Evaluation of Glycosaminoglycan in the Lumbar Disc Using Chemical Exchange Saturation Transfer MR at 3.0 Tesla:Reproducibility and Correlation with Disc Degeneration

Key words: 
• Glycosaminoglycan /
• Chemical Exchange Saturation Transfer (CEST) /
• Reproducibility /
• Disc degeneration

Abstract: ObjectiveThis study aims to explore the clinical applicability and relevance of glycosaminoglycan Chemical Exchange Saturation Transfer (gagCEST) for intervertebral disc. Methods25 subjects ranging in age from 24 yrs to 74 yrswere enrolled.gagCESTwas acquired using a single-slice TSE sequence on a 3T. Saturation used a continuous rectangular RF pulse with B1=0.8 μT and a fixed duration time =1100 ms. Sagittal image was obtained firstly without saturation pulse, and then saturated images were acquired at 52 offsets ranging from ±0.125 to ±7 parts per million (ppm). MRT2 relaxivity map was acquired at the identical location. Six subjects were scanned twice to assess scan-rescan reproducibility. ResultsGagCEST intraclass correlation coefficient(ICC)of six subjects was 0.759 fornucleus pulposus (NP) and 0.508 forannulus fibrosus (AF). Bland-Altman plots showed NP had a mean difference of 0.10%(95% limits of agreement:-3.02% to 3.22%);whilethat of AF was0.34% (95% limits of agreement:-2.28% to 2.95%). For the25 subjects,gag CEST in NP decreased as discdegeneration increased, with a similar trend to T2 relaxivity.GagCEST of AF showed a bettercorrelation withdisc degenerationthanT2 relaxivity. ConclusionGagCEST in NP and AF decreased as discdegeneration increased, whilegagCEST in AF showed a bettercorrelation thanT2 relaxivity.