Fig. 1

Representative axial T2 and IDEAL maps obtained at the level of L4/L5. Images with manually traced ROIs of multifidus and erector spinae muscles in a 24-year-old patient with AS and a 29-year-old healthy control: (a, g) conventional T2 mapping without fat saturation; (b, h) conventional T2 mapping with fat saturation; (c, i) T2 mapping pseudo-color image without fat saturation; (d, j) T2 mapping pseudo-color image with fat saturation; (e, k) T2 IDEAL water image; and (f, l) T2 IDEAL fat image; note the higher fatty infiltration in the muscles of the patient with AS in comparison to the healthy control. AS, ankylosing spondylitis; IDEAL, iterative decomposition of water and fat with echo asymmetric and least-squares estimation; MF, multifidus; ES, erector spinae