Takamiya H, Kusaka Y, Seo Y, Noguchi M, Ikoma K, Morimoto T, Hirasawa Y
Department of Orthopaedic Surgery, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, 602-0841 Japan.
Jpn J Physiol. 2000 Dec;50(6):569-76. doi: 10.2170/jjphysiol.50.569.
The molecular behavior of water in normal and regenerating tendons was analyzed using the transverse relaxation time (T(2)) measured by spin-echo proton nuclear magnetic resonance ((1)H-NMR) spectroscopy at 2.34 T (25 degrees C). A section of the Achilles tendon was dissected from an anesthetized Japanese white rabbit, and its longitudinal axis was oriented at 0, 35, 54.7, 75, and 90 degrees to the static magnetic field. In the normal tendon, the T(2) relaxation of water presented biexponential relaxation and anisotropy in both the long T(2) (5.41 to 6.21 ms) and short T(2) (0.41 to 1.43 ms) components, in which the greatest values were obtained at 54.7 degrees. However, the range of the anisotropy was much narrower than we expected from the (1)H dipolar interaction of water bound to the collagen fibers in the tendon. The apparent fractions of water proton density also varied with orientation: the fraction of the longer T(2) components was at its maximum at 54.7 degrees. These results suggest that a simple two-compartment model could not be applicable to orientational dependency of the T(2) value of the tendon, and the well ordered water in the short T(2) relaxation component may show an elongated T(2) relaxation time that falls in the range of the long T(2) relaxation component at 54.7 degrees. This hypothesis can explain both the narrower range of the T(2) relaxation time and the orientational dependency on the apparent fraction of (1)H density. Regenerating processes of the Achilles tendon were followed for 18 weeks by analyzing the T(2) relaxation time. There is only a long T(2) relaxation time component (21.8 to 28.0 ms) up to 3 weeks after transection. Biexponential relaxation is revealed at 6 weeks and thereafter, whereby (i) the T(2) relaxation times become shorter, (ii) there is anisotropy in the short and long T(2) values, and (iii) the orientational dependency of the apparent fraction of water proton density becomes evident with maturation of the regenerating tendon. From these results, the (1)H T(2) relaxation time of water might be used to monitor the healing process of collagen structures of the tendon non-invasively.
利用在2.34 T（25℃）下通过自旋回波质子核磁共振（(1)H-NMR）光谱测量的横向弛豫时间（T(2)），分析正常和再生肌腱中水的分子行为。从一只麻醉的日本白兔身上解剖出一段跟腱，并将其纵轴与静磁场成0、35、54.7、75和90度角放置。在正常肌腱中，水的T(2)弛豫呈现双指数弛豫，且长T(2)（5.41至6.21毫秒）和短T(2)（0.41至1.43毫秒）成分均存在各向异性，其中在54.7度时获得最大值。然而，各向异性的范围比我们根据肌腱中与胶原纤维结合的水的(1)H偶极相互作用所预期的要窄得多。水质子密度的表观分数也随取向而变化：较长T(2)成分的分数在54.7度时达到最大值。这些结果表明，简单的双室模型不适用于肌腱T(2)值的取向依赖性，并且短T(2)弛豫成分中排列良好的水可能表现出延长的T(2)弛豫时间，该时间在54.7度时落入长T(2)弛豫成分的范围内。这一假设可以解释T(2)弛豫时间较窄的范围以及对(1)H密度表观分数的取向依赖性。通过分析T(2)弛豫时间，对跟腱的再生过程进行了18周的跟踪。横断后3周内只有一个长T(2)弛豫时间成分（21.8至28.0毫秒）。6周及之后出现双指数弛豫，由此（i）T(2)弛豫时间变短，（ii）短和长T(2)值存在各向异性，并且（iii）随着再生肌腱的成熟，水质子密度表观分数的取向依赖性变得明显。根据这些结果，水的(1)H T(2)弛豫时间可能用于无创监测肌腱胶原结构的愈合过程。
