Development of a bone-mimicking phantom and measurement of its acoustic impedance by the interference method

Fractures due to osteoporosis have increasingly become a problem. In order to investigate methods that measure osteoporosis using ultrasound, an appropriate bone-mimicking phantom is required. However, no appropriate phantom is currently available. Therefore, we have developed a bone-mimicking phantom that disperses calcium in oil jelly (a plasticizing material that contains oil and resin) and measured its acoustic impedance using the interference method. The phantoms were dispersed in oil jelly with calcium weight percentages of 50, 55 and 59%. The experiment was conducted at 3.5 MHz. The impedances of the phantoms were 2.0, 2.2 and 2.6 × 10⁶ kg/m²·s, respectively. In order to confirm the change in acoustic impedance due to the varying calcium content, impedance measurements were also conducted by measuring the speed of sound and the density of the phantoms. The measured values for these two methods were similar with an error of around +10%.