Multidimensional Correlation Spectroscopic Imaging of Exponential Decays: From Theoretical Principles to In Vivo Human Applications

TL;DR

This paper introduces a multidimensional correlation spectroscopic imaging method for multiexponential MR signal decay analysis, improving tissue microstructure mapping by addressing ill-posed inverse problems through multidimensional contrast encoding and regularization.

Contribution

It presents a novel multidimensional imaging approach that reduces ambiguities in multiexponential modeling, with theoretical, simulated, and initial in vivo validation.

Findings

Enhanced resolution of tissue compartments in simulations

Improved stability of parameter estimation with multidimensional encoding

Successful initial application in human MRI experiments

Abstract

Multiexponential modeling of relaxation or diffusion MR signal decays is a popular approach for estimating and spatially mapping different microstructural tissue compartments. While this approach can be quite powerful, it is also limited by the fact that one-dimensional multiexponential modeling is an ill-posed inverse problem with substantial ambiguities. In this paper, we present an overview of a recent multidimensional correlation spectroscopic imaging approach to this problem. This approach helps to alleviate ill-posedness by leveraging multidimensional contrast encoding (e.g., 2D diffusion-relaxation encoding or 2D relaxation-relaxation encoding) combined with a regularized spatial-spectral estimation procedure. Theoretical calculations, simulations, and experimental results are used to illustrate the benefits of this approach relative to classical methods. In addition, we demonstrate an initial proof-of-principle application of this kind of approach to in vivo human MRI experiments.