MRI Scanning

Studies were conducted on a 3 Tesla (T) clinical scanner (Signa Pioneer, GE Healthcare, USA) using a medium soft coil, and the dominant leg was scanned. A 3D double-echo UTE-Cones sequence (TR/TE₁/TE₂, 11.5/0.032/4.4 ms; FOV, 16 cm; slice thickness, 3 mm; flip angle, 9˚; bandwidth, 62.5 kHz; in-plane spatial resolution, 0.89mm*0.89mm; 12 axial images; and scan time, 54 s) was adopted to get tibial images. To locate the thickest part of the tibial cortex, in the positioning phase, the spine coil was used to image the full length of the tibia and was then positioned at the thickest plane (approximately in a 38% place of the tibial length close to the lateral malleolus) of the tibia in the coronal and sagittal planes.

The reason for tibial cortex used for our study is mainly due to two reasons: (1) In the study of bone pore water, the tibial cortex and the femoral neck cortex are often selected parts (8, 20, 22, 26, 27). (2) According to other research and our pre-experiment, compared with the femoral neck cortex, the tibial cortex is very thick, and the boundary with the bone marrow is very clear, which is more beneficial to accurately draw the ROI of bone cortex.