Thornton J S, Ordidge R J, Penrice J, Cady E B, Amess P N, Punwani S, Clemence M, Wyatt J S
Department of Medical Physics and Bioengineering, University College London, UK.
Magn Reson Imaging. 1997;15(4):433-40. doi: 10.1016/s0730-725x(96)00378-5.
Measurements of tissue water apparent diffusion coefficient (ADC) performed with diffusion sensitization applied separately along the x, y, and z axes revealed significant diffusion anisotropy in both cerebral white and gray matter in six newborn (< 24 h old) piglets. Mean baseline white matter ADC for a particular region of interest was 125.8% (SD 32.0%; p < .001) greater when the diffusion gradients were applied along the y axis as compared to along the x. For the cortical gray matter region considered, the situation was reversed, the mean ADC value measured along x exceeding that along y by 15.2% (SD 6.1%; p < .01). Forty-three hours subsequent to a transient cerebral hypoxic-ischaemic insult, phosphorous MRS measurements indicated that the animals had suffered severe secondary cerebral energy failure. This was accompanied by a significant (p < .01) decrease in the white matter anisotropy, such that the mean y direction ADC now exceeded that along the x by only 70.9% (SD 29.4%; p < .03). There was no change in the gray matter anisotropy. The average of the ADC values measured in the x, y, and z directions had decreased by 35.3% (SD 18.5%; p < .01) in white matter and 31.4% (SD 21.9%; p < .05) in cortical gray matter. Diffusion anisotropy measurements may provide additional information useful in the characterisation of hypoxic-ischaemic injury in the neonatal brain, and must be considered if tissue water ADC values are to be unambiguously interpreted in this context.
对6只新生（<24小时龄）仔猪分别沿x、y和z轴施加扩散敏感化进行组织水表观扩散系数（ADC）测量，结果显示脑白质和灰质均存在明显的扩散各向异性。与沿x轴施加扩散梯度相比，当沿y轴施加扩散梯度时，特定感兴趣区域的平均基线白质ADC高125.8%（标准差32.0%；p<0.001）。对于所考虑的皮质灰质区域，情况相反，沿x轴测量的平均ADC值比沿y轴测量的值高15.2%（标准差6.1%；p<0.01）。在短暂性脑缺氧缺血损伤后的43小时，磷磁共振波谱测量表明这些动物遭受了严重的继发性脑能量衰竭。这伴随着白质各向异性的显著降低（p<0.01），使得现在y方向的平均ADC仅比沿x轴的ADC高70.9%（标准差29.4%；p<0.03）。灰质各向异性没有变化。在白质中，沿x、y和z方向测量的ADC值的平均值下降了35.3%（标准差18.5%；p<0.01），在皮质灰质中下降了31.4%（标准差21.9%；p<0.05）。扩散各向异性测量可能提供有助于表征新生儿脑缺氧缺血损伤的额外信息，并且如果要在此背景下明确解释组织水ADC值，就必须考虑这一点。
