Fast multicomponent 3D‐T_1ρrelaxometry

Abstract

NMR relaxometry can provide information about the relaxation of the magnetization in different tissues, increasing our understanding of molecular dynamics and biochemical composition in biological systems. In general, tissues have complex and heterogeneous structures composed of multiple pools. As a result, bulk magnetization returns to its original state with different relaxation times, in a multicomponent relaxation. Recovering the distribution of relaxation times in each voxel is a difficult inverse problem; it is usually unstable and requires long acquisition time, especially on clinical scanners. MRI can also be viewed as an inverse problem, especially when compressed sensing (CS) is used. The solution of these two inverse problems, CS and relaxometry, can be obtained very efficiently in a synergistically combined manner, leading to a more stable multicomponent relaxometry obtained with short scan times. In this paper, we will discuss the details of this technique from the viewpoint of inverse problems.

In Vivo Myelin Water Quantification Using Diffusion–Relaxation Correlation MRI: A Comparison of 1D and 2D Methods

“…Almeida-Martins et al, Reymbaut et al, and Martin et al increased the dimensionality to 5D and 6D correlation MRI, by additionally varying the shape of b-tensors to encode diffusion and solving the inverse problem with a Monte Carlo-inversion [ 1 , 41 , 51 ]. Zibetti et al jointly solved image reconstruction and multi-component relaxometry, leveraging sparsity and spatial correlation [ 66 ]. Avram et al used voxel-wise optimized L2 regularization for T1-D correlation in vivo [ 5 ].…”

Pilot study quantifying muscle glycosaminoglycan using bi-exponential T1ρ mapping in patients with muscle stiffness after stroke

“…However, mono-exponential T 1ρ is a macro measurement of an extremely complex microenvironment in the ECM of the muscle. A number of studies have suggested that bi-exponential T 1ρ mapping may better represent the diverse microenvironment that gives rise to the relaxation times in tissue types such as cartilage 23 – 25 , brain 26 , 27 , liver 28 as well as skeletal muscle 29 . There have been no studies on the application of multi-exponential T 1ρ mapping for the measurement of the muscle microenvironment in muscle stiffness.…”