Adw 4.4 workstation

Two experienced readers independently assessed the morphology of the IVDs from L1/2 to L5/S1 according to the Pfirrmann grading system on sagittal T2 FSE images. The Pfirrmann grading system is primarily based on changes in signal intensity from the NP, the distinction between the NP and the annulus fibrosus, and disc height[23 (link)–25 (link)]. The distribution of the 101 IVDs with respect to the Pfirrmann grades was determined independently by an experienced musculoskeletal radiologist (XJP) with 15 years’ experience, and a spinal surgeon (CYD) with 20 years’ experience. A senior radiologist with 13 years’ experience manually selected the regions of interest (ROIs) on the working station (Function Software, ADW 4.4 workstation, GE Medical Systems, Waukesha, WI, USA) to measure the mapping values (S1 Fig). The ROIs for the IVDs were drawn on T2, T2* and T1ρ maps according to the subject’s anatomic shape. In addition, one large, circular ROI was selected for the NP, and two smaller circular ROIs were selected for the anterior annulus fibrosus (AAF) and the posterior annulus fibrosus (PAF), respectively. The ROI of the NP in the mid-sagittal line was about 50% to 60% of the disc diameter. The ROIs of the LFJs were drawn on each map across both articular surfaces of each FJ. All ROIs were selected and calculated on the left and right sides.

An orbital MRI was performed for all participants using a 3.0 T MRI system (Signa HDxt, GE Healthcare, Pittsburgh, PA, USA). The T2RTs of the EOMs were measured using a multi-slice multi-spin echo pulse sequence with a TR of 1500 ms, 7 TE values (22, 33, 44, 55, 66, 77, and 88 ms), a 180 × 180 mm field of view, 3.0 mm slice thickness, a 256 × 256 matrix, and 1 NEX. The color-coded T2 calculation was generated by a single exponential curve fitting using T2 mapping software (ADW4.4 workstation, GE Healthcare, Pittsburgh, PA, USA) (Figure 1a). The T2RTs (ms) and the areas (mm²) of five EOMs (inferior rectus (IR), superior rectus/levator complex (SRLCLC), medial rectus (MR), lateral rectus (LR), and superior oblique (SO)) were measured (Figure 1b). The maximum value for the T2RT or the area on the coronal section of each EOM was recorded as the final T2RT or area value.