title: UCEPR: Ultrafast localized CEST-spectroscopy with PRESS in phantoms and in vivo.
abstract: OBJECTIVE
  Chemical exchange saturation transfer (CEST) is a contrast mechanism enhancing low-concentration molecules through saturation transfer from their exchangeable protons to bulk water. Often many scans are acquired to form a Z-spectrum, making the CEST method time-consuming. Here, an ultrafast localized CEST-spectroscopy with PRESS (UCEPR) is proposed to obtain the entire Z-spectrum of a voxel using only two scans, significantly accelerating CEST.
  
  
  METHODS
  The approach combines ultrafast nonlocalized CEST spectroscopy with localization using PRESS. A field gradient is applied concurrently with the saturation pulse producing simultaneous saturation of all Z-spectrum frequencies that are also spatially encoded. A readout gradient during data acquisition resolves the spatial dependence of the CEST responses into frequency. UCEPR was tested on a 3T scanner both in phantoms and in vivo.
  
  
  RESULTS
  In phantoms, a fast Z-spectroscopy acquisition of multiple pH-variant iopamidol samples was achieved with four- to seven-fold acceleration as compared to the conventional CEST methods. In vivo, amide proton transfer (APT) in white matter of healthy human brain was measured rapidly in 48 s and with high frequency resolution (≤ 0.2 ppm).
  
  
  CONCLUSIONS
  Compared with conventional CEST methods, UCEPR has the advantage of rapidly acquiring high-resolution Z-spectra. Potential in vivo applications include ultrafast localized Z-spectroscopy, quantitative, or dynamic CEST studies.
authors.affiliation: Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.|Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.|Philips Medical Systems, Highland Heights, Ohio, USA.
authors.forename: Ivan E
authors.initials: IE
authors.lastname: Dimitrov
authors.affiliation: Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.|Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lenkinski
authors.affiliation: Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Asghar
authors.initials: A
authors.lastname: Hajibeigi
authors.affiliation: Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.|Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Vinogradov
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging* / Q000502:physiology; D003287:Contrast Media / Q000737:chemistry; D064368:Healthy Volunteers; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007479:Iopamidol / Q000737:chemistry; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D011522:Protons; D011846:Radio Waves; D013053:Spectrophotometry / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D003287:Contrast Media; D011522:Protons; D014867:Water; D007479:Iopamidol
keywords: APT; PRESS; broadband saturation; iopamidol; ultrafast localized CEST