pH-sensitive MRI demarcates graded tissue acidification during acute stroke - pH specificity enhancement with magnetization transfer and relaxation-normalized amide proton transfer (APT) MRI.
pH-sensitive MRI demarcates graded tissue acidification during acute stroke - pH specificity enhancement with magnetization transfer and relaxation-normalized amide proton transfer (APT) MRI.
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pH 敏感 MRI 划分急性中风期间的分级组织酸化 - 通过磁化转移和弛豫归一化酰胺质子转移 (APT) MRI 增强 pH 特异性
DOI：
10.1016/j.neuroimage.2016.07.025
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发表时间：
2016-11-01
期刊：
影响因子：
5.7
通讯作者：
Sun PZ
中科院分区：
文献类型：
--
作者：
Guo Y;Zhou IY;Chan ST;Wang Y;Mandeville ET;Igarashi T;Lo EH;Ji X;Sun PZ
ph敏感性酰胺质子转移（APT） MRI提供了替代代谢生物标志物，补充了广泛使用的灌注和扩散成像。然而，内源性APT MRI通常使用不对称分析（MTRasym）计算，由于伴随的半固体磁化转移（MT）和核overhauser （NOE）效应，该分析容易受到不均匀偏移的影响。虽然完整的脑组织pH值变化不大，但MTRasym图像显示白质和灰质明显。结果表明，与pH无关的非均质MTRasym位移与MT比（MTR）和纵向松弛率（R1w）高度相关，可以通过多元回归分析进行合理修正。由于急性脑卒中期间MT和R1w的变化相对较小，我们假设磁化转移和弛豫归一化APT （MRAPT）分析比常规MTRasym图像增加了MRI对酸中毒的特异性，从而有助于缺血性病变的分割。我们发现灌注、pH和弥散病变体积有显著差异（P<0.001，方差分析）。此外，mmrt MRI显示了分级的缺血性酸中毒，弥散病变中酸中毒最严重（- 1.05±0.29%/s）， pH/扩散失配区（即代谢半暗区，- 0.67±0.27%/s）内酸化中度，灌注/pH失配区pH变化较小（即良性低血症，- 0.04±0.14%/s），为缺血性组织损伤提供了精细的分层。
pH-sensitive amide proton transfer (APT) MRI provides a surrogate metabolic biomarker that complements the widely-used perfusion and diffusion imaging. However, the endogenous APT MRI is often calculated using the asymmetry analysis (MTRasym), which is susceptible to an inhomogeneous shift due to concomitant semisolid magnetization transfer (MT) and nuclear overhauser (NOE) effects. Although the intact brain tissue has little pH variation, white and gray matter appears distinct in the MTRasym image. Herein we showed that the heterogeneous MTRasym shift not related to pH highly correlates with MT ratio (MTR) and longitudinal relaxation rate (R1w), which can be reasonably corrected using the multiple regression analysis. Because there are relatively small MT and R1w changes during acute stroke, we postulate that magnetization transfer and relaxation-normalized APT (MRAPT) analysis increases MRI specificity to acidosis over the routine MTRasym image, hence facilitates ischemic lesion segmentation. We found significant differences in perfusion, pH and diffusion lesion volumes (P<0.001, ANOVA). Furthermore, MRAPT MRI depicted graded ischemic acidosis, with the most severe acidosis in the diffusion lesion (−1.05±0.29%/s), moderate acidification within the pH/diffusion mismatch (i.e., metabolic penumbra, −0.67±0.27%/s) and little pH change in the perfusion/pH mismatch (i.e., benign oligemia, −0.04±0.14%/s), providing refined stratification of ischemic tissue injury.
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