Goodman James A, Ackerman Joseph J H, Neil Jeffrey J
Department of Radiology, Washington University, St. Louis, Missouri 63110, USA.
Magn Reson Med. 2008 Jan;59(1):65-72. doi: 10.1002/mrm.21418.
Spectroscopic resolution of intracellular and extracellular compartments can be used to probe the kinetic environment of those spaces and the compartment-specific changes that occur following injury. This is important for understanding the biophysical mechanisms that underlie the remarkable diffusion-weighted MRI contrast of injured central nervous system (CNS) tissue. Cesium-133 is a physiologic analog of potassium that is actively taken up by cells and resides primarily in the intracellular space. The (133)Cs(+) signal can, thus, be exploited to probe the kinetic environment of the intracellular space. Two principal (133)Cs(+) resonances were observed at 11.74 T. These resonances arise separately from (133)Cs(+) in brain and temporalis muscle. The apparent diffusion coefficient (ADC) of Cs(+) in brain decreased from 1.0 +/- 0.2 microm(2)/ms in healthy tissue to 0.24 +/- 0.04 microm(2)/ms following global ischemia (average ADC +/- average uncertainty), while there was no significant change in the ADC of Cs(+) in temporalis muscle after injury. This finding underscores the tissue-specific nature of the decrease in ADC that accompanies brain injury. Further, as the Cs(+) ADC should reflect water ADC in the intracellular space, these results strongly support the hypothesis that the decrease in water ADC associated with CNS injury arises largely from kinetic changes taking place in the intracellular space.
细胞内和细胞外区室的光谱分辨率可用于探究这些空间的动力学环境以及损伤后发生的区室特异性变化。这对于理解损伤的中枢神经系统（CNS）组织显著的扩散加权磁共振成像对比的生物物理机制很重要。铯 - 133是钾的生理类似物，可被细胞主动摄取并主要存在于细胞内空间。因此，（133）Cs（+）信号可用于探究细胞内空间的动力学环境。在11.74 T时观察到两个主要的（133）Cs（+）共振。这些共振分别来自大脑和颞肌中的（133）Cs（+）。大脑中Cs（+）的表观扩散系数（ADC）在全脑缺血后从健康组织中的1.0±0.2μm²/ms降至0.24±0.04μm²/ms（平均ADC±平均不确定度），而颞肌损伤后Cs（+）的ADC没有显著变化。这一发现强调了伴随脑损伤的ADC降低的组织特异性。此外，由于Cs（+）的ADC应反映细胞内空间中的水ADC，这些结果有力地支持了以下假设：与CNS损伤相关的水ADC降低主要源于细胞内空间发生的动力学变化。
