High quality three-dimensional gagCEST imaging of in vivo human knee cartilage at 7 Tesla

Purpose: To develop a new faster and higher quality three-dimensional (3D) gagCEST MRI technique for reliable quantification of glycosaminoglycan (GAG) present in the human knee cartilages. Methods: A new magnetization-prepared 3D gradient echo-based MRI pulse sequence has been designed to obtain the B₀ inhomogeneity, B₁ inhomogeneity, and CEST Z-spectra images. Results: The gagCEST values of different compartments of knee cartilage are calculated using a newly developed technique for healthy subjects and a symptomatic knee cartilage degenerated subject. The effect of the acquired CEST saturation frequency offset step-size was investigated to establish the optimal step-size to obtain reproducible gagCEST maps. Our novel 3D gagCEST technique demonstrates markedly higher gagCEST contrast value than the previously reported 3D gagCEST studies. This study demonstrates the need for separate B₀ and B₁ inhomogeneity estimation and correction. Conclusion: The new technique provided high quality gagCEST maps with clearer visualization of different layers of knee cartilage with reproducible results. Magn Reson Med 77:1866–1873, 2017.