Fig. 1.

a 500-kHz axial transmission (AT) multi-channel probe positioned on the facies medialis and aligned with the z-axis of a tibia specimen. The arrow indicates the movement of the probe during the acquisition of 400 individual measurements. b Top left sketch of probe showing the number and positions of central receivers and adjacent lateral emitters. The distal ends of each tibia (pointed line box) were imaged using micro-computed tomography (μCT, 39 μm isotropic voxel size). A cross-section (dashed line box) was extracted from the AT measurement region. The proximal surface of the cross-section was scanned with 100-MHz scanning acoustic microscopy (SAM). A parallelepiped sample of around 2 × 3 × 4 mm³ was obtained from the facies medialis of this cross-section and imaged with μCT (7.4 μm isotropic voxel size). Typical waveforms acquired after one ultrasound transmission at the tibia ex vivo (c) and in a water tank of 65 mm depth (d)