TOPOGRAPHIC DIFFERENCES OF H-1-NMR RELAXATION-TIMES (T(1), T(2)) IN THE NORMAL INTERVERTEBRAL DISC AND ITS RELATIONSHIP TO WATER-CONTENT

H-1-nuclear magnetic resonance studies, in vitro, on normal interverte bral discs dissected from adult bovine (3-or 4-year-old) coccygeal ver tebrae were performed to clarify topographic differences in relaxation times (T1, T2) and relationships between the relaxation times and wat er content. Immediately after death, intervertebral discs were dissect ed from 1st/2nd and 2nd/3rd coccygeal vertebrae and divided into three specimens: the nucleus pulposus, inner anulus fibrosus, and outer anu lus fibrosus. T1, T2, and water content were measured for the specimen s collected from 15 intervertebral discs (untreated group). Secondly, specimens were similarly collected from 12 intervertebral discs and we re treated to changed water contents (dehydrated group and hydrated gr oup). For each treated specimen, T1, T2, and water content were measur ed. The results showed highly significant differences (P < 0.01) in T1 values among the nucleus pulposus, inner anulus fibrosus, and outer a nulus fibrosus, and also in T2 values between the nucleus pulposus and anulus fibrosus. In each of the nucleus pulposus and anulus fibrosus, a positive linear relationship (r = 0.97, P < 0.01) was found between T1 and water content. The respective regression lines for the nucleus pulposus and anulus fibrosus had different slopes, and the slope of t he nucleus pulposus was significantly greater than that of the anulus fibrosus. Thus, the decrease in water content shortens the T1 in inter vertebral discs, and changes in water content have a greater influence on T1 in the nucleus pulposus than in the anulus fibrosus. Concerning the relationship between T2 and water content, the shortening of T2, according to the decrease in water content, was found at approximately 75% or more of water content in each of the nucleus pulposus and anul us fibrosus. No marked changes in T2 were found below 75% of water con tent. In conclusion, T1 and T2 vary within the nucleus pulposus, inner anulus fibrosus, and outer anulus fibrosus, and have characteristic r elationships with water content in normal intervertebral discs.