In our work, “Analysis of Convective and Diffusive Transport in the Brain Interstitium”, published in this journal (2019, 16:6), we estimate the interstitial superficial velocity by comparison of transport model simulations to published experimental Real-Time Iontophoresis (RTI) data. In the Discussion section, we calculate a value for perfusion rate, or volumetric flow rate per unit mass of tissue, from these fundamental results of superficial velocity. Drs. Hladky and Barrand have proposed an alternative method for choosing the surface area per volume used to calculate perfusion rate from superficial velocity, using our model domain. Their method seems reasonable to us, as does ours. Upon reflection, a range of volumetric flow per unit mass values should have been reported in our paper, 1–40 μL/min-g. The value calculated using Drs. Hladky and Barrand surface area is a likely upper-bound on this range and the value in the paper is a low estimate at the bottom of the range. We are confident in the estimates of interstitial velocity reported in our article, using the assumptions of the model. Peclet (Pe) numbers, which compare convective and diffusive transport rates for different molecules, were calculated using the superficial velocity estimates; and we continue to believe these values are correct along with all other major results and conclusions presented in the paper.

中文翻译：

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回应“脑灰质细胞外空间内的溶质运动主要是由扩散还是流动引起的？”

在我们发表在本期刊 (2019, 16:6) 的“脑间质对流和扩散传输分析”的工作中，我们通过将传输模型模拟与已发表的实验性实时离子电渗疗法 (RTI) 进行比较来估计间质表面速度） 数据。在讨论部分，我们根据这些表观速度的基本结果计算灌注率或每单位质量组织的体积流量值。博士 Hladky 和 ​​Barrand 提出了一种替代方法，用于使用我们的模型域选择用于从表观速度计算灌注率的单位体积表面积。他们的方法对我们来说似乎是合理的，就像我们的一样。经过反思，我们的论文中应该报告了每单位质量的体积流量值范围，1–40 μL/min-g。使用 Drs 计算的值。Hladky 和 ​​Barrand 表面积可能是该范围的上限，论文中的值是该范围底部的一个低估计值。使用模型的假设，我们对我们文章中报告的间隙速度的估计充满信心。Peclet (Pe) 数用于比较不同分子的对流和扩散传输速率，使用表面速度估计值计算；我们仍然相信这些值以及论文中提出的所有其他主要结果和结论都是正确的。比较不同分子的对流和扩散传输速率，使用表面速度估计值计算；我们仍然相信这些值以及论文中提出的所有其他主要结果和结论都是正确的。比较不同分子的对流和扩散传输速率，使用表面速度估计值计算；我们仍然相信这些值以及论文中提出的所有其他主要结果和结论都是正确的。