Computed tomography image showing highlighted areas of skeletal muscle mass (red). The protocol for measuring areas of skeletal muscle mass is as follows: after converting image type to 8-bit, set scale and double check the scale with the vertical and horizontal ruler. Draw the two regions of interest (ROIs) including the whole section and visceral only, respectively (in the inner line, we excluded spinal cord because some part of spinal cord is at the same density range). Use the XOR function to set the third ROI of the area excluding visceral. Smooth the section twice to reduce noise of image before setting the predefined threshold and measuring the highlighted area.