Quantitative MRI Using Multiparametric Mapping

By using protons as intrinsic probes of their molecular environment, MRI can resolve the microstructural diversity of soft biological tissues. The mobility of protons, and consequently the MR signal decay, depends on how tightly the protons are bound to their surrounding molecular structure. This molecular environment can be “seen” by an MRI scanner through the relaxation rates of the associated MR signals. Therefore, the quantification of relaxation times is fundamental for characterizing the underlying microstructural tissue composition. This chapter will provide an overview of the multiparameter mapping (MPM) approach which allows to robustly quantify maps of physical tissue parameters which are linked to the microstructural tissue composition, i.e., the longitudinal relaxation time (T1), effective transverse relaxation time (T2*), magnetization transfer saturation (MT), and the underlying proton density (PD). The fundamental contrast mechanisms will be discussed, including details of the time-efficient MPM acquisition protocol and the quantification process. Important applications will be highlighted to illustrate the transformative potential of MPM-based quantitative MRI for basic and clinical research toward the translation of MPM measures into noninvasive in vivo histology.