(2), post-contrast T-1-weighted and 3D gradient-echo imaging at 3T. For the largest lesion per person, two radiologists independently evaluated the presence of additional information on DWI compared with postcontrast MR images using a 4-point scoring system. On DW images, one radiologist measured the lesion-to-brain contrast ratio (LBCR). Results: Compared with postcontrast studies, radiologists 1 and 2, respectively, assigned more apparent lesion conspicuity in 2 (17%) and 1 (8%) DWI at b = 1000 s/mm(2) and 4 (33%) and 5 (42%) DWI at b = 3000 s/mm(2) studies. For one of them, the mean score was significantly higher for b = 3000 s/mm(2) than b = 1000 s/mm(2) (P < 0.05). Interobserver agreement for DWI at b = 1000 s/mm(2) and b = 3000 s/mm(2) was very good (kappa = 0.85; 95% CI, 0.63-1.00) and excellent (kappa = 0.93; 95% CI, 0.78-1.00), respectively. The mean LBCR was significantly higher for DWI at b = 3000 s/mm(2) than DWI at b = 1000 s/mm(2) (P < 0.01). Conclusion: In the detection of disseminated lesions in patients with primary malignant brain tumors, 3T DWI has an additive value relative to contrast-enhanced MR imaging. DWI at b = 3000 s/mm(2) may be more useful than DWI at b = 1000 s/mm(2).