Effects of diffusion time and diffusion gradient strength on the mean diffusivity of water molecules in healthy human brain

作     者：GAO Song, WANG Xiaoying and BAO Shanglian ( Laboratory of Medical Physics & Engineering, Peking University, Beijing 100871, China Department of Radiology, The First Affiliated Hospital of Peking University, Beijing 100034, China) 

作者机构：Peking Univ Lab Med Phys & Engn Beijing 100871 Peoples R China Peking Univ Affiliated Hosp 1 Dept Radiol Beijing 100034 Peoples R China 

出 版 物：《Progress in Natural Science:Materials International》 (自然科学进展·国际材料(英文))

年 卷 期：2006年第16卷第7期

页      面：706-711页

核心收录：

学科分类：0831[工学-生物医学工程（可授工学、理学、医学学位）] 08[工学] 0836[工学-生物工程] 

基　　金：Supported by National Natural Science Foundation of China (Grant No  10527003)Joint Research Fund of Beijing (SYS100010401) The Research Fund for the Doctoral Program of Higher Education (20040001003) 

主　　题：diffusion time diffusion gradient strength diffusion-weighted imaging diffusion tensor imaging mean diffusivity. 

摘      要：Diffusion time and diffusion gradient strength are two important parameters of pulsed gradient spin echo (PGSE) that is the most commonly used method in diffusion-weighted magnetic resonance imaging. However, the effects of the diffusion time on the mean diffusivity (MD) in previous studies are controversial. In this study, a new experimental protocol was designed to evaluate the effects of the two parameters on the results of PGSE. It was found that MD decreased significantly with the increased diffusion time or increased diffusion gradient strength, which cannot be explained by the previous theories. Through theoretical analysis, we found the flaw in the pulsed gradient spin echo (PGSE) method, which is the explanation for the controversial results of diffusion time obtained by oth- ers.