| 摘要 |
<p>An apparatus for diagnosing osteoporosis which repeatedly radiates ultrasonic impulses (Ai) to a cortical bone (Mb) of a subject and receives echos (Ae) from the bone (Mb). The reception signal is converted to a digital echo signal by an A/D converter (8), and an echo level is detected by a CPU (11). The CPU (11) extracts a maximum echo level from among the echo levels detected during the measurement period and calculates an acoustic impedance (Zb) of the cortical bone on the basis of the maximum echo level so extracted. The bone density of the subject is calculated from the calculated acoustic impedance (Zb) of the cortical bone by using a predetermined recurrent formula. The acoustic impedance of the bone is given by the square root of [elastic modulus x density] of a bone, and the elastic modulus of the bone increases (or decreases) with the increase (or decrease) of the bone density. Therefore, the elastic modulus of the bone and the bone density synergistically contribute to the acoustic impedance. For this reason, the acoustic impedance (Zb) of the bone is a good guide for judging the bone density.</p> |
