目的:提出并评估一种新的用于成像亚体素组织区室的多维方法,称为扩散-松弛相关光谱成像。
方法:MR扩散或弛豫数据的多指数模型通常用于推断许多不同的微观组织区室,这些区室为宏观MR成像体素提供信号。然而,众所周知,多指数估计是困难和不适的。观察到这种不恰当性在理论上在更高的维度上被减少了,扩散-弛豫相关光谱成像使用一种新的多维成像实验,联合编码扩散和弛豫信息,然后使用一种新颖的约束重建技术为每个体素生成多维扩散-弛豫相关谱。预期多维光谱的峰对应于存在于每个宏观成像体素内的不同组织微环境。
结果:使用数值模拟,来自定制幻影的实验数据,和创伤性脊髓损伤小鼠模型的实验数据,与传统的基于扩散和弛豫的方法相比,扩散-弛豫相关光谱成像被证明可以提供更好的多隔室分辨率。
结论:扩散-弛豫相关光谱成像方法为解析多室组织模型的不同成分提供了强大的新功能,并且可以利用MRI在组织微观结构研究中提供的见解。MagnResonMed78:2236-2249,2017.©2017国际医学磁共振学会。
OBJECTIVE: To propose and evaluate a novel multidimensional approach for imaging subvoxel tissue compartments called Diffusion-Relaxation Correlation Spectroscopic Imaging.
METHODS: Multiexponential modeling of MR diffusion or relaxation data is commonly used to infer the many different microscopic tissue compartments that contribute signal to macroscopic MR imaging voxels. However, multiexponential estimation is known to be difficult and ill-posed. Observing that this ill-posedness is theoretically reduced in higher dimensions, diffusion-relaxation correlation spectroscopic imaging uses a novel multidimensional imaging experiment that jointly encodes diffusion and relaxation information, and then uses a novel constrained reconstruction technique to generate a multidimensional diffusion-relaxation correlation spectrum for every voxel. The peaks of the multidimensional spectrum are expected to correspond to the distinct tissue microenvironments that are present within each macroscopic imaging voxel.
RESULTS: Using numerical simulations, experiment data from a custom-built phantom, and experiment data from a mouse model of traumatic spinal cord injury, diffusion-relaxation correlation spectroscopic imaging is demonstrated to provide substantially better multicompartment resolving power compared to conventional diffusion- and relaxation-based methods.
CONCLUSIONS: The diffusion-relaxation correlation spectroscopic imaging approach provides powerful new capabilities for resolving the different components of multicompartment tissue models, and can be leveraged to significantly expand the insights provided by MRI in studies of tissue microstructure. Magn Reson Med 78:2236-2249, 2017. © 2017 International Society for Magnetic Resonance in Medicine.