title: On the transmit field inhomogeneity correction of relaxation-compensated amide and NOE CEST effects at 7 T.
abstract: High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B1inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST. In this work, two B1correction algorithms for the most studied CEST effects, amide-CEST and nuclear Overhauser enhancement (NOE), were analyzed. Both methods rely on fitting the multi-pool Bloch-McConnell equations to the densely sampled CEST spectra. In the first method, the correction is achieved by using a linear B1correction of the calculated amide and NOE CEST effects. The second method uses the Bloch-McConnell fit parameters and the desired B1amplitude to recalculate the CEST spectra, followed by the calculation of B1-corrected amide and NOE CEST effects. Both algorithms were systematically studied in Bloch-McConnell equations and in human data, and compared with the earlier proposed ideal interpolation-based B1correction method. In the low B1regime of 0.15-0.50 μT (average power), a simple linear model was sufficient to mitigate B1inhomogeneity effects on a par with the interpolation B1correction, as demonstrated by a reduced correlation of the CEST contrast with B1in both the simulations and the experiments.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Khlebnikov
authors.affiliation: Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Windschuh
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.|Spinoza Centre for Neuroimaging, Amsterdam, The Netherlands.
authors.forename: Jeroen C W
authors.identifier: http://orcid.org/0000-0001-5079-2868
authors.initials: JC
authors.lastname: Siero
authors.affiliation: Division of Medical Physics in Radiology, Deutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center], Heidelberg, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Zaiss
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Luijten
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Dennis W J
authors.initials: DW
authors.lastname: Klomp
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Hoogduin
mesh_terms: D000465:Algorithms; D000577:Amides / Q000378:metabolism*; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D057054:Molecular Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
chemical_list: D000577:Amides
keywords: B1 correction; Bloch-McConnell equations; relaxation-compensated NOE CEST; relaxation-compensated amide-CEST; transmit field inhomogeneity