Free‐breathing, non‐ECG, simultaneous myocardial T₁, T₂, T₂*, and fat‐fraction mapping with motion‐resolved cardiovascular MR multitasking

Abstract

Purpose To develop a free‐breathing, non‐electrocardiogram technique for simultaneous myocardial T1, T2, T2*, and fat‐fraction (FF) mapping in a single scan. Methods The MR Multitasking framework is adapted to quantify T1, T2, T2*, and FF simultaneously. A variable TR scheme is developed to preserve temporal resolution and imaging efficiency. The underlying high‐dimensional image is modeled as a low‐rank tensor, which allows accelerated acquisition and efficient reconstruction. The accuracy and/or repeatability of the technique were evaluated on static and motion phantoms, 12 healthy volunteers, and 3 patients by comparing to the reference techniques. Results In static and motion phantoms, T1/T2/T2*/FF measurements showed substantial consistency (R > 0.98) and excellent agreement (intraclass correlation coefficient > 0.93) with reference measurements. In human subjects, the proposed technique yielded repeatable T1, T2, T2*, and FF measurements that agreed with those from references. Conclusions The proposed free‐breathing, non‐electrocardiogram, motion‐resolved Multitasking technique allows simultaneous quantification of myocardial T1, T2, T2*, and FF in a single 2.5‐min scan.

Systematic review of reconstruction techniques for accelerated quantitative MRI

“…This work describes and categorizes the different reconstruction techniques used for undersampled qMRI acquisitions in a unified mathematical framework, focusing on their methodological contribution while ignoring case-specific variables. Accelerated qMRI methods have enabled for example T 1 and T 2 mapping of the whole brain with 1 mm 3 resolution in just 3 min 126,152 and cardiac T 1 and T 2 mapping with a single breath-hold scan in about 16 s. 141 Accelerated qMRI is an active, fast-growing research field, a trend supported by the observation that around half of the papers included in this work were published in the last 3 years. The growing number of publications and the emergence of new methodologies, such as learning-based techniques, indicate the interest of the research community in further acceleration of qMRI as well as in more accurate and trustworthy techniques.…”

“…To account for subject motion, some techniques based on partially separable functions have been proposed. In these techniques, different subspace basis functions related to the contrasts and motion can be separately designed and used during the reconstruction 145,150‐156 . Specifically, the contrast images $$$ \boldsymbol{I} $$$ can be decomposed into multiple tensors using a higher‐order singular value decomposition, such as the Tucker decomposition.…”

“…During the reconstruction the spatial weights $$$ \overset{\check{} }{\boldsymbol{\sigma}} $$$ are estimated. Equation () is limited to two bases but this number can be increased to include more aspects of the signal evolution 130,152,158‐161 . By including SMS in the acquisition protocol, the scan time for such techniques can be further reduced 160 .…”

“…This work describes and categorizes the different reconstruction techniques used for undersampled qMRI acquisitions in a unified mathematical framework, focusing on their methodological contribution while ignoring case‐specific variables. Accelerated qMRI methods have enabled for example $$$ {\mathrm{T}}_1 $$$ and $$$ {\mathrm{T}}_2 $$$ mapping of the whole brain with 1 $$$ {\mathrm{mm}}^3 $$$ resolution in just 3 min 126,152 and cardiac $$$ {\mathrm{T}}_1 $$$ and $$$ {\mathrm{T}}_2 $$$ mapping with a single breath‐hold scan in about 16 s 141 …”

“…Equation ( 14) is limited to two bases but this number can be increased to include more aspects of the signal evolution. 130,152,[158][159][160][161] By including SMS in the acquisition protocol, the scan time for such techniques can be further reduced. 160 Along similar lines, it has been proposed to separate the spatial weight 𝜎 into a magnitude and a unit phase component that represents the phase variations.…”