Lees S, Tao N J, Lindsay S M
Forsyth Dental Center, Boston, MA 02115.
Connect Tissue Res. 1990;24(3-4):187-205. doi: 10.3109/03008209009152148.
A measure of the elastic properties of tissue can be found from the propagation of sound in the tissue. Longitudinal sonic velocities were measured for mineralized turkey leg tendon (density 1.50 g/cc), deer antler (1.77 g/cc) and cow tibia (2.05 g/cc) in the 10 GHz frequency regime by means of Brillouin light scattering using a nine pass Fabry-Perot interferometer. Wet, air dried, mineralized and demineralized specimens were tested. Sonic velocity in each tissue increased with mineral content and decreased when the tissue was wet. All wet values are higher than for wet rat tail tendon collagen, axially and radially, but with considerably less anisotropy. The results are interpreted to indicate that bone matrix collagen is more highly crosslinked than tail tendon collagen. The loss of anisotropy is taken to correspond to a much higher crosslinking density between adjacent collagen molecules in mineralized tissue compared to rat tail tendon. The axial sonic velocity of dried rat tail tendon is almost that for low density dried mineralized tissue and greater than the radial sonic velocity of these tissues, but the radial sonic velocity for dried rat tail tendon is much lower, again corresponding to less crosslinking in this tissue. Longitudinal modulus, K, is defined as the tissue density times the square of the velocity. The compliance, 1/K, was found to be a linear function of density for each of the four conditions. It suggests that a Reuss formalism describes the elastic properties. Since the difference between the compliance for wet and dry tissue is also a linear function of density, the effect of water on the compliance is additive. The axial sonic velocity for cow bone is essentially constant over a frequency range spanning 10 orders. Presumably the axial sonic velocity is controlled by the continuity of the collagen fibers lying along the bone axis. The radial velocity decreases by 30% over this frequency range, probably due to the many levels of structure observed in long bone like osteons, Haversian canals and blood vessels, as well as internal surfaces like cement lines and between lamellae. The sonic anisotropy of hard tissues decreases considerably with increasing frequency. While rat tail tendon collagen is very anisotropic both sonically and optically, hard tissues whether wet, dry, mineralized or demineralized show much less anisotropy. The optical index of refraction, both axially and radially, was found by Brillouin scattering for the air dried demineralized tissues. A close match was found between optical and sonic anisotropy for all the demineralized tissues.
可以通过声音在组织中的传播来找到一种衡量组织弹性特性的方法。利用九程法布里 - 珀罗干涉仪，通过布里渊光散射在10吉赫兹频率范围内测量了矿化火鸡腿肌腱（密度1.50克/立方厘米）、鹿角（1.77克/立方厘米）和牛胫骨（2.05克/立方厘米）的纵向声速。对湿的、风干的、矿化的和脱矿的标本进行了测试。每种组织中的声速随矿物质含量增加而增加，在组织湿润时降低。所有湿组织的值在轴向和径向上都高于湿大鼠尾腱胶原蛋白的值，但各向异性程度要小得多。结果表明，骨基质胶原蛋白比尾腱胶原蛋白的交联程度更高。各向异性的丧失被认为对应于矿化组织中相邻胶原蛋白分子之间的交联密度比大鼠尾腱高得多。干燥大鼠尾腱的轴向声速几乎与低密度干燥矿化组织的轴向声速相同，且大于这些组织的径向声速，但干燥大鼠尾腱的径向声速要低得多，这再次表明该组织中的交联较少。纵向模量K定义为组织密度乘以速度的平方。发现对于四种情况中的每一种，柔量1/K都是密度的线性函数。这表明赖斯形式主义描述了弹性特性。由于湿组织和干组织的柔量之差也是密度的线性函数，所以水对柔量的影响是累加的。牛骨的轴向声速在跨越10个数量级的频率范围内基本保持恒定。据推测，轴向声速由沿骨轴排列的胶原纤维的连续性控制。在这个频率范围内，径向速度下降了30%，这可能是由于在长骨中观察到的许多结构层次，如骨单位、哈弗斯管和血管，以及像黏合线和薄片之间的内表面。硬组织的声各向异性随着频率的增加而显著降低。虽然大鼠尾腱胶原蛋白在声学和光学上都非常各向异性，但硬组织无论是湿的、干的、矿化的还是脱矿的，各向异性都要小得多。通过布里渊散射测量了风干脱矿组织的轴向和径向光学折射率。发现所有脱矿组织的光学各向异性和声各向异性之间有密切匹配。
