| 摘要 |
PROBLEM TO BE SOLVED: To exactly estimate the state of bone density and to easily perform high-reliability diagnosis. SOLUTION: An ultrasonic impulse is radiated toward the cortical bone, echo returned from the surface of the cortical bone of is received, the echo level is measured by an A/D converter 8, etc., later. A CPU 11 extracts the maximum echo level among the measured echo levels and calculates the coefficient of ultrasonic wave reflection on the interface between the soft tissue of an examinee and the cortical bone based on the extracted maximum echo level. Next, an acoustic impedance at the cortical bone is calculated based on the calculated ultrasonic wave reflection coefficient, and the bone density of the examinee is calculated from the calculated acoustic impedance. Since the acoustic impedance at the cortical bone is expressed by the square root of 'elastic modulus×density' of the cortical bone, when the bone density is decreased and the elastic modulus is lowered, the acoustic impedance is remarkably decreased sensitively in response to the synergistic effect of these factors. Therefore, the acoustic impedance at the cortical bone becomes a good index for judging the bone density.
|
