Papadakis N G, Xing D, Huang C L, Hall L D, Carpenter T A
Herchel Smith Laboratory for Medicinal Chemistry, University of Cambridge School of Clinical Medicine, University Forvie Site, Robinson Way, Cambridge, England, CB2 2PZ, United Kingdom.
J Magn Reson. 1999 Mar;137(1):67-82. doi: 10.1006/jmre.1998.1673.
This study has investigated the effects of the selection of the diffusion-weighted (DW) gradient directions on the precision of a diffusion tensor imaging (DTI) experiment. The theoretical analysis provided a quantitative framework in which the noise performance of DTI schemes could be assessed objectively and for the development of novel DTI schemes, which employ multiple DW gradient directions. This generic framework was first applied to the examination of two commonly used DTI schemes, which employed 6 DW gradient directions and hitherto were used indiscriminately under the sole condition of noncollinearity. It was then used to design and assess a novel 12-DW-gradient-direction DTI protocol, which employed the same total number of DW acquisitions as the two conventional schemes (12). This theoretical investigation was then corroborated using rigorous simulation and DTI experiments on both an isotropic phantom and a healthy human brain. Both the theoretical and the experimental analysis demonstrated that the two conventional schemes showed a significantly different noise performance and that use of the new multiple-DW-gradient-direction scheme clearly improved the precision of the DTI measurements.
本研究调查了扩散加权（DW）梯度方向的选择对扩散张量成像（DTI）实验精度的影响。理论分析提供了一个定量框架，在此框架中，可以客观地评估DTI方案的噪声性能，并用于开发采用多个DW梯度方向的新型DTI方案。这个通用框架首先应用于对两种常用DTI方案的检验，这两种方案采用6个DW梯度方向，迄今为止，在非共线性这一唯一条件下被不加区分地使用。然后，它被用于设计和评估一种新型的12-DW梯度方向DTI方案，该方案采用与两种传统方案相同的DW采集总数（12次）。然后，通过在各向同性体模和健康人脑上进行严格的模拟和DTI实验，证实了这一理论研究。理论分析和实验分析均表明，两种传统方案表现出显著不同的噪声性能，并且使用新的多DW梯度方向方案明显提高了DTI测量的精度。
