title: Extracranial measurements of amide proton transfer using exchange-modulated point-resolved spectroscopy (EXPRESS).
abstract: Chemical exchange saturation transfer (CEST) imaging has been used experimentally in a large range of applications. However, full quantification of CEST effects in vivo using standard imaging sequences is time consuming as a large number of saturation frequency offsets, each followed by an imaging readout, are required to define a z spectrum. Furthermore, outside the brain, the presence of fat can confound the interpretation of z spectra. A novel acquisition and post-processing technique is presented in this study, named exchange-modulated point-resolved spectroscopy (EXPRESS), which aims to address these limitations and to enable spatially localised, high signal-to-noise measurements of CEST effects in vivo. Using amide proton exchange (APT) measurements in tumours, it is demonstrated that the acquisition of two-dimensional EXPRESS spectra composed of chemical shift and saturation frequency offset dimensions allows the correction of CEST data containing both fat and water signals, which is a common confounding property of tissues found outside the brain.
authors.affiliation: UCL Centre for Advanced Biomedical Imaging, Department of Medicine and Institute of Child Health, University College London, London, UK. simon.walkersamuel@ucl.ac.uk
authors.forename: Simon
authors.initials: S
authors.lastname: Walker-Samuel
authors.forename: S Peter
authors.initials: SP
authors.lastname: Johnson
authors.forename: Barbara
authors.initials: B
authors.lastname: Pedley
authors.forename: Mark F
authors.initials: MF
authors.lastname: Lythgoe
authors.forename: Xavier
authors.initials: X
authors.lastname: Golay
mesh_terms: D000577:Amides / Q000032:analysis*; D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000737:chemistry* / Q000175:diagnosis*; D008055:Lipids / Q000032:analysis*; D051379:Mice; D008819:Mice, Nude; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D000577:Amides; D014408:Biomarkers, Tumor; D008055:Lipids; D011522:Protons