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.
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Dr. Rebecca E. Millman
Science Liaison Officer
York Neuroimaging Centre
The Biocentre
York Science Park
Heslington
YO10 5DG
Tel: +44 (0) 1904 567614
Fax: +44 (0) 1904 435356