当同时使用多切片加速时，扩散传播算子度量有偏差
Diffusion propagator metrics are biased when simultaneous multi-slice acceleration is used
摘要：
正在探索先进的扩散MRI模型，以更高的精度研究大脑的复杂微观结构。然而，这些技术需要长的采集时间。同时多切片（SMS）通过同时激发多个图像切片并使用数学模型分离重叠切片来加速数据采集。然而，这种切片分离是不精确的，并且导致同时激励的切片之间的串扰。虽然这种残余泄漏很小，但它会影响定量MRI技术，如扩散成像。在这项研究中，SMS加速的影响，从MAP-MRI技术获得的传播度量的准确性进行了研究。用SMS加速多壳扩散MRI采集对10名健康志愿者进行扫描。进行组分析以研究通常受SMS加速影响的大脑区域。此外，从基于图谱的感兴趣的纤维束的扩散度量进行了分析，以调查如何传播度量在主要的纤维束偏置2和3波段SMS加速。当使用SMS加速度时，零位移度量和非高斯度量都显著改变。根据SMS-3计算的MAP-MRI指标显示与SMS-2存在显著差异。此外，当使用由SMS加速提供的较短TR时，该偏置的特征已经改变。这对使用具有SMS加速的扩散MRI研究疾病或损伤对脑组织的影响具有影响。
英文摘要：
Advanced diffusion MRI models are being explored to study the complex microstructure of the brain with higher accuracy. However, these techniques require long acquisition times. Simultaneous multi-slice (SMS) accelerates data acquisition by exciting multiple image slices simultaneously and separating the overlapping slices using a mathematical model. However, this slice separation is not exact and leads to crosstalk between simultaneously excited slices. Although this residual leakage is small, it affects quantitative MRI techniques such as diffusion imaging. In this study, the effects of SMS acceleration on the accuracy of propagator metrics obtained from the MAP-MRI technique was investigated. Ten healthy volunteers were scanned with SMS accelerated multi-shell diffusion MRI acquisitions. Group analyses were performed to study brain regions typically affected by SMS acceleration. In addition, diffusion metrics from atlas based fiber tracts of interest were analyzed to investigate how propagator metrics in major fiber tracts were biased by 2- and 3-band SMS acceleration. Both zero-displacement metrics and non-Gaussianity metrics were significantly altered when SMS acceleration was used. MAP-MRI metrics calculated from SMS-3 showed significant differences with respect to SMS-2. Furthermore, when shorter TR afforded by SMS acceleration was used, the characteristics of this bias have changed. This has implications for studies using diffusion MRI with SMS acceleration to investigate the effects of a disease or injury on the brain tissues.
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