Study Design. Evaluation of a new quantitative imaging technique in a prospective study design. Objective. To assess glycosaminoglycan (GAG) content of lumbar intervertebral discs (IVDs) in healthy volunteers with chemical exchange saturation transfer (CEST). Summary of Background Data. Biochemical alterations of lumbar discs are present before the appearance of morphological changes. GAG loss plays a central role in these degenerative processes. Methods. Lumbar intervertebral discs of healthy controls (26 women, 22 men; mean age 31 ± 8 years; range: 21–49 years) without lumbar back pain were examined at a 3 Tesla magnetic resonance imaging (MRI) scanner in this prospective study. None of the participants were overweight or had previous surgery of the lumbar spine. The MRI protocol included standard morphological, sagittal and transversal T2-weighted (T2w) images to assess Pfirrmann score and to detect disc disorders according to the Combined Task Force classification of five lumbar IVDs (L1 to S1). A prototype glycosaminoglycan chemical exchange saturation transfer (gagCEST) sequence was applied to measure GAG content of the nucleus pulposus (NP) and annulus fibrosus (AF) by identifying the magnetization transfer asymmetry ratio (MTR_asym) in a region-of-interest analysis. Morphological and biochemical imaging analysis were statistically tested for quantitative differences between different grades of IVD degeneration and disc disorders. Results. gagCEST values of NP demonstrated a significant negative correlation with morphological Pfirrmann score (r = −0.562; P < 0.0001). The MTR_asym values were higher in non-degenerative lumbar IVDs (Pfirrmann 1–2) compared with degenerative lumbar discs (Pfirrmann 3–5; 2.92% ± 1.42% vs. 0.78% ± 1.38%; P < 0.0001). The MTR_asym values of NP were significantly higher in normal appearing discs compared with herniated IVDs (2.83% ± 1.52% vs. 1.55% ± 1.61%; P < 0.0001). We found a significant negative correlation between gagCEST values and the graduation of disc herniation (r = −0.372; P < 0.0001). Conclusion. Biochemical imaging with gagCEST distinguished morphologically degenerative from non-degenerative lumbar IVDs (in NP and AF) of healthy volunteers at a clinical 3T-MRI system. The depletion of GAG content in degenerative lumbar discs correlated significantly with the morphological disc classification. We could demonstrate that disc disorders, such as protrusion and extrusion, were accompanied by lower GAG content. Level of Evidence: 2

Purpose: To analyze age‐dependency of glycosaminoglycan content using gagCEST (glycosaminoglycan chemical exchange saturation transfer) imaging in lumbar intervertebral discs of healthy volunteers.Materials and Methods: In all, 70 volunteers without low back pain (mean age 44 ± 14 years, range: 21–69 years) were examined withT₂‐weighted and gagCEST imaging with a 3T MR scanner, with approval of the local Ethics Committee after written informed consent was obtained. Pfirrmann grading and classification into discs without bulging and herniation, discs with bulging, and discs with herniation were performed. Only intervertebral discs without bulging and herniation were analyzed. A region‐of‐interest‐based gagCEST analysis of nucleus pulposus (NP) and annulus fibrosus (AF) was performed. Correlation between age and gagCEST was tested within groups of equal Pfirrmann score.Results: GagCEST effects decreased significantly from 3.09 ± 1.12% in 20–29 years old volunteers to −0.24 ± 1.36% in 50–59 years old volunteers (P < 0.001). In the case of Pfirrmann scores 2 and 3, a significant correlation was observed between gagCEST effect and age (Pfirrmann score 2, NP: ρ = –0.558,P < 0.001; Pfirrmann score 3, NP: ρ = –0.337,P = 0.048). For Pfirrmann scores 1 and 4, no significant correlation was obtained (Pfirrmann score 1, NP: ρ = –0.046,P = 0.824; Pfirrmann score 4, NP: ρ = –0.316,P = 0.188).Conclusion: We show a decreased gagCEST effect likely corresponding to decreasing glycosaminoglycans with aging. Hence, age‐matched analysis of gagCEST imaging may be necessary in future studies. J. MAGN. RESON. IMAGING 2015;42:1517–1523.

Introduction: Synovial inflammation and joint destruction in rheumatoid arthritis (RA) may progress despite clinical remission. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is increasingly used to detect synovial inflammation in RA. Although small joints such as metacarpophalangeal (MCP) joints are mainly affected by RA, MRI findings have never been directly compared to histological synovitis in MCP synovial tissue. The objective of the current study was therefore to analyse if DCE-MRI relates to histological signs of synovitis small RA joints. Methods: In 9 RA patients, DCE-MRI (3 Tesla, dynamic 2D T1 weighted turbo-flash sequence) of the hand was performed prior to arthroscopically-guided synovial biopsies from the second MCP of the imaged hand. Maximum enhancement (ME), rate of early enhancement, and maximum rate of enhancement were assessed in the MCP. Synovial biopsies were stained for determination of sublining CD68 and the Synovitis Score. Correlations between MRI and histological data were calculated according to Spearman. Results: ME of the MCP significantly correlated to sublining CD68 staining (r = 0.750, P = 0.02), the Synovitis Score (r = 0.743, P = 0.02), and the subscores for lining layer hypertrophy (r = 0.789, P = 0.01) and cellular density (r = 0.842; P = 0.004). Conclusions: Perfusion imaging of synovial tissue in RA finger joints employing DCE-MRI reflects histological synovial inflammation. According to our study, ME is the most closely associated parameter amongst the measures considered.