Modulation of CEST images in vivo by T 1 relaxation: A new approach in the design of responsive PARACEST agents

S. James Ratnakar, Todd C. Soesbe, Lloyd Laporca Lumata, Quyen N. Do, Subha Viswanathan, Chien Yuan Lin, A. Dean Sherry, Zoltan Kovacs

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


A novel approach for the design of responsive paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) agents has been developed where the signal is "turned on" by altering the longitudinal relaxation time (T1) of bulk water protons. To demonstrate this approach, a model Eu(DOTA-tetraamide) complex (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) containing two nitroxide free radical units was synthesized. The nitroxide groups substantially shortened the T1 of the bulk water protons which, in turn, resulted in quenching of the CEST signal. Reduction of paramagnetic nitroxide moieties to a diamagnetic species resulted in the appearance of CEST. The modulation of CEST by T1 relaxation provides a new platform for designing biologically responsive MRI agents.

Original languageEnglish (US)
Pages (from-to)14904-14907
Number of pages4
JournalJournal of the American Chemical Society
Issue number40
StatePublished - Oct 9 2013

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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