A pH-Responsive MRI Agent that Can Be Activated Beyond the Tissue Magnetization Transfer Window

Angew Chem Int Ed Engl. 2015 Jul 20;54(30):8662-4. doi: 10.1002/anie.201502497. Epub 2015 Jun 11.


A terbium-based complex that displays a water exchange CEST resonance well outside the normal magnetization transfer (MT) frequency range of tissues provides a direct readout of pH values by MRI. Deprotonation of the phenolic proton in this complex results in a frequency shift of 56 ppm in a bound water molecule exchange peak between pH 5 and 8. This allows direct imaging of pH without prior knowledge of the agent concentration and with essentially no interference from the tissue MT signal.

Keywords: imaging agents; lanthanides; magnetic resonance imaging; magnetization transfer; paraCEST.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Contrast Media / chemistry
  • Coordination Complexes / chemistry*
  • Hydrogen-Ion Concentration
  • Magnetic Phenomena
  • Magnetic Resonance Imaging / methods*
  • Mice
  • Phenol / chemistry
  • Protons
  • Terbium / chemistry*


  • Contrast Media
  • Coordination Complexes
  • Protons
  • Terbium
  • Phenol