Fig. 1

Shows the measurement of thoracolumbar vertebral BMD by using PL-QCT. The blue circle in (A) refers to the ROI of the measured vertebral body, The ROI is selected from the cancellous region in the middle of the vertebra to maximize ROI while avoiding the cortical bone, basal vein of the vertebral body, osteophyte and other areas. The red circle indicates the ROI of subcutaneous fat and paravertebral muscle on the same layer of the measured vertebral body. (B) shows that vertebral BMD is calibrated by CT values of the ROI of paravertebral muscle and subcutaneous fat on the same level of the measured vertebral body, and the ROI region needs to be adjusted to a normal distribution on the calibration curve. (C) shows coronal ROI.