Description: Publication date: December 2014 Source: Magnetic Resonance Imaging, Volume 32, Issue 10 Author(s): Caroline Mesmann , Monica Sigovan , Lise-Prune Berner , Adva Abergel , François Tronc , Y. Berthezène , P. Douek , Loic Boussel Purpose To compare diffusion weighted imaging with background suppression (DWIBS) sequence with classic spectral diffusion sequence (DWI) with and without respiratory gating in mediastinal lymph node analysis at 3 T. Materials and methods 26 patients scheduled for mediastinoscopic lymph node analysis, prospectively undergone a thoracic 3 T MRI with DWIBS (FatSat = STIR; TR/TE = 6674.1/44.7 ms; IR = 260 ms) and DWI sequences (FatSat = SPIR; TR/TE = 1291/59.6 ms) (b = 0-400-800 s/mm2) with and without (free breathing) respiratory gating. Images at b = 800 were analyzed by two radiologists. They performed qualitative analysis of fat-sat homogeneity and motion artifacts, rated from 0 to 4, and quantitative evaluation by studying signal to background (STB) of lymph nodes. Results Quality of fat suppression was significantly higher for DWIBS than for DWI both for free-breathing (score 3.48 ± 0.65 vs. 1.76 ± 0.96, p 〈 0.0001) and respiratory-gated scans (3.17 ± 0.77 vs. 1.72 ± 0.73, p = 0.0001). Similarly, artifacts were reduced with DWIBS (3.16 ± 0.47 vs. 1.76 ± 0.59, p 〈 0.0001; 3.0 ± 0.73 vs. 2.04 ± 0.53, p = 0.0001). Quantitative analysis showed higher STB with DWIBS (3.26 ± 1.83 vs. 0.98 ± 0.44, p 〈 0.0001; 3.56 ±, 2.09 vs. 0.92 ± 0.59, p 〈 0.0001). Gating did not improve image quality and STB on DWIBS (p > 0.05). Conclusion In thoracic MRI, ungated DWIBS sequence improves fat-sat homogeneity, reduces motion artifacts and increases STB of lymph nodes. Respiratory gating does not improve DWIBS image quality.