Magnetic Resonance Elastography (MRE) and Diffusion Tensor Imaging (DTI) represent MRI techniques that involve the application of diffusion sensitizing and motion encoding gradients. In MRE, mechanically introduced intra-voxel coherent motion is encoded into the phase of the MR signal, which enables assessment of diagnostically relevant tissue stiffness. DTI is sensitive to direction-dependent intra-voxel incoherent motion (e.g., Gaussian diffusion of magnetically labeled water molecules) and enables visualization of tissue anisotropy for the diagnostic assessment of conditions, where anisotropic tissue structure changes. It is improbable that either MRE or DTI alone will provide a complete picture of the microstructural environment in the brain. Rather, current evidence suggests that MRE and DTI are both sensitive measures of microstructural integrity and provide overlapping, but not identical, information regarding the microstructural integrity of regions of the medial temporal lobe as they relate to behavior. It has also been shown that the fusion of DTI and MRE data at multiple vibration frequencies improves the diagnostic sensitivity for Alzheimer's disease compared to using information from MRE or DTI alone. Therefore, the combination of the two techniques will be critical to advance our ability both to detect disruptions of the microstructural environment of the brain as they appear in neurocognitive disorders or as results of neurobiological mechanisms of aging and to quantitatively characterize them. We propose a technique for the concurrent acquisition of 3D MRE wave images and diffusion-weighted maps with respect to multiple gradient directions. Multifrequency DTI-MRE (mDTI-MRE) enables the acquisition of the displacement vector (at three vibration frequencies) and of the Diffusion Tensor simultaneously. As such, mDTI- MRE has the potential to increase the clinical acceptance of DTI and MRE by providing the radiologist with co- registered multi-parametric diagnostic information without increasing imaging time. The proposed project aims to optimize mDTI-MRE for in vivo human brain applications and to implement and validate mDTI-MRE on a human 3.0T MRI scanner. Comparative studies will be performed between conventional approaches and mDTI- MRE of in vivo human brain.
Simultaneous encoding of the 3D displacement vector at multiple frequencies and of the Diffusion Tensor using the concept of multifrequency Diffusion Tensor Imaging - Magnetic Resonance Elastography (mDTI- MRE) enables rapid acquisition and immediate co-registration of Diffusion MRI and MRE data at multiple vibration frequencies. mDTI-MRE has the potential to increase the clinical acceptance of DTI and MRE by providing the radiologist with co-registered multi-parametric diagnostic information without increasing imaging time.