Longitudinal wave in cancellous bone separates into fast wave and slow waves depending on the structure of trabeculae. Slow wave is influenced by the properties of bone marrow. We measured ultrasonic properties (wave velocity and attenuation) of bovine bone marrow. The bone marrow showed a transition point at 22 ℃, which was accompanied with a weak relaxation. The weak frequency dispersion of velocity in bone marrow was observed at temperatures lower than the transition temperature. The frequency dependence of attenuation was comparatively large at low temperatures. Compared with properties in water, the frequency and temperature dependence were quite different, whereas the measured ultrasonic velocities were similar.%海綿骨中を伝搬する縦波超音波は高速波，低速波の二種類の波に分離する.このうち低速波は骨髄の物性に大きく影響される.そこでウシ骨髄を用いて骨髄の超音波物性（音速・減衰）を測定した.骨髄は転移点を22-23℃付近にもち，弱い緩和現象を示した.また転移点以下の低温で音速・減衰共に大きな周波数依存性を示した.骨髄中の音速は水と似ているものの，周波数・温度特性は異なるものであり，減衰は水より大きいものであった.
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