Benefit of 3T diffusion-weighted imaging in comparison to contrast-enhanced MR imaging for the evaluation of disseminated lesions in primary malignant brain tumors

Abstract

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/mm2, post-contrast T1-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/mm2 and 4 (33%) and 5 (42%) DWI at b = 3000 s/mm2 studies. For one of them, the mean score was significantly higher for b = 3000 s/mm2 than b = 1000 s/mm2 (P < 0.05). Interobserver agreement for DWI at b = 1000 s/mm2 and b = 3000 s/mm2 was very good (κ = 0.85; 95% CI, 0.63−1.00) and excellent (κ = 0.93; 95% CI, 0.78−1.00), respectively. The mean LBCR was significantly higher for DWI at b = 3000 s/mm2 than DWI at b = 1000 s/mm2 (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/mm2 may be more useful than DWI at b = 1000 s/mm2.