Comparison of glycosaminoglycan chemical exchange saturation transfer using Gaussian‐shaped and off‐resonant spin‐lock radiofrequency pulses in intervertebral disks

Purpose To investigate, if a train of spin‐lock pulses (chemical exchange saturation transfer with spin‐lock pulses = CESL) improves biochemical glycosaminoglycan imaging compared with conventional chemical exchange saturation transfer with Gaussian‐shaped pulses (CEST) in lumbar intervertebral discs. Methods T 2 , CEST, and CESL imaging was performed in lumbar intervertebral discs of 15 healthy volunteers at 3 Tesla. Mean and standard deviation of the asymmetric magnetization transfer ratio (MTR asym ), the asymmetric spin‐lock ratio (SLR asym ) and T 2 values were calculated for nucleus pulposus (NP) and annulus fibrosus (AF). Wilcoxon test was used to analyze differences between MTR asym and SLR asym . Pearson correlation was used to determine the relationship between MTR asym , SLR asym and T 2 . Results Data showed no significant difference between MTR asym and SLR asym (NP: P  = 0.35; AF: P  = 0.34). MTR asym and SLR asym values differed significantly between NP and AF (MTR asym : P  = 0.014, SLR asym : P  = 0.005). T 2 values correlated significantly with MTR asym (NP: ρ = 0.76, P  < 0.001; AF: ρ = 0.60, P  < 0.001) and SLR asym (NP: ρ = 0.73, P  < 0.001; AF: ρ = 0.47, P  < 0.001). Conclusion CESL does not improve the chemical exchange asymmetry effect compared with conventional CEST, but leads to comparable results. Magn Reson Med 78:280–284, 2017. © 2016 International Society for Magnetic Resonance in Medicine