Objectives: To evaluate glycosaminoglycan-dependent chemical exchange saturation transfer (gagCEST) imaging at 3-T magnetic resonance imaging (MRI) for quantification of glycosaminoglycan (GAG) content in intervertebral discs (IVDs) in patients with low-back pain (LBP).
Methods: Sixteen patients with LBP were examined in this Institutional Review Board-approved study using a clinical whole-body system. The MRI protocol included standard morphological imaging, sagittal T2-mapping and gagCEST imaging. IVD grading according to the Pfirrmann score and region-of-interest analysis of the annulus fibrosus (AF) and the nucleus pulposus (NP) in gagCEST and T2 maps were performed before data were statistically tested for correlations between imaging techniques and quantitative differences between different grades of IVD degeneration.
Results: GagCEST values of the NP were significantly (P < 0.001) lower in degenerative IVDs (Pfirrmann 3 + 4) compared with non-degenerative IVDs (Pfirrmann 1 + 2), but only a weak linear correlation (r = 0.299) with the T2 relaxation times was found. GagCEST values of the NP exhibited a moderate negative correlation with Pfirrmann grades (r = -0.449).
Conclusions: The known loss of GAG in the NP with increasing grade of morphological degeneration can be assessed using gagCEST imaging at 3.0 T. The correlation with single Pfirrmann grades and T2 relaxation times only seems to be moderate, indicating a substantial difference in information provided by the techniques.