Simultaneous assessment of bone thickness and velocity for ultrasonic computed tomography using transmission-echo method

The robustness and accuracy of the transmission-echo (TE) method is investigated on simultaneous thickness and velocity estimation of double-layered thin bone samples. Twenty-two pairs of bovine cortical samples were assembled and measured by two pairs of immersion transducers with nominal frequencies of 1MHz and 2.25MHz. For each measurement, the TOF of six pulses contained by one transmission and two echo signals were detected and then used for the calculation. The mean relative errors of effective samples for 1MHz and 2.25MHz transducers are 4.87% and 7.13% on cortical thickness estimation, and 4.65% and 5.88% on velocity assessment, respectively. For both thickness and velocity measurement, the experiments in low frequency provide more accurate estimations, and the velocity measurement shows more stability. It is demonstrated that the TE method has the potential to simultaneously estimate the cortical thickness and ultrasonic wave velocity for the mimic model of long bones.