Perman W H, Thomasson D M, Bernstein M A, Turski P A
Department of Medical Physics, University of Wisconsin, Madison 53706.
Magn Reson Med. 1989 Feb;9(2):153-60. doi: 10.1002/mrm.1910090202.
The MR behavior of the sodium-23 nucleus in vivo is a complex problem which has generated considerable interest over the last 20 years. Early studies on excised tissue samples revealed that the sodium nucleus exhibited a two-component T2 relaxation. This biexponential T2 relaxation was characterized by a short component with a T2 = 0.7-4.8 ms, and a long component with a T2 = 7.0-26.0 ms. We have developed a 3D pulse sequence capable of performing multiple Hahn echo in vivo sodium-23 imaging at echo times as short as 2.5 ms. This sequence obtains the shorter spin echo times by presaturating the spins outside of the desired imaging region, allowing the use of nonselective rf pulses. Using this sequence we have been able to quantify the long and short T2 components of normal brain tissue, vitreous humor of the eye, and a rabbit VX-2 carcinoma. We found that gray matter and white matter of normal brain have a monoexponential T2 relaxation with T2 = 17.6 +/- 2.4 ms. The vitreous humor T2 relaxation is also monoexponential with T2 = 56.8 +/- 2.1 ms. However, we find that some of the rabbit VX2 carcinomas exhibit a biexponential T2 decay with a short component of 3.3 +/- 4.6 ms and a long component of 22.0 +/- 9.0 ms.
体内钠 - 23原子核的磁共振行为是一个复杂的问题，在过去20年中引起了相当大的关注。早期对切除组织样本的研究表明，钠原子核表现出双组分T2弛豫。这种双指数T2弛豫的特征是短组分的T2 = 0.7 - 4.8毫秒，长组分的T2 = 7.0 - 26.0毫秒。我们开发了一种3D脉冲序列，能够在短至2.5毫秒的回波时间下进行体内钠 - 23成像的多次哈恩回波。该序列通过预饱和所需成像区域之外的自旋来获得较短的自旋回波时间，从而允许使用非选择性射频脉冲。使用这个序列，我们能够量化正常脑组织、眼玻璃体液和兔VX - 2癌的长T2和短T2组分。我们发现正常脑的灰质和白质具有单指数T2弛豫，T2 = 17.6±2.4毫秒。玻璃体液的T2弛豫也是单指数的，T2 = 56.8±2.1毫秒。然而，我们发现一些兔VX2癌表现出双指数T2衰减，短组分的T2为3.3±4.6毫秒，长组分的T2为22.0±9.0毫秒。
