Dear Users

This *Wednesday* (4-5 pm in YNiC) there will be a talk by Dr. Peter van Zijl from Johns Hopkins University and the Kennedy Krieger Institute.

http://www.kennedykrieger.org/kki_staff.jsp?pid=1064

The title of Dr van Zijl's talk is "Chemical Exchange Saturation Transfer (CEST) contrast agents". Please see below for the talk abstract.

Everyone is welcome to attend and refreshments will be provided after the talk.

Best wishes Rebecca

Abstract: CEST agents^1,2 exploit exchangeable protons to achieve contrast in MRI. This can be accomplished by using radiofrequency saturation at the NMR frequency of these protons and monitoring of the transfer of this saturation to the water protons imaged in MRI. When continuous saturation is applied, strong sensitivity enhancements (factors of hundred to hundreds of thousands depending on the protons) can be attained to image micromolar compounds. CEST agents have been broadly classified in terms of containing paramagnetic metals (paraCEST) or not (diaCEST). The main characteristic of diaCEST agents is that the chemical shift range of their exchangeable protons is limited to a range of approximately 6-7 ppm positive with respect to the water signal, which can be extended by another 6-7 ppm through hydrogen bonding of the exchangeable site. Currently, protons used for diaCEST include OH (hydroxyl, ~0-3ppm from water), NH2 (amine ~0-3 ppm from water), NH (amide, ~3- 4ppm from water; imino, ~5-7ppm from water). The main compounds are carbohydrates (sugars), peptides and proteins, and nucleic acids, which is important to mention because these are natural bio-organic substances. MRI is an insensitive method and, contrary to PET and optical approaches, the application of contrast agents often requires physiologically incompatible (micromolar-millimolar) concentrations. Unlike paramagnetic metallic contrast agents, diaCEST provides natural, non-metallic labels. As a consequence, this methodology has already allowed the use of many agents in vivo in animals, while endogenous markers such as cellular peptides and sugar derivatives are even been studied in humans. Recent data suggest that amide proton transfer (APT) may provide a biomarker for separating tumor recurrence from treatment necrosis in the brain. ^3 In this presentation, an overview will be given of current diaCEST agents as well as of their applications and pitfalls. Based on its non-invasive character, diaCEST is expected to revolutionize the rapid translation of contrast agents to the clinic. The field is evolving rapidly and many novel exogenous agents and endogenous markers are expected to be discovered in the near future. Reference: 1) Ward KM et al. J Magn Reson 2000;143:79–87. 2) van Zijl PC, Yadav NN. Magn Reson Med. 2011;65(4):927-48. 3) Zhou J. et al. Nat Med. 2011;17(1):130-4.