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Highly accelerated chemical exchange saturation transfer (CEST) measurements with linear algebraic modeling.

ABSTRACT: In clinical studies, compartmental average chemical exchange saturation transfer (CEST) measurements rather than voxel-by-voxel CEST images may suffice for evaluating its diagnostic value. A recently developed method-spectroscopy with linear algebraic modeling, or SLAM-could directly provide compartmental measures with dramatically reduced scan time and optimal signal-to-noise ratios. Here, we test whether SLAM can be adapted to significantly accelerate CEST acquisitions.Conventional anatomical images and raw CEST image k-space data were acquired from seven brain tumor patients. SLAM was applied to the CEST data using acceleration factors of R?=?1-45, after segmenting compartments from co-registered images. SLAM-CEST measures were compared with average values from the identical compartments obtained by conventional Fourier transform (FT) CEST.SLAM generated compartmental average CEST z-spectra that were indistinguishable from conventional FT-CEST for R???45. SLAM-CEST z-spectra at ±3.5 ppm were highly correlated with FT-CEST measures (r(2) ???0.98 for R???9; r???0.995 for R???45). The average error of SLAM-CEST versus FT-CEST measures was ?10% for R???45, in acquisitions requiring as few as a single k-space phase-encoding step.Applied to patients with brain tumors, SLAM-CEST can yield results that are quantitatively equivalent to conventional CEST up to 45 times faster, which could prove enabling in clinical settings where scan time is limiting. Magn Reson Med 76:136-144, 2016. © 2015 Wiley Periodicals, Inc.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC4548835 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Highly accelerated chemical exchange saturation transfer (CEST) measurements with linear algebraic modeling.

Zhang Yi Y Heo Hye-Young HY Jiang Shanshan S Lee Dong-Hoon DH Bottomley Paul A PA Zhou Jinyuan J

Magnetic resonance in medicine 20150824 1

<h4>Purpose</h4>In clinical studies, compartmental average chemical exchange saturation transfer (CEST) measurements rather than voxel-by-voxel CEST images may suffice for evaluating its diagnostic value. A recently developed method-spectroscopy with linear algebraic modeling, or SLAM-could directly provide compartmental measures with dramatically reduced scan time and optimal signal-to-noise ratios. Here, we test whether SLAM can be adapted to significantly accelerate CEST acquisitions.<h4>Theo ...[more]

PMID: 26302147

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Project description:Accurate quantification of chemical exchange saturation transfer (CEST) effects, including dipole-dipole mediated relayed nuclear Overhauser enhancement (rNOE) saturation transfer, is important for applications and studies of molecular concentration and transfer rate (and thereby pH or temperature). Although several quantification methods, such as Lorentzian difference (LD) analysis, multiple-pool Lorentzian fits, and the three-point method, have been extensively used in several preclinical and clinical applications, the accuracy of these methods has not been evaluated. Here we simulated multiple-pool Z spectra containing the pools that contribute to the main CEST and rNOE saturation transfer signals in the brain, numerically fit them using the different methods, and then compared their derived CEST metrics with the known solute concentrations and exchange rates. Our results show that the LD analysis overestimates contributions from amide proton transfer (APT) and intermediate exchanging amine protons; the three-point method significantly underestimates both APT and rNOE saturation transfer at -3.5 ppm (NOE(-3.5)). The multiple-pool Lorentzian fit is more accurate than the other two methods, but only at lower irradiation powers (?1 ?T at 9.4 T) within the range of our simulations. At higher irradiation powers, this method is also inaccurate because of the presence of a fast exchanging CEST signal that has a non-Lorentzian lineshape. Quantitative parameters derived from in vivo images of rodent brain tumor obtained using an irradiation power of 1 ?T were also compared. Our results demonstrate that all three quantification methods show similar contrasts between tumor and contralateral normal tissue for both APT and the NOE(-3.5). However, the quantified values of the three methods are significantly different. Our work provides insight into the fitting accuracy obtainable in a complex tissue model and provides guidelines for evaluating other newly developed quantification methods.

Dataset Information

Highly accelerated chemical exchange saturation transfer (CEST) measurements with linear algebraic modeling.

Publications

Highly accelerated chemical exchange saturation transfer (CEST) measurements with linear algebraic modeling.

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