Defining the ROI in the femoral head. The ROI in the femoral head is defined in the FHON group as the section cross with the biggest lesion, and we set 6 ROIs in the section. In the control group, the section crossed the fovea of the femoral head. The ROIs were separated into a 2-tier network and arranged ectoentad. FHON = femoral head osteonecrosis, ROI = region of interest.