查看更多>>摘要：目的 探讨3.0 T MRI化学交换饱和转移（CEST）成像在体外模型和实验动物中定量评估肾脏氧化还原代谢的可行性。 方法 制备生理浓度的氧化还原代谢物体外模型，包括还原型代谢物（谷氨酸、丙氨酸、谷胱甘肽）和氧化型代谢物（2-酮戊二酸、丙酮酸、谷胱甘肽二硫化物、氢氧化铵），采用3.0 T MRI扫描仪进行CEST成像，成像方法为固定射频持续时间为2 000 ms，采集不同饱和脉冲强度（B1）值（1、2、3、4 μT）的CEST图像；固定B1值为2 μT，采集不同射频持续时间（1 500、2 000 ms）的CEST图像，获取最佳扫描参数。采用最佳扫描参数对7只正常实验兔左侧肾脏进行CEST成像，测量兔肾皮质和外髓的非对称磁化传递率（MTRasym），差异的比较采用配对t检验。 结果 体外模型实验显示氧化还原代谢物CEST扫描最佳B1值为2 μT、最佳射频持续时间为2 000 ms。谷胱甘肽二硫化物、谷胱甘肽、谷氨酸、丙氨酸的MTRasym峰值分别在3.75、3.5、3、1.5 ppm处，丙酮酸、2-酮戊二酸、氢氧化铵的峰值在1 ppm处，且还原型代谢物的MTRasym信号峰值高于氧化型代谢物。在B1值为2 μT、射频持续时间为2 000 ms的条件下，在1、3、3.5、3.75 ppm处，兔肾皮质的MTRasym信号分别为（2.60±1.10）%、（2.86±1.32）%、（3.04±1.06）%、（2.98±0.91）%，兔肾外髓的MTRasym信号分别为（1.00±0.56）%、（2.43±0.94）%、（2.29±0.88）%、（1.98±0.58）%，兔肾皮质的MTRasym信号均高于外髓信号，差异有统计学意义（t=3.04，P=0.023；t=2.56，P=0.043；t=3.50，P=0.013；t=3.45，P=0.014）。 结论 3.0 T MRI CEST成像可用于定量评估体外模型及正常实验兔肾脏氧化还原代谢。 Objective To explore the feasibility of chemical exchange saturation transfer (CEST) imaging at 3.0 T MRI in quantifying renal redox metabolism in vitro models and experimental animals. Methods Redox metabolites in vitro models with physiological concentrations were prepared, including reduced metabolites (glutamate, alanine, glutathione) and oxidized metabolites (2-ketoglutarate, pyruvate, glutathione disulfide, ammonium hydroxide). CEST examinations were performed at 3.0 T MRI. The imaging parameters were as follows: CEST images with different saturation pulse intensity (B1) (1, 2, 3, 4 μT) and a fixed radio frequency (RF) duration of 2 000 ms CEST images with different RF durations (1 500 and 2 000 ms) were acquired with a fixed B1 value of 2 μT to obtain the optimal scanning parameters. CEST examinations with optimized parameters were performed on the left kidneys of seven healthy rabbits, and the differences in magnetic resonance ratio asymmetry (MTRasym) between rabbit renal cortex and outer medulla were measured. A paired t-test was used to compare the differences. Results The optimal B1 for CEST examination of redox metabolites was 2 μT, and the optimal RF duration was 2 000 ms. The MTRasym peaks of glutathione disulfide, glutathione, glutamic acid, and alanine were at 3.75, 3.5, 3, and 1.5 ppm, respectively. The MTRasym peaks of pyruvate, 2-ketoglutarate, and ammonium hydroxide were at 1 ppm. The MTRasym peak values of reduced metabolites were higher than those of oxidized metabolites. When the B1 value was 2 μT and the RF duration was 2 000 ms, the MTRasym signal of the renal cortex was (2.60±1.10) %, (2.86±1.32) %, (3.04±1.06) %, and (2.98±0.91) % at 1, 3, 3.5, and 3.75 ppm, respectively. The MTRasym signal of the outer medulla was (1.00±0.56) %, (2.43±0.94) %, (2.29±0.88) % and (1.98±0.58) %, respectively. The MTRasym signal of the renal cortex was higher than that of the outer medulla, and the differences were statistically significant (t=3.04, P=0.023 t=2.56, P=0.043 t=3.50, P=0.013 t=3.45, P=0.014). Conclusion CEST imaging at 3.0 T MRI can be used to quantitatively evaluate redox metabolism of healthy rabbit kidneys in vitro model and normal experimental rabbits.
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