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 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