Quantitative Tissue Structure Characterization with Temporal Diffusion Spectroscopy

Introduction: Diffusion-weighted magnetic resonance imaging (DWI) is dependent on the micro-structural properties of biological tissues, so it is possible to obtain quantitative structural information non-invasively from DWI measurements (1). However, due to hardware limitations, the diffusion times achieved in practice using conventional pulsed gradient spin echo (PGSE) methods are relatively long and insensitive to sub-cellular structure variations. In contrast, the oscillating gradient spin echo (OGSE) method has been reported to have the ability to probe short diffusion time behavior and is sensitive to intracellular structure variations, such as nuclear sizes (2). In the present work, we provide analytical expressions for MR signals with OGSE methods for restricted diffusion in some typical structures, such as spheres, based on the theory of temporal diffusion spectroscopy (3). A novel model is introduced to interpret DWI data obtained from OGSE measurements to quantitatively characterize tissue structures, such as obtaining averaged cell nuclear sizes. Methods and Results: Analytical Equations: Based on the theory of temporal diffusion spectroscopy, we derived analytical expressions for the DWI signal attenuation for restricted diffusion with the cosine-modulated OGSE sequence, namely exp(-β(2τ)) where ( ) 2 2 2 2 2 2