Multiva 1.5t

The MRI scanning equipment included Signa Excite 3.0T (GE Medical Systems, GE Medical Systems, Chicago, IL), Discovery HD 750 3.0T (GE Medical Systems), Aera 1.5T (Siemens Healthcare Engineers, Siemens Healthcare Engineers, Erlangen, Germany), Ingenia 3.0T (Philips Medical Systems, Philips Medical Systems, Achieva, The Netherlands), Achieva 3.0T (Philips Medical Systems), Multiva 1.5T (Philips Medical Systems) and uMR 790 3.0T (United Imaging Healthcare, United Imaging Healthcare, Shanghai, China). The scanning sequences included conventional sagittal T1WI, T2WI, axial T2WI and fat suppression T₂WI (FS‐T₂WI). Supplementary Table 1 lists the sequence and parameters of MRI.

After being approved by the local institutional review board, medical records of those patients who were positive for AMA and diagnosed with myositis were retrospectively reviewed. Informed consent from the included cases was obtained according to the approved study protocol. The results of clinical evaluation including symptoms, duration of muscle weakness, and Medical Research Council (MRC) scale for muscle strength were extracted from the medical records. The presence of AMA was tested by indirect immunofluorescence, and AMA-M2 was titrated by enzyme-linked immunosorbent assay. Muscle MRI examinations of both thighs were performed in patients using a 1.5T MR scanner (GE 1.5T Signa Twin Speed, GE Healthcare; Multiva 1.5T, Philips Healthcare) with axial scanning in conventional T1-weighted imaging (T1WI) and short time inversion recovery (STIR) sequences. The top part of the coil was at the level of the anterior superior iliac spine, and the scanning range covered from the pelvis to the thigh. The patients were asked to rest for at least 30 min before imaging to avoid the effects of activity or exercise. The muscles were scanned in a noncontracted state. The total acquisition time for the axial T1-weighted and STIR images was approximately 20 min.