MRI protocol

All scans were performed using a 1.5-T MR scanner (Aera, SIEMENS, Erlangen, Germany) with the patient in the supine position. The following sequences were used to acquire images, from which features were extracted for the radiomics model: axial T2-weighted imaging (T2WI) (repetition time/echo time = 4500 ms/80 ms, slice thickness = 6 mm, gap = 1 mm, field of view (FOV) = 320 * 240, flip angle = 160°, number of excitation = 2, with fat saturation), and axial diffusion-weighted imaging (DWI) (repetition time/echo time = 5200 ms/80 ms, field of view = 250 * 200, slice thickness = 6 mm, gap = 1 mm, flip angle = 90°, number of excitation = 6, b-value = 0, 800). The apparent diffusion coefficient (ADC) value was derived according to the following equation:

where S(b) and S(b0) represent the signal intensity of a certain voxel in the presence and absence of diffusion sensitization, respectively.