Quantitative platform for accurate and reproducible assessment of transverse (T ) relaxation time.

MRI's transverse relaxation time (T ) is sensitive to tissues' composition and pathological state. While variations in T values can be used as clinical biomarkers, it is challenging to quantify this parameter in vivo due to the complexity of the MRI signal model, differences in protocol implementations, and hardware imperfections. Herein, we provide a detailed analysis of the echo modulation curve (EMC) platform, offering accurate and reproducible mapping of T values, from 2D multi-slice multi-echo spin-echo (MESE) protocols. Computer simulations of the full Bloch equations are used to generate an advanced signal model, which accounts for stimulated echoes and transmit field (B ) inhomogeneities. In addition to quantifying T values, the EMC platform also provides proton density (PD) maps, and fat-water fraction maps. The algorithm's accuracy, reproducibility, and insensitivity to T values are validated on a phantom constructed by the National Institute of Standards and Technology and on in vivo human brains. EMC-derived T maps show excellent agreement with ground truth values for both in vitro and in vivo models. Quantitative values are accurate and stable across scan settings and for the physiological range of T values, while showing robustness to main field (B ) inhomogeneities, to variations in T relaxation time, and to magnetization transfer. Extension of the algorithm to two-component fitting yields accurate fat and water T maps along with their relative fractions, similar to a reference three-point Dixon technique. Overall, the EMC platform allows to generate accurate and stable T maps, with a full brain coverage using a standard MESE protocol and at feasible scan times. The utility of EMC-based T maps was demonstrated on several clinical applications, showing robustness to variations in other magnetic properties. The algorithm is available online as a full stand-alone package, including an intuitive graphical user interface.