Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST)

Friedman, Jonathan A.; Xia, Ding; Regatte, Ravinder R.; Jerschow, Alexej

doi:10.1016/j.jmr.2015.04.010

Cited by 14 publications

(16 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ideas range from multi-parametric fitting, 17,32,[48][49][50] to the incorporation of several types of exchange rate filters, [24][25][26]47,[51][52][53] to the suppression of confounding signals by simultaneous pre-saturation at various frequency offsets. 30,[54][55][56] Although these approaches work appropriately and allow the isolation of the prominent amide proton resonance at Δω = +3.5 ppm or the rNOE-CEST signal of aliphatic protons at around Δω = −3.5 ppm, the assignment of these signals exclusively to mobile proteins remains questionable. With respect to the amide proton signal, a considerable part originates from small peptides and various metabolites.…”

Section: Discussionmentioning

confidence: 99%

Dual‐frequency irradiation CEST‐MRI of endogenous bulk mobile proteins

et al. 2018

View full text Add to dashboard Cite

A novel MRI contrast is proposed which enables the selective detection of endogenous bulk mobile proteins in vivo. Such a non-invasive imaging technique may be of particular interest for many diseases associated with pathological alterations of protein expression, such as cancer and neurodegenerative disorders. Specificity to mobile proteins was achieved by the selective measurement of intramolecular spin diffusion and the removal of semi-solid macromolecular signal components by a correction procedure. For this purpose, the approach of chemical exchange saturation transfer (CEST) was extended to a radiofrequency (RF) irradiation scheme at two different frequency offsets (dualCEST). Using protein model solutions, it was demonstrated that the dualCEST technique allows the calculation of an image contrast which is exclusively sensitive to changes in concentration, molecular size and the folding state of mobile proteins. With respect to application in humans, dualCEST overcomes the selectivity limitations at relatively low magnetic field strengths, and thus enables examinations on clinical MR scanners. The feasibility of dualCEST examinations in humans was verified by a proof-of-principle examination of a brain tumor patient at 3 T. With its specificity for the mobile fraction of the proteome, its comparable sensitivity to conventional water proton MRI and its applicability to clinical MR scanners, this technique represents a further step towards the non-invasive imaging of proteomic changes in humans.

show abstract

Section: Discussionmentioning

confidence: 99%

Dual‐frequency irradiation CEST‐MRI of endogenous bulk mobile proteins

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The acquisition of such a reference scan is a common problem in the field of CEST, and many techniques have been developed to obtain Z ref without using the opposite frequency. These are Lorentzian difference approaches (21,34,(44)(45)(46), extrapolation of MT (50), three-point methods (9,10,51), variable flip angle methods (40,42), variable delay-time approaches (43) or transfer rate edited CEST approaches (52). In a similar manner, multi-pool systems can be handled if the various signals are spectrally separated for each Ω-plot.…”

Section: ω-Plot For Shaped Pulses In Phantoms At 7 Tmentioning

confidence: 99%

Quantitative pulsed CEST-MRI usingΩ-plots

et al. 2015

View full text Add to dashboard Cite

Chemical exchange saturation transfer (CEST) allows the indirect detection of dilute metabolites in living tissue via MRI of the tissue water signal. Selective radio frequency (RF) with amplitude B1 is used to saturate the magnetization of protons of exchanging groups, which transfer the saturation to the abundant water pool. In a clinical setup, the saturation scheme is limited to a series of short pulses to follow regulation of the specific absorption rate (SAR). Pulsed saturation is difficult to describe theoretically, thus rendering quantitative CEST a challenging task. In this study, we propose a new analytical treatment of pulsed CEST by extending a former interleaved saturation-relaxation approach. Analytical integration of the continuous wave (cw) eigenvalue as a function of the RF pulse shape leads to a formula for pulsed CEST that has the same structure as that for cw CEST, but incorporates two form factors that are determined by the pulse shape. This enables analytical Z-spectrum calculations and permits deeper insight into pulsed CEST. Furthermore, it extends Dixon's Ω-plot method to the case of pulsed saturation, yielding separately, and independently, the exchange rate and the relative proton concentration. Consequently, knowledge of the form factors allows a direct comparison of the effect of the strength and B1 dispersion of pulsed CEST experiments with the ideal case of cw saturation. The extended pulsed CEST quantification approach was verified using creatine phantoms measured on a 7 T whole-body MR tomograph, and its range of validity was assessed by simulations.

show abstract

“…Several editing approaches with alteration of sequence parameters have been suggested, striving to enhance CEST/ NOE contrast. 16,[66][67][68] Zu et al 68 optimized the average saturation power (constant for i ), which, however, is insufficient for a strong or asymmetric background. Results from the MTRA analysis 69 would still appear biased and CEST/NOE peaks remain obstructed.…”

Section: Discussionmentioning

confidence: 99%

A new approach to Z‐spectrum acquisition: prospective baseline enhancement (PROBE) for CEST/Nuclear Overhauser Effect

Lenich

Pampel

Mildner

et al. 2018

Magnetic Resonance in Med

View full text Add to dashboard Cite

Purpose To develop a prospective baseline enhancement that compensates for intermingled background effects in Z‐spectra to achieve sensitivity enhancement of peaks related to CEST and nuclear Overhauser effect. Methods An MRI sequence–specific compensation of background effects is achieved through variation of the pulsed saturation power, ω1,max, with the chemical shift, δ. After a “scout acquisition” of a standard Z‐spectrum, the background is modeled through an appropriate spin system. Subsequently, an optimization procedure yields ω1,maxfalse(δfalse) values that compensate for background contributions yielding a flat baseline. Contributions from metabolites not considered in the optimization procedure are enhanced as distinct perturbations to the baseline. For experimental verification, mapping of the lactate concentration in the presence of cross‐linked bovine serum albumin was performed in phantoms at 7 T. As proof of concept, explorative experiments were performed in healthy human subjects at 3 T. Results Nuisance contributions from direct water saturation, macromolecular magnetization transfer, and exchanging background protons were successfully removed from the Z‐spectrum in phantoms and in brain tissue. The lactate methyl, methine, and hydroxyl peaks were readily observable in vitro. The peak areas correlated linearly with known concentrations. Improvement of the detection limit was achieved by a sparse distribution of saturation frequencies, allowing for more efficient signal averaging. Conclusion An optimization framework for high‐resolution metabolite mapping by means of CEST/nuclear Overhauser effect was developed. It offers full flexibility to select spin‐pool moieties, whose influence on the Z‐spectrum will be compensated. Deviations from this background model will provide a contrast at the respective offset frequencies.

show abstract

Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST)

Cited by 14 publications

References 25 publications

Dual‐frequency irradiation CEST‐MRI of endogenous bulk mobile proteins

Dual‐frequency irradiation CEST‐MRI of endogenous bulk mobile proteins

Quantitative pulsed CEST-MRI usingΩ-plots

A new approach to Z‐spectrum acquisition: prospective baseline enhancement (PROBE) for CEST/Nuclear Overhauser Effect

Contact Info

Product

Resources

About