title: Multislice CEST MRI improves the spatial assessment of tumor pH.
abstract: Multislice maps of extracellular pH (pHe) are needed to interrogate the heterogeneities of tumors and normal organs. To address this need, we have developed a multislice chemical exchange saturation transfer (CEST) MRI acquisition method with a CEST spectrum-fitting method that measures in vivo pHe over a range of 6.3 to 7.4.
  
  
  
  The phase offset multiplanar (POMP) method was adapted for CEST fast imaging with steady-state free precession (FISP) MRI to acquire multiple image slices with a single CEST saturation pulse. The Bloch-McConnell equations were modified to include pH based on a calibration of pH and chemical exchange rate for the contrast agent iopamidol. These equations were used to estimate the pixel-wise pHe values throughout the multislice acidoCEST MR images of the tumor, kidney, bladder, and other tissues of a MDA-MB-231 tumor model.
  
  
  
  Multislice acidoCEST MRI successfully mapped a gradient of pHe from 6.73 to 6.81 units from the tumor core to rim, and also mapped a gradient of pHe 6.56 to 6.97 across the mouse kidney. The bladder was found to be pHe 6.3.
  
  
  
  AcidoCEST MRI with POMP acquisition and Bloch-McConnel analysis can map pHe in multiple imaging slices through the tumor, kidney, and bladder. This multislice evaluation facilitates assessments of spatial heterogeneity of tissue pHe. Magn Reson Med 78:97-106, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Randtke
authors.affiliation: Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA.
authors.forename: Jeffry C
authors.initials: JC
authors.lastname: Granados
authors.affiliation: Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA.
authors.forename: Christine M
authors.identifier: 0000-0001-7878-961X
authors.initials: CM
authors.lastname: Howison
authors.affiliation: Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Pagel
authors.affiliation: Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA.|Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA.
authors.forename: Julio
authors.initials: J
authors.lastname: Cárdenas-Rodríguez
mesh_terms: D000818:Animals; D005260:Female; D006863:Hydrogen-Ion Concentration; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000737:chemistry* / Q000000981:diagnostic imaging*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D062211:Spatio-Temporal Analysis
keywords: CEST MRI; CEST-FISP; POMP MRI; extracellular pH; iopamidol