Chemical exchange saturation transfer (CEST) and MR<i>Z</i>-spectroscopy<i>in vivo</i>: a review of theoretical approaches and methods

Zaiß, Moritz; Bachert, Peter

doi:10.1088/0031-9155/58/22/r221

Cited by 261 publications

(416 citation statements)

References 138 publications

(276 reference statements)

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“…Visualisation of dynamic changes in free creatine in exercised muscle (107) IMAT, intermuscular adipose tissue; CT, computed tomography; UTE, ultra-short echo-time imaging; IMCL, intramyocellular lipid; SM, skeletal muscle; DTI, diffusion tensor imaging; MRS, magnetic resonance spectroscopy; CEST, chemical exchange saturation transfer.…”

Section: Ultrasoundmentioning

confidence: 99%

Skeletal muscle mass and quality: evolution of modern measurement concepts in the context of sarcopenia

et al. 2015

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Conference on 'Nutrition and age-related muscle loss, sarcopenia and cachexia' The first reports of accurate skeletal muscle mass measurement in human subjects appeared at about the same time as introduction of the sarcopenia concept in the late 1980s. Since then these methods, computed tomography and MRI, have been used to gain insights into older (i.e. anthropometry and urinary markers) and more recently developed and refined methods (ultrasound, bioimpedance analysis and dual-energy X-ray absorptiometry) of quantifying regional and total body skeletal muscle mass. The objective of this review is to describe the evolution of these methods and their continued development in the context of sarcopenia evaluation and treatment. Advances in these technologies are described with a focus on additional quantifiable measures that relate to muscle composition and 'quality'. The integration of these collective evaluations with strength and physical performance indices is highlighted with linkages to evaluation of sarcopenia and the spectrum of related disorders such as sarcopenic obesity, cachexia and frailty. Our findings show that currently available methods and those in development are capable of non-invasively extending measures from solely 'mass' to quality evaluations that promise to close the gaps now recognised between skeletal muscle mass and muscle function, morbidity and mortality. As the largest tissue compartment in most adults, skeletal muscle mass and aspects of muscle composition can now be evaluated by a wide array of technologies that provide important new research and clinical opportunities aligned with the growing interest in the spectrum of conditions associated with sarcopenia.

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Section: Ultrasoundmentioning

confidence: 99%

Skeletal muscle mass and quality: evolution of modern measurement concepts in the context of sarcopenia

et al. 2015

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“…The power of chemical exchange saturation transfer (CEST) MR imaging as a marker for tumor diseases is the indirect detection of intracellular compounds like functional metabolites (1)(2)(3)(4) or mobile proteins (5,6) in vivo by use of the exchange processes with water pool protons (7). Two distinct saturation transfer (ST) effects apparent in vivo are attributed to protons of mobile proteins: at 3.5 ppm the backbone amide signals with their base catalyzed proton transfer (APT) and at -3.5 ppm the nuclear Overhauser enhancement (NOE) mediated aliphatic proton magnetization transfer (so called exchangerelayed NOE or relayed-NOE (rNOE) ST) (8,9).…”

Section: Introductionmentioning

confidence: 99%

Downfield‐NOE‐suppressed amide‐CEST‐MRI at 7 Tesla provides a unique contrast in human glioblastoma

Zaiß

Windschuh

Goerke

et al. 2016

Magnetic Resonance in Med

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Purpose: The chemical exchange saturation transfer (CEST) effect observed in brain tissue in vivo at the frequency offset 3.5 ppm downfield of water was assigned to amide protons of the protein backbone. Obeying a base-catalyzed exchange process such an amide-CEST effect would correlate with intracellular pH and protein concentration, correlations that are highly interesting for cancer diagnosis. However, recent experiments suggested that, besides the known aliphatic relayednuclear Overhauser effect (rNOE) upfield of water, an additional downfield rNOE is apparent in vivo resonating as well around þ3.5 ppm. In this study, we present further evidence for the underlying downfield-rNOE signal, and we propose a first method that suppresses the downfield-rNOE contribution to the amide-CEST contrast. Thus, an isolated amide-CEST effect depending mainly on amide proton concentration and pH is generated. Methods: The isolation of the exchange mediated amide proton effect was investigated in protein model-solutions and tissue lysates and successfully applied to in vivo CEST images of 11 glioblastoma patients. Results: Comparison with gadolinium contrast enhancing longitudinal relaxation time-weighted images revealed that the downfield-rNOE-suppressed amide-CEST contrast forms a unique contrast that delineates tumor regions and show remarkable overlap with the gadolinium contrast enhancement. Conclusion: Thus, suppression of the downfield rNOE contribution might be the important step to yield the amide proton CEST contrast originally aimed at.

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“…Table 2 lists the fitting results with k 1 , and the value of the squared 2-norm of the residual (resnorm). Usually, the amide group has a slow exchange rate, 34) and the CEST effect for the amide protons increases as pH increases because the exchange rate increases in a low pH. 26,27) We showed the pseudo-exchange rates of Glu and Gly were decreased with increasing the acidity.…”

Section: Results Of Measurements Of the Chemical Exchange Rate At 3tmentioning

confidence: 79%

Physical Modeling of Chemical Exchange Saturation Transfer Imaging

Jahng

2017

Prog Med Phys

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Chemical Exchange Saturation Transfer (CEST) imaging is a method to detect solutes based on the chemical exchange of mobile protons with water. The solute protons exchange with three different patterns, which are fast, slow, and intermediate rates. The CEST contrast can be obtained from the exchangeable protons, which are hydroxyl protons, amine protons, and amide protons. The CEST MR imaging is useful to evaluate tumors, strokes, and other diseases. The purpose of this study is to review the mathematical model for CEST imaging and for measurement of the chemical exchange rate, and to measure the chemical exchange rate using a 3T MRI system on several amino acids. We reviewed the mathematical models for the proton exchange. Several physical models are proposed to demonstrate a two-pool, three-pool, and four-pool models. The CEST signals are also evaluated by taking account of the exchange rate, pH and the saturation efficiency. Although researchers have used most commonly in the calculation of CEST asymmetry, a quantitative analysis is also developed by using Lorentzian fitting. The chemical exchange rate was measured in the phantoms made of asparagine (Asn), glutamate (Glu), γ-aminobutyric acid (GABA), glycine (Gly), and myoinositol (MI). The experiment was performed at a 3T human MRI system with three different acidity conditions (pH 5.6, 6.2, and 7.4) at a concentration of 50 mM. To identify the chemical exchange rate, the "lsqcurvefit" built-in function in MATLAB was used to fit the pseudofirst exchange rate model. The pseudo-first exchange rate of Asn and Gly was increased with decreasing acidity. In the case of GABA, the largest result was observed at pH 6.2. For Glu, the results at pH 5.6 and 6.2 did not show a significant difference, and the results at pH 7.4 were almost zero. For MI, there was no significant difference at pH 5.6 or 7.4, however, the results at pH 6.2 were smaller than at the other pH values. For the experiment at 3T, we were only able to apply 1 s as the maximum saturation duration due to the limitations of the MRI system. The measurement of the chemical exchange rate was limited in a clinical 3T MRI system because of a hardware limitation.

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Chemical exchange saturation transfer (CEST) and MRZ-spectroscopyin vivo: a review of theoretical approaches and methods

Cited by 261 publications

References 138 publications

Skeletal muscle mass and quality: evolution of modern measurement concepts in the context of sarcopenia

Skeletal muscle mass and quality: evolution of modern measurement concepts in the context of sarcopenia

Downfield‐NOE‐suppressed amide‐CEST‐MRI at 7 Tesla provides a unique contrast in human glioblastoma

Physical Modeling of Chemical Exchange Saturation Transfer Imaging

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