核磁気共鳴画像による脳浮腫の実験的研究—ラット脳切片を用いた検討

NUCLEAR MAGNETIC RESONANCE (NMR) IMAGING OF BRAIN EDEMA FROM SLICED RAT BRAIN PRELIMINARY REPORT

　抄録　脳組織の含水量を経時的・非侵襲的に測定することは，とりわけ小動物においては従来不可能であった。核磁気共鳴（NMR）によれば非破壊的に生体組織内の元素を観測でき，またNMR信号強度は元素の密度に比例するから，¹H-NMR信号に基づいた生体断面の画像は水素原子核（プロトン）の密度分布を表示しうる。われわれはNMR断層撮像装置（NMR・CT）の実験機を用い，生体撮像の前段階として厚さ1.2mmのラット脳切片の画像を得た。その結果大脳内部の巨視的構造を正確に画像化できること，凍結損傷後の浮腫鎖域拡大と修復過程での含水量変化を画像により経時的に捉えうることを示せた。われわれは先に浮腫組織では水分子中プロトンのNMR緩和時間に顕著な変化が出現したことを報告したが（Asato etal．，1981），今回の実験の結果NMR・CTを用いて浮腫脳組織を生体内で測定し得ることが示せた。近い将来，含水量変化の観察にとどまらず組織水についてin vivoでの分子論的検討を行なうことが可能になると考えられ，今後脳神経外科学頷域の研究において　NMRが有力な分析手段として用いられていくと思われる。

A series of the sliced rat brain were imaged by proton nuclear magnetic resonance (¹H-NMR)using a Carr-Purcell-Meiboom-Gill sequence. The slices were obtained from the adult male Wistar rats, normal or suffering from vasogenic brain edema at 2, 6, 24Hr, 2Wk and 2Mo period after the application of cryo-injury. The imaging time was arranged 17 to 22 minutes dependently upon signal to noise ratio. The slice thickness was 1.2 mm, and pixel dimensions were 0.2×0. 2 mm, Whereas a voxel size in our images is mere 1/1,200 compared to that reported about the pro-totype human NMR imaging devices, high reso-lution has been realized. The spatial resolution is very fine, as evidenced by the appearance of ma-Jor internal structures of rat brain, and the obje-ct contrast is so high that cerebral white-gray contrast is excellent, although the difference in water concentration between them is only 7%.

It has been impossible to measure serially in vivo change in water concentration of small or-gans as rat brain. NMR has the capability to generate images in response to tissue state of hydration, therefore we can easily recognize the extent and intensity of the brain edema, which has been defined as an expansion of the brain volume resulting from an increase in its fluid content. And in this study, using the prototype mini-NMR･CT of excellent spatial and contrast resolution, we have been able to show this advan-tage of NMR as a new tool for research in the field of neurological surgery.