Review ArticlesToward Quantification Microstructure and Magnetic Resonance FingerprintingKiselev, Valerij G. PhD∗; Körzdörfer, Gregor PhD†; Gall, Peter PhD† Author Information From the ∗Medical Physics, Department of Radiology, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg †Siemens Healthineers, Erlangen, Germany. Received for publication July 13, 2020; and accepted for publication, after revision, September 19, 2020. Conflicts of interest and sources of funding: none declared. Correspondence to: Peter Gall, PhD, Siemens Healthineers, Allee am Röthelheimpark 2, 91052 Erlangen, Germany. E-mail: [email protected]. Investigative Radiology 56(1):p 1-9, January 2021. | DOI: 10.1097/RLI.0000000000000738 Buy Metrics Abstract Quantitative magnetic resonance imaging (MRI) is a long-standing challenge. We advocate that the origin of the problem is the simplification applied in commonly used models of the MRI signal relation to the target parameters of biological tissues. Two research fields are briefly reviewed as ways to respond to the challenge of quantitative MRI, both experiencing an exponential growth right now. Microstructure MRI strives to build physiology-based models from cells to signal and, given the signal, back to the cells again. Magnetic resonance fingerprinting aims at efficient simultaneous determination of multiple signal parameters. The synergy of these yet disjoined approaches promises truly quantitative MRI with specific target-oriented diagnostic tools rather than universal imaging methods. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.