Auckland Bioengineering Institute, University of Auckland Auckland, New Zealand ; Department of Optometry and Vision Sciences, University of Auckland Auckland, New Zealand.
Front Physiol. 2013 Mar 1;4:33. doi: 10.3389/fphys.2013.00033. eCollection 2013.
We describe our development of the diffusion tensor imaging modality for the bovine ocular lens. Diffusion gradients were added to a spin-echo pulse sequence and the relevant parameters of the sequence were refined to achieve good diffusion weighting in the lens tissue, which demonstrated heterogeneous regions of diffusive signal attenuation. Decay curves for b-value (loosely summarizes the strength of diffusion weighting) and TE (determines the amount of magnetic resonance imaging-obtained signal) were used to estimate apparent diffusion coefficients (ADC) and T2 in different lens regions. The ADCs varied by over an order of magnitude and revealed diffusive anisotropy in the lens. Up to 30 diffusion gradient directions, and 8 signal acquisition averages, were applied to lenses in culture in order to improve maps of diffusion tensor eigenvalues, equivalent to ADC, across the lens. From these maps, fractional anisotropy maps were calculated and compared to known spatial distributions of anisotropic molecular fluxes in the lens. This comparison suggested new hypotheses and experiments to quantitatively assess models of circulation in the avascular lens.
我们描述了为牛眼晶状体开发的扩散张量成像方式。在自旋回波脉冲序列中添加扩散梯度，并改进序列的相关参数，以在晶状体组织中实现良好的扩散加权，这表明扩散信号衰减的异质区域。使用 b 值衰减曲线（大致总结扩散加权的强度）和 TE（确定磁共振成像获得的信号量）来估计不同晶状体区域的表观扩散系数（ADC）和 T2。ADC 的变化幅度超过一个数量级，揭示了晶状体中的扩散各向异性。为了改善整个晶状体的扩散张量本征值（相当于 ADC）图谱，在培养的晶状体上施加了多达 30 个扩散梯度方向和 8 个信号采集平均值。从这些图谱中，计算了各向异性分数并与晶状体中各向异性分子通量的已知空间分布进行了比较。这种比较提出了新的假设和实验，以定量评估无血管晶状体循环的模型。
