In vivo diffusion‐weighted MRS using semi‐LASER in the human brain at 3 T: Methodological aspects and clinical feasibility,NMR in Biomedicine

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In vivo diffusion‐weighted MRS using semi‐LASER in the human brain at 3 T: Methodological aspects and clinical feasibility
NMR in Biomedicine ( IF 2.7 ) Pub Date : 2020-01-13 , DOI: 10.1002/nbm.4206
Guglielmo Genovese _{1,

2} , Małgorzata Marjańska ₃ , Edward J Auerbach ₃ , Lydia Yahia Cherif _{1,

2} , Itamar Ronen ₄ , Stéphane Lehéricy _{1,

2} , Francesca Branzoli _{1,

2}

Affiliation

Diffusion‐weighted (DW‐) MRS investigates non‐invasively microstructural properties of tissue by probing metabolite diffusion in vivo. Despite the growing interest in DW‐MRS for clinical applications, little has been published on the reproducibility of this technique. In this study, we explored the optimization of a single‐voxel DW‐semi‐LASER sequence for clinical applications at 3 T, and evaluated the reproducibility of the method under different experimental conditions. DW‐MRS measurements were carried out in 10 healthy participants and repeated across three sessions. Metabolite apparent diffusion coefficients (ADCs) were calculated from mono‐exponential fits (ADC_exp) up to b = 3300 s/mm², and from the diffusional kurtosis approach (ADC_K) up to b = 7300 s/mm². The inter‐subject variabilities of ADCs of N‐acetylaspartate + N‐acetylaspartylglutamate (tNAA), creatine + phosphocreatine, choline containing compounds, and myo‐inositol were calculated in the posterior cingulate cortex (PCC) and in the corona radiata (CR). We explored the effect of physiological motion on the DW‐MRS signal and the importance of cardiac gating and peak thresholding to account for signal amplitude fluctuations. Additionally, we investigated the dependence of the intra‐subject variability on the acquisition scheme using a bootstrapping resampling method. Coefficients of variation were lower in PCC than CR, likely due to the different sensitivities to motion artifacts of the two regions. Finally, we computed coefficients of repeatability for ADC_exp and performed power calculations needed for designing clinical studies. The power calculation for ADC_exp of tNAA showed that in the PCC seven subjects per group are sufficient to detect a difference of 5% between two groups with an acquisition time of 4 min, suggesting that ADC_exp of tNAA is a suitable marker for disease‐related intracellular alteration even in small case–control studies. In the CR, further work is needed to evaluate the voxel size and location that minimize the motion artifacts and variability of the ADC measurements.

中文翻译：

在 3 T 下在人脑中使用半激光的体内扩散加权 MRS：方法学方面和临床可行性

扩散加权 (DW-) MRS 通过探测体内代谢物扩散来研究组织的非侵入性微结构特性。尽管人们对 DW-MRS 临床应用的兴趣日益浓厚，但关于这种技术的可重复性的报道很少。在本研究中，我们探索了单体素 DW-半激光序列在 3 T 下临床应用的优化，并评估了该方法在不同实验条件下的重现性。DW-MRS 测量在 10 名健康参与者中进行，并在三个疗程中重复进行。代谢物表观扩散系数 (ADC) 由单指数拟合 (ADC _exp ) 计算得出，直至b = 3300 s/mm ²，并由扩散峰度法 (ADC _K) 高达b = 7300 s/mm ²。N-乙酰天冬氨酸+ N-乙酰天冬氨酰谷氨酸 ( tNAA )、肌酸 + 磷酸肌酸、含胆碱化合物和肌酸的 ADC 的受试者间差异在后扣带皮层 (PCC) 和放射冠 (CR) 中计算了肌醇。我们探讨了生理运动对 DW-MRS 信号的影响，以及心脏门控和峰值阈值对信号幅度波动的重要性。此外，我们使用自举重采样方法研究了受试者内变异性对采集方案的依赖性。PCC 的变异系数低于 CR，可能是由于两个区域对运动伪影的敏感性不同。最后，我们计算了 ADC _exp的可重复性系数，并进行了设计临床研究所需的功效计算。_{ADC exp}的功率计算tNAA 的研究表明，在 PCC 中，每组 7 名受试者足以检测到两组之间 5% 的差异，采集时间为 4 分钟，这表明 tNAA 的 ADC _exp是疾病相关细胞内改变的合适标志物，即使在小范围内病例对照研究。在 CR 中，需要进一步的工作来评估体素大小和位置，以最大限度地减少运动伪影和 ADC 测量的可变性。

更新日期：2020-01-13

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