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

Abstract

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: T2, 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 (MTRasym), the asymmetric spin-lock ratio (SLRasym) and T2 values were calculated for nucleus pulposus (NP) and annulus fibrosus (AF). Wilcoxon test was used to analyze differences between MTRasym and SLRasym. Pearson correlation was used to determine the relationship between MTRasym, SLRasym and T2. Results: Data showed no significant difference between MTRasym and SLRasym (NP: P = 0.35; AF: P = 0.34). MTRasym and SLRasym values differed significantly between NP and AF (MTRasym: P = 0.014, SLRasym: P = 0.005). T2 values correlated significantly with MTRasym (NP: ρ = 0.76, P < 0.001; AF: ρ = 0.60, P < 0.001) and SLRasym (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.