Feasibility of filter-exchange imaging (FEXI) in measuring different exchange processes in human brain
Feasibility of filter-exchange imaging (FEXI) in measuring different exchange processes in human brain
复制标题
滤光交换成像（FEXI）测量人脑不同交换过程的可行性
DOI：
10.1016/j.neuroimage.2020.117039
复制
发表时间：
2020-10-01
期刊：
影响因子：
5.7
通讯作者：
Basser, Peter
中科院分区：
文献类型：
--
作者：
Bai, Ruiliang;Li, Zhaoqing;Basser, Peter
跨膜水交换，包括血管内到血管外和血管内到细胞外的水交换，是诊断和理解癌症、脑部疾病和其他疾病的潜在生物标志物。过滤器交换成像（FEXI），扩散交换光谱（DEXSY）适用于临床应用的特殊情况下，有可能揭示不同的生理水交换过程使用相同的MRI序列。在这项研究中，我们的目的是探索的可行性，FEXI在测量不同的水交换过程中，通过调制的扩散过滤器（B（f））和检测块FEXI。在3 T MRI临床扫描仪上执行两种FEXI协议，并在7名健康志愿者的脑组织中显示不同的表观交换率（AXR）对比。根据B（f）= 250 s/mm（2）的FEXI方案估计的AXR（预期专门滤除血管水）显著大于B（f）= 900 s/mm（2）的FEXI方案的AXR。此外，B（f）= 250 s/mm（2）的FEXI的过滤效率显示出与血管密度的强相关性，血管密度是一种估计为表现出体素内非相干运动（IVIM）的水的分数的度量。B（f）= 250 s/mm（2）的FEXI的AXR与其他独立测量报告的血管水流出速率常数一致，尽管B（f）= 900 s/mm（2）的FEXI的AXR的生理基础尚不清楚。总的来说，我们目前的结果表明，FEXI在体内测量不同的水交换过程的可行性，以及FEXI针对血管水可以帮助表征血管内到血管外的水交换过程。
Transmembrane water exchange, including intra-to-extravascular and intra-to-extracellular ones, are potential biomarkers in the diagnosis and understanding of cancers, brain disorders, and other diseases. Filter-exchange imaging (FEXI), a special case of diffusion exchange spectroscopy (DEXSY) adapted for clinical applications, has the potential to reveal different physiological water exchange processes using the same MRI sequence. In this study, we aim to explore the feasibility of FEXI in measuring different water exchange processes by modulating the diffusion filter (b(f)) and detection blocks in FEXI. Two FEXI protocols were implemented on a 3T MRI clinical scanner and reveal distinct apparent exchange rate (AXR) contrast in brain tissues in seven healthy volunteers. AXR estimated from a FEXI protocol with b(f) = 250 s/mm(2), which is expected to filter out the vascular water specifically, are significantly larger than those of a FEXI protocol with b(f) = 900 s/mm(2). Besides, the filter efficiency of FEXI with b(f) = 250 s/mm(2) shows a strong correlation with vascular density, a metric estimated as the fraction of water exhibiting intravoxel incoherent motion (IVIM). AXR of FEXI with b(f) = 250 s/mm(2) agrees with the vascular water efflux rate constants reported by other independent measurements, although the physiological basis of the AXR of FEXI with b(f) = 900 s/mm(2) is not clear yet. Collectively, our current results demonstrate the feasibility of FEXI in measuring different water exchange processes in vivo, and that FEXI targeting the vascular water could help characterize the intra-to-extravascular water exchange process.