Jolesz F A, Kirschner D A, Jakab P, Lorenzo A V
Department of Radiology, Harvard Medical School, Boston, MA.
J Neurol Sci. 1989 Jun;91(1-2):85-96. doi: 10.1016/0022-510x(89)90078-6.
The role of myelin in determining the magnetic resonance (MR) characterization of the central nervous system (CNS) was investigated in unmyelinated brains of normal fetal mice, as well as myelin-deficient adult mutant mice (shi, qk, mld) and their age-matched controls. In vitro NMR relaxation time measurements at 10 MHz for whole brains showed consistently longer T1 (range 558 +/- 8 to 580 +/- 27 msec) and T2 (range 81 +/- 3 to 89 +/- 3 msec) values for the adult myelin-deficient animals than the age-matched controls (T1 = 496 +/- 31, T2 = 79 +/- 4 msec). The fetal brains exhibited even more prolonged relaxation times (T1 = 976 +/- 60, T2 = 158 +/- 7 msec). MR images obtained at 81 MHz using spin echo (SE) sequences, which unlike the in vitro approach allowed discrimination between white and gray matter areas, revealed an absence of gray-white matter contrast in the brains of mutant mice, consistent with longer than normal relaxation of the myelin-deficient white matter. While larger tissue water components such as those present in the immature brain and edematous white matter contribute a greater effect, myelin and its associated bound water may still play an important role in the MR characterization of normal gray and white matter.
在正常胎儿小鼠的无髓鞘脑以及髓鞘缺陷的成年突变小鼠（shi、qk、mld）及其年龄匹配的对照中，研究了髓鞘在确定中枢神经系统（CNS）磁共振（MR）特征中的作用。对全脑进行的10 MHz体外核磁共振弛豫时间测量显示，成年髓鞘缺陷动物的T1（范围为558±8至580±27毫秒）和T2（范围为81±3至89±3毫秒）值始终比年龄匹配的对照更长（T1 = 496±31，T2 = 79±4毫秒）。胎儿脑的弛豫时间甚至更长（T1 = 976±60，T2 = 158±7毫秒）。使用自旋回波（SE）序列在81 MHz获得的MR图像，与体外方法不同，该序列允许区分白质和灰质区域，结果显示突变小鼠脑中缺乏灰白质对比度，这与髓鞘缺陷白质的弛豫时间长于正常情况一致。虽然较大的组织水成分（如未成熟脑和水肿白质中存在的那些）起更大作用，但髓鞘及其相关的结合水可能仍在正常灰质和白质的MR特征中发挥重要作用。
