Premium
QUESP and QUEST revisited – fast and accurate quantitative CEST experiments
Author(s) -
Zaiss Moritz,
Angelovski Goran,
Demetriou Eleni,
McMahon Michael T.,
Golay Xavier,
Scheffler Klaus
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26813
Subject(s) - saturation (graph theory) , chemistry , exchange rate , linearity , paramagnetism , yield (engineering) , nuclear magnetic resonance , biological system , analytical chemistry (journal) , statistical physics , thermodynamics , physics , chromatography , condensed matter physics , mathematics , combinatorics , quantum mechanics , biology , economics , macroeconomics
Purpose Chemical exchange saturation transfer (CEST) NMR or MRI experiments allow detection of low concentrated molecules with enhanced sensitivity via their proton exchange with the abundant water pool. Be it endogenous metabolites or exogenous contrast agents, an exact quantification of the actual exchange rate is required to design optimal pulse sequences and/or specific sensitive agents. Methods Refined analytical expressions allow deeper insight and improvement of accuracy for common quantification techniques. The accuracy of standard quantification methodologies, such as quantification of exchange rate using varying saturation power or varying saturation time, is improved especially for the case of nonequilibrium initial conditions and weak labeling conditions, meaning the saturation amplitude is smaller than the exchange rate (γB 1 < k). Results The improved analytical ‘quantification of exchange rate using varying saturation power/time’ (QUESP/QUEST) equations allow for more accurate exchange rate determination, and provide clear insights on the general principles to execute the experiments and to perform numerical evaluation. The proposed methodology was evaluated on the large‐shift regime of paramagnetic chemical‐exchange‐saturation‐transfer agents using simulated data and data of the paramagnetic Eu(III) complex of DOTA‐tetraglycineamide. Conclusions The refined formulas yield improved exchange rate estimation. General convergence intervals of the methods that would apply for smaller shift agents are also discussed. Magn Reson Med 79:1708–1721, 2018. © 2017 International Society for Magnetic Resonance in Medicine.